ENV spacecraft
ACKNOWLEDGEMENT
This book, “Indian Remote Sensing Missions
and Payloads - A Glance” is an attempt to provide
in one place the information about all Indian
Remote Sensing and scientific missions from
Aryabhata to RISAT-1 including some of the
satellites that are in the realization phase.
This document is compiled by IRS Program
Management Engineers from the data available at
various sources viz., configuration data books, and
other archives.
These missions are culmination of the efforts
put by all scientists, Engineers, and supporting
staff across various centres of ISRO. All their
works are duly acknowledged
Indian Remote Sensing Missions & Payloads
A Glance
IRS Programme Management Office
Prepared By
P. Murugan
P.V.Ganesh
PRKV Raghavamma
Reviewed By
C.A.Prabhakar
D.L.Shirolikar
Approved By
Dr.M. Annadurai
Program Director, IRS & SSS
ISRO Satellite Centre
Indian Space Research Organisation
Bangalore – 560 017
Table of Contents
Sl.No
Chapter Name
Page No
Introduction
1
1
Aryabhata
1.1
2
Bhaskara 1 , 2
2.1
3.
Rohini Satellites
3.1
4
IRS 1A & 1B
4.1
5
IRS-1E
5.1
6
IRS-P2
6.1
7
IRS-P3
7.1
8
IRS 1C & 1D
8.1
9
IRS-P4 (Oceansat-1)
9.1
10
Technology Experiment Satellite (TES)
10.1
11
IRS-P6 (ResourceSat-1)
11.1
12
IRS-P5 (Cartosat-1)
12.1
13
Cartosat 2,2A,2B
13.1
14
IMS-1(TWSAT)
14.1
15
Chandrayaan-1
15.1
16
Oceansat-2
16.1
17
Resourcesat-2
17.1
18
Youthsat
18.1
19
Megha-Tropiques
19.1
20
RISAT-1
20.1
Glossary
References
INTRODUCTION
The Indian Space Research Organisation (ISRO) planned a long term
Satellite Remote Sensing programme in seventies, and started related activities like
conducting field & aerial surveys, design of various types of sensors for aircraft
surveys and development of number of application/utilization approaches. These
were followed by planning, designing, fabrication of experimental remote sensing
missions viz., Aryabhata, Bhaskara 1 & II etc. These missions gave experience in
developing futuristic remote sensing satellites, setting up of ground-based data
reception and processing systems, experience in over-all mission management etc.
The launch of IRS-1A satellite on 17th March, 1988 into the orbit is the start
of operational remote sensing era of IRS programme. The IRS Satellites are
providing imagery data for many projects of national importance and applications.
Some of the remote sensing applications being catered are provided below
Agriculture and soils
Phase level information of soils
Improved
multiple
crop
discrimination
Crop monitoring &condition
assessment
Crop canopy water stress
Crop yield estimates
Crop management
Cropping system analysis
Damage assessment
Surveillance of pests and diseases
Forestry
Inventory and updating
Forest landscape analysis
Forest infra-structure mapping
Forest encroachment
State of forests
Wildlife habitat analysis
Bio-diversity
Fire damage
Implementation of forest policies
Environment
Hydrologic units
Land unit maps
Soil contamination maps
Quarries and waste identification
Desertification analysis
Oil spills
Point and non-point sources of
pollution
Environmental impact assessment
Geology and Exploration
Rock type mapping
Tectonic geo- structure mapping
Mining pollution analysis
Off/on shore seeps analysis
Coal fire analysis
Mining subsidence analysis
Landslide vulnerability / risk
Geo-energy
Water cycle study
Ocean application
Phytoplankton observation
Chlorophyll content,
Yellow substance
Suspended sediments
Sea surface winds,
Sea roughness monitoring
Sea surface temperature
Identifying the potential fishing
zones,
Coastal zone management,
Ship routing,
Operations of offshore oil rigs
Indian Remote Sensing Missions & Payloads – A glance
1
Meteorology
Water vapour in an atmospheric
column,
Cloud formation
Low pressure zone identification
Cyclone movement speed &
direction
Weather predictions,
Infrastructure and Utilities
Road networks
3D-city models
Infrastructure maps
Siting of hydro-power locations
Site suitability
Rural and urban infrastructure
Structural
and
hydrological
inventory
Municipal GIS
Utility corridor mapping
Transportation network
Rural road connectivity
Tracking changes in road
Telecom facilities
Recreation Facilities
Tourism
Violations
Damage assessment
Cartography
Updating topo-maps
Augmenting Databases
Image maps as base maps
Watershed management
Terrain evaluation
City models
Road and infrastructure maps
Site suitability assessment
Cadastral map generation
Defence
Strategic target monitoring
Mission planning
Training
Treaty verification
Demining
Lunar & Stellar Observation
Understand the way planets
created
Stellar movement,
Celestial body feature study
Studying radiations coming from
stars
Different elements available on
stellar objects
Above said applications can be categorized in the following way as part of National
Natural Resources planning as well as in other areas.






Multiple crop production estimates,
o Area estimate, crop health estimate
Land and Water Resources optimization,
Urban planning and management,
o Infrastructural plan
Coastal zone studies and regulation
o Fishing, chlorophyll, phytoplankton etc.
Mapping and inventory of forests, wastelands, land use,
Lunar & stellar observation missions
The aim of this document is to collect the Indian Remote Sensing payload
details available at various sources and consolidate to bring them in a single
document. This document provides brief, condensed information of various IRS
Indian Remote Sensing Missions & Payloads – A glance
2
Missions and payloads. This document will serve the new entrant engineers to
understand the evolution of Remote sensing Programme in India. Information
provided in this document is collected from various sources like configuration data
books, internet sources, Journals and books. The list of references is provided in
annexure-1.
IRS missions can be classified based on their applications as follows.







Land and Water Resource Observation Series
Ocean and Atmospheric Observation Series
Cartographic Satellite Series
Microwave Remote Sensing Series
Environmental monitoring series
Space Science Series
Micro and Nano Satellite Series
Land and Water Resource Observation Series
These satellites cater to the requirements of following applications:
Agriculture, forestry, land use, land cover, soil, geology, terrain, water
resources, disaster management like flood, forest fire, drought, land slide, etc.
Satellites launched for these applications are IRS-1A, IRS-1B, IRS-1C, IRS1D, IRS-P6 (Resourcesat-1), Resourcesat-2, and IMS-1A. Resourcesat-2 satellite
with improved performance having three payloads namely, LISS-IV with 5.8m
Resolution and 70 km swath in 3 bands, LISS-III with 23.5m Resolution and 140 km
swath and AWIFS with 56m Resolution and 740 km swath was launched on 20thApril
2011 and successfully operationalized and is providing data for above said
applications.
Presently the following IRS Satellites are operational and providing data for above
applications


IMS-1A
Resoucesat-2
Ocean and Atmospheric Observation Series
Under Ocean and Atmospheric Observation Series, satellites were launched
to meet the needs of potential fishing zone (PFZ) forecasting, sea state forecasting,
coastal zone studies and to provide inputs for weather forecasting and for climatic
studies:
Satellites launched for this application are Oceansat-1, Oceansat-II, and
Megha Tropiques
Oceansat-2: satellite with Ocean Colour Monitor (OCM) payload with 360m
spatial resolution and 1420 km swath and Ku-Band pencil beam scatterometer and
Indian Remote Sensing Missions & Payloads – A glance
3
Radio Occultation for Sounding of Atmospheric (ROSA) was launched on 23rd
September 2009 was successfully operationalized for providing data for the above
applications.
Megha-Tropiques: Under Ocean and Atmospheric Observation series to
study the convective systems that influence the tropical weather and climate. The
Megha-Tropiques mission was launched on 12th October 2011. The MeghaTropiques spacecraft carries 4 payloads namely:




MADRAS (A Microwave Imager to study the precipitation and cloud
properties).
SAPHIR (A Microwave Sounder for the retrieval of water vapour vertical
profiles).
SCARAB (A Radiometer for the measurement of outgoing radiative fluxes at
the top of the atmosphere) and
ROSA (Radio Occultation for Sounding of Atmosphere) to provide vertical
profiling of temperature.
The Megha-Tropiques mission will provide sampling of water and energy
budget of the Tropical Convective Systems in the inter-tropical band.
Cartographic Satellite Series
In order to meet the large scale and thematic maps for urban & rural
infrastructure development & management and to provide National Digital Elevation
Model (DEM) for cadastral overlay these satellites were launched. They cater
cartographic applications, coastal features mapping, coral reef mapping and for
mineral studies also
The features of these satellites are : TES with <1 m resolution PAN,
Cartosat-1 with 2.5m Resolution PAN and 30km swath with along track stereo
imaging capability, Cartosat-2,2A,2B with 0.8m Resolution PAN with 9.6 km swath
In order to meet the increased demand for large scale mapping and other
cartographic applications for cadastral level and for urban and rural infrastructure
development & management Cartosat-2A and Cartosat-2B with 0.8m Resolution
PAN with 9.6 km swath were launched for above applications.





Technology Experimental satellite (TES)
Cartosat-1 (since May 2005)
Cartosat-2 (since January 2007)
Cartosat-2A (April 2008)
Cartosat-2B (since July 2010)
Microwave Remote Sensing Satellite Series
Indian Remote Sensing Missions & Payloads – A glance
4
In order to provide data during the cloud cover seasons (Kharif) over the
tropical regions for many applications like agriculture and damage assessment during
flood and for mitigation effects Microwave Remote Sensing Satellites are planned.
The RISAT-1 with C-Band synthetic Aperture Radar (SAR) launched on
26 April 2012
th
The spacecraft can operate in different modes of operation and provides
various resolution imageries like:




High Resolution Spotlight Mode (HRS) provides 1 - 2m resolution with 10
km x 10 km spot scenes.
Fine Resolution Strip Mode (FRS-I) provides 3 - 9m resolution with 30 km x
30 km scenes.
Fine Resolution strip mode (FRS-2) provides 6 - 9m resolution with 30 km
swath.
Medium Resolution Scan SAR Mode (MRS) with 25m resolution with a
swath of 120 km.
The RISAT-1 is expected to provide all weather day and night imageries for
applications in the areas of Agriculture for identifications, detection and classification
for acreage estimation, forest type plantations and accurate bio-mass estimation,
flood mapping to provide accurate flood inundation zones for early relief measures,
soil moisture and Hydrology including snow cover and snow wetness, etc.
Space Science and Planetary Series
The study of Lunar and stellar sources provide better understanding about
the universe and planet creation etc. Following satellites are in this series.
IRS-P3: This satellite carried X ray monitor
CHANDRAYAAN-1: The launch of Chandrayaan-1 has demonstrated the
technological capabilities of reaching the outer planets and has confirmed the
scientific findings of the previous International Missions, like the presence of water
molecules and other precious elements on the surface of the moon.
The significant scientific finding have provided impetus to further space
research activities in the country and has created special awareness and enthusiasm
among the younger generation.
Micro, Nano and Pico Satellite Series
IMS-1: With the advances in miniaturization and the advances in high
performance devices and techniques, it has become feasible to realize the functions of
bigger satellites into Micro & Nano satellites. The ISRO's first Mini Satellite (IMS-1)
with 36m Resolution Mx with 141 km swath and 505 m resolution Hyper-spectral
Indian Remote Sensing Missions & Payloads – A glance
5
Imager (HySI) with 64 bands has been realized within 85 kgs and was launched
successfully during April 2008.
Youthsat: This satellite is second in IMS-1 series, carrying three payloads
namely SOLRAD, LiVHiSI and RaBIT. It was launched into space on 20th April
2011 by PSLV-16 along with Resourcesat-2. The SOLRAD payload monitors the
Solar activities through hard X-rays gamma rays and particle mostly electrons and
protons. The effect of the solar activities on atmosphere is studied by the RaBIT. The
effect on the thermosphere, which co-exists with the ionosphere, is monitored by
LiVHySI.
The interest and the enthusiasm created by the launch of many Nano
satellites in a single launch by the PSLV induced many students community from
Colleges, Universities, and Indian Institute of Technologies to involve in the
development of many Micro and Nano satellites for various applications.
The STUDSAT, the first pico satellite conceived and designed by seven
Engineering Colleges of Karnataka and Andhra Pradesh was successfully launched
during July 2010.
JUGNU from IIT-Kanpur and SRMSAT were successfully launched on 12th
October 2011.
PRATHAM from lIT-Bombay and Sathyabhama-sat from Sathyabhama
Universities are under advanced stages of realization for many EO and environmental
monitoring applications.
Some more premier educational institutions of India are ready to get an
opportunity for making satellites.
Environment Monitoring Series
In order to provide data for various studies in the atmospheric domain
pertaining to climate modeling and prediction, series of satellites are planned. The
increase in quantity of some gases causes global warming. The detection and
monitoring these trace gases is important to control them. For this purpose suitable
payload parameter were studied and finalised. Satellite proposal is also prepared.
Metrological applications payload series
ISRO provides continuous service to the meteorological observation through
its multi-utilization platforms (INSAT & GEOSAT satellite). Some satellites are
launched for dedicated meteorological applications. This chapter provides the
configuration of Very High Resolution Radiometer (VHRR) used for this application
and its evolution in last two decades.
Satellites launched for this application are INSAT-2A, 2B, 2E, Kalpana-1,
and INSAT-3A. INSAT-3D is under development with advanced features.
Indian Remote Sensing Missions & Payloads – A glance
6
List of Satellites and Payloads
Sl.No
Satellite Name
1
Aryabhata
2
Bhaskara 1 , 2
3
Rohini Satellites
4
IRS 1A & 1B
5
IRS-1E
6
IRS-P2
7
IRS-P3
8
IRS 1C & 1D
9
IRS-P4
10
TES
Payload
X-ray
Aeronomy
Solar Neutrons & Gamma
SAMIR,
TV Camera
Astronomy/ stellar
LISS-I,
LISS-II
LISS-I
MEOSS
LISS-II
WiFS
MOS
IXAP
PAN,
LISS-III,
WIFS
OCM,
MSMR
PAN
Indian Remote Sensing Missions & Payloads – A glance
Abbreviation
X-Ray
Aeronomy experiment
Solar Neutrons & Gamma detection
Satellite Microwave Radiometer
Two Band TV Camera
X-ray , Gamma ray Detection
Linear Imaging Self Scanner -I
Linear Imaging Self Scanner -II
Linear Imaging Self Scanner -1
Monocular Electro-Optical Stereo Scanner
Linear Imaging Self Scanner -II
Wide Field Sensor
Multispectral Opto-Electronic Scanner
Indian X-Ray Astronomy Payload (IXAP)
Panchromatic
Linear Imaging Self Scanner –III
Wide Field Sensor
Ocean Colour Monitor
Multi-frequency Scanning Microwave Radiometer
Panchromatic
7
Sl.No
Satellite Name
11
IRS-P6
12
Cartosat-1
13
Cartosat 2,2A,2B
14
IMS-1
15
Chandrayaan-1
Payload
LISS-IV,
LISS-III*, AWiFS
PAN-AFT,
PAN- FORE
PAN
Mx,
HYSI
TMC
HySI
LLRI
HEX
MIP
LEX
MINISAR
SIR-2
RaDoM
SARA
Abbreviation
Linear Imaging Self Scanner –IV
Linear Imaging Self Scanner –III*
Advanced Wide Field Sensor
Pan camera - Looking Forward
Pan camera - Looking Forward
Panchromatic
Multispectral Camera
Hyper Spectral Camera
Terrain Mapping Camera
Hyper Spectral Imager (0.2u to 0.9u)
Lunar Laser Ranging Instrument (LLRI)
High Energy X-ray payload (HEX)
Moon Impact Probe(MIP)
Low Energy X-ray (LEX) Payload (CIXS).
Mini SAR from Applied Physics Laboratory (APL, USA
SIR-2 from Max Plank Institute / ESA
Radiation Dose monitor from Bulgarian Academy of
sciences.
Sub-KeV Atom Reflecting Analyser (SARA) Experimental
developed jointly by IRE Sweden, SPL-VSCC India,
ISAS/JAXA Japan and VBE Switzerland
Moon Mineralogy Mapper (M3) from HJPL, USA
MMM
Indian Remote Sensing Missions & Payloads – A glance
8
Sl.No
16
Satellite Name
Oceansat-2
17
Resourcesat-2
18
Youthsat
19
Megha Tropiques
20
RISAT-1
Payload
OCM,
Scatterometer,
ROSA
Abbreviation
Ocean Colour Monitor
Ku Band Scatterometer
Radio Occultation Sounder for Atmosphere
ScaRaB,
ROSA
Linear Imaging Self Scanner –IV
Linear Imaging Self Scanner –III*
Advanced Wide Field Sensor
Hosted Indian Payload
Solar Radiation Monitor
Limb-View Hyper spectral Imager
Radio Beacon for Ionospheric tomogram
Microwave Analysis and Detection of Rain and Atmospheric
Structures
Soundeur Atmospherique du Profile d’Humidite Interopicale
par Radiometrie
Scanner for Radiation Budget
Radio Occultation Sounder for Atmosphere
C-Band SAR
Synthetic Aperture Radar
LISS-IV,
LISS-III*,
AWiFS
HIP
SOLRAD,
LiHySI,
RaBIT
MADRAS
SAPHIR
Indian Remote Sensing Missions & Payloads – A glance
9
Sl.No
21
Satellite Name
SARAL
22
Astrosat
23
Chandrayaan-2
24
25
INSAT missions
Aditya
26
Mars Orbitr Mission
Payload
ARGOS,
ALTIKA
SCBT
LAXPC
CZT
SXT
SSM
UVIT
CPM
ChACE-2
CLASS
XSM
SAR
IIRS
TMC-2
APIXS
Rover Imager
LIBS
VHRR
Abbreviation
Advanced Research and Global Observation Satellite
Altimeter Ka-band
Solid state C – Band Transponder
Large area xenon-filled proportional counter
Cadmium Zink Telluride
Soft X-Ray imaging Telescope
Scanning Sky Monitor
Ultra Violet imaging telescope
Charge Particle Monitor
Chandrayaan-2 Altitudinal Composition Explorer
Chandrayaan-2 Large Area Soft x-ray spectrometer
Solar X-ray Monitor
L and S band Synthetic Aperture Radar
Imaging IR Spectrometer
Terrain Mapping Camera
Alpha Particle Induced X-ray Spectroscope
Rover Imager
Laser Induced Break Down Spectroscope
Very High Resolution Radiometer
Solar Coronagraph
MCC, MSM, TIRIS, LAP and
MENCA
Indian Remote Sensing Missions & Payloads – A glance
10
Experimental Satellites
Satellites
Aryabhata
Bhaskara-1
RTP
RS-1
RS-D1
Bhaskara-2
RS-D2
SROSS-1
SROSS-2
SROSS C
SROSS-C2
Altitude
km
Payloads
X-ray
Gamma ray
Aeronomy
TV Camera
Micrometer
LV Monitor instruments
LV Monitor instruments
Landmark tracker
TV Camera micrometer
Smart sensor
Inclination
deg
Mass
kg
Power
W
619 x 562
50.7
358
46
Intercosmos
19-04-75
519 x 541
50.6
442
47
C1-Intercosmos
07-06-79
35
35
38
444
41.5
150
150
106.1
115
3
16
16
47
16
90
90
45
45
SLV-3
SLV-3
SLV-3
C1-Intercosmos
SLV-3
ASLV
ASLV
ASLV
ASLV
10-08-79
18-07-80
31-05-81
20-11-81
17-04-83
24-03-87
13-07-88
20-05-92
04-05-94
Not achieved
305 x 919
186 x 418
541 x 557
371 x 861
44.7
46
50.7
46
Not Achieved
MEOSS
GRB, RPA
GRB, RPA
267 x 391
430 x 600
45
45
Launch Vehicle
Launch Date
Lunar and Stellar Observation Satellites
Satellites
Payloads
Mass
(Kg)
Power
(W)
Launch Vehicle
Launch Date
Chandrayaan-1
TMC,Hysi,LLRI,
HEX,MIP,CIXS,SIR-2,
SARA,MINISAR,
M3,RADOM
1380
700
PSLV-XL
22-10-08
Indian Remote Sensing Missions & Payloads – A glance
11
Operational Earth Observation Satellites
Satellites
IRS-1A
IRS-1B
IRS-1E
IRS-P2
IRS-1C
IRS-P3
IRS-1D
IRS-P4 (Oceansat-1)
TES
IRS-P6
Resourcesat-1
IRS-P5 (Cartosat-1)
CartoSat-2
Cartosat-2A
IMS-1 (TWSAT)
Oceansat-2
Cartosat-2B
Resourcesat-2
Payloads
Liss-I, Liss-II
Liss-I, Liss-II
LISS-I,
MEOSS
LISS-II
Liss-3
Panchromatic
WiFS
WiFS, MOS
IXAE
Liss-3
Panchromatic
WiFS
MSMR, OCM
Panchromatic
Liss-3, Liss-4
AWiFS
PAN(Fore)
PAN(Aft)
Panchromatic
Panchromatic
Mx, HySI
OCM, Scatterometer
ROSA
Panchromatic
Liss-3 , Liss-4
AWiFS, HIP
Altitude
Inclination Local Time
(hr.mm)
(km)
(deg)
904
99.08
10.30
904
99.08
10.30
Not achieved
Mass
(kg)
975
975
846
Power
709
709
415
Vostak
Vostak
PSLV-D1
17-03-88
29-08-91
04-05-94
(EOL) (W )
Launch Vehicle Launch Date
817
817
98.68
98.68
10.30
10.30
804
1250
510
809
PSLV-D2
Molniya
15-10-94
28-12-95
817
98.68
10.30
920
817
PSLV-D3
21-03-96
740 x 817
98.73
10.30
1250
809
PSLV-C1
27-09-97
720
560
817
98.28
97.65
98.68
12.00
9.30
10.30
1050
1108
1360
750
800
1250
PSLV-C2
PSLV-C3
PSLV-C5
26-05-99
22-10-01
17-10-03
618
97.87
10.30
1560
1020
PSLV-C6
05-05-05
635
635
636.2
720
97.91
97.91
97.91
98.28
9.30
9.30
9.30
12.00
650
690
83.2
960
1200
1200
229
1360
PSLV-C7
PSLV-C9
PSLV-C9
PSLV-C14
10-01-07
28-04-08
28-04-08
23-09-09
630
97.71
9.30
694
1200
PSLV-C15
12-07-10
822
98.73
10.30
1206
1250
PSLV-C16
20-04-11
Indian Remote Sensing Missions & Payloads – A glance
12
Youthsat
Megha Tropiques
RISAT
SARAL
Astrosat
Chandrayaan-2
Aditya
SOLRAD
RaBiT, LivHySI
MADRAS
SHAPHIR
SCARAB
ROSA
C-Band SAR
ARGOS,
ALTIKA
SCBT
LAXPC, CZT
SXT, SSM
UVIT, CPM
ChACE-2, CLASS,
XSM, SAR, IIRS,
TMC-2,
APIXS,
Rover Imager, LIBS
Solar Coronagraph
822
98.73
10.30
90
229
PSLV-C16
20-04-11
867
20.00
---
998
1180
PSLV-C18
12-10-11
536.4
789 x 773
97.554
98.53
6.00
18.00
1858
412
1514 (min)
800
PSLV-C19
PSLV-C20
26-04-12
25-02-2013
Indian Remote Sensing Missions & Payloads – A glance
13
Indian Remote Sensing Missions & Payloads – A glance
14
1
ARYABHATA
1.1 Introduction
The Indian Space research activities started with initiating sounding rocket
progamme in 1963 at Thumba for conducting scientific experiments for the study of
upper atmosphere and ionosphere. In addition to this ISRO started a systematic
programme for setting up a full-fledged indigenous base for the design, fabrication,
and qualification and in orbit operation of satellites for variety of scientific
applications. ISRO signed an agreement with the USSR Academy of Sciences in
1972 for launching Indian satellite from a Soviet Cosmodrome, using Intercosmos
rocket carrier. The ISRO Satellite System Project (ISSP) was established at Peenya,
at the outskirts of Bangalore. The successful launch of Aryabhata, the first satellite
designed and fabricated by India on 19th April 1975, was the major milestone of
space research of India.
1.2 Mission objectives
The primary objectives of Aryabhata mission were:




Indigenous design and fabrication of a space worthy system and
evaluation of its performance in orbit;
Evolving the methodology of conducting a series of complex operations
on the satellite in its orbital phase;
Setting up the necessary ground-based receiving, transmitting and
tracking systems; and
Establishing the relevant infrastructure for the fabrication, testing and
qualification of spacecraft systems
1.3 Orbit Details
Table 1.1 Orbit details of Aryabhata satellite
Sl.No
Parameter
1
Mass
Aryabhata
358 Kg
2
Power
25 W (Generated 46W)
3
Altitude
619 x 562 Km
4
Orbit
Near circular
5
Inclination deg.
50.7
6
Stabilization
Spin Stabilization
7
Spin rate
10 to 90 rev/min
Indian Remote Sensing Missions & Payloads – A glance
1-1
7
Launch Date
19th April 1975
8
Orbital Time
95.2 min.
9
Launched by
Soviet Intercosmos rocket
1.4 Salient features of Aryabhata Systems
Table 1.2 Features of Aryabhata Systems
Sl.No.
Parameter
Values
1
Structure
2
Thermal
3
Power
Quasispherical shape with 26 flat faces,
1.59 m equivalent dia. and 1.19 m
height.
Quasispherical shape was selected to get
more surface area get illuminated by
Sun
Passive
thermal
control
system
employing paints of required emissivity
and absorptivity.
Temp Range 0 - 40 Deg.C
Body mounted silicon solar cells (36,800
cm2)
Ni-Cd Chemical batteries 10 A-H
Avg. raw power generated 46 W
Four buses +14,+9,-14 and -9V
4.
Telecommand system
TTC Uplink
TTC Downlink
5
AOCS
6
Payloads
(ISAC)
7
8.
Ground stations
Mass
PCM/AM/AM at 1 KW transmitter
(Total 35 Commands) 148.25 MHz
PCM/FM/PM,
91
Parameters
monitored, 256 bits/sec, 4 min data
transmission, 137.44 MHz
Triaxial magnetometers and digital sun
sensors.
Measurement accuracy < 1 Deg.
Coning angle < 0.1 deg.
Controlled by Gas bottles
 X-ray astronomy payload (2.5-150
KeV),ISAC
 Solar neutron and gamma rays
experiment,TIFR
 Aeronomy experiment,PRL
Receiving and commanding from SHAR
358 Kg
Indian Remote Sensing Missions & Payloads – A glance
1-2
Figure 1.1 View of Aryabhata Satellite
Figure 1.2 View of Ground antenna at SHAR
Indian Remote Sensing Missions & Payloads – A glance
1-3
1.5 Payloads
The payload system of aryabhata consists of three sensors. Thay are for



X-ray astronomy Experiment
o To investigate celestial x-ray sources primarily in relation to their
time variation effect in energy range of 2.5-150 Kev.
Solar neutrons and gamma rays detection and monitoring
o To detect high energy neutrons and gamma rays from the sun both
during quiet times and flares.
Aeronomy experiment
o To detect super thermal electrons up to 100ev and to measure the
intensities of Lyman alpha and oxygen line at F-region altitudes of
the earth’s ionosphere
1.5.1 X-Ray astronomy Experiment
The main objectives of the x-ray astronomy experiment onboard Aryabhata
were
1.
The determination of flux and energy spectra of X-ray sources in the
energy range 2.5 keV to 155 keV;
2. The exploration of new / transient x-ray sources with a sensitivity of 0.1
photon cm-2 s-1 in the 2.5 – 18.75 keV and 10-2 photons cm-2 s-1 in the 15.5 –
155 keV range;
3. Study of the time variation in the intensity of strong x-ray sources with time
scales of the order of a minute or more.
1.5.1.1
X ray telescopes
The X ray with energy range of 2.5 – 18.75 keV was investigated using a gas
proportional counter telescope. The proportional counter was filled with a mixture of
organ and carbon dioxide in the ratio of 9: 1 to a pressure of one atmosphere. The
entrance window was 50 micron thick beryllium.
The sensitivity depth was 3 cm. Charge particle induced events were eliminated by
an additional gas depth of 1.5 cm with an independent anode wire and setting the top
anode events in anticoincidence with the bottom anode events. Addition to this the
pulse shape discrimination (PSD) technique was employed for minimizing
contamination due to non-x-ray events such as those due to gamma rays. The detector
was imparted directionality by the use of a set of cylindrical collimators made out of
an aluminum block.
The X-ray telescope for the higher energy range (15.5 keV to 155 keV)
consisted basically of a NaI (TI) crystal of 3.8 cm diameter and 4 mm thickness
placed in a cylindrical plastic scintillator NE102A anticoincidence wall. The
Indian Remote Sensing Missions & Payloads – A glance
1-4
cylindrical graded shield of lead, tin and copper used as the internal lining or the
plastic scintillator imparted directionality to the telescope. The entire assembly was
viewed from the bottom by a Dumont K – 2227 photomultiplier of 5 cm cathode
diameter. The charged particle – induced events were eliminated by the pulse shape
discrimination technique, which separated the events having 10 ns rise time from
those in NaI(TI) that had 250 ns risetime. The physical configuration of scientillation
counter telescope is shown in figure 1.4.
Figure 1.3 Physical configuration of proportional counter telescope
Indian Remote Sensing Missions & Payloads – A glance
1-5
Figure 1.4 scintillation counter telescope
Table 1.3 Specifications of the telescopes
Nature of
telescope
Effecti
ve area
Nature
of
window
Viewing
condition
Collimater
Angular
response (in
deg. FWHM)
Telescopic
geometrical
factor
Energy
range
(keV)
Proportio
nal
counter
telescope
15.2
cm2
50 um
Be with
1/e cut
off
energy
of 2.5
keV
Along the
spin axis
Aluminum
block with a
number
of
cylindrical
holes.
12.5o
0-58
cm2
streradian
2.5-18.75
Scientilla
tion
counter
telescope
11.3
cm2
0.285
mm Be
Across the
belly band
perpendic
ular to the
spin axis
Graded shield
of 0.1 cm lead,
0.3 cm tin and
0.05 cm copper
14.5o
11 cm2
15.5
155.0
Indian Remote Sensing Missions & Payloads – A glance
–
1-6
Figure 1.5 Location of X- ray telescopes on satellite
1.5.2 Solar neutron and gamma ray telescope
The second payload for the detection and measurement of high energy
neutron and gamma rays from the sun was developed at Tata Institute of
Fundamental Research.
The objective of this payload was
1. To detect simultaneously the possible impulsive emission of energetic
neutron(10-500 MeV) and gamma rays (0.2-20 MeV at times of intense solar
activity. The possibility of observing the delayed signal from neutrons with
respect to the gamma rays is an important capability of the experiment.
2. To detect any steady or quasi-steady solar emission of energetic neutrons and
gamma rays.
3. To measure the splash albedo flux of neutron and gamma rays as a function
of latitude.
4. To detect gamma ray bursts of the type first discovered by Vela satellites and
any other type so far not discovered.
1.5.2.1
Configuration of the payload
The method of the detection and separation of the neutrons and gamma rays
is based on the fact that in an inorganic crystal scintillator like CsI(TI), the high rate
of ionization due to the low energy protons and helium nuclei caused by neutrons,
Indian Remote Sensing Missions & Payloads – A glance
1-7
gives rise to a pulse shape different from the low rate of ionization due to the fast
electrons originating from gamma ray interactions in the crystal.
The experimental payload consisted of two boxes, referred as Ex-21 and Ex-22.
They were placed one above the other, with Ex-21 near the deck plate as shown in
fig. 1.6 The main detector crystal housed in Ex-21 was viewed by a 12.5 diameter
photo multiplier tube and completely surrounded by a 1 cm thick NE-102 plastic
scientillator viewed by four 3.81 cm diameter photomultipler tubes; the latter served
as the charged particle anticoincidence shield for the main detector. The amplifiers
for the CsI(TI) and plastic scientillator logic electronics and high voltage supply for
photomultipliers were housed at Ex-21.
Figure 1.6 Schematic diagram showing the position of the experiment in the
satellite.
Indian Remote Sensing Missions & Payloads – A glance
1-8
1.5.3 The aeronomy experiment
This experiment was mainly designed to study the global distribution of
suprathermal electron, ionosphere-magnetosphere coupling, the F-region anomaly
and the hydrogen geo-corona. This experiment consisted of a retarding potential
analyser and two ultraviolet ion chambers. The first one was designed to measure the
flux of suprathermal electrons in the earth’s atmosphere and the second one was
designed to measure the intensity of the resonantly scattered hydrogen Lymen alpha
(1216 A) and photo-electronically excited OI (1304 A) emissions.
1.5.3.1
Retarding Potential Analyser (RPA)
This detector was designed to measure the flux of electrons in the energy range
between 2.5 eV and 80 eV. The RPA consisted of a system of five tungsten grids G1
to G5 and a collector plate. Grids G1 and G4 were connected to the satellite body
while G2 was connected to +14 V and G3 to the retarding potential varying from -2.5
to -80 V. The grid G5 was connected to -1.0 V and the collector plate was biased at +
14 V. A small annular metallic ring concentrically mounted on RPA detector and
electrically insulated from it, was used for measuring floating potential with respect
to the spacecraft potential. This measurement was required to determine the effective
retarding potential as applied to grid G3 of the RPA.
Indian Remote Sensing Missions & Payloads – A glance
1-9
1.5.3.2
UV Detectors
Two UV chambers similar to each other but with different spectral pass bands
were used for the experiment. The first chambers was fitted with a magnesium
fluoride window and filled with NO gas at a pressure of about 10 to 20 mm of Hg.
The spectral pass band of this chamber was from 1120 to 1340 A. The second
chamber with calcium fluoride window and filled with NO had a pass band from
1250 to 1340 A. Both chambers were operated in the unity gain mode with a bias
voltage of +45 V and were mounted at the satellite equatorial plane. The 2.5 cm dia.
look windows of each detector provided a field of view of about + 22.5 deg.
The two experiments the RPA and UV detectors were programmed to operate in a
pre- arranged time-sequence. Each experiment was switched on 12 seconds before
data were collected from it for stabilization of its electronics.
Figure 1.7 Block diagram for the payload electronics of the RPA and UV
experiments.
Indian Remote Sensing Missions & Payloads – A glance
1-10
2
BHASKARA-1 & 2
2.1 Introduction
The dream of making Earth Observation Satellite by India came to true
through the BHASKARA-I mission. It is the first experimental Terrain remote
sensing satellite built by India and launched in 7th June 1979. This was followed by a
follow-on mission BHASKARA-II with some modification on and was launched on
20th November 1981. The technologies developed for ARYABHATA were used in
BHASKARA with some improvements such as spin rate and spin axis control, using
Infrared Horizon sensor for earth reference and high bit rate telemetry for payload
data transmission. These missions provided a system experience on End-to-End
basis, configure, design, develop, and assemble a satellite for remote sensing to
reception and processing of remotely sensed data and generation of data products as
per user requirement.
2.2 Mission objectives
The primary objectives of Bhaskara-I mission were:



To conduct earth observation experiments that would yield useful data in the
areas of metrology, hydrology and forestry using a two band TV camera
system operating in the 0.54 to 0.66 microns visible band and 0.75 to 0.85
micron near Infrared band (The earth imagery obtained from an altitude of
525 Km provides a spatial resolution of 1 Km X 1 Km in a picture frame of
341 x 341 Km)
To conduct ocean surface studies using a three chain radiometer operating
at microwave frequencies.
To evolve the methodology of reception, processing and dissemination of
data and thus establish visibility of management of earth resources through
remote sensing satellites.
The secondary objectives are



To develop the technology for relaying data collected from the unattended
platforms to a central receiving station to obtain useful meteorological data
on an experimental scale, from presently inaccessible regions at short turnaround times and thus develop the expertise and infrastructure for large
scale applications of automatic data collection platforms.
To study the performance of indigenously developed solar cells, thermal
paints and heat pipe under prolonged exposure to space environments.
To study the time variations of celestial X-ray sources and detect transient
sources.
Indian Remote Sensing Missions & Payloads – A glance
2-1
The Basic Objective of the Bhaskara – II was to provide continuity to the Bhaskara-I
experiment.
2.3 Orbit Details
Bhaskara I & II comparison
Table 2.1: Orbit details of Bhaskara satellites
Sl.No
1
2
3
4
5
6
7
8
9
Parameter
Mass
Power
Altitude
Eccentricity deg.
Orbit
Inclination deg.
Stabilization
Launch Date
Orbital Time
Bhaskara-I
444 Kg
47 W
534 Km
0.0023
Near circular
50
Spin Stabilization
June 7, 1979
95.2 min.
Bhaskara-II
444 kg
47 W
548.269 Vs 514.304 Km
0.002459
Near circular
50.635
Spin Stabilisation
Nov. 20 1981
95.2 min.
2.4 Salient features of Bhaskara-I and Bhaskara-II Systems
The Bhaskara-I project, originally known as the Satellite for Earth
Observation (SEO) was conceived as one of the key intermediate steps towards going
for a full-fledged operational remote sensing satellite system for India.
Figure 2.1 View of Bhaskara satellite
Indian Remote Sensing Missions & Payloads – A glance
2-2
Figure 2.2 Exploded view of Bhaskara satellite
Indian Remote Sensing Missions & Payloads – A glance
2-3
Table 2.2 salient Features of Bhaskara satellite
Sl.No.
Parameter
1
Structure
2
Thermal
3
Power system
Values
Similar to Aryabhata
Overall height inclusive of antenna 1559 mm
Distance between axes of nozzles 1900
Passive systems
Temperature limit 0 to 40 deg. C.
Body mounted solar panels backed by 10 AH
NiCd Battery
PCM/FM/AM at 148.25 MHz.
TTC Uplink
PCM/FM/AM at 137.20 MHz.
4.
TTC Downlink LBT
(224 Bits/Sec)
PCM/BSK at 137.20 MHz
TTC downlink HBT
(91 Kbs)
Tracking System
5
AOCS
Type of stabilization
Spin Rate range
Spin axis orientation
Attitude determination
6
Payloads
(SAC)
7
Mass
148.61 MHz uplink
137.1 Mhz downlink with tones 32 Hz top 20
MHz
Cold gas jet –spin stabilization
6 to 11 RPM
Within 3 deg of orbit normal
Within 1 deg.
TV slow scan videcon cameras operating in the
visible Band 0.54 – 0.66 microns
and IR Band 0.75 to 0.85 microns
Microwave Radiometers operating at 19 and 22
GHz (in Bhaskara II, 32 GHz chain included)
444 Kg(436 for Bhaskara- II)
2.5 Payload
In an ideal case an earth observation satellite system should be three axes
stabilized so that the sensors can point towards the earth continuously. However to
gain time, the satellite configuration of the first Indian satellite ARYABHATA was
adopted and images were acquired while spacecraft was spinning. 'BHASKARA-I'
was launched on June 7, 1979 from a Soviet Cosmodrome in a near circular orbit of
mean altitude 534 kms and inclination 50.deg. The 444 Kg satellite carried two major
remote sensing payloads namely a two band TV camera system and a three frequency
microwave radiometer. The satellite was spin stabilised with its spin axis maintained
at right angles to the orbital plane. Such configuration enables both the payloads to
'look' along the local vertical once during every spin. 'Bhaskara-II' was launched on
November 20, 1981. It is an improved version of 'Bhaskara-I' having a three
Indian Remote Sensing Missions & Payloads – A glance
2-4
frequency radiometer to enable differentiation between water vapour and liquid
water in the atmosphere.
2.5.1 Multispectral TV Camera
Bhaskara TV payload system consists of two TV cameras, one operating in
the 0.54 to 0.66 micron band and the other in the 0.75 to 0.85 micron band. Each
picture frame covers an area of 340 km x 340 km with a ground resolution of about
one km and a typical over lap of 10% between successive picture frames. The built in
marks and in flight radiometric calibration help in producing geometrically and radiometrically corrected picture on the ground. The camera is mounted on the spacecraft
with its optical axis at the right angles to the spin axis. The cameras are exposed at
the instant when the optical axis of the camera points to the local vertical. Read out
takes place at a slower rate commensurate with the telemetry capability of the
spacecraft. The basic sensor of the TV camera payload is a Super Vidicon Camera
Tube consisting of an image intensifier with a gating facility coupled to a storage
type vidicon tube. A specially designed multi-element lens is used for each camera.
The focal length of the lens and the active face plate area together decide the field of
view of the camera. A summary of the camera specifications is given below.
Table 2-2:
Sensor Type
Imaging lens
Spectral channels
Picture Frame
Ground Resolution
Exposure control
Power
TV Camera paylaod specifications
Slow scan vidicon coupled to an image intensifier
F/no.1.9, Focal length 18.46 mm, FOV 49.37°
Camera-1 0.54 – 0.66 microns
Camera-2 0.75 – 0.85 microns
340 x 340 Km2 for a 525 Km altitude
About 1Km
1, 1.5, 2 ms selectable by gorund command
22.5 W average
The system can be put in 'calibration mode’ by ground command. The
mechanical shutters do not operate during the calibration mode and the tube face
plate is illuminated by flashing an LED source. In one calibration cycle, the cameras
are exposed to four different intensity levels, one of which is zero illumination and
other three are spread out, over the dynamic range. This calibration cycle then repeats
itself during the calibration mode. The exposure duration can be changed by ground
command to get additional calibration levels.
The initial 'switch ON' of BHASKARA-I TV camera payload was not
successful. Extensive ground simulation studies indicated that the anomalous
behavior during the switch on of the TV camera was due to a corona discharge in the
high voltage section of the payload. Poor adhesion of the potting compound with the
Indian Remote Sensing Missions & Payloads – A glance
2-5
high voltage standoff, coupled with trapped air, caused the corona. With time, the
trapped air leaked out and camera-l was switched on successfully on May 16, 1980.
BHASKARA-II payload was suitably modified to take care of the problems
observed in BHASKARA-I and the camera performance was satisfactory in
BHASKARA-II. The imagery received from both bands was comparable in quality to
any other imagery of similar resolution. Multiband imagery from the TV payload has
been received over the complete Indian subcontinent. The multiband imagery
received from BHASKARA-II has been used to demonstrate various applications in
the field of geology, hydrology, and forestry.
2.5.2 Satellite Microwave Radiometer (SAMIR)
The SAMIR system of BHASKARA-I consisted of three independent
channels operating at 19.1, 19.6, and 22.235 GHz frequency bands. Each channel
contains a scalar horn antenna, dicke switch, mixer/preamplifier, square law detector,
suitable D.C. amplifiers, and telemetry interface circuits. In the case of
BHASKARA-II one of 19 GHz channels has been replaced by a channel at 31.4
GHz.
In BHASKARA-I the spatial resolution of the 19 GHz radiometer was 150
km and the spatial resolution of the 22 GHz radiometer was 230 km respectively. In
BHASKARA-II all the three radiometers had same spatial resolution of 125 km.
Broad specifications of the radiometers are given in Table 2-3.
Table 2-3:
System Parameter
Frequency (GHz)
Specificatios of SAMIR
Bhaskara – I
Bhaskara - II
R-1
R-2
R-3
R-1
R-2
R-3
19.1
19.6
22.23
31.4
19.35
22.23
5
5
Bandwidth(MHz)
250
250
250
250
250
250
Integration
350
350
470
300
300
300
Temp Sensitivity
1
1
1
1
1
1
System Noise Fig.
6.5
6.5
7.5
8.5
6.5
7.5
150
150
230
125
125
125
Time(ms
(dB)
Spatial Resolution
Indian Remote Sensing Missions & Payloads – A glance
2-6
The SAMIR system can be operated in two possible modes, depending upon
the spin-axis orientation. In the 'Normal Mode' the spin axis of the satellite is normal
to the orbital plane and hence the antenna would scan along the satellite track. In the
‘Alternate Mode' the spin axis of the satellite would lie in the orbital plane, tangential
to the orbit at a certain latitude, thus converting the radiometers effectively into a
scanning system. In the 'Alternate Mode' data will be sampled at fourteen different
angular positions and the effective coverage during each orbit will be around 1000
km with a 125 km ground resolution at nadir.
Analog data from all the channels is sampled at various angular positions
around nadir, depending upon the mode of operation. As the data acquisition and
telemetry transfer rate are not synchronous, data is held in various sample and hold
circuits, till it is transferred to the satellite data stream.
Various tests conducted during the initial phase operations and operational
phase have confirmed the consistent performance of SAMIR Radiometers onboard
BHASKARA-I & II. SAMIR data was used for a number of meteorological
applications. These include estimation of water vapor and liquid water content, rain
fall estimation over ocean area, estimation of wind speed over ocean, study of floods
etc.
After realizing the mission objectives the Bhaskara-II mission was
terminated in March 1981.
Indian Remote Sensing Missions & Payloads – A glance
2-7
Bhaskara-1
Indian Remote Sensing Missions & Payloads – A glance
2-8
3
ROHINI (RS) AND STRETCHED ROHINI SATELLITE
SERIES (SROSS)
3.1 Introduction
The Rohini satellites were launched with various remote sensing payloads
for X-ray observations and as payloads for the SLV launch vehicles which were
under development.
Rohini Satellite Series had four satellites of 35 kg class namely

RTP (Rohini Test Project), RS, RS-D1, RS- D2
Stretched Rohini Satellite series had four satellites of 150 kg class namely

SROSS-1, SROSS-2, SROSS-C1, SROSS-C2
3.2 RTP - Rohini Test Project
RTP carried Launch vehicle monitor equipments. The mass of the satellite
was 35 Kgs. It was launched on 10-08-79. Launce failed
RTP Rohini Test Project
Mission
Experimental
Weight
35 kg
onboard power
3 Watts
Communication
VHF band
Stabilization
Spin stabilized
(spin
axis
controlled)
Payload
Launch vehicle
monitoring
instruments
Launch date
August
10,1979
Launch site
SHAR Centre,
Sriharikota,
India
Launch vehicle
SLV-3
Orbit
Not achieved
Indian Remote Sensing Missions & Payloads – A glance
3.1
3.3 RS-1
Mission Objectives:
To monitor the launch vehicle performance.
RS-1
Mission
Weight
Onboard power
Communication
Stabilization
Payload
Experimental
35 kg
16 Watts
VHF band
Spin stabilized
Launch
vehicle
monitoring instruments
July 18,1980
SHAR
Centre,
Sriharikota, India
SLV-3
305 x 919 km
44.7 deg.
1-2 years
20 months
Launch date
Launch site
Launch vehicle
Orbit
Inclination
Mission life
Orbital life
3.4 RS-D1
Mission Objectives:
Carried a Land Mark sensor payload whose solid state camera performed to
specifications. The satellite re-entered the earth's atmosphere nine days after launch
on account of the launch vehicle's injecting the satellite into a lower than expected
altitude.
RS_D1
Mission
Weight
onboard power
Communication
Stabilization
Payload
Launch date
Launch site
Launch vehicle
Orbit
Inclination
Orbital life
Experimental
38 kg
16 Watts
VHF band
Spin stabilized
Landmark Tracker ( remote
sensing payload)
May 31,1981
SHAR Centre, Sriharikota, India
SLV-3
186 x 418 km (achieved)
46 deg
Nine days
Indian Remote Sensing Missions & Payloads – A glance
3.2
3.5 RS-D2
Mission Objective: The Smart Sensor Camera was the primary payload on
board the satellite. It was operated for over five months and sent more than 2500
pictures frames in both visible and infrared bands for identification of landmarks and
altitude and orbit refinement. The camera had on-board processing capability to use
the data for classifying ground features like water, vegetation, bare land, clouds and
snow. After completing all its mission goals, RS-D2 was closed down on Sept. 24,
1984.
RS-D2
Mission
Weight
Onboard power
Communication
Stabilization
Payload
Launch date
Launch site
Launch vehicle
Orbit
Inclination
Mission life
Orbital life
Experimental
41.5 kg
16 Watts
VHF band
Spin stabilized
Smart sensor (remote
sensing
payload),
L-band beacon
April 17, 1983
SHAR Centre, Sriharikota,
India
SLV-3
371 x 861 km
46o
17 months
Seven years (Re-entered
on April 19, 1990)
3.5.1 Payload Smart Sensor Onboard ROHINI Satellite
Rohini series of satellites are launched by the Indian launch vehicle SLV-3.
A two band solid state camera was designed for Rohini Satellite. A 256 element
photo diode array is used as the basic detector. The satellite is spin stabilised with
spin axis normal to the orbital plane. During each spin the camera scans the earth
approximately ±4.5° to the local vertical producing 80 scan lines thereby generating a
picture frame of 250 km x 80 km. The image resolution is about 1 km from 500 km
orbit.
One of the unique features of the camera is that it is capable of carrying out
limited feature identification onboard. This is realized by taking the ratio of the 2
band output and having a decision circuitry to discriminate between the different
classes based on rationing. The feature identification code and video information
Indian Remote Sensing Missions & Payloads – A glance
3.3
from anyone of the cameras is transmitted. The camera specifications are given in
Table 3-4.
Table 3-4:
Rohini Smart Sensor Specifications
Resolution
Spectral bands
Channel-1
Channel-2
Swath
Overlap
Optics size
Memory
Power
Weight
1Km(Nominal)
0.65±0.05 microns
0.85±0.05 microns
25Km
30%
Focal length 25mm, f/1.4 system
140 kbits
4 watts
3Kg
The Rohini satellite (RS-D2) carrying this payload was launched on April 17,
1983 from the Indian launch station at Sriharikota. The camera functioned normally
as planned and it was possible to establish the possibility of limited feature
identification on board. Water bodies, biomass, bare land and clouds can be easily
identified with onboard processing.
3.6 SROSS-1(Stretched Rohini Satellite Series)
The satellite was launched onboard the first developmental a flight of ASLV. It did
not reach the orbit.
SROSS-1
Mission
Weight
Onboard power
Communication
Stabilization
Propulsion
system
Payload
Indian Remote Sensing Missions & Payloads – A glance
Experimental
150 kg
90 Watts
S-band and VHF
Three
axis
body
stabilized
(biased
momentum)
with
a
Momentum Wheel and
Magnetic Torquer
Monopropellant
(Hydrazine
based)
Reaction control system
Launch
Vehicle
Monitoring
Platform(LVMP),
Gamma
Ray
Burst
(GRB) payload and
Corner
Cube
Retro
Reflector (CCRR) for
3.4
Launch date
Launch site
Launch vehicle
Orbital life
Mission
Weight
laser tracking
March 24, 1987
SHAR
Centre,
Sriharikota, India
Augmented
Satellite
Launch Vehicle (ASLV)
Not realised
Experimental
150 kg
3.7 SROSS-2
SROSS-2
Mission
Weight
Onboard power
Communication
Stabilization
Propulsion
system
Payload
Launch date
Launch site
Launch vehicle
Orbit
Experimental
150 kg
90 Watts
S-band and VHF
Three
axis
body
stabilized
(biased
momentum) with a
Momentum Wheel and
Magnetic Torquer
Monopropellant
(Hydrazine
based)
Reaction Control System
Gamma
Ray
Burst
(GRB) payload and
Mono-ocular
ElectroOptic Stereo Scanner
(MEOSS) built by DLR,
Germany
July 13, 1988
SHAR
Centre,
Sriharikota, India
Augmented
Satellite
Launch Vehicle (ASLV)
Not realised
3.8 SROSS-C
SROSS-C
Mission
Experimental
Weight
Onboard power
106.1 kg
45 Watts
Indian Remote Sensing Missions & Payloads – A glance
3.5
Communication
Stabilization
Payload
Launch date
Launch site
Launch vehicle
Orbit
Mission life
S-band and VHF
Spin stabilized with a
Magnetic
Torquer
and
Magnetic Bias Control
Gamma Ray Burst (GRB)
experiment & Retarding
Potential Analyser (RPA)
experiment
May 20,1992
SHAR Centre, Sriharikota,
India
Augmented Satellite Launch
Vehicle (ASLV)
267 x 391 km
Two months (Re-entered on
July15,1992)
3.9 SROSS-C2
SROSS_C2
Mission
Weight
Onboard power
Communication
RCS
Payload
Launch date
Launch site
Launch vehicle
Orbit
Inclination
Experimental
115 kg
45 Watts
S-band and VHF
Monopropellant Hydrazine
based
with
six
1 Newton thrusters
Gamma Ray Burst (GRB) &
Retarding
Potential Analyser (RPA)
May 04,1994
SHAR Centre, Sriharikota,
India
Augmented Satellite Launch
Vehicle (ASLV)
430 x 600 km.
45 deg.
3.9.1 Mission Objectives
To monitor celestial gamma ray bursts in the energy range 20-3000 KeV
To measure temporal variations of gamma ray burst with high time
resolution(2 ms, 16ms and 2556 ms) to search for periodicities in the emitted
radiation.
Indian Remote Sensing Missions & Payloads – A glance
3.6
To measure temporal evolution of burst energy spectra to search for
cyclotron lines and features in the energy range 20-100 KeV and possible
red-shifted annihilation radiation in the energy range 400-500 KeV.
To study the characteristic features of the thermal structure of the equatorial
and low latitude ionosphere
To study the effect of magnetic storms and Spread-F on thermal structure
To Study the behavior of electron density anomaly in the low latitude region
3.9.2 Salient features of SROSS-C
Sub system
Features
Structure
Aluminum frames and honeycomb decks
Thermal
Using passive elements and 2W heaters. Temp.
limit is 0 to 40 deg.
Power
TTC
Solar Panel
Four units of body mounted panels (each unit
with two panels bonded at 135 deg. Along the
vertical edge.
Battery
18 AH Ni-Cd cells connected in series.
Electronics
DC/DC converter, Under/Over volt detector
circuits, E/N logic Battery Voltage control Logic
Telemetry
Format-1 mode and Dwell mode with
reentrancy. PROM based main system and
microprocessor based (RCA 1802) Redt. system
256 BPS, PCM/PSK/PM, 2245.68 MHz
Telecommand Microprocessor (RCA 1802) Based Main
Decoder and Hardware redt. Decoder Unit.100
bps, S-Band PCM/FSK/FM/PM,
2067.897 MHz
AOCS
Mass
Sensors
Magnetometer, Twinslit Sun sensor
Stabilisation
Spin stabilisation
106.1 Kg
Indian Remote Sensing Missions & Payloads – A glance
3.7
Figure 3.1Exploded view of SROSS-C1
3.9.3 Salient features of Payloads
Payload consists of two sensors namely
Gamma Ray Burst Detection (GRB) Experiment
Retarding Potential Analyser (RPA) Payload
3.9.3.1
Gamma Ray Burst detector
The gamma ray burst payload consists of a main and a redundant
scintillation detector viewed by separate photomultiplier tubes and powered by
independent high voltage supplier. A common microprocessor based (RCA
Indian Remote Sensing Missions & Payloads – A glance
3.8
CDP1802) electronics system process the signals from either of the detectors. The
main detector consists of a 76 mm diameter and 12,5mm thick CsI(Na) scintillator
optically coupled to an EMI 9758 NA PMT. The redt. detector is also CsI(Na) crystal
and has a diameter of 38mm and a thickness of 12.5 mm. It is viewed by RCA 7151Q
tube. The scintillator is coupled to the PMT. By means of DC-93-500 potting
compound.
3.9.3.2
Retarding Potential Analyser (RPA)
The RPA experiment is proposed to investigate the characteristics and
energies of the equatorial and low latitude ionosphere and thermosphere which is an
important element in understanding the sun-earth relationship and the effects of
dynamics, turbulence and storms on the thermal behavior. It indents to study
characteristics variation of electron density over the equator and around it ( + 15 deg
latitude). This involves measuring plasma parameters like density & temp. to
characterize the ionosphere. It also indented to identify understand and estimate
various energy deposition and loss process to derive thermospheric temp.
Indian Remote Sensing Missions & Payloads – A glance
3.9
Indian Remote Sensing Missions & Payloads – A glance
3.10
4
IRS-1A & 1B
4.1 Introduction
The successful launch and operation of Bhaskara-I and II satellites provided
experience in setting up of ground-based data reception and processing systems,
gaining experience in over-all mission management, receiving data from other
satellites like LANDSAT and activities related to data analysis, interpretation &
utilization.
The experience gained in conceptualisation and implementing a space
segment with necessary ground based data reception, processing and interpretation
system, and integrating the satellite based remote-sensed data with conventional data
systems for resource management, provided a way for a programme for
operationalising the remote-sensing system for the country. The evolution of National
Natural Resources Management System (NNRMS) is the outcome of all the above
efforts and IRS-1A mission is the first step in such an operational resources
management system for the country.
IRS-1A, the first of the series of indigenous state-of-art operating remote
sensing satellites, was successfully launched into a polar sun-synchronous orbit on
March 17, 1988 from the Soviet Cosmodrome at Baikonur. IRS-1A carried two
cameras, LISS-I and LISS-II with resolutions of 73 metres and 36.25 metres
respectively with a swath of about 140 km during each pass over the country.
Mission completed during July 1996 after serving for 8 years and 4 months.
IRS-1B, with some improved features compared to its predecessor like gyro
referencing for better orientation sensing, time tagged commanding facility for more
flexilibility in camera operation and line count information for better data product
generation, was launched on 29.08.1991. Mission completed on December 20, 2003
after serving for 12 years and 4 months.
4.2 Mission Objectives
The main objectives of IRS-1A mission are


To design, develop, and deploy a three axis stabilised polar sunsyncronise satellite carrying near state-of-art-multiple solid state
pushbroom cameras operating in visible and near infrared bands for
aquiring imageries for each resources applications on an operational
basis.
To establish and routinely operate ground based systems for
spacecraft data reception, recording, processing, generation of data
products, analysis, and archival as well as mission control facilities.
Indian Remote Sensing Missions & Payloads – A glance
4.1

To use the data from IRS in conjunction with supplementary/
complementary information from other sources for survey and
management of resources in imporatnt areas such as agriculture,
geology and hydrology in association with the user agencies, that will
additionally enable characterisation of a future operational system for
the country at the optimum level.
4.3 Orbit Details
IRS-1A was launched into a
polar sun synchronous orbit at an
altitude of 904 Kms. In the sunsyncronous orbit, the orbit plane
rotates at the same rate as the mean
rotation rate of the earth around the
sun (0.9856 deg/day). Thus the
satellite passes over particular
latitude approximately at the same
local time. It enables the ground
illumination conditions at subsatellite regions to be constatnt
throughout
the
mission. The
equatorial crossing time of the descending node for IRS-1A is around 10.25 AM.
Figure 4.1
Sun Synchronous orbit
As the orbital period of IRS1A is nearly 103 minues, with the
satellite completing 14 orbits/day,
each successive orbit is shifted
westward over earth’s surface by
25.798
degree
of
longitude,
corresponding to 2872 kms at equator.
The satellite’s path is shifted by 1.17
~1.1 deg longitude to the west every
day corresponding to 130.84 km at the
equator. The satellite completes one
coverage cycle of the Indian
subcontinent in 22 days(307 orbits)
Figure 4.2
Indian Remote Sensing Missions & Payloads – A glance
Swath coverage
4.2
Table 4.1:
Parameters
Altitude
Inclination
Eccentricity
Equatorial Crossing Time
Orbital period
Recurrence
Repetition cycle
Daily shift at equator
Node
Orbit details
IRS-1A
904 Km
99.028 deg
0.008
10.30 A.M
103.192 min.
14 orbits/day
22 days (307 orbits)
130.54 Km westward
(1.17 deg)
Descending
IRS-1B
904 Km
99.028 deg
0.008
10.30 AM
103.192 min.
14 orbits/day
22 days (307 orbits)
130.54 Km westward
(1.17 deg)
Descending
4.4 Salient Features of Spacecrafts
Figure 4.3
Stowed mode view of IRS-1A
Indian Remote Sensing Missions & Payloads – A glance
4.3
Figure 4.4
Table 4.2:
Parameter
Mission
Structure
Thermal
Components
Temp. Range
Mechanis
m
Power
SADA
Solar Array
Battery
Telemetry
Communic
ation
Exploded view of IRS-1A
Salient features of IRS-1A & 1B
IRS-1A
IRS-1B
Launched as experimental satellite later declared as
Operational.
Aluminium and Aluminium honeycomb structure
Central load bearing cylinder and 6 honeycomb
panels.
Passive control using tapes , OSR, MLI Blankets
and semi-active/active control using proportionate
temperature controller and heaters
20+5 deg.C range for imaging sensors electro-optics
5+5 deg. C for Chemical Batteries
0 to 40 deg.C for electronic packages
Solar Panel Deployment and Drive Mechanism
8.5 m2 area, deployable and sun tracking panel,
Power generation at EOL is 620 Watts (Totally 6
panels)
Two Ni-Cd batteries of 40 AH capacity each
House Keeping(HK) information in S-Band;
PCM/PSK Real Time rate 256 bps and play back
rate 4 Kbps; Onboard storage capacity of 98 minutes
of HK data
Indian Remote Sensing Missions & Payloads – A glance
4.4
Telecommand
Tracking
Attitude
and Orbit
Control
(AOCS)
Attitude
sensors
IR Horizon sensors(Conical and Static), Star sensor,
sun sensors, Dynamically Tuned Gyros (DTG)
Attitude control
Reaction Wheel(three 5NMS and one 10 NMS),
Magnetic torquers, Hydrazine thrusters(16 one
Newton)
Monopropellant hydrazine thrusters
Orbit Control
OrbitDetermination
accuracy
Attitude
Determination
Accuracy
Payload
S-Band : PCM/PSK/FM/PM, and
VHF : PCM/FSK/AM
Facility for ON/OFF and Data commands
S-Band tone ranging and two way Doppler
LlSS-1
LlSS-2A and
LlSS-2B
Mass
Launch
date
Launch
site
Launch
vehicle
1 Km
0.1 deg.
(72.5 meter resolution),
(36.25 meter resolution)
975 kg
March 17, 1988
August 29, 1991
Baikanur Cosmodrome ,Kazakhstan
Vostok-II
4.5 Payloads
IRS missions envisage primarily meeting the specific Indian application
needs in the areas of agriculture, hydrology, and geology. Hence the basic mission
characteristics like spectral bands and resolutions, spatial and radiometric resolutions;
repetivity and choice of local time have been arrived keeping these applications in
view.
It is well known that to increase the accuracy of interpretation, the
information has to be collected in more than one spectral band. A number of studies
and experiments with Landsat data showed that four spectral bands covering visible
and near infrared wavelength regions are adequate for most of the applications. Thus
payloads should have multi spectral imaging capability, with four spectral bands in
the visible and near infrared regions of the electro-magnetic spectrum.
Indian Remote Sensing Missions & Payloads – A glance
4.5
Table 4.3:
Spatial resolution and repetivity considerations
Application
Agriculture
Spatial resolution
40-70 meters resolution
Hydrology
40-100 meters resolution
Geology
100-150 meters
resolutions
Coastal studies
100-150 meters
resolution; sea food study
needs 70-100 meters
resolutions
Weekly / monthly repetivity, for
coastline delineation, yearly
repetivity sufficient
Land use
planning
80 meters resolution
Yearly repetivity
Table 4.4:
Spectral
Bands
microns
0.45-0.52
0.52-0.59
0.62-0.68
0.77-0.86
Temporal resolution
Weekly / monthly repetivity
Soil classification needs seasonal
considerations also
Weekly observation for soil
moisture study for penetration
beyond surface prefers microwave
Repetivity can be monthly and more
Spectral resolution consideration
Characteristics of bands
Strong relationship between spectral reflectance in this region and
plant pigment and has comparatively higher penetration in water.
This band is useful for mapping suspended sediments/water quality
and various studies related to coastal region.
Centered on the first local maxima of the vegetation reflectance,
useful for vegetation discrimination and the study of senescence
rate of leaves. Also sensitive to ferric iron oxides.
Centered around the chlorophyll absorption band of vegetation
and, useful for identification of plant species. Greater soil contrast
is found in this region. The upper end is limited to 0.68 to avoid
the atmospheric absorption at 0.69 microns
Shows high reflectance for healthy vegetation and useful for green
biomass estimation and crop vigor studies. Water absorption in this
region clearly demarcates land water boundary. The upper end is
limited to 0.86 microns to avoid the broad water vapor absorption
band centered around 0.92 micron. In addition, this also helps to
improve the Modulation Transfer Function (MTF) of this band
since CCD MTF falls fast as wavelength increases in the near
infrared region
Indian Remote Sensing Missions & Payloads – A glance
4.6
Figure 4.6 LISS-II
Figure 4.5 LISS-I
The IRS-1A cameras operated in four spectral bands which are mentioned in
the table 4.4. Each Band has
separate
optical
system,
spectral filters, thermal filters
and detector.
Figure 4.7 Push Broom Concept
The payload system of
IRS-1A is a Linear Imaging
Self-Scanning Sensor (LISS)
working on the ‘push-broom
scanning’ concept. In this
mode of operation, each line
of the image is electronically
scanned by a linear array of
detectors (Charge Coupled
Devices
(CCD))
and
successive lines of the image
are produced as a result of
satellite’s forward motion.
The payload system consists of two solid state cameras operating in four
spectral bands in the visible and near- IR range using Charge Coupled Devices
(CCD) linear arrays as sensors. There are two cameras, one is called LISS-1, and the
other one is called LISS-II (It has two modules, IRS-IIA and IRS-IIB). LISS-I
provide geometrical Instantaneous Field of View (IGFOV) of 73 meters and cover a
swath of 148 Kms on ground, while LISS-II provides an IGFOV of 36.5 meters and
Indian Remote Sensing Missions & Payloads – A glance
4.7
individual swath of 74 Kms each. The combined swath of both LISS-II cameras is
145 kms with a 3 km side lap between them.
The data handling system, consisting of baseband and RF modules, receives
digital data from payload, formats it and after modulation transmits the data to
ground station as a PCM stream LISS-I data is transmitted through a BPSK
modulator in S-band at 5.2 MBPS and the data from both LISS-II cameras is
transmitted through a QPSK systems in X-band at 10.4 MBPS.
Table 4.5:
Payload specification
Optics
Equivalent Focal Length
(EFL)(mm)
Spectral Bands(um)
Band-1
Band-2
Band-3
Band-4
Field of View
Detector
CCD
No. of pixels
Pixel size (um)
System
Payload specification
Refractive , F/4.5
162.2
Refractive , F/4.5
324.4
0.45 – 0.52
0.52 - 0.59
0.62 – 0.68
0.77 – 0.86
9.4 deg.
0.45 – 0.52
0.52 - 0.59
0.62 – 0.68
0.77 – 0.86
4.7 Deg (each)
Linear array
2048
13 x 13
Linear array
2048
13 x 13
Indian Remote Sensing Missions & Payloads – A glance
4.8
Geometrical IGFOV (meters)
Angular IFOV (microradians)
Swath (Km)
73
80
148
Integration time (m sec)
No. of radiometric levels
Data rate (Mbps)
Noise equivalent reflectance
(NEdP)
Signal – To – Noise Ratio(SNR)
11.2
128
5.2
<1 %
Square wave response (SWR) at
40 Lines per millimeter (lpmm)
Band -1
Band -2
Band –3
Band - 4
Band to Band registration
(Pixel)
Operating temperature range
EO module
Electronics (PLE)
Power(W)
Imaging mode
Cal. Mode
Mass(Kg)
EO Module
Electronics
Power supply
36.5
40
74 each
(145 combined)
5.6
128
10.4 x 2
<1%
>127 for all bands at saturation level
exposure
>40
>40
>30
>20
+/- 0.25
>40
>40
>30
>20
+/- 0.25
20+5 deg. C
0 to 40 deg. C
20+5 deg. C
0 to 40 deg C
34.2
37.9
34.2 x 2
37.9 x 2
27.50
4.48
6.44
70.00 x 2
4.41 x 2
6.44 x 2
4.6 Ground Segment
The IRS-1A Ground segment controlled and monitored the satellite
throughout the mission and performed the image data reception, processing,
generation/dissemination and archival of data products.
The major elements of IRA-1A ground segment were




Telemetry, Tracking and Command (TTC) network
Spacecraft Control Centre (SCC)
Data Reception System
Data Products System
Indian Remote Sensing Missions & Payloads – A glance
4.9
Ground segments location and functionality
Element
Location
ISTRAC
stations
at
Telemetry,
Tracking
& Bangalore and Lucknow
(Selective Support from
Command(TTC)
External stations)
ISTRAC,
Peenya
Spacecraft
Control
Centre Bangalore, India.
(SCC)






National Remote Sensing
Agency(NRSA),
Shadnagar,
Hyderabad,
India.(Now it is National
Remote
Sensing
Centre(NRSC).
Balanagar,
Data Processing, NRSA,
Hyderabad, India
Dissemination
Space Application Centre
and Archival
(SAC) Ahmedabad, India.
Data Acquisition







Functions
Satellite
Health
data
reception and recording
Spacecraft commanding and
tracking
Network coordination and
control
Spacecraft Operations
Spacecraft health analysis
and control
Orbit
and
attitude
determination
Communication links
Reception and recording of
Image data
Quick-look imagery and
display.
Ancillary data generation for
further processing of data.
Generation and distribution
of Browse and Standard
products.
Generation of precision and
special products.
Data quality evaluation.
Indian Remote Sensing Missions & Payloads – A glance
4.10
IRS-1A Image
Indian Remote Sensing Missions & Payloads – A glance
4.11
Indian Remote Sensing Missions & Payloads – A glance
4.12
5
IRS-1E
5.1 Introduction
IRS-1E satellite, derived from the engineering model of IRS-1A
incorporating a Monocular Electro-Optical Stereo Scanner developed by DLR,
Germany, and a LISS-I camera similar to that on IRS-1A, could not be placed into
orbit by the PSLV-D1 launched in September 1993.
The mission was not realised due to problems faced by Launch Vehicle. It
was the first development flight of PSLV.
5.2 Mission Objectives



The spacecraft was realized as a payload for the First developmental
flight of PSLV to carry 846 kg payload of IRS class in 817 km polar sun
synchronous orbit.
Combine stereo capability of MEOSS data along with multi spectral LISSI data and evolve stereo products on experimental basis
To support IRS-IA/IB LISS-1 Users.
5.3 Orbital Details
Orbit
Power
Mass
Launch Date
Launch Vehicle
Not Realised
415
846
September 20, 1993
PSLV-D1
5.4 Salient features of Spacecraft
Parameter
Mission
IRS-1E
The spacecraft was realized as a payload for the
First developmental flight of PSLV to carry 860
kg payload of IRS class in 817 km polar sun
synchronous orbit.
Structure
Aluminium and aluminium honeycomb
structure
(IRS-1A’s EM)
Passive control using tapes , OSR, MLI
Blankets and semi-active/active control using
proportionate temperature controller and heaters
20+5 deg.C range for imaging sensors electrooptics
Thermal
Components
Temp. Range
Indian Remote Sensing Missions & Payloads – A glance
5.1
5+5 deg. C for Chemical Batteries
0 to 40 deg.C for electronic packages
Mechanism
Solar Panel
Power
Solar Array
Battery
Telemetry
Communication
Telecommand
Tracking
Attitude and
Orbit Control
(AOCS)
House Keeping(HK) information in S-Band;
PCM/PSK Real Time rate 256 bps and play
back rate 4 Kbps; Onboard storage capacity of
102 minutes of HK data
S-Band
VHF
Facility for ON/OFF and Data commands
S-Band tone ranging and two way Doppler
Attitude
sensors
IR Horizon sensors(Conical and Static), sun
sensors, Dynamically Tuned Gyros (DTG)
Attitude
control
Reaction Wheel(three 5NMS and one 10 NMS),
Magnetic torquers, Hydrazine thrusters( 16 one Newton)
80kg fuel , dry mass 34 kg
Monopropellant hydrazine thrusters
Orbit Control
Payload
Solar Panel hold down and Deployment
Mechanism
5.72 m2 area, deployable and sun tracking panel,
Power generation at EOL is 415Watts (Totally
4 panels)
Two Ni-Cd batteries of 40 AH capacity each
OrbitDetermination
accuracy
Attitude
Determination
Accuracy
LlSS-1
MEOSS
1 Km
0.4 deg.
65.5 meter resolution
143 meter IGFOV, 50.3m along track
Data handling
Datarate: 5.2 + 2 x 10.4
Mass
860kg
Launch site
SHAR
Launch vehicle
PSLV-D1
Indian Remote Sensing Missions & Payloads – A glance
5.2
Figure 5.1 Deployed view of IRS-1E
Figure 5.2 Exploded view of IRS-1E
Indian Remote Sensing Missions & Payloads – A glance
5.3
5.5 Payloads
5.5.1 LISS-1 (Linear Imaging Self scanning Sensor)
The payload system consists of solid state cameras operating in four spectral
bands in the visible and near- IR range using Charge Coupled Devices (CCD) linear
arrays as sensors. LISS-I provide an IGFOV of 65.5m and cover a swath of 134km.
The along track sampling corresponding to the integration time of 11.2ms is 74m.
Payload specification
Optics
Equivalent Focal Length
(EFL)(mm)
Spectral Bands(um)
Band-1
Band-2
Band-3
Band-4
Field of View
Detector
CCD
No. of pixels
Pixel size (um)
Refractive , F/4.5
162.2
0.45 – 0.52
0.52 - 0.59
0.62 – 0.68
0.77 – 0.86
+ 4.7 deg.
Linear array
2048
13 x 13
System
Geometrical IGFOV (meters)
Angular IFOV (microradians)
Swath (Km)
Integration time (m sec)
No. of radiometric levels
Data rate (Mbps)
Noise equivalent reflectance
(NEdP)
Signal – To - Ratio(SNR)
Square wave response (SWR)
at 40 Lines per millimeter
(lpmm) %
Band -1
Band -2
Band –3
Band - 4
Band to Band registration
(Pixel)
Operating temperature range
EO module
65.5
80
134
11.2
128
5.2
<1 %
>127 for all bands at saturation level
exposure
>40
>40
>30
>20
+/- 0.25
20+5 deg. C
Indian Remote Sensing Missions & Payloads – A glance
5.4
Electronics (PLE)
Power(W)
Imaging mode
Cal. Mode
Mass(Kg)
EO Module
Electronics
Power supply
0 to 40 deg. C
34.2
37.9
27.50
4.48
6.44
5.5.2 MEOSS (Monocular Electro Optical Stereo Scanner)
The MEOSS payload developed by DLR, Germany is the second payload of
IRS-IE mission. MEOSS is a solid state push broom scanner operating in a single
spectral band of 0.57-0.70 microns.
Three 3456 element ccd are placed in the focal plane of imaging optics to image the
small ground scene with an oblique view of +/- 23 deg in the along track direction
thus providing a stereoscopic viewing capabilities.
The major specification of MEOSS given below:
Payload specification
Optics
Equivalent Focal Length
(EFL)(mm)
Spectral Band(um)
Detector
CCD
No. of pixels
Pixel size (um)
System
Geometrical IGFOV (meters)
Along track sampling(meters)
Swath (Km)
No. of radiometric levels
Data rate (Mbps)
Noise equivalent reflectance
(NEdP)
MTF
Refractive , F/7.2
61.1
0.57-0.7
Linear array
3456
10.7 x 10.7
143
50.8
463
256
10.4
<1 %
25
Position of CCDs
Roll direction
Distance between CCDs 26.7mm
Pitch direction
CCD1,CCD3 w.r.t CCD2 is +/-25micron
Indian Remote Sensing Missions & Payloads – A glance
5.5
Yaw direction
Parallism of CCDs
Deviation from focal plane +/25microns
5microns
Figure 5.3 View direction of MEOSS
Figure 5.4 EO module of MEOSS
Indian Remote Sensing Missions & Payloads – A glance
5.6
6
IRS-P2
6.1 Introduction
IRS-P2 was the fourth in the series of Indian Remote Sensing operational
Satellites. It was launched into the sun synchronous orbit of 817 Kms on October 15,
1994. This is the first Spacecraft successfully orbited onboard by the second
developmental flight of PSLV.
6.2 Mission Objective
The mission objective of IRS-P2 is to be the payload of the second
developmental flight of PSLV
6.3 Orbit details
Parameter
Values
Polar sun synchronous Orbit
817 Km
98.68o
24 days
10.30 AM
October 15, 1994
SHAR Centre, Sriharikota, India
PSLV-D2
1997
Orbit
Altitude
Inclination
Repetivity
Equatorial crossing time
Launch date
Launch site
Launch vehicle
Mission completed on
6.4 Salient Features of Spacecraft
Table 6.1:
Parameter
Structure
Components
Thermal
Temp. Range
Mechanis
m
Power
Solar Panel
Solar Array
Salient features of IRS-P2
IRS-P2
Aluminium and aluminium honeycomb structure
4 vertical and 2 horizontal Al Honeycomb panels.
Passive control using tapes , OSR, MLI Blankets
and semi-active/active control using proportionate
temperature controller and heaters
20+5 deg. C
for imaging sensors electro-optics
5+5 deg. C
for Chemical Batteries
0 to 40 deg. C for electronic packages
Solar Panel deployment and drive mechanism
6.424 m2 area,(2 x 2 panels) deployable and sun
tracking panel, Power generation at EOL is 620
Watts
Indian Remote Sensing Missions & Payloads – A glance
6.1
Battery
Electronics
Telemetry
Communic
Telecommand
ation
Tracking
Attitude sensors
Attitude
Actuators
and Orbit
Control
Orbit-Determination
(AOCS)
accuracy
Attitude
Determination
Accuracy
Payload
LISS-II*
Data
Handling
42V, Ni-Cd(2), 21 AH, 28 cells each, 27.64 Kg
TCR, domestic regulators, battery individual cell
monitoring, K relay emergency Relay Bus parallel
relays, DC/DC Converters
House Keeping (HK) information in S-Band;
PCM/PSK Real Time rate 256 bps and play back
rate 4 Kbps; Onboard storage capacity of 98
minutes of HK data
S-Band : PCM/PSK/FM/PM, and
VHF : PCM/FSK/AM
Facility for ON/OFF and Data commands
S-Band tone ranging and two way Doppler Xband beacon
IR Horizon sensors(Conical and Static), Star
sensor, Yaw sun sensors, Dynamically Tuned
Gyros (DTG)
Reaction Wheels (three 5NMS and one 10 NMS),
Magnetic torquers, Hydrazine thrusters(16 one
Newton)
1 Km
0.1 deg.
LISS-II* was achieved by mounting two CCDs
per optical lens system in staggered mode (Shown
in fig.)
10.4 Mbps
Spacecraft+ P/L
975 kg
Payload
98 Kg.
Mass
Indian Remote Sensing Missions & Payloads – A glance
6.2
Figure 6.1: Exploded view of IRS-P2
6.5 Payload
The LISS-II payload is a solid state camera operating in four spectral bands
in the visible and near IR range using 2048 elements linear array CCDs as sensors.
Unlike in IRS-1A/1B satellites in which the LISS-II camera was made of two
separate electro optical modules, in this camera two CCDs per band are placed in the
focal plane of the same optics in a staggered configuration. These are designated as
LISS-IIA and LISSIIB. Each camera provides an IGFOV of 32.74 meters and
individual swath of 67 Km the along track separation between the two CCDs is above
62 Kms on ground which will result in a combined swath of 128 Kms.
The data handling system, consisting of Base band and RF Modules,
receives the digital data from Payload, formats it and after modulation transmits the
data to ground station as a PCM stream.
Table 6.2 Features of IRS-P2 Payload
Sl.No
1
2
3
Parameter
Value
OPTICS
Type of Optics
Refractive F/4.5
Equivalent
Focal 324.4
Length(EFL)mm
Spectral Bands (Microns)
Band1 : 0.45 - 0.52
Indian Remote Sensing Missions & Payloads – A glance
6.3
18
Field of view
Detector
Detector Type
Number of Pixel
Pixel Size (Microns)
System
Geometrical IGFOV (m)
Along Track Sampling (m)
Angular IFOV (microradians)
Swath (Km)
Integration Time (ms)
Quantisation
Data Rate
Signal to Noise Ratio (SNR)
@ saturation exposure
Square Wave response SWR @
40 lp/mm
Band
to
Band
registration(Pixels)
Operating Temperature Range
19
Power in watts
20
Mass (Kg)
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Band2: 0.52 - 0.59
Band3 : 0.62 - 0.68
Band4: 0.77 – 0.86
+5.2 degs
CCD 143 Linear Array
2048
13 x 13
32.74
37.24
40
67 km each CCD (128 km Combined)
5.6
7 Bits
10.2 Mbps
>128
Band1: >0.4
Band2: >0.4
Band3: >0.3
Band4: >0.2
Less than + 0.25
EO module
20+5 deg C
Electronics
0 to 40 deg. C
Imaging mode
:32
Calibration mode
:34
72
Payload configuration
The payload consists of three major elements



6.5.1.1
Electro-optical Module
Payload electronics
Payload Power Supply
Electro optical Module
The EO module contains imaging optics including the spectral band pass
filters and neutral density filters (ND), CCD detectors and detector electronics. The
four band assembles in the camera use refractive optical systems and these are
Indian Remote Sensing Missions & Payloads – A glance
6.4
coupled to the detectors through Invar housings. These four single band assemblies
are mounted on a welded aluminum bracket with their optical axes parallel to each
other. To minimize the variation of BBR with temperature gradients, the four band
assemblies are coupled through Invar plates at lens end, detector end and middle
flanges. Two CCDs are mounted in the focal plane of each lens separated by a
distance (in along track direction) of about 25 mm and a gap of 4 pixels (in the across
track direction). Two LEDs per CCD mounted at an angle of 60 deg are used for on
board calibration. DE packages mounted on EO module Houses the Bias Voltage
generator, clock driver as well as pre-amplifier circuits for the operation of each
CCD.
The payload electronics are similar to IRS-1A/1B.
Figure 6.2: CCD arrangement in detector
plane as seen from detector Plane
Figure 6.3: Swath coverage of LISSIIA and LISS-IIB of IRS-P2
Indian Remote Sensing Missions & Payloads – A glance
6.5
Indian Remote Sensing Missions & Payloads – A glance
6.6
7
IRS-P3
7.1 Introduction
IRS-P3 was an experimental EO (Earth Observation) mission, a follow-up
mission to IRS-P2, considered to be pre-operational, and served in parallel for
technology evaluation and scientific methodology studies. A portion of the payload
was provided by DLR (German Aerospace Center). In addition, DLR provided data
reception support (Neustrelitz) and launch phase support. The secondary use of the
mission is to enhance and improve the IRS mission capabilities toward
operationalisation and application. This mission had two payload pointing modes, ie
Earth pointing and stellar/inertial pointing.
7.2 Mission Objective
The Mission Objectives of IRS-P3 are




To provide the opportunity for RS application in the areas of land,
atmosphere and oceanographic investigations.
To validate new RS methods and develop affiliated application potential.
To provide opportunity for experiments in X-ray astronomy.
As payload for the third developmental flight of PSLV.
Objectives of Earth pointing mode

To provide continued remote sensing data services in the areas of improved
crop discrimination, crop yield, crop stress and disaster management.
 Remote sensing of ocean atmosphere system and coastal waters and to
retrieve quantitative values about the co-existing c-varying water
constituents like chlorophyll sediments and gelbstoff
 To provide dynamic target for calibrating PCMC radars during Indian
Launch campaigns.
Objective of Stellar pointing mode



To study periodic and aperiodic intensity and spectral variations of galactic
and extragalatic X-ray sources by making pointed mode observations of
specific X- ray objects.
To discover pulsations of binary nature and quasi-periodic oscillations of XRay sources
Study of light curves and spectral evolution of transient & flaring X-ray
sources
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7-1
7.3 Orbit details
Table 7.1:
IRS-P3 Orbit Details
Orbit
Sun-synchronous
Altitude
817 Km
Orbital Period
101.35 minutes
Orbit inclination
98.7 deg
Equatorial Crossing Time
10.30 AM
Repeat Cycle
24 Days
Launch vehicle
PSLV-D3
7.4 Salient features of Spacecraft:
The IRS-P3 spacecraft structure was of IRS-P2 heritage. The bus design had
of four vertical panels and two horizontal decks supported on a central load-bearing
cylinder of 930 mm diameter and 1188 mm height. The payload was accommodated
on the outer side of the upper deck, which was oriented in flight direction (Roll axis).
The onboard power generation was achieved by a pair of deployable, sun-tracking,
un canted solar panels (9.636 m2), which generates a power of 873 W. Two Ni-Cd
batteries (21 Ah/24 Ah) catered to the eclipse and peak load demands.
Figure 7.1: Stowed configuration of IRS-P3
The spacecraft was three-axis stabilized. The AOCS employed Earth sensors,
sun sensors and dynamically tuned gyros as attitude sensors; actuation was provided
Indian Remote Sensing Missions & Payloads – A glance
7-2
by reaction wheels, magnetic torquers and an RCS (Reaction Control System). An
Earth pointing accuracy of better than 0.20º in all axes and better than 0.05º in all
axes for stellar pointing (X-ray observation mode) was provided. In addition to these
attitude sensors, AOCS also employed a star sensor in control loop in order to
maintain the attitude during stellar pointing mode. The star sensor was an area array
CCD imager of 288 x 384 pixels (FOV of 6º x 8º). It worked as a star tracker with
respect to a set of optical stars, identified a priori in conjunction with the X-ray
package. The star sensor was mounted on positive roll axis and co-aligned with the
X-ray payload's optical axis. When the spacecraft was inertially oriented and locked
to a specified X-ray source, the star sensor works in a static mode. Therefore, the star
sensor always locks to a specific scene about the roll axis.
Total S/C mass = 922 kg, a hydrazine propulsion system (84 kg of fuel
sufficient for three years) with 16 thrusters is used for orbit maintenance.
The IRS-P3 bus was derived from the flight proven IRS-1A,1B buses. New
systems were the processor based attitude and orbit control system (AOCS) which
was derived from INSAT-II for large angle maneuvers, the processor based
telecommand system and FPGA based telemetry system. ISRO developed Ni-Cd
batteries (24 Ah) were used.
Table 7.2 Salient features of IRS-P3
Subsystem
Structure
Thermal
Control
Limits
Mechanism
Solar Panel
IRS-P3
Four vertical and two horizontal decks supported
on a central load bearing cylinder of 930 mm
dia. And 1188 mm height. Decks are made up of
Aluminum/aluminum honeycomb panel. On
Inner surfaces packages were mounted. Outside
of Earth viewing panel carried payload data
antennae, the TTC antenna and attitude sensors.
The payloads were on outside of top deck
The design philosophy was maximum use of
passive elements and minimum use of semiactive elements. This was achieved by extensive
use of thermal control coatings, Thermal control
tapes, optical solar reflectors (OSRs), multilayer
insulation blankets(MLI), conductive grease etc.
Electronic packages: between 0 to 40 deg C
Battery: 5+5 Deg C
Solar Panel Hold down deployment and drive
mecghanism
Indian Remote Sensing Missions & Payloads – A glance
7-3
Power system
Solar Panel
Battery
Electronics
Telecommand
Communication Telemetry
Tracking
Pointing
Accuracy
AOCS
Sensors
Actuator
Payload Data
Two sections feeding two batteries (Total 870 W
generated)
9.7 Square Meter rigid panels.
Controlled by Shunt switches. Battery charging
control by dissipation less PWM taper charge
regulators.
Battery : Two 24 AH, Ni-Cd batteries
comprising 28 cells each
370 W continuously, 40 V Bus
Operated
in
S-Band
PCM/FSK/FM/PM
modulation
System Based on PCM/PSK modulation in SBand with dwell mode facility. One orbit data
storage was implemented..
The Tracking is provided by range and Doppler
measurements using S-band TTC transponder.
AOCS Supported Nadir mode WiFS and MOS
payloads and Stellar mode for X-Ray Payloads.
Pointing accuracy : 0.2 deg. Nadir Mode 0.01
deg. Stellar mode
Sensors: Earth,Sun and star sensor
Star sensor inloop mode was used for stellar
pointing mode.
Actuators: Two Magnetic torquers, four Wheels,
8 one newton thrusters and one 8 newton
thruster. Fuel loaded : 84 kg
The payload data was transmitted in S-Band
2280 MHz with BPSK modulation (Data rate
55.2 MBPS)
Indian Remote Sensing Missions & Payloads – A glance
7-4
7.5 Payloads
7.5.1 WiFS (Wide Field Sensor):
WiFS was an pushbroom
imager of IRS-1C and IRS-1D heritage.
WiFS was an extended version of 3
channels on IRS-P3: 0.62 - 0.68 µm,
0.77 - 0.86 µm, with an additional
channel at 1.55-1.75 µm (SWIR). Each
band had two detectors centered at a
FOV of ±13.6º to achieve a swath of 770
km (repeat cycle of 5 days). The optics
system consists of eight lenses with
spectral bandpass and neutral density
filters for each spectral band. The
dynamic range in each gain was 7 bits.
The absolute radiometric accuracy was
better than 10% with relative in-band
accuracy of 2%. The data rate for the
VNIR data (2 channels) was 2.6 Mbit/s,
for the SWIR data it was 1.73 Mbit/s.
WiFS had a mass of 25 kg and used 50
Figure 7.2WiFS Swath coverage on earth
Indian Remote Sensing Missions & Payloads – A glance
7-5
W. The objectives of WiFS observations were to monitor the vegetation index on
land and to observe the ocean surface.
Table 7.3: WIFS camera specifications
Spectral bands (µm)
Spatial resolution
Swath width
Repetition cycle
SNR at saturation radiance
Misregistration
Data quantization
Integration time
Data rate
Mass
Power
0.62 - 0.68,
0.77 - 0.86,
1.55 - 1.75 (SWIR)
188 m
770 km (FOV of ±13.6º), 4096 pixels
5 days
>128
0.25 pixel
7 bit (radiometric resolution of 128 grey
levels)
28.42 ms
2.06 Mbit/s
25 Kg
50 W
7.5.2 MOS (Multispectral Optoelectronic Scanner):
MOS is an experimental imaging push-broom spectrometer for VNIR/SWIR
range observations. MOS is provided by DLR (German Aerospace Center), Berlin.
The objective is to monitor the Earth's surface (surface-atmosphere interaction, ocean
color, phytoplankton, regional and global distributions of man-made aerosols and
their links to gaseous admixtures, spectral and spatial cloudiness characteristics, etc.)
in the VNIR/SWIR region of 0.4 - 1.6 µm.
The goals of MOS payload are





To design and build a spectral imaging instrument, dedicated for ocean
colour Remote Sensing with many > 10 narrow spectral channels in the VISNIR range (400-1000nm)
To separate the problem of object signature and atmospheric disturbance by
independent measurements in different spectral regions and with special
designed optical means.
To make experiments to prove the instrument concept and to get experience
in high spectral data handling and image processing.
To develop algorithms and test the methodological concept with emphasis on
CASe-2 coastal water
To make measurements at different ocean/coastal regions, by satellite and
synchronous ground truth to verify the algorithm or carry out its “ regional
tuning, if necessary.
Indian Remote Sensing Missions & Payloads – A glance
7-6
The sensor apparatus consists of three complementary instruments. MOS
operation requires at least one calibration per month (with respect to the sun).
• MOS-A is an atmospheric spectrometer with four narrow channels in the
O2A-absorption band at about 760 nm for the measurement of atmospheric turbidity.
The data from MOS-A are used for correction of the atmospheric influence
(scattering) on the multispectral data of MOS-B. In addition the O2A-method permits
the measurement of aerosol content and profile.
• MOS-B is a 13-channel spectrometer in the spectral range of 408 to 1010
nm. The center wavelengths of the channels are chosen with the objective for the
quantitative retrieval of ocean and coastal zone parameters. They also provide a
capability for vegetation signature determination (red edge) and estimation of H2O
(water vapor) content in the atmosphere from the NIR-measurements.
• MOS-C is a line camera at 1.6 µm with a bandwidth of "50 nm. The SWIR
channel data is used for improved surface term and roughness estimation. In addition
the data of the SWIR channel may be used for the following applications:
cloud/snow/ice discrimination, cloud type discrimination, estimation of sea surface
roughness, and for the improvement of atmospheric correction algorithms.
Table 7.4: Specifications of the MOS instruments
Parameter
MOS-A
MOS-B
MOS-C
Spectral range (nm)
755 - 768 nm
408 - 1010
SWIR
No. of channels
4
13
1
Wavelengths (nm)
408; 443; 485; 520; 570;
615; 685; 750; 870; 1010;
815; 945 (H2O-vapor)
10 nm (FWHM)
1600
Spectral resolution
756.7; 760.6;
763.5; 766.4
(O2A-band)
1.4 nm (FWHM)
FOV along-track
FOV across-track
Swath width
0.344º
13.6º
195 km
0.094º
14.0º
200 km
100 nm
(FWHM)
0.14º
13.4º
192 km
No. of pixels per
row
Spatial resolution
(ground pixel size)
Measuring range
Lmin-Lmax
-2
-1 -1
\[µWcm nm sr \]
Data quantization
140
384
299
1.57 km x 1.4 km
0.52 km x 0.52 km
0.1 - 40
0.2 - 65
0.52 km x
0.64 km
0.5 - 18
Data rate
16 bit
1.3 Mbit/s
Indian Remote Sensing Missions & Payloads – A glance
7-7
MOS calibration: In-orbit calibration measurements are performed using
internal reference lamps (prior to each data take). In addition sun calibration
measurements are performed once a month. This is achieved with a diffuser in front
of the entrance optics of the sensor. The following calibration functions are
performed:

DSNU (Dark Signal Non-Uniformity) and PRNU (Photo Response NonUniformity)
 Absolute sensitivity calibration
 Linearity control
 Spectral alignment control
MOS in-orbit inter calibrations with sensors from other missions are
attempted when orbital opportunities arise for a common target area or test sites.
Examples are: MOS on IRS/P3 with MOS on Priroda, or with SeaWiFS on Seastar,
or with OCTS on ADEOS.
Principle of the imaging pushbroom spectrometer operation: A strip (swath)
of the Earth's surface is imaged through the entrance optics on the field stop. The
collimator optics realizes parallel light rays falling onto the grating. The grating
disperses the different “colors” that are focussed by the imager into the focal plane.
Corresponding to the desired wavelength, CCD line arrays are mounted into the focal
plane.
Indian Remote Sensing Missions & Payloads – A glance
7-8
Figure 7.3 Optical schematic of the MOS
Figure 7.4 Illustration of the MOS (Modular Optoelectronic Scanner)
instrument
Figure 7.5 Schematic illustration of the optical block of MOS-B
Sensor calibration
The demanded radiometric data quality was guaranteed by two on-board
calibration concepts realized in hardware. 1. An internal sensitivity check 2. an
external calibration to the sun (SUNCAL). The internal check is made in each block
with two small filament lamps mounted besides the entrances slit. Through the
auxiliary slits the lamps are illuminating the collimator optic and after dispersion at
the grating are illuminated the CCD – lines in the focal plane. By powering the
lamps in four high stabilized current levels and superposing of both lamps we have
Indian Remote Sensing Missions & Payloads – A glance
7-9
16 levels of different illumination intensities for each channels in MOS-A and MOSB. In MOS-C CCD was illuminated directly by the lamps.
Figure 7.6: Optical Schematic of MAS-A and MOS-B
Figure 7.7 Optical Schematic of MOS-C
7.5.3 IXAE (Indian X-ray Astronomy Experiment):
IXAE is an ISRO/ISAC and TIFR (Tata Institute of Fundamental Research,
Mumbai, India) cooperative experimental astronomy instrument package with the
objective to study periodic and aperiodic intensity and spectral variations in X-ray
sources. Source observation is achieved by `pointed mode observations,' employing
an array of three co-aligned collimated PPC (Pointed Proportional Counter). The
system operates in mutual anti-coincidence fashion for significant reduction of
background noise (cosmic rays and Compton interaction of gamma rays).
Indian Remote Sensing Missions & Payloads – A glance
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Another objective is the study of light curves and the spectral evolution of
transient and flaring X-ray sources as well as long-term intensity monitoring of
known binary X-ray stars and other bright X-ray sources. This is achieved by means
of XSM (X-ray Sky Monitor), based on the principle of a pin hole placed above a
position sensitive to PPC in anti-coincidence mode.
Table 7.5 PPC and XSM instrument specification
PPC
XSM
Energy range
2 - 20 keV
Energy range
2 - 8 keV
FOV
2º x 2º
FOV
90º x 90º
No of PPC
3
Pin hole size
1 cm2
No of layers per PPC
3
Distance to detector
16 cm
No. of anode
cells/layer
18
Detector
Size of cell
1.1 cm x 1.1 cm
Detector cell size
Entrance window
25µm , 500 Å, Al
coated
Window
Filling gas
Ar+CH4, at 800 torr
Filling gas
32
proportional
counters
1 cm x 1 cm
x 32 cm
25 µm
Mylar, Al
coated
Ar+CH4
The principle objective of the IXAE is to carry out timing studies of X-ray
pulsars, X-ray binaries, and other rapidly varying X-ray sources. The XSM detects
transient X-ray sources and monitors the light intensity of bright X-ray binaries. Each
of the detectors (PPC, XSM) are controlled by independent microprocessor based
processing electronics. A common electronics subsystem acts as an interface with the
satellite bus. An oven controlled oscillator (accuracy one part in 109) provides high
timing accuracy.
The PPC is a multi-cell multi-layer proportional counter array with active
anticoincidence on three sides. The total geometric area is about 400 cm2, the filling
gas is 90% Argon + 10% Methane. A 25 µm aluminized mylar acts as the entrance
window. The field of view is restricted to 2º x 2º using a passive collimator. The
detector has a command controlled high voltage unit. The processing electronics for
the PPC has an onboard memory of 512 kByte, the spectra (64 channels spanning 2
to 30 keV) and light-curves are stored onboard with the command selectable
integration times.
Indian Remote Sensing Missions & Payloads – A glance
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The XSM is a planar position sensitive proportional counter with a pin-hole
of 1 cm2 positioned 16 cm above the detection plane. The FOV is 90º x 90º. The
detection plane consists of 32 proportional counter cells with a resistive wire (NiCr)
as the anode. Position resolution along the wires is achieved by charge division and
perpendicular to the wires it is achieved by cell placement (1 cm). The energy range
of the detector is 2 to 8 keV.
Figure 7.8 Schematic view of the IXAE instrumentation
7.5.4 C-Band Transponder
The C-Band transponder system consists of three portions as given below and is
used for calibrating ground radars at SHAR
1. Receiving section which operates at 5.660 GHz with sensitivity of -70 dBm
2. Transmitting section which operates at 5510 MHz and 5800 MHz with a
peak power of 400 watts
3. DC/DC converter which provides constant output voltages
Single antenna is used for receiving and transmitting Operations.
Receiver: The RF input received by the antenna is fed to the circulator. The signal
passes from circulator to the pre-selector filter. This filter is used as selector. Output
from this filter/selector is fed to a mixer. Output of local oscillator (LO) which is
Indian Remote Sensing Missions & Payloads – A glance
7-12
fundamental oscillator generates C-Band frequency is also fed into the mixer. Mixer
performs as a down converter and converts C-Band signal to the IF frequency. The
amplified IF signal is detected by a solid state detector, filtered by a low pass filter,
am0plified and passed to digital section through a buffer. The digital circuits provide
triggers to the modulator which produces a high voltages negative pulse for cathode
pulsing of the magnetron.
Transmitter: The Transmitter is a mechanically tuned C-Band magnetron oscillator.
The power output is provided to the unit through 4 port circulator.
DC/DC converter: The DC/DC converter provides input to CBT at 23 V +2% and
1.2 A. the initial surge current requirement under all conditions is 1.5A.
Image from MOS Payload
Indian Remote Sensing Missions & Payloads – A glance
7-13
Indian Remote Sensing Missions & Payloads – A glance
7-14
8
IRS-1C&1D
8.1 Introduction
IRS-1C is the second generation Remote sensing operational satellite
developed by ISRO that carried three distinct and mutually complementary imaging
payloads. The combination of payloads enhanced the capabilities of IRS-IC as
compared to IRS- IA/1B in terms of spatial resolution, provision of an additional
spectral band, ability to acquire stereoscopic images and inclusion of a wide field
sensor for improved temporal resolution. IRS-1D was the follow-on mission.
8.2 Mission Objective of IRS-1C and 1D
Mission objectives of IRS-1C and 1D are as given below


To design develop launch and operate state of art three axis body
stabilised satellite for providing continued space based remote sensing
services to the user community with enhanced resolution capability
compared to IRS-1A/1B
Further develop new areas of user applications to take fiull advantages of the
enhanced resolution and capacity of IRS-1C/1D spacecraft.
8.3 Orbit Details
IRS-1C and 1D were launched into polar sun syncronous near circular orbit
to ensure ground illumination conditions are nearly the same for imageries collected
on different days. Local time equtorial crossing was chosen 10.30 AM based on
application needs of the users. .
Table 8.1: Orbital parameters of IRS-1C&1D
Sl.No
1
2
3
4
5
6
7
Parameter
Orbit
IRS-1C
Polar sun
synchronous
Altitude
817 Km
Inclination
98.69 deg
Period
101.35 minutes
Local Time
10.30 A.M
Repetivity Cycle
24 Days (For Liss-3)
5 Days (for Pan
5 Days (for PAN
revisit)
Distance
between 117.5 Km
adjacent Traces
Indian Remote Sensing Missions & Payloads – A glance
IRS-1D
Polar sun
synchronous
740 x 817 Km
98.6
101.35 minutes
10.30 A.M
24 Days (For Liss-3)
5 Days (for Pan
5 Days (for PAN
revisit)
117.5 Km
8-1
8
9
10
11
Minimum
Picture
Overlap for LISS-3
Off Nadir coverage +/26 deg (for PAN)
Distance
between
successive
Ground
tracks
Ground Trace velocity
22.5 Km
22.5 Km
398 Km
398 Km
2828 Km
2828 Km
6.65 Km/s
6.65 Km/s
8.4 Salient features of IRS-1C&1D
Though most of the systems were fabricated similar to IRS-1B, based on the onboard
experiences of IRS-1A and IRS-1B satellites, and in view of launching the satellite
using Indian launch vehicle (PSLV), some modifications/ improvements were carried
out in IRS-1D spacecraft. Features comparison of 1C/1D with IRS 1A/1B is given in
table 8-2.
Table 8.2. Salient features of IRS-1C/1D
Subsystem
Structure
Thermal
Mechanism
Power
IRS-1A/1B
IRS-1C/1D
Al. honeycomb structure Shear webs added to increased the
with central load bearing frequency to cater to PSLV launch.
Al. Cylinder
CFRP cylinder (370 mm height 930
mm dia) for thermal isolation of
payload deck incorporated.
Passive, Semi-active with Experience gained from IRS-1A for
heaters
evolving IRS-1C thermal design,
Payload
module
had
new
configurations and power dissipation in
IRS-1C was more and hence a new
design and analysis made.
Solar Panel deployment Solar panel deployment mechanism
mechanism
used as it is ‘PAN’ camera deployment
and steering mechanism newly
developed.
Solar Panel
9.636 m2, 6 panels 1.1 x 1.46 m2
(Each)
BSR (SCA) 813 watts (10% area
increased)
Battery
2 batteries, 42V, 28 Cells, Ni-Cd 21
AH
Power electronics
More efficient power electronics
Indian Remote Sensing Missions & Payloads – A glance
8-2
TTC
S-Band transponder
PROM based telemetry
Telecommand
system
(418 ON/OFF, 21 data
commands)
X Band for LISS_2(10.4
x 2 MBPS) with 20 watts
TWTA
Sensors
AOCS
Actuator
AOCE
developed. Additionally CUK type of
DC/DC converters developed.
S-band transponder used as it is
Modified to meet mission specific
requirements
Modified to meet mission specific
requirements including time tag
commands (704 ON/OFF and 46 data
commands)
40 watts TWTA used . 84 MBPS and
42 MBPS data Handling system
Developed.
Sun sensors (4 PI, TWSS, FSS, PYS)
PYS improved to reject any spurious
signals Conical earth sensors ,
Dry tuned gyro for yaw control. Two
gyros in a cluster Three gyros in a
cluster. All three axis to be controlled
by gyro.
Star sensor based-on linear CCD Star
sensor based on area array CCD (for
providing attitude information about all
three axes)
Mono propellant 1 Newton system. 80
Kg Capacity. 11 Newton thruster
developed for IRS-1C, 5 NMS
Reaction Wheels
Hardwired system PWPFM controller.
Hardwired system as a back up only for
microprocessor based linear controller.
Improved KF used
LISS-III, PAN and WiFS
Payloads
LISS-I and LISS-II
Data
Handling
S-Band for LISS-1(5.2 PAN and LISS-3 data in two
MBPS)
independent X-band chains. QPSK
modulator developed.
Indian Remote Sensing Missions & Payloads – A glance
8-3
Figure 8.1 IRS-1D spacecraft Stowed View
Indian Remote Sensing Missions & Payloads – A glance
8-4
8.5 Payloads
The payload system of IRS-1C&1D consists of three cameras namely



Panchromatic camera (PAN),
Linear Imaging Self scanning Sensor (LISS-III) and
Wide Field Sensor (WiFS)
All cameras operate in the push-broom scanning mode employing linear
array charge coupled devices (CCD).
8.5.1 Panchromatic camera (PAN)
The PAN camera provides a spatial
resolution of 5.8 meters at nadir and
operates in a single (0.5- 0.75)
panchromatic spectral band. This camera
covers a ground swath of 70 kms which is
steerable upto 26 deg. from nadir in the
across track direction. This off nadir
viewing provides the capability to revisit
any given site with a maximum delay of
five days. The major specifications of the
IRS-IC PAN camera are given in table 8.3
Figure 8.2 CCD Arrangement in IRS-1C/1D PAN camera
Indian Remote Sensing Missions & Payloads – A glance
8-5
Optical design Of PAN
The PAN camera uses an all reflective off axis telescope, while LISS-III and
WiFS are realised using refractive optics. The PAN optical system is a 980mm focal
length (f/4.5) unobscured three mirror system i.e there is no obstruction to the
incoming beam by any part of the optical system. The optical design features an off
axis primary hyperboloid mirror, a spherical secondary mirror and an off axis
ellipsoidal tertiary mirror. By using off axis sections of conic surfaces, obstruction of
the incoming radiation is avoided resulting in higher modulation transfer function for
a given aperture. Since the image format (85mm) is too large to be covered by a
single CCD, an arrangement of 3 CCDs is used to cover the full swath. A prism with
two reflecting sides is placed slightly ahead of the image plane. The light rays from
the tertiary mirror falling on the sides of the prism are reflected out in opposite
directions. The prism angles are so configured that the light rays from 0.3 deg. of
nadir, along track, form two image lines on either side of the prism. These two image
lines when projected on ground are separated by 8.6 km. One of the image lines is
covered by two CCDs with a gap corresponding to the coverage by one CCD
between them. The second image line is imaged by a single CCD which is centrally
located.
The telescope mirrors are fabricated out of zerodur and are mounted in multi
bladed mirror mounts using an appropriate glue in such a way that surface
deformation on the mirrors do not occur. The super invar mirror mounts have been
designed to withstand storage temperature and mechanical loads generated during the
launch. The use of zerodur mirrors with the invar structure reduces the drop in MTF
due to temperature variation within the operating temperature of 17-23°C. Further,
the mirror surface does not show any non elastic behavior in the storage temperature
range of -30°C to +60°C. Baffles in the optical assembly have been designed to
reduce out of field radiation and reduce the drop in MTF from stray light. The baffles
have been located near secondary and tertiary mirror mounts. The design value of
MTF is greater than 0.6. In practice after taking to account the fabrication, tolerance,
alignment etc., it is possible to realize MTF of 0.5.
Table 8.3: Characteristics of PAN
S.No
1
2
3
4
Parameters
Instantaneous Geometric field of view *
(meters)
A)
Swath* (km)
B)
Swath Steering Range
(degree)
C)
step Size (Degree)
Spectral Band (micron)
Camera SWR ( At Nyquist frequency)
Parameters
5.8
70
± 26
± 0.09
0.50-0.75
0.20
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8-6
5
6
7
8
9
10
11
12
Quantization (bits)
System Noise
Saturation radiance (nominal )
(MW/Cm2- STR-micron)
Detector
6
1 LSB
47
Size of EO Module (Envelope ) (mm)
Weight (kg)
EO Module
PLE Package
Power (W)
Imaging Mode
CAL Mode
Data Rate (MBPS)
3 x 4096 pixel CCD (7 x 7
micron)
605 (R) X 903 (P) X 861 (Y)
105 (without PSM)
20
55
65
84.9
Figure 8.3 PAN Off nadir viewing capability /Swath coverage of PAN
Figure 8.4
Swath coverage of IRS-1C/1D
Figure 8.5 Swath coverage of IRS1C/1D
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8-7
8.5.2 LISS-3 Camera
The LISS-3 camera is a
multispectral imaging system operating in
four spectral bands, three in the visible
and Near IR (VNIR) region which are
identical to B2, B3 and B4 of IRS- IA/1B
and one in short wave infrared (SWIR)band B5. LISS-3 provides a ground
resolution of 23.5 m in VNIR and 70.5 m
in SWIR with a swath of 141 km and 148
km respectively for VNIR and SWIR.
Following Table gives the specifications
of LISS-3 camera.
Figure 8.6 LISS-3 Camera
Figure 8.7 LISS-3 EO Module
The lens design is derived from double Gauss concept. The design is
optimized separately for each spectral band to obtain the best MTF performance. The
design features a very low sensitivity of EFL, FD and collinearity to temperature
variation. The lenses for bands B2, B3 and B4 having an f/no. of 4.35, and a focal
length of 347.5 mm operate at 50 lp/mm whereas band B5 has focal length of 301 .04
mm with f/no. 4.35 and operates at 20 lp/mm .
To minimize the impact of surface reflections, each surface of the optical
elements carries antireflection (AR) coatings. The AR coatings have been provided
on all lens elements, thermal filter and outer surfaces of the interference filter. The
Indian Remote Sensing Missions & Payloads – A glance
8-8
lens is purged with dry Nitrogen and sealed with a membrane. After the launch, when
the differential pressure is more than 500 mbar the membrane ruptures and allows
the evacuation of the lens assembly. The assembly of the camera takes into account
the change in focal length from laboratory environment to the vacuum conditions in
orbit.
Hard coated four cavity interference filters have been used in these lenses,
for spectral selection. The thermal filter made of fused silica, makes an angle of one
degree with the optical axis of the lens assembly to avoid ghost images at the CCD
plane. It has a provision to allow rotation of this angle around the optical axis to take
into account the CCD detector orientation with respect to the mounting holes of the
flange.
Figure 8.8 Calibration LEDs arrangement In LISS-3
Table 8.4 Characteristics of LISS-3 Payload
S.No
2
Parameters
Instantaneous Geometric field of
view * (meters)
Swath* (km)
3
Spectral Band (micron)
4
Camera SWR ( At Nyquist
frequency)
1
5
6
7
Quantization (bits)
System Noise
Saturation radiance (nominal )
(MW/Cm2- STR-micron)
Parameters
23.5 B2, B3, B4
70.5 SWIR(B5)
>141
B2 0.52-0.59 B3 0.62-0.68
B4 0.77-0.86 B5 1.55-1.70
B2 40
B3 40
B4 35
B5 30
7
>1 LSB
B2 29± 1.5
B3 28 ± 1.5
Indian Remote Sensing Missions & Payloads – A glance
8-9
8
9
10
11
12
Detector
Size of EO Module (Envelope )
T(mm)
Weight (kg)
EO Module
camera
Power (W)
Imaging Mode
CAL Mode
Data Rate (MBPS)
B4 31 ± 1.5
B5 3.5 ± 0.3
10 x 7 micron 6000 element CCD
for Visible
26 x 26 micron 2100 element CCD
for NIR
455 (R) X 522 (P) X 500 (Y)
76.5
95
74
78
B2,B3,B4
B5
35.8
1.4
8.5.3 WiFS Camera
The WIFS camera has a spatial resolution of 188 meters covering a swath of
804 km. This wide swath coverage results in a repeatable observation of the same
ground location after every 5 days. The WIFS operates in two spectral bands B3 and
B4 of LISS-III (0.62 - 0.68 and 0.77 - 0.86 ). Performance parameters of WiFS are
given in
In the case of LISS-III , each
band is realized using a lens and
detector at the focal plane. The basic
design WiFS Camera
For the WiFS camera, the
total field to be covered was 52°. If
this was realized using single lens for
each band, due to the large variation
in the incidence angle at the
interference filter, there will be
considerable shift in the band edge
positions over the field of view. To
minimize the above effect, the total
Figure
8.9Wifs
Camera
of
IRS-1C
FOV is realized by two lenses for each band. The two lenses are mounted with their
optical axes canted 13° on either side of nadir. The basic optical design is similar to
LISS III except for the focal length of 56 mm.
Indian Remote Sensing Missions & Payloads – A glance
8-10
Table 8.5:
Characteristics of WiFS Camera
S.No
1
2
3
Parameters
Instantaneous Geometric field of view * (meters)
Swath* (km)
Spectral Band (micron)
4
Camera SWR ( At Nyquist frequency)
5
6
7
8
Quantization (bits)
System Noise
Saturation radiance (nominal ) (MW/Cm2- STRmicron)
Size of EO Module (Envelope ) (mm)
9
Weight (kg)
10
11
Power (W)
Data Rate (MBPS)
EO Module
camera
Parameters
188
804
B3 0.62-0.68
B4 0.77-0.86
B3 >34
B4 >20
7
<1 LSB
B3 28 ± 1.5
B4 31 ± 1.5
250 (R) X 335 (P) X
170 (Y)
18
23
28
2.1
Figure 8.10 Ground Segment of IRS-1C
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8-11
Picture taken by PAN camera of IRS-ID
Indian Remote Sensing Missions & Payloads – A glance
8-12
Indian Remote Sensing Missions & Payloads – A glance
8-13
Indian Remote Sensing Missions & Payloads – A glance
8-14
9
IRS-P4 (OCEANSAT-1)
9.1 Introduction
The oceans occupying more than two-third surface area of Earth, have great
influence on the global climate, affecting the economy and day-to-day life of people.
As the measurement of the oceanic parameters by conventional methods using ships,
buoys and other in-situ methods is difficult and expensive, remote sensing method
which give frequent, accurate updates and economical is preferred .
IRS-P4 in the series of Indian Remote Sensing Satellites (IRS) was designed
to serve the applications in the area of oceanography. Ocean Colour Monitor (OCM)
and Multi-frequency Scanning Microwave Radiometer (MSMR) were the two
payloads. The OCM operated in the visible and near infra-red bands and MSMR in
Microwave bands. Both the payloads are configured to serve the application areas
related to oceanography. Accordingly the satellite is called OCEANSAT-1.
These instruments were used to sense such important geophysical parameters
as, chlorophyll content, yellow substance and suspended sediments in ocean waters;
sea surface temperature, sea surface winds, water vapour in an atmospheric column,
identifying the potential fishing zones, coastal zone management, ship routing,
operations of offshore oil rigs and water content in clouds.
The 720 Km altitude orbit was selected to achieve systematic coverage of the
whole globe in two days considering the swaths of 1400 km. The satellite mainframe
derives its heritage from the earlier IRS mission. The data from both the payloads
were received and processed by National Remote Sensing Agency (NRSA) at
Hyderabad.
9.2 Mission Objective
Mission objective of IRS-P4 are as follows



To gather data for oceanograpics, land (vegetation dynamics) and
atmospheric applications.
To develop new application areas, using IRS-P4 data as
complimentary / supplimentary to the data from already operating
remote sensing satellites.
To provide opportunity for conducting technological / scientific
experiments that are of relevance for future developments.
Indian Remote Sensing Missions & Payloads – A glance
9-1
9.3 Orbit Details
Table 9.1 Orbit details of IRS-P4
Parameters
Values
Orbit
Polar Sun-synchronous
Altitude (Km)
720
Inclination (Deg)
98.27°
Equatorial Crossing Time (ECT)
12.00 noon (descending node)
Orbital period (Min)
99.31
Distance between adjacent orbital 1382
traces (km)
Distance
between
ground traces (km)
successive 2764
Repetivity
2 days (29 orbits)
9.4 Salient features of Spacecraft
Table 9.2
Subsystem
IRS-P4
Aluminum / aluminum honey comb with CFRP
elements for MSMR payload structures
Structure
Thermal
Salient features of IRS-P4
Thermal
control
Passive/ semi active thermal control with paints,
MLI blankets, OSR and close loop temperature
control
values
All electronics 0-40degC,
Battery 0-10 degC,
OCM 15+2 deg,
MSMR 10-30 degC
Solar panel
Solar panel hold down and deployment mechanism
Sun pointing through SADA
OCM
Hold down and tilt mechanism
MSMR
Payload antenna scanning mechanism
Solar panel
9.636 m2, 6 panels 1.1 x 1.46 m2 (Each)
BSR (SCA) 800 watts (EOL)
Batteries
2 x 21 AH, 42V, 28 Ni-Cd Cells,
Mechanism
Power
Indian Remote Sensing Missions & Payloads – A glance
9-2
Electronics
More efficient power electronics developed. Two
raw buses (28-42V) supplying power to all
subsystems. Modular type of DC-DC converters for
payload and data handling
Telecommand
Modulation, Time tag command facility
Conventional systems backed by micro processor
based, both for main and redundant.
Telemetry
ASIC based telemetry system. Storage capacity of 4
orbits, modulation
Transponder
Uplink frequency , Downlink frequency
TTC
Data rate 2 X 10.4 MBPS
Transmission frequency: X-band
Modulation QPSK
Recording facility: global data for MSMR and 10
minutes average data anywhere in the orbit for OCM
Data
Handling
Specification
Pointing accuracy:
Pitch : +0.15o Roll: +0.15o
Yaw: +0.20o
Drift rate: 3.6 X 10-4 o/s
Sensors
Conical Earth sensor (2), Dual cone earth sensor(1),
PYS (2), 4 pi sun sensors(4), Magnetometers(2),
IRU
Actuators
Magneto torquers(2), Reaction wheels(4), 1 N
thrusters (8) and 11 N thruster (1)
AOCE
1750 architecture based micro processor system for
main and redundant
Orbit
Orbital Accuracy 100-150 m (Autonomous mode
using SPS)
AOCS
Mass
1050 Kg
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9-3
Figure 9.1 Deployed view of IRS-P4
Figure 9.2 Stowed mode view of IRS-P4
Indian Remote Sensing Missions & Payloads – A glance
9-4
9.5 Payloads
9.5.1 OCM payload
OCM operates in eight spectral bands.
The imaging principle of OCM is based on
push-broom technique which is the same as for
the Linear Imaging Self-Scanner (LISS)
cameras used in earlier missions. There is
separate refractive optics for each band. Each
band has a linear charge coupled devices
(CCD) array in the focal plane of the optics as
the detector. The detector outputs are
processed by the payload electronics which
provide serial digital data stream of each band
to the data handling system.
Monitoring the colour of the ocean
water leads to the information on the
phytoplankton
concentration,
suspended
Figure 9.3 OCM Payload
sediments and yellow substance. OCM
characteristics like observation bands and their bandwidths, spatial resolution, etc. are
dictated by these water constituents. Additionally, the applications of OCM data for
land-based applications, where frequent information is required on regional scale, are
also kept in view while choosing the OCM parameters. The OCM is characterized by
coarse spatial resolution, eight narrow spectral bands, high radiometric resolution,
large field of view (± 43° providing a swath of 1420 km). Designing OCM for low
ocean surface radiance and wide FOV were some of the challenges in its realization.
While only about 20% of the signal received by the OCM optics in the orbit
comprises ocean radiance, 80% is the contribution from intervening atmosphere.
Thus, to extract information on ocean colour, the contribution from atmosphere needs
to be eliminated, and, therefore, accordingly correction is carried out by using data
from band 7 and 8. Ocean radiance being low, 12 noon has been chosen as the time
of equatorial crossing for descending pass to maximize the signal. This has an
associated phenomenon of sun glint entering into the field of view of OCM, time of
which is a function of season and latitude. To get over the problem of sun glint, a
provision to tilt the OCM payload by ± 20° in steps has been provided. Its position
can be fixed according to the latitude of observation and season. Tilt mechanism
ensures a glint-free observation anywhere on the globe.
Indian Remote Sensing Missions & Payloads – A glance
9-5
Table 9.3 OCM specifications
S.No
1.
2.
3.
4.
5.
Parameters
IGFOV
Swath
Repetivity
Quantisation
Spectral range
6.
Spectral bandwidth
7.
SNR @ saturation radiance
8.
Spectral bands (microns)
Integration time (ms)
Detector
Number of pixel
Video readout rate/port
Data rate / band
Total data rate generated
Camera MTF @ Nyquist
15.
frequency
16. Size (mm) E-O module
17. Weight(Kg)
9.
10.
11.
12.
13.
14.
9.5.1.1
Specifications
360m (across track) X 252m (along track)
>1420 Kms
2 days (29 orbits)
12 bit
402-885 nm
20 nm (B1-B6)
40 nm (B7, B8)
>512
Spectral Bands
Saturation radiance
B1: 402-422,
B1: 35.5,
B2: 433-453,
B2: 28.5,
B3: 480-500,
B3: 22.8,
B4: 500-520,
B4: 25.7,
B5: 545-565,
B5:22.4 ,
B6: 660-680,
B6: 18.1,
B7: 745-785, and
B7: 9.0,
B8: 845-885
B8: 17.2
34.75
CCD191A
Total : 6000 Used: 3730
86.6 KHz
2.08 Mbits
16.64 Mbits
>0.2
701 (R) x 527 (P) x 420 (Y)
EO module: 64 and camera: 78
E.O Module
The EO module consists of Imaging lens assembly, EOM Structure, Detector
head assembly, Detector electronics and payload tilt mechanism.
9.5.1.2
Optical system
It consists of eight spectral bands in visible and near infrared region having
spectral bands between 0.4 um and 0.885 um with 20nm band width for bands B1 to
B6 and 40 nm bandwidth for B7 & B8. Each band consists of its own collecting
optical system and a linear array detector (CCD). The optical system consists of 10
refractive lens elements, a thermal filter in front and interference filter at back end
close to the detector. The rear surface of the first lens is aspherical. A "telecentric"
optical system is selected to provide minimum distortion, uniformity of illumination
Indian Remote Sensing Missions & Payloads – A glance
9-6
and good MTF over wide field angle which provides two days repetivity. The optical
system is composed of a divergent component at the front end and a convergent
group at the back end. This configuration gives longer back focal length than
effective focal length and the main ray for each FOV goes out parallel to the optical
view. The maximal angle of ray allowed to reach the focal plane is just 7 deg. This
allows placing the band pass filter behind the optical system just in front of the CCD.
Table 9.4 OCM Optics specifications
S.NO
Parameters
values
1.
Equivalent focal length (EFL) (mm)
20.0+ 0.1
2.
F-number
3.
Field of View (degrees)
4.3 for B1 & 62
4.5 for B3 to 68
> + 43 (86 deg total)
4.
Clear working distance (mm)
>16
5.
Distortion
<+0.02%
Figure 9.4 OCM Lens assembly
Figure 9.5 Optical Ray trace Diagram of OCM
Indian Remote Sensing Missions & Payloads – A glance
9-7
9.5.1.3
EOM structure
The main structure of EO module is made out of single block of Al. Alloy
6061 material. This material is selected for its matching coefficient of thermal
expansion, which helps in maintaining the separation between the lens focal plane
and detector within ±2.0 micron over a temperature variation of 15± 2°C. Eight
Detector Electronics boxes are mounted on a support structure of four DE mounting’s
which are mounted on the EOM main structure.
Four thermal covers fitted on the EOM will cover the EO module on +ve
Yaw, -ve Yaw, +ve pitch and -ve pitch direction. Thermal cover is black painted on
its inside surfaces and covered by thermal blanket outside. Auto-control heaters are
mounted on the inside surface of thermal cover. Lens side and detector side thermal
covers have one cut-out for viewing and wire harness. A common hood with a slit
aperture is placed in front of each row of the lenses. These hoods limit the Field of
View of the lenses to ± 45° along pitch axis and + 2° along the roll axis.
9.5.1.4
OCM Electronics
The OCM electronics is modular, takes into account the realizability and
testability, satisfies the mission goal that no single point failure shall lead to nonavailability of two or more bands data. It has separate electronics for each band
without any redundancy. But cross coupling exists between camera electronics and
BDH.
OCM Electronics consists of Detector Head, Detector Electronics
9.5.1.5
Detector Head
A 6000 element 7 x 10 um pixel size linear array CCD (CCD191A same as
that used in IRS-1C/1D LISS-3 VNIR bands) is used as detector. This detector needs
four bias voltages and nine clocks for its operations. The detector electrical
interfaces, voltage levels are similar to IRS-1C except the readout speed. In IRS-1C
to meet the high readout rate (866 KHz per port), two shift registers of the detector
are read out simultaneously but in OCM phased readout mode of CCD operation is
implemented like in CCD 143A of IRS-1A. This reduces 8 video processors.
Each lens assembly has different back focal length. Suitable spacers are used
to place the Detector in focal plane. Considering the variation of the focal length with
reference to temperature the most matching material is found to be Aluminium.
However CCD is made out of ceramic which has very low Coefficient of Thermal
Expansion (CTE). Hence Invar material is chosen for CCD Holder. Thermal stability
among these two dissimilar materials will be achieved by using a dowel screw at one
end and free screw at other end. In addition to these two LED holders are located on
detector head. Each LED holder would accommodate two LEDs.
Indian Remote Sensing Missions & Payloads – A glance
9-8
9.5.1.6
Detector Electronics
The detector electronics consists of bias generator and clock drivers located
on the Electro Optic Module. The configuration of these circuits are similar to IRS1C/1D except for additional drivers for reset clock and integration control, two
phased readout and exposure control.
9.5.1.7
Calibration
Four LEDs of type HP 1 N6092 are mounted on the detector mount. Their
optical axis is at 71deg from the normal due to the limited space between the detector
and the imaging optics. In view of this large angle, the LEDs illuminate a larger
photosensitive area compared to the imaging mode in the lateral direction of the
detector array.
Table 9.5: Comparison of OCM and SeaWiFS Parameters
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9.5.2 Multi-frequency Scanning Microwave Radiometer
It
is a day-night-all
weather sensor, designed to
measure
sea
surface
temperature, sea surface wind
speed, atmospheric water vapour
and liquid water content in the
clouds.
Four
microwave
frequencies, in both horizontal
and vertical polarizations, have
been chosen which are sensitive
to these geophysical parameters.
MSMR has a 862 mm x
800 mm off-axis parabola as the
antenna
reflector,
and
a
corrugated feed to receive the
emitted radiation from earth and
its atmosphere. The antenna reflector is rotated at 11.16 rpm to get a circular scan of
1360 km width at the earth’s surface, and 49.7° constant incidence angle at the beam
centre. The feed meets the requirements of multi-frequency and multi-polarization
operation. It is characterized by high-polarization purity, high-beam efficiency and
low-ohmic losses. The receiver following the feed is a Dicke receiver which switches
its inputs between incoming signal, reference load and cold-sky calibration horns.
MSMR was fully calibrated on ground for various return losses and receiver
parameters. Various challenges in MSMR design included the stringent alignment
stability requirement of 0.01° during launch and over a wide temperature range,
antenna steering mechanism, and feed and a sensitive receiver.
The MSMR is a dual polarised radiometer system and is designed to estimate
and monitor geophysical parameters related to the land, the ocean and the
atmosphere. The frequencies and polarisation for MSMR have been arrived at by
considering the applications like atmospheric water vapour, Sea Surface Temperature
(SST), over oceans, ocean surface winds, cloud liquid water, snow/ice coverage etc.
S.No
1
2
3
Specifications
Swath
Repetivity
Frequencies
Temperature
Values
1360 Km
2 days (29 orbits)
6.6GHz(V&H)
10.65 GHz (V & H) 18GHz(V&H)
21 GHz(V&H)
Better than 1°K
Indian Remote Sensing Missions & Payloads – A glance
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MSMR consists of following systems




9.5.2.1
Antenna
Receiver
Data acquisition and control system (DACS)
Analog & Digital telemetry sub-systems(ADTMS)
MSMR antenna system
The MSMR is configured with a scanning antenna system which consists of
an offset parabolic reflector with a 80 cm diameter collecting aperture and a
multifrequency feed assembly. The antenna reflector is mechanically rotated with a
constant angular velocity for scanning the antenna beam across the satellite trace in
order to give the required swath of 1360 Km
MSMR antenna consists of following subsystems
 Offset parabolic reflector
 Multifrequency Dual Polarised Feed
o Multifrequency Ortho mode Transducers
o Calibration Horn for 6.6 & 10.65 GHz
o Calibration Horn for 18 & 21 GHz
o Support structure
o Antenna Scan Mechanism (ASM)
Table 9.6:
Specifications of MSMR Antenna
Frequency(GHz)
Bandwidth(MHz)
Beamwidth
Polarisation
Cross Pol.(dB)
Return loss(dB)
Beam efficiency
Scan offset angle
9.5.2.2
6.6
+ 112
42° ± 0.2°
V&H
< - 23
<-17
90%
43.32°
10.65 18
+ 112 + 160
2.6° ±0.15°
V&H
< -23
<-17
90%
4332°
21
+ 170.5
1.6° ± 0-1°
V&H
< -23
<-17
90%
43.32°
6.6
+ 112
1.4° ± 0.1°
V'&H
< - 23
<-17
90%
43.32°
Reflector
The offset parabolic reflector is of elliptical shape (862mm x 800 mm) and
renders a projected diameter of 800 mm aperture. The offset reflector is having
F/D=1.8 and an offset angle of 43.32°. This helps in achieving a clear field of view as
well as 50° the Earth incidence angle of the beam. The reflector is having embedded
copper mesh on the reflecting surface to enable the operation at 18 & 21 GHz of the
system. The overall RMS variation of surface accuracy is 0.10 mm over the elliptical
Indian Remote Sensing Missions & Payloads – A glance
9-11
size of (8 62.0 X 862.8) the reflecting surface. The reflector is fabricated out of
CFRP sandwich of aluminium-honey comb.
9.5.2.3
Feed
The feed consists of Horn and Ortho Mode Transducers (OMT). Corrugated
horn has been used because of the pattern symmetry, low cross polarisation and low
side lobe levels are achievable with this type of horn.
9.5.2.4
Support structure
In MSMR payload antenna, reflector and multifrequency feed are at a
distance of 1667 mm apart. The phase centre of the feed being 337 mm from the
aperture of the feed, the resulting seperation of 1330 mm between the reflector and
the feed aperture plane has been considered in achieving overall 2029 mm length of
CFRP support structure. The support structure supports the view of Scanning
Mechanism (ASM) and the reflector at one side and the feed, front end electronic
packages, two number of calibation horns which are interconnected with each other
by plumbing waveguides and RF cables on the other side.
9.5.2.5
Antenna Scanning Mechanism
The spatial resolutin of MSMR is decided by the foot print of the antenna
beam. Circular scan is adopted for the MSMR because it provides more integration
tme and least torque requirement due to continuous constant angular rotation. In
additon to this, due to non reversal of angular momentum, the scan mechanism will
have minimal effect on the satellite attitude. The scan geometry of constant incident
angle of 50 degrees makes the elliptical footprint with larger axis across the scan
direction. The 3 dB foot print in scan direction is decided by the slant range and the
antenna 3 dB beamwidth.
Figure 9.5 Scan Path illustration
Figure 9.6 Swath generation by MSMR
Indian Remote Sensing Missions & Payloads – A glance
9-12
Frequency
(GHz)
6.6
10.65
18
21
Beam Foot Print (KM)
Along Scan
Across scan
77
119
47
73
30
46
25
39
Cell dimention
processing) KM2
120 X 120
80 X 80
40 X 40
40 X 40
(After
ground
The scan period is fixed in such a way that 10 % overlap is provided for the
smallest footprint ie. 21 GHz channel. This corresponds to an angular scan speed of
11.173 RPM ( 5.37 seconds per rotation). The integration time corresponding to
11.173 RPM for various frequencies are listed below. The onboard integration time
implemented corresponds to half that for 21 GHz channel which provides smallest
foot print. The temperature sensitivity of MSMR depends upon receiver predetection
bandwidth, Integration time, type of receiver, antenna and receiver temperature and
gain measurement accuracy.
Table 9.7 Integration time
Frequency (GHz)
6.6
10.65
18
21
9.5.2.6
Integration Time(oveall in Integration
time
msec)
implemented (msec)
96
18
60
18
36
18
32
18
MSMR receiver
MSMR payload has six receiver chains, catering to 21 GHz-V pol, 21 GHz H pol, 18 GHz- V pol, 18 GHz-H pol, 10.65 GHz and 6.6 Ghz bands. For 6.6 and
10.65 GHZ bands single receiver is used to collect both polarisations using a
polarisation select switch at the input.
Table 9.8
Frequency (GHz)
No of channels
Predetection bandwith (MHz)
Noise Figure of receiver (dB)
Dicke clock
Integration Time
Input dynamic range
Output signal level
Sensitivity
Receiver stability
Specifications of MSMR Receiver
6.6
10.65
1(V/H)
1(V/H)
100
100
4
4
1 KHz
18 msec
2.7 degK-330 degK
0-10V
~1degK
0.01db
Indian Remote Sensing Missions & Payloads – A glance
18
2(V/H)
150
4.5
21
2(V/H)
150
4.5
9-13
The function of radiometer is to measure the noise power incident at the
antenna. In MSMR dicke type configuration is used for the receiver. In dicke type
radiomater, a SPDT switch used to periodically switch the receiver input between the
antenna and a constant noise sourse (Tref) at a switching rate higher than the highest
significant spectral component in the gain variation spectrum.
9.5.2.7
Local Oscillators (LO)
While dielectric Resonators are used for 6.6 GHz and 10.65 MHz oscillators,
Gunn diodes mounted in short circuited half guide wavelength cavity used for 18
GHz and 21 GHz oscillators. Schottky barrier diode is being used as the device for
detection. The diode is biased and designed arround flat detector configuration to
achieve the required banwidth.
9.5.2.8
Precision baseband processing subsystem (PBPS)
This lies between the RF front end and the quantiser of the DACS (Data
Acquisition and control System), forming tail end of receiver. PBPS has to generate a
DC signal demodulation, and converts it to a format suitable to the quantiser.
9.5.2.9
Data acquition and control subsystem
The Data Acquisition and Control Subsystem (DACS) is the tail end of the
MSMR payload. DACS carries out data digitisation, timing sequence generation and
control signal generation for the MSMR payload electronics. The on-board
integration time selected is 18 msec. The MSMR data will be digitised in 12
bits/sample to achieve digitisation accuracy better than 0.1 deg K over the specified
range of antenna temperature. 12 bit data of each radiometer channel is serialised at 8
KHz rate, multiplexed and transferred to on-board baseband data handling system
(BDH). Alongwith serial data, an additional strobe at every 12th bit is also provided
to spacecraft BDH.
The six channel MSMR sensor and calibration data are digitised with 12-bit
resolution to achieve the required accuracy for specified range of antenna
temperature. Uniform onboard integration and sampling intervals of 18 msecs amd 9
msecs have chosen for all the six channels to reduce overall MSMR hardware
complexity. The table gives the polarisation switching sequence & sampling interval
details for the different MSMR channels. The total data rate is about 5.6 Kbps.
Frequency
21.0 GHz
21.0 GHz
18.0GHz
18.0 GHz
Polarization
Even cycle
V
H
V
H
Odd cycle
V
H
V
H
Sampling Interval (msec)
Even cycle
9
g
9
9
9
9
9
9
Indian Remote Sensing Missions & Payloads – A glance
9-14
Frequency
10.65 GHz
6.6 GHz
Polarization
V
V
H
H
Sampling Interval (msec)
9
9
9
9
The MSMR Antenna Scan Mechanism (ASM) provides an anti-clockwise
scanning of antenna footprint on ground. A scan Start pulse which corresponds to the
angular position of - 90 Deg with reference to roll axis in each circular scan cycle, is
provided by BDH to DACS. The first half cycle from the SCAN START in each scan
cycle is utilised for sensor data collection and the remaining period is utilised for
calibration sequence and collection of temperature information from Analog &
Digital Telemetry Subsystem (ADTMS).DACS acquires the multichannel radiometer
data and also generates the timing and control signals required for Precision Base
Band Processing Subsystem (PBPS), ADTMS and data transfer to BDH.
The timing and sequence generator receives 8 kHz clock and SCAN START
from BDH. All timing windows and clock signals required to acquire the sensor,
calibration and data acquisition slot for ADTMS are generated with reference to the
SCAN START.
S.No
I
2
3
4
5
6
7
8
Parameter
No. Channels
Analog Input
AID Resolution
Sampling period
Total Cycle duration
Data words per cycle
Data rate
Digitizer
Specification
6
0 to 10
12 bits
9 msec.
5376 ms
2521
~ 5.6 Kbps
± I LSB rms
The time sequencer generates various timing waveforms with reference to
the Scan Start pulse signal from BDH. In addition to these it generates Dickie
switching clock (1 KHz) and sampling clock (9 ms). All the timing windows are
generated with 9 msec resolution and realised using a programmable synchronous
counter chain.
9.5.2.10 Analog & Digital telemetry subsystem (ADTMS)
The MSMR payload has several systems, the physical temperatures of which
form the part of the system calibration data. The knowledge of the absolute
temperatures of these is necessary in order to model/calibrate the system functionally.
The analog & Digital Telemetry subsystem (ADTMS) of the MSMR payload is
meant for this precision temperature monitoring application.
Indian Remote Sensing Missions & Payloads – A glance
9-15
Temperature is monitored at 51 points to an accuracy of + 0.1 deg. C. By
using thermisters and platinum Resistance Devices. The voltages sensed are
quantised using a 12 bit ADC. The total ADTMS data stream consists of 64 words of
12 bits each which are transferred to S/C data handling unit using a synchoronous
serial transmission philosophy. This transfer is carried out in the time slot of MSMR
pay!oad at the basic clock frequency of 8 KHz. The digital interfaces for ADTMS are
the basic clock input. ADTMS acquisition slot. 9 ms sampling clock from DACS and
data, strobe and gate lines to the S/C.
9.5.2.11 Calibration
In MSMR two point internal calibration approach has been utilised by using
dedicated horn antennas viewing the cold space (2.7 deg K) and a black body at a
high temperature will be used for the hot reference. As the circular conical scan
method is used in MSMR, the fore half period is utilised for data collection whereas
the aft half period be utilised for cold and hot calibration sequences. During the aft
half cycle, two sets of internal calibration are envisaged just before and after data
collection cycle.
Indian Remote Sensing Missions & Payloads – A glance
9-16
Indian Remote Sensing Missions & Payloads – A glance
9-17
Indian Remote Sensing Missions & Payloads – A glance
9-18
10 TECHNOLOGY EXPERIMENT SATELLITE (TES)
10.1 Introduction
The TES (Technology Experimental Satellite) is the first high resolution (<1
m) satellite launched by ISRO. It was launched to demonstrate more than eleven new
technologies developed by various design groups across the centres
Critical technologies tested in the TES are given below











Attitude and orbit control system (AOCS) for step and stare imageries in
desired direction.
Two mirror on-axis optics (RC Type) for payload (providing <1m nadir
resolution at 560 kms altitude)
X-band phased array antenna (PAA) with two beam generation capability for
payload data transmission
Single surface tension propellant tank of large capacity RCS tank
High torque reaction wheels : 0.1 NM and 10 NMS
standardized PW, TM, TC system
Tetrahedral wheel configuration which provides 0.23 NM torque and 23 Nm
sec. angular momentum capacities about each axis.
Improved satellite positioning system
Two Advanced solid state recorder with 32 Gb each for storage of 6 mins of
payload data
Data security by encryption technique (encryption by stream ciphering
scheme inclusion/exclusion option and key changing provision.
Honeycomb type central cylinder.
10.2 Mission Objective
The mission objectives of TES are
To design and develop a technology experimental satellite incorporating a
set of critical technologies to provide on-orbit demonstration and validation of these
technologies for future enhanced capability missions, and also to provide hands on
experience in complex mission operations like step and stare maneuvers and onboard
earth rotation compensation etc.
10.3 Orbital parameters
Parameter
Altitude (Km)
Repeat Cycle(Days)
Normal Orbit
560
1
Special orbit 1
410
2
Indian Remote Sensing Missions & Payloads – A glance
Special orbit 2
501
5
10-1
Parameter
No. of orbits per cycle
Inclination (Deg)
Ground trace Velocity
(Km/s)
Decay rate (m/day)
Orbital Time (min)
Local
Time
(descending) AM
Normal Orbit
15
97.65
6.97
Special orbit 1
31
97.08
7.2
Special orbit 2
91
97.45
7.04
61 to 27
96
10.30
410 to 232
92.9
10.30
125 to 61
94.73
10.30
10.4 Salient Features of Spacecraft
Subsystem
Structure
Thermal
Thermal
control
Thermal
Limits
Mechanism
Solar panel
Solar panel
Power
Batteries
Electronics
Telecommand
TTC
Telemetry
Transponder
Data
Handling
TES
Aluminum / Aluminum honey comb elements,
Cuboid main frame similar to IRS-P4
Passive/ semi active thermal control with paints,
MLI blankets, OSR and close loop temperature
control
All electronics 0-40deg C,
Battery 0-10 deg C,
PAN : 20+3 deg C
Solar panel hold down and
deployment
mechanism similar to 1A/1B
Sun pointing through SADA
Rigid ,Sun tracking, 9.636 m2, 6 panels 1.1 x
1.46 m2 ,(Each), BSR (SCA) , 800 watts (EOL)
2 batteries, 28-42V, 28 Cells, Ni-Cd, 21 AH
More efficient power electronics developed. Two
raw buses (28-42V) supplying power to all
subsystems. Modular type of DC-DC converters
for payload and data handling
Conventional systems backed by micro processor
based, time tagged and payload sequencer both
for main and redundant.
ASIC based telemetry system.
Uplink frequency
Downlink frequency S-band
Data rate
:2 X 42.4515 Mbps
Transmission frequency X-band Modulation
:
QPSK
Indian Remote Sensing Missions & Payloads – A glance
10-2
Specification
AOCS
Sensors
Actuators
AOCE
Recording facility: 2 x 32 GB (SSR)
Pointing accuracy
Pitch : +0.15o Roll: +0.15o
Yaw: +0.20o
-4 o
Drift rate: 3 X 10 /s
Earth sensor (2+1), PYS (1), 4 pi sun sensors(4),
Magnetometers(2), IRU
Magneto torquers(2), Reaction wheels(4), 1 N
thrusters (8) and 11 N thruster (1)
1750 architecture based micro processor system
for main and redundant
Figure 10.1 Stowed View of TES S/C
10.5 Payload
10.5.1 Panchromatic Camera
The Technology Experiment Satellite (TES) carries one PANchromatic
camera called PAN-TES. This camera works on the ‘push-broom scanning’ concept
using linear array Charge Coupled Devices (CCD) as sensors. Four 4K, 7um x 7um
are used to cover a swath of about 13.5 km at Nadir. In this mode of operation, each
line of the image is electronically scanned and contiguous lines are imaged by the
forward motion of the satellite. The improved along track resolution is achieved by
step and stare method.
The PAN-TES camera is a high resolution camera with a Instantaneous
Geometrical Field of View (IGFOV) of better than 3 meters. Totally this camera
covers a swath of better than 13.5 Kms. The satellite is agile and can be rotated to +/Indian Remote Sensing Missions & Payloads – A glance
10-3
45 deg w.r.t pitch axis and +/- 26 deg w.r.t roll axis. The focal length of 3920 mm
provides an across track IGFOV of better than 3 meter at nadir view from 560 km
altitude. The pitch bias and rate enable the camera to provide better than 3 meter
along track resolution. The capability of having maximum +/- 26 deg. bias w.r.t roll
axis provide 5 days revisit of the same location as well as stereo viewing capability in
across the track direction.
10.5.1.1 System configuration
The PAN-TES camera had three elements. They are


Electro-optics module (EOM)
Payload electronics
o Detector electronics
o Payload electronics packages
 Payload power supply
o Payload power converters
o Payload power regulators
Electro-optics module (EOM)
PAN-TES camera is a single band camera covering the spectral range from
0.5 to 0.85 microns wavelength. The EOM contains
o Imaging Optics
o Detector Head assembly
o Detector electronics
The imaging optics is a Ritchy-chretian (RC) type reflective system with
three field correction lens covering a FOV of +0.85 deg. The optical system has a
F/no of 7 and effective focal length of 3920 mm. The two mirror system is chosen
because of its compactness. The use of hyperboloids for both mirrors
allows
simultaneous correction of third order spherical aberration and third order coma. The
lenses extend the FOV of the telescope by reducing the Field aberrations and give a
flat image. The optical design of the telescope features an on-axis concave
hyperboloidal primary mirror and a convex hyperboloidal secondary mirror and three
spherical field correcting lens elements(for extending the FOV of telescope) The
lenses are housed in a barrel with an appropriate flange and are refereed as lens
assembly. Bothe primary and secondary mirrors are coated with enhanced aluminum
coating, To avoid the oxidization of aluminum a protective layer of MgF2 coated on
the aluminum coating
Indian Remote Sensing Missions & Payloads – A glance
10-4
Figure 10.2 Optical Schematic of TES PAN Payload
Figure 10.3 Multiple focal plane generation
Figure 10.4Exploded View of TES Payload
Indian Remote Sensing Missions & Payloads – A glance
10-5
Figure 10.5 TES PAN camera and Detector Head
The Optical elements specifications are as given below.
10.5.1.2 PAN TES Specification
OPTICS
Type
: RC Type
Primary mirror
Material
: Zerodur
Diameter (mm)
: 570 mm (Usable (560 mm)
Center thickness (mm)
: 65
Weight (kg)
: 30
Aspect ratio
: 1: 10
Obscuration
: 11.5 %
Opening radius at the center(mm): 190
Secondary mirror
Material
Radius of curvature Ro
Conic Constant
Surface figure
Center thickness (mm)
Diameter (mm)
Weight (kg)
: Zerodur
: 905 +/- 2 mm
: -5.057
: lambda/10(rms(lambda/67)
: 35
: 190
:2
Field corrector
No. Lenses
Max. lens diameter
Focal length
Housing material
:3
: 128 mm
: 1310 mm
: titanium
Indian Remote Sensing Missions & Payloads – A glance
10-6
Optical system specification
Effective focal length (EFL)
Spectral Band (micron)
F-Number
Field of View
Optical system length
Diffraction limited MTF
Design MTF
Achieved optical system MTF
(Optics level)
: 3920 mm
: 0.5 – 0.85
: F/7
: + 0.85 deg.
: 1068 mm
: 0.42
: 0.39
: 32
The four numbers of 4k CCD with 7 x 7 micron size pixels were used to
cover a swath of greater than 11 kilometers. The rays come out from the secondary
are spilt by a isosceles prism and two image planes are created. To mount four
devices a specific assembly was designed and detector 1 & 3 are mounted on one side
and 2 & 4 were mounted on another side of the detector head. The CCDs are
mounted on PCBs which in turn are supported by a carrier plates. Detector 1 & 3
view along nadir where as detectors 2 & 4 are shifted in the image plane in the along
track direction. The actual along track distance between these two planes was 22.533
mm. Each detector had separate interference filter and LED Panels (consisting of
four LEDs, two for optical bias and two for calibration mode operation). The earth
rotation effects on the swath are taken care by adjusting the location of CCDs.
Detector parameters are given below.
Detector
Type
Detector material
Spectral response
No. of pixels
Pixel arrangement
No. Output ports
No. of CCD devices
: Charge Coupled Devices
: Silicon
: 0.4 um to 0.85 um
: 4096/CCD (TH7833)
: inline
: 4/CCD
:4
Indian Remote Sensing Missions & Payloads – A glance
10-7
Figure 10.6: illustration of CCD projection on Ground
Payload electronics
Payload electronics is similar to IRS-1D payload electronics with four
chains. The payload electronics consists of
1. Detector electronics
2. Payload electronics
10.5.1.3 Detector electronics (DE)
Each DE package consists of four preamplifiers, bias voltage generators,
clock drive optical bias LED drivers. Detector driver electronics supplies bias
voltages and clocks required for CCDs. The two LEDs required for Optical Bias of
CCDs are driven in series with a constant current drive. Designed around LM 723
regulator. The power supply lines to the DE are filtered Using Line filters before
being fed to the circuits. The charge collected by the detector pixels are read
simultaneously from all four ports and converted to voltages. This signal is amplified
by the DE and pre-amplified signals from DE are provided to the Payload electronics
(PLE) package.
10.5.1.4 Payload electronics
The signals from the DE are amplified in the programmable gain amplifier.
The three levels pulse amplitude modulated (PAM) signals of 1.2 MHz is preamplified in DE and is further processed in PLE. A constant DC bias is subtracted
from total signal to subtract the optical bias in the summing amplifier. There are four
Gain settings for the amplifier for each Band which are selectable through ON/OFF
commands. The amplified signal is DC restored and digitized. The seven bit parallel
Indian Remote Sensing Missions & Payloads – A glance
10-8
data with hot redundancy is available at PLE output on separate buffers for BDH
main and BDH redt.
The timing logic receives the Line start pulse( WLS repetition Rate: 0.8836
ms, pulse width 1.48 microseconds) and Bit Rate Clock (BRC) of 28.301 MHz with
50% duty cycle from baseband data handling system and generates the required clock
wave forms to read out the data from CCDs The input clocks from BDH main and
redt,. are cross coupled with logic main and redt. and also the output signals of
timing logic are cross coupled and given to BDH.
On-board calibration scheme
In calibration mode the detectors were directly illuminated by the two LEDs
which were mounted at an angle of 15 deg. to the optical axis. Calibration mode
operations were done during night passes. Provision to operate the individual CCDs
or all CCDs together in Cal Mode was provided.
System Specifications
IGFOV (m)
Swath kms
Integration time (msec)
Quantization level
Number of gains
Signal to noise ratio
: < 3meters
: better than 13 kms
: 0.883
: 128 (7 bits)
:4
: > 128 (at saturation)
Step and Stare method
A new imaging method called Step and Stare method implemented first time
in this mission. In this method the ground trace is slowed down by changing the look
angle continuously and the along track resolution is improved..
Indian Remote Sensing Missions & Payloads – A glance
10-9
Figure 10.7 Step and Stare method of TES
Figure 10.8: Ground Projection of Detector
Indian Remote Sensing Missions & Payloads – A glance
10-10
Vidhana soudha
Majastic Bus Station
Indian Remote Sensing Missions & Payloads – A glance
10-11
Indian Remote Sensing Missions & Payloads – A glance
10-12
11 IRS-P6 (RESOURCESAT-1)
11.1 Introduction
IRS-P6 is the continuation of IRS-1C/1D missions with enhanced
capabilities. Panchromatic camera of IRS-1C/1D is improved to Multispectral by
using three 12 K detectors. The spatial resolution of AWIFS is improved to 56 m
from ~188m.
11.2 Mission Objective
Mission objectives of the IRS-P6 are as given below


To provide continued Remote Sensing data services on an operational basis
for integrated land and water resources management at micro level with
enhanced multi spectral/ spatial coverage and stereo imaging
To further carry out studies in advanced areas of User applications like
improved crop discrimination, crop yield, crop stress, pest/disease
surveillance, disaster management etc.
11.3 Orbit Details
The IRS-P6 is with payloads similar to the IRS-1C/1D. Choice of the orbit
is same as that of IRS-1C i.e Sun synchronous orbit at an altitude of 817 Kms
Table 11.1 Orbit details of IRS-P6
Sl.No
1
2
3
4
5
6
7
Parameter
Orbit
Altitude
Inclination
Eccentricity
Period
Local Time
Repetivity Cycle
8
9
10
Distance between adjacent Traces
Minimum Picture Overlap for LISS-3
Off Nadir coverage +/- 26 deg (for
PAN)
Distance between successive Ground
tracks
11
IRS-P6
Polar sun synchronous circular
817 Km
98.69 deg
0.0004
101.35 minutes
10.30 A.M
24 Days (For LISS-3)
5 Days (for AWiFS)
5 Days (for LISS-4 revisit)
117.5 Km
22.5 Km
398 Km
2820 Km
Indian Remote Sensing Missions & Payloads – A glance
11-1
Sl.No
12
13
Parameter
Ground Trace velocity
Liss-4 Coverage with steering of + 26
Deg
IRS-P6
6.65 Km/s
+ 398 Km
11.4 Salient features of IRS-P6
The S/C mainframe is of IRS-1C/1D -P3 heritage. The S/C structure consists
of two modules, the main platform and the payload module. The main platform is
built around a central load bearing cylinder of 915 mm diameter and consists of four
vertical panels and two horizontal decks. The bottom of cylinder is attached to an
interface ring which interfaces with the launch vehicle. The vertical panels and the
horizontal decks carry various subsystem packages. Various attitude sensors, SPS
(Satellite Positioning System) and data transmitting antennas are mounted on the
outside surfaces of the equipment panels and the bottom deck. Two star trackers are
mounted with skewed orientation on the top deck. The payload module in turn is
comprised of a two-tier system, the payload module deck and the rotating deck. The
payload module deck accommodates LISS-3, AWIFS-A and AWIFS-B camera
modules.
Indian Remote Sensing Missions & Payloads – A glance
11-2
Table 11.2 Salient features of IRS-P6
Subsystem
Structure
Control
Thermal
Limits
Solar Panel
Mechanism
LISS-4
Solar Panel
Power
Battery
Power
Electronics
Telemetry
TTC
Telecommand
Data Handling
IRS-P6
Shear webs added to increase the frequency to
cater to PSLV launch. CFRP cylinder (370 mm
height 930 mm dia) for thermal isolation of
payload deck incorporated.
Temperature control is with passive techniques
using Paints, multilayer blankets, Optical solar
Reflector, and active thermal elements like
heaters also. Heat pipe radiator panel is used to
maintain the temperature of LISS-4 detector
head assembly.
All electronics packages 0-40oC,
Battery 0-10oC,
Payload EO modules : 17 to 23oC
Solar panel deployment mechanism and Drive
Mechanism
Deployment and steering mechanism for the
LISS-4 Payload to cover +/- 26 deg. w.r.t. roll .
Sun tracking, rigid,15.12 M2 6 panels 1.4 x 1.8
m2 (Each),
1250 W at EOL, BSR(SCA)
2 batteries, 28 to 42V, 28 Cells, Ni-Cd 24 AH
PWM TCR, FCL, 10 Strings
1024 words/frame, , storage: 6.29 x 106 Bits
PCM/PSK/PM, 16 Kbps
PCM/FSK/FM/PM,.
The payload data are transmitted in X-band at a
data rate of 105 Mbit/s. The BDH (Baseband
Data Handling) system consists of two separate
chains, one for LISS-3 and AWiFS data, and the
second chain for LISS-4 data. The LISS-4 data
Indian Remote Sensing Missions & Payloads – A glance
11-3
Subsystem
IRS-P6
are transmitted on carrier-1 and LISS-3 +
AWiFS data are transmitted on carrier-2
Data
Transmission
40 watts TWTA used. 105 MBPS data Handling
system
Pointing Accuracies: Yaw: + 0.05o Roll: +
0.05o Pitch: + 0.05o (3 sigma)
Drift rate : 5 x 10-4 deg/sec (3 sigma)
Earth sensor(1), DSS(2), Star Sensors(2), 4Pi
SS(4), Magnetometer (2) IRU(3 DTG), SPS(2)
Reaction Wheels, 5 NMS(4 in tetrahedral),
Magnetic Torquers ( 2) , 1N Thrusters(8) 11 N
Thruster(4) Fuel (100 Kg)
Improved SADA used to increase the torque
margin
Hardwired system as a back up only for micro
processor based linear controller. Improved KF
used
LISS-III, PAN and AWiFS
1360 Kg
Spec.
Sensors
AOCS
Actuators
SADA
AOCE
Payloads
Mass
11.5 Payload
Resourcesat-1 carries three payloads. They are



A high resolution linear imaging self-scanner (LISS-IV)
A medium resolution linear imaging self-scanner (LISS-III)
AWiFS (Advanced Wide Field Sensor).
11.5.1 LISS-4 (Linear Imaging Self-Scanning Sensor-4)
The LISS-4 multispectral highresolution camera is the prime instrument.
LISS-4 is a three-band pushbroom camera
of LISS-3 heritage (same spectral VNIR
bands as LISS-3) with a spatial resolution of
5.8 m and a swath of 70 km. LISS-4 can be
operated in either of two support modes:
Multispectral (MS) mode: Data is
collected in 3 bands corresponding to preselected 4096 contiguous pixels with a
swath width of 23.9 km (selectable out of
70 km total swath). The 4 k detector strip
can be selected anywhere within the 12 k
Indian Remote Sensing Missions & Payloads – A glance
11-4
pixels by commanding the start pixel number using the electronic scanning scheme.
Mono mode: Data of the full 12 k pixels of any one single selected band,
corresponding to a swath of 70 km, can be transmitted. Nominally, band-3 data (B3)
are being observed and transmitted in this mode.
LISS-4 has ±26º steering capability in the cross-track direction which
provides a 5-day revisit cycle. The optoelectronic module of LISS-4 is identical to
that of the PAN camera of IRS-1C/1D. The CCD array features 12,288 elements for
each band. The instrument has a mass of 169.5 kg, power of 216 W, and a data rate
of 105 Mbit/s. The detector temperature control is implemented using a radiator plate
coupled to each band CCD through heat pipes and copper braid strips.
The LISS-4 camera is realized using the three mirror reflective telescope
optics (same as that of the PAN camera of IRS-1C/1D) and 12,288 pixels linear array
CCDs with each pixel of the size 7 µm x 7 µm. Three such CCDs are placed in the
focal plane of the telescope along with their individual spectral bandpass filters. An
optical arrangement comprising an isosceles prism is employed to split the beam into
three imaging fields which are separated in along track direction. The projection of
this separation on ground translates into a distance of 14.2 km between the B2 and
B4 image lines. While B3 is looking at nadir, B2 is looking ahead and B4 is looking
behind in the direction of velocity vector. Detector type: THX31543A of Thomson.
Figure 11.1 LISS-4 Payload
Figure 11.2 Optical Schematic of LISS-4
Schematic
LISS-4 calibration: An in-flight calibration scheme is implemented using
LEDs (Light Emitting Diodes). Eight LEDs positioned in front of the CCD (without
obstructing the light path during imaging). These LEDs are driven with a constant
current and the integration time is varied to get 16 exposure levels, covering the
dynamic range in a sequential manner. This sequence repeats in a cyclic form.
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11-5
Figure 11.3 Possible Image coverage due to Steering of LISS-3
11.5.2 LISS-3 (Linear Imaging Self-Scanning Sensor-3):
LISS-3 is a medium-resolution multispectral camera. The pushbroom
instrument is identical to LISS-3 on IRS-1C/1D (with regard to lens modules,
detectors, and electronics) in the three VNIR bands, each with a spatial resolution of
23.5 m. The resolution of the SWIR band is now also of 23.5 m on a swath of 140
km. The optics design and the detector of the SWIR band are modified to suit the
required resolution; B5 uses a 6,000 element Indium Gallium Arsenide CCD with a
pixel size of 13 µm. The SWIR CCD is a new device employing a CMOS readout
technique for each pixel, thereby improving noise performance. The VNIR CCD
array features 6,000 elements for each band. The instrument has a mass of 106.1 kg, a
power consumption of 70 W, and a data rate of 52.5 Mbit/s.
Indian Remote Sensing Missions & Payloads – A glance
11-6
Figure 11.4 LISS III Payload
The in-flight calibration of the LISS-3 camera is carried out using 4 LEDs
per CCD in the VNIR bands and 6 LEDs for the SWIR band. These LEDs are
operated in pulsed mode and the pulse duration during which these LEDs are ON is
varied in specific steps. Each LED has a cylindrical lens to distribute the light
intensity onto the CCD. Each calibration cycle consists of 2048 lines providing six
non zero intensity levels.
11.5.3 AWiFS (Advanced Wide Field Sensor):
AWiFS is a wide-angle medium resolution (56 m) camera with a swath of
740 km (FOV=±25º) of WiFS
heritage.
The
pushbroom
instrument operates in three
spectral bands which are
identical to two VNIR bands
(0.62 - 0.68 µm, 0.77 - 0.86
µm) and the SWIR band (1.551.70 µm) of the LISS-3
camera. The AWiFS camera is
realized using two separate
optoelectronic modules which
are tilted by 11.94º with respect
to nadir. Each module covers a
swath of 370 km providing a
combined swath of 740 km with a side lap between them. The wide swath coverage
enables AWiFS to provide a five-day repeat capability. The optoelectronic modules
Indian Remote Sensing Missions & Payloads – A glance
11-7
contain refractive imaging optics along with band pass interference filter, a neutral
density filter and a 6000 pixels linear array CCD detector for each spectral band.
The in-flight calibration is implemented using 6 LEDs in front of each CCD.
For the VNIR bands (B2, B3, B4), the calibration is a progressively increasing
sequence of 16 intensity levels through exposure control. For the SWIR band, the
calibration sequence is similar to that of LISS-3 through a repetitive cycle of 2048
scan lines.
Table 11.3 Summary of the IRS-P6 instrument parameters
Parameter/Instrument
Spatial resolution or IFOV
(Instantaneous Field of View)
Spectral bands (µm)
Swath width
Detector line arrays x No of
elements
Data quantization
Square wave
Nyquist
response
Power consumption
Instrument mass
Date rate
at
LISS-4
5.8 m
LISS-3
23.5 m
B2: 0.52-0.59,
(green)
B3: 0.62-0.68,
(red)
B4: 0.77-0.86
(NIR)
B2: 0.52-0.59,
(green)
B3: 0.62-0.68,
(red)
B4: 0.77-0.86,
(NIR)
B5: 1.55-1.70
(SWIR)
141 km
AWiFS
56 m (nadir)
(70 m a swath
edge)
B2: 0.52-0.59,
(green)
B3: 0.62-0.68,
(red)
B4: 0.77-0.86,
(NIR)
B5: 1.55-1.70
(SWIR)
740 km
4 x 6,000
4 x 2 x 6,000
7 bit (VNIR),
10 bit (SWIR)
10 bit
216 W
169.5 kg
B2> 0.40, B3>
0.40
B4> 0.35, B5>
0.20
70 W
106.1 kg
B2> 0.40, B3>
0.40
B4> 0.35, B5>
0.20
114 W
103.6 kg
105 Mbit/s
52.5 Mbit/s
52.5 Mbit/s
23.9 km in MS
mode
70 km in PAN
mode
1 x 12,288 PAN
mode
3 x 12,288 MS
mode
10 bit (selected 7
bit are provided to
the data handling
system)
> 0.20
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11-8
Figure 11.5 IRS-6 Three tier imaging and swath coverage
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Indian Remote Sensing Missions & Payloads – A glance
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IRS-P6 IMAGERY, BANGALORE LISS-4, MONO, & LISS-3 MERGED
Indian Remote Sensing Missions & Payloads – A glance
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IRS-P6 IMAGERY SHARJAH
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Indian Remote Sensing Missions & Payloads – A glance
11-14
12 IRS-P5 (CARTOSAT-1)
12.1 Introduction
IRS-P5 is a first spacecraft designed to acquire stereoscopic Imageries. The
objectives of the IRS-P5 mission are directed at geo-engineering (mapping)
applications, calling for high-resolution panchromatic imagery with high pointing
accuracies. The spacecraft features two high-resolution panchromatic cameras for inflight stereo imaging. Hence, IRS-P5 is also referred to as Cartosat-1. The data
products are intended to be used in DTM (Digital Terrain Model)/DEM (Digital
Elevation Model) generation in such applications as cadastral mapping and updating,
land use as well as other GIS applications.
12.2 Mission Objective
Followig are the mission objectives


To design and develop an advanced 3-axis body stabilised remote senisng
satellite for providing the enhanced spatial resolution (better than 2.5 m) with
stereo imaging capability for the cartographic applications.
To further stimulate new areas of user applications in the areas of cartographic
applications; urban management; disaster assesment, relief planning and
management; environmental assesment and other GIS applications.
12.3 Orbit Details
In selection orbit following factors were considered.
 A marching orbit
 Early revisit of adjacent path
 A faster revisit to cover the region of interest
Two orbits were selected for envisage two different operation modes called
stereoscopic image mode and wide swath mode.
Table 12.1 Orbit Details of IRS-P5
Parameter
Altitude (Km)
Orbit
Semi Major Axis (Km)
Inclination (deg)
Orbital Period (min)
Stereoscopic Mode
~618
Polar sun synchronous
Orbit
6996.14
97.87
97.1826
Indian Remote Sensing Missions & Payloads – A glance
Wide swath Mode
~618
Polar sun synchronous
Orbit
6996.14
97.87
97.1826
12-1
Parameter
Equatorial crossing time
Cycle Time
Orbits in cycle
Launch Vehicle
Stereoscopic Mode
10.30 AM
126 days
1867
Wide swath Mode
10.30 AM
131 Days
1941
PSLV-C6
12.4 Salient Features of Spacecraft:
The spacecraft structure is of IRS-P6 heritage, having a size of about 2.4 m x
2.7 m (height). The structure of the spacecraft consists of the MPL (Main Platform)
and the PPL (Payload Platform). The MPL consists of main cylinder assembly, four
vertical panels, top deck and bottom deck. The cylinder assembly comprises of a
central load bearing cylinder, satellite interface ring and top ring. The top ring of the
cylinder interfaces with the top deck. The PPL consist of a CFRP cone, PPL deck,
wedges for camera mounting, bracket to mount the payload electronic package near
to the Detector Head assembly, and star sensor mounting wedge. The CFRP interface
cone isolates the PPL Deck and the MPL. The two cameras are encompassed within a
thermal cover assembly with two hoods and anchored to the PPL deck
AOCS (Attitude and Orbit Control Subsystem): The platform is three-axis
stabilized (star sensors in loop, magnetic bearing reaction wheels in tetrahedral
configuration, 16 nozzles with 1 N thrusters, 4 nozzles with 11 N thrusters). The
pointing accuracies are ±0.05º in all axes, attitude knowledge = 0.01º, the stability
(attitude drift) is 5 x 10-5 º/s, and the ground location accuracy is < 220 m. The S/C
provides a body-pointing capability in the cross-track direction to facilitate a better
observation coverage of points of interest, the FOR (Field of Regard) is ±26º. The
AOCS employs a MIL-STD 31750 processor.
A power of about 1.1 kW (EOL) is provided. The power subsystem of
Cartosat-1 consists of six deployable solar panels, with three panels in each wing
(sun side and anti sun side), each panel of size 1.4 m x 1.8 m. A SADA (Solar Array
Drive Assembly) is employed for maximum power tracking. Two NiCd batteries,
each of 24 Ah capacity, provide power during the eclipse phases of the orbit. The
power bus is formed by ohmic interconnection of solar array strings (current source)
and battery (voltage source). There are two raw bus lines called Bus-A and Bus-B.
The raw bus is essentially the battery whose voltage ranges from 28 - 42 V. Bus
control is by PWM based TCR (Taper Charge Regulator).
RCS (Reaction Control Subsystem): The RCS of Cartosat-1 is a
monopropellant hydrazine system using nitrogen as pressurant and operating in a
blow-down mode. The RCS is used for correcting the satellite injection errors in
attitude and inclination, attitude acquisition and maintenance of the desired sun
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synchronous orbit. Eight nozzles of 1 N and four 11 N thrusters are mounted on the
bottom deck.
The Thermal control subsystem maintains the temperature of different
subsystems within the specified limits using semi-active and active thermal control
elements like paints, MLI (Multi Layer Insulation) blankets, optical solar reflectors
and auto-temperature controllers All the surfaces of PAN cameras are thermally
treated with black paint. All MFD (Mirror Fixing Devices) are provided with black
tapes. The payload CCD cold finger is connected to heat pipe by a copper braid. Each
CCD has one heat pipe which runs over the thermal cover and gets attached to the
sun side radiator plate and anti-sun side radiator plate respectively.
12.1. IRS-P5 Viewed from EP-01 side
12.2 IRS-P5 Viewed from EP-03 side
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12-3
Table 12.2
Subsystem
Structure
Control
Thermal
Limits
Mechanism
Solar Panel
Solar Panel
Power
Battery
Power
Electronics
Telemetry
TTC
Telecommand
Data Handling
Data
Transmission
BDH
SSR
Spec.
AOCS
Sensors
Salient features of IRS-P5
IRS-P5
Cuboid,
Aluminum aluminum Honeycomb
structure, Payload support structure with CFRP to
separate payload platform from main bus
Temperature control is with passive techniques
using Paints, multilayer blankets, Optical solar
Reflector, and active thermal elements like
heaters also. Heat pipe radiator panel is used to
maintain the temperature of LISS-4 detector head
assembly.
All electronics packages 0-40oC,
Battery 0-10 oC ,
Payload EO modules : 17 to 23oC
Solar panel deployment mechanism and Drive
Mechanism
SADA with microstepping
Rigid, deployable, Sun tracking, CFRP Faceskin,
15.12 M2 , 6 panels 1.4 x 1.8 m2 (Each), 58.8 Kg,
50 mic. Kaptan insulator, 133 cells in series, 35 in
parallel 8 string.
1020 W at EOL, BSR
2 batteries, 28 to 42V, 28 Cells, Ni-Cd 24 AH
2 buses, PWM TCR, FCL, 8 Strings
1024 bits, storage: 6.29 x 106 Bits PCM/PSK/PM,
16 Kbps
PCM/FSK/FM/PM,
The payload data are transmitted in X-band at a
data rate of 105 Mbit/s. The BDH (Baseband Data
Handling) system consists of two separate chains,
one for LISS-3 and AWiFS data, and the second
chain for LISS-4 data. The LISS-4 data are
transmitted on carrier-1 and LISS-3 + AWiFS
data are transmitted on carrier-2
X-Band, PCM/QPSK, 2 carriers, data rate: 2 x
52.5 Mbps/carrier
PAA( 64 elements) RHCP
JPEG like compression(3.2:1)
120 Gbit(EOL),
Pointing Accuracies: Yaw: + 0.05o Roll: + 0.05o
Pitch: + 0.05o (3 sigma)
Driftrate : 5 x 10-5 deg/sec (3 sigma)
Earth sensor(1), DSS(2), Star Sensors(1 Indian, 1
imported)), 4Pi SS(4), Magnetometer (2), IRU(3
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Subsystem
IRS-P5
Actuators
AOCE
Payloads
Mass
DTG), SPS
Reaction Wheels 5 NMS(4 in tetrahedral),
Magnetic Torquers (2) , 1N Thrusters(8) 11 N
Thruster(4) Fuel (131 Kg) Dry Mass(36 Kg)
Hardwired system as a back up only for
microprocessor based linear controller.
PAN Aft, PAN Fore mass(250 Each)
1560 Kg
12.5 Payload
The payload instrumentation consists of two panchromatic cameras of PAN
heritage as flown on the IRS-1C/D satellites. The objective is to obtain fore-aft stereo
imagery with two fixed (body-mounted) instruments (i.e., a two-line stereo
configuration). They are mounted with a tilt of + 26 deg. (Fore) -5 deg (Aft) from
yaw axis in Yaw roll plane. Both cameras are identical in optical electrical and
mechanical design. It also has off-nadir capacity up to + 22 deg by providing roll
biasing in the orbit ref. frame. The discrimination of elevation differences of better
than 5 m make the data particularly suitable for map-making and terrain modeling
12.5.1 PAN-F
(Panchromatic Forward-pointing Camera) featuring a fixed forward tilt of
26º.
12.5.2 PAN-A
(Panchromatic Aft-pointing Camera), it is fixed at an aft tilt of -5º.
Each camera provides a spectral range of 0.5 - 0.85 µm, a spatial resolution
of 2.5 m, a swath width of 30 km, and data quantization of 10 bits. Stereo imagery is
acquired with a small time difference (about 50 s) due to the forward and backward
look angles of the two cameras. The major change in imaging conditions during this
time period is due to rotation of Earth. An algorithm for Earth rotation compensation
is being used to eliminate the delayed observations of the two cameras.
Table 12.3
Features of IRS-P5 Payload
Parameter
PAN-F Camera
Spectral range
Along-track tilt angle with respect to nadir
Spatial resolution (cross-track x along-track)
500 - 850 nm
+26º
2.5 m x 2.78 m
PAN-A
Camera
-5º
2.22 m x 2.23
m
Radiometric resolution
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Parameter
PAN-F Camera
a) saturation radiance
b) data quantization
c) SNR
Swath width (for stereo imagery)
55 mW/(cm2 sr µm)
10 bit
345 at saturation radiance
29.42 km
26.24 km
Swath width (for monoscopic observation
mode)
CCD array (No of arrays x No of elements)
Detector element size
Optics:
Telescope aperture diameter
No of mirrors
Effective focal length
F number
FOV (Field of View)
Integration time
Detector
Quantization
SWR @ nyquist frequency
SNR Signal To Noise Ratio
MTF (Modulation Transfer Function)
Onboard calibration
Data compression
55 km (with swath overlaps)
Data rate
Nominal B/H ratio for stereo
Power
Mass
1 x 12,288
7 µm x 7 µm
PAN-A
Camera
1 x 12,288
7 µm x 7 µm
50 cm
3
1945 mm
f/4
±1.08º
0.336 ms
12 K CCD
10 Bits
>0.20
>256
cross-track = 20, along-track = 23
Relative, using LEDs
JPEG algorithm, compression ratio
= 3.2:1 (max)
105 Mbit/s (source data rate of 340
Mbit/s)
0.62
110 W (Per Camera)
< 250 Kg (Per Camera)
Payload consists of
 Electro optical module
 Payload Electronics
 Power Electronics
12.5.2.1 Electro-optical Module
Each optical module consists of axis three mirror optical system and detector
Head assembly consisting of 12K CCD, spectral Band filter and calibration LED
Optical system
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12-6
The optical system is extended version of the panchromatic camera of IRS1C/1D. i.e un-obscured off-axis reflective system. The focal length of the system is
1945 mm and the FOV is +1.3 deg across track and + 0.2 deg in along track. The
optical system of each PAN camera is designed with a three-mirror off-axis reflective
telescope with an off-axis concave hyperboloidal primary mirror, convex spherical
secondary mirror and an off-axis concave ellipsoidal tertiary mirror - to meet the
required resolution and swath width.
The mirrors are made from special Zerodur glass blanks. The mirrors are
polished to an accuracy of lambda/80 and are coated with enhanced AlO2coating. The
mirrors are mounted to the electro-optical module using iso-static mounts, so that the
distortion on the light weighted mirrors are reduced to a minimum.
Interference spectral filter
Shape
Dimension
Coated area
: Rectangular
: 115 x 20 x 6 mm3
: 110 x 18 mm2
Figure 12.3 Optical schematic of IRS-P5 PAN
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12-7
Figure 12.4 Electro optical Module of IRS-P5 Camera
Figure 12.5 PAN camera under testing
12.5.2.2 Detector Head Assembly
Each camera has separate DHA. The Detector is a linear CCD detector
array of 12,288 pixels which is mounted in a DHA.
The DHA Consists of DHA Housing, 12K Linear CCD, CCD Holder, 16
LEDs per CCD, LED Holder, Interference Spectral Filter, cold finger, Bias voltage
generating circuits, clock driver circuits and Thermal control systems.
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12-8
Figure 12.6 Detector Head Assembly
12.5.2.3 Detector
Each DHA uses 12 K element linear CCD Thomson make (THX31543A)
with a pixel size of 7 micron x 7 micron staggered by 35 microns. Silicon is used as
photo sensitive element which is sensitive upto 1.1 micron. The detector provides
video data on 8 ports 4 ports for odd pixel and 4 ports for even pixels. Each port
provides video data for 1520 pixels including 20 prescan pixels.
Indian Remote Sensing Missions & Payloads – A glance
12-9
Figure 12.7: Staggered arrangement of pixels in 12 K CCD
Figure 12.8 12K CCD Architecture
Wide Swath by attitude
changes
Figure 12.9: Schematic of imaging modes of IRS-P5
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12-10
Figure 12.10: Along-track imaging geometry of the CartoSat-1 fore- and aftviewing cameras
The imagery of the 2-line along-track stereo camera may be used for a
variety of applications, among them for the generation of DEMs (Digital Elevation
Models). The data is expected to provide enhanced inputs for large scale mapping
applications and stimulate newer applications in the urban and rural development.
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12-11
FRONT view
Rear view
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Indian Remote Sensing Missions & Payloads – A glance
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13 CARTOSAT-2/2A/2B
13.1 Introduction
The Cartosat-2 series is a set of high resolution agile satellites with less
inertia. This satellite is used to acquire spot images and strip images up to 200 km.
The various type of image pattern possible is provide in the figure 13.4
13.2 Mission Objective
The main objectives of the Cartosat-2 mission are –


To design and develop a high agility advanced satellite with a high spatial
resolution of around 1.0 m in panchromatic band with an operational life of 5
years and mission reliability of 0.75.
To meet the ever – increasing user demands for cartographic applications at
cadastral level urban and rural management, coastal land use and regulation,
utilities mapping and development and various other GIS applications.
13.3 Orbit Details
Table 13.1: Orbit details of Cartosat-2/2A/2B
Parameters
Altitude (Km)
Semi Major Axis (Km)
Eccentricity
Inclination (Deg)
Argument Of
Perigee(Deg)
Local Time
Revisit (Days)
Repetivity
Orbits/day
Period(min)
Nominal
Recurrent
630.6
7008.6
9.999 E-004
97.914
90
560
6938.1
9 .30 A.M
4
310 days
14.
97.446
9.30 AM
1
1
15
96
Indian Remote Sensing Missions & Payloads – A glance
97.91
87.19
13-1
13.4 Salient features of Spacecraft
Table 13.2: Salient features of Cartosat-2/2A/2B
Parameter
Structure
Thermal
Components
Temp. Range
Mechanism
DGA Drive
Solar Array
Deployment
Power
Solar Array
Battery
Electronics
Telemetry
Communication
Telecommand
Tracking
BMU
(AOCE+TM/TC)
Attitude/Orbit
sensors
Attitude control
Cartosat-2/2A/2B
Hexagon shaped Aluminum and aluminum
honeycomb structure
Passive control using tapes , OSR, MLI
Blankets and semi-active/active control using
proportionate temperature controller and
heaters, Detector cooling via heatpipe
20+5 deg.C range for imaging sensors
electro-optics
5+5 deg. C for Chemical Batteries
0 to 40 deg.C for electronic packages
Dual Gimbal antenna hold down and drive
mechanism.
Solar arrays deployment is done by solar
array hold down and deployment
mechanism.
Four (2+2), 4.64 m2 (1.45m x 0.8 m each),
Rigid deployable panels, without SADA,
Sun pointing. 23 cells(Triple junction) series,
60 in parallel 9 strings.
1200 W @ EOL
42V, SAFT, NiCd, 18 AH, 2 Batteries, 28
cells in series
Modularized distribution Package, Mother
Board-daughter Board control Package.
S-Band; HK Real Time rate 4 Kbps;
PB/SPS/Star sensor Data : 16 Kbps, Dwell
data : 4Kbps
S-Band : 4 Kbps
Facility for ON/OFF and Data commands
S-Band tone ranging and two way Doppler
X-band beacon
Star sensor(2), 4 PI sun sensors(4),
Dynamically Tuned Gyros (DTG)(3),
Magnetometers(2), SPS for orbit
determination)
15 NMS, 0.3 Nm RW (4) mounted in
tetrahedral configuration, Magnetic
torquers(3), Hydrazine thrusters(8 one
Newton) 63 Kg Fuel
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Orbit Control
OrbitDetermination
accuracy
Attitude
Determination
Accuracy
Data Handling
Payload
Panchromatic
Mass
Bus
Payload
Monopropellant hydrazine thrusters
<40 meters
40 Arc sec along bore sight of Star Sensor
10 Arc sec across bore sight
105 Mbps ;
QPSK; X band
~1 m resolution ;
RC type optics
C2:678.Kg (Bus+ Payload)
Payload:119.5 Kg
13.5 Payload
13.5.1 Panchromatic camera
Optical system is a modified RC system consisting of two-mirror RC type
telescope, three lenses, a window and a band pass filter. Field correcting optics
consisting three lens elements is used to correct the aberrations at the larger field of
view (+/- 0.5 deg.) and also to flatten the image. A band pass filter placed close to
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13-3
the CCD defines the band shape. The camera operates in the spectral band of 0.5 –
0.8 m using 12000 elements CCD array. The CCD covers a swath of about 9.6 km.
The two CCDs are located within the focal plane along with band pass filters
and calibration system using LEDs. Two independent chains of Camera Electronics
are planned to cater to two CCDs.
13.5.1.1 Panchromatic camera specifications:
Camera
Resolution
Swath
Spectral Band
Detector
Optics Type
Optics
Spectral Band
FOV
Size of The Primary Mirror
Size of The Secondary Mirror
CCD
No. Of Pixels /Detector
Pixel Size
No. Of Output Ports / Detector
System
IGFOV
Integration time
Radiometric Quantization
Quantization Levels
SNR (at saturation)
55 Mw/Sr/µM
10 Mw/Sr/µM
Camera Size
Camera Weight
Power
: ~1m
: ~9.6 Km
: 0.5 to 0.8 M
: 12 K Linear Array CCD
: RC type
: F/8, 5.6m Focal Length
: 0.5 To 0.85 m
: + 0.43 Across track)
+ 0.2 (along Track)
: 700mm
: 199mm
: 12000
: 7 m X 7m
:8
: ~1 M (for non- tilt conditions)
: 366µsec
: 10 bits
: 1024 (for 10 bits)
: 180
: 80
: 760mm (dia) X 1600mm (height)
: ~ 120 Kg
: < 60 W
13.5.1.2 Payload Configuration
The payload consists of a Telescope-having an obscured two-mirror system
with field correcting optics, two CCDs located within the focal plane along with the
band pass filters and calibration system using LEDs. The payload is a single
panchromatic camera (0.5 to 0.8 microns) with a spatial resolution of around 1m and
swath of 9.6 km. Two CCD’s – One main and one redt. have been provided. The
main CCD interfaces with the BDH (M) and RF (M), while the redt. CCD interfaces
with BDH (R) and RF (R). The camera is mounted on a highly agile platform
Indian Remote Sensing Missions & Payloads – A glance
13-4
capable of being steered across and along the track to provide spot imageries of the
desired locations.
The camera system requirements are as follows:
Provide images with ground projection of better than 1 m in panchromatic
band.
Provide swath of about 10 Km.
Cover 100% albedo for an observation time of around 09.30 AM
Configuration shall have low moment of Inertia.
Two independent chains of Camera electronics to cater to two CCDs and are
planned to be located close to the detector. The CCDs are mounted in two identical
DHAs (Detector Head Assembly) and are configured to have cold redundancy and
one of them will be ON at a time.
Each DHA consists of:





12 K Linear array CCD.
Bias voltage generating circuits
Clock driver circuits
LEDs for onboard calibration
Heaters and thermistors for thermal control.
Indian Remote Sensing Missions & Payloads – A glance
13-5
13.5.1.3 Detector
Detector is a 12 K element linear charge coupled device THX31543A with a
pixel size of 7 µ x 7µ staggered by 35 µ. It provides video data on 8 ports; four
ports for odd pixels and four ports for even pixels. Each port provides video data for
1520 pixels including 20 pre-scan cells. CCD has anti blooming & integration control
facilities the Integration time selected is 366 µs.
Figure 13.1
12K CCD architecture
13.5.1.4 CCD Drive
CCD requires a total of 20 bias voltage lines for its operation. These are
generated using the series regulators with an input supply of 18 V.CCD needs a total
of 20 clocks for operation. DHA receives clock signals at TTL level from timing and
control logic circuits and are conditioned to suitable voltage levels to drive the
required loads of CCD.
13.5.1.5 Calibration:
There is provision for in-flight calibration. Total eight LEDs are provided in
each DHA as two sets of four LEDs in series.
13.5.1.6 Heaters and thermistors for CCD temp control
CCD temperature variation is required to be controlled to a narrow range of
about 20 + 2 deg. C to minimise the impact of photo response variation on
radiometer. The heaters are put ON whenever CCD is OFF to minimise temperature
variation near the CCD. These heaters are mounted on cold fingers. DHA also
Indian Remote Sensing Missions & Payloads – A glance
13-6
requires to maintained at a nominal setting of 20 deg. C and control range of + 2 deg.
C; for this DHA requires to be cooled. This is achieved by attaching copper braids to
the cold finger used for holding the CCD. The copper braid in turn is attached to
radiator plate through heat pipes. There are control heaters along with controller to
maintain the DHA at 20 + 2 deg.
13.5.1.7 Camera electronics:
The camera electronics consists of:
Port wise video processing chain
Timing and control logic
Exposure control logic for imaging and calibration modes
Clock distribution circuit
Calibration drivers.
Camera electronics provides necessary clocks for detector operation and
constant current for calibration LEDs. It receives video signal from detector,
processes and digitises it, extract true video and provide it to BDH subsystem for
further processing. Fig: 3.1.6 Shows the Block Schematic of Camera Electronics.
13.5.1.8 Video Processor
It receives analog video from DHA, amplifies the signal, restricts the
bandwidth, and extracts digitised data corresponding to true video by converting
analog data. After processing the data it transmits the same to the Base Band Data
Handling System.
The major specification of Video Processor is given below:
Signal Type
DC Offset
Signal Range (mV)
Total number of pixels to be read/port
Pixel Duration (ns)
Video Time
Settled Video time(ns)
Settled reference time (ns)
Detector output impedence
Terminating resistor at VP end (ohm)
Cable Type
:
:
:
:
:
:
:
:
:
:
:
3 level PAM
11V typical
0 –138 mV
1536
238
119
51
42
220 + 5
274
RG 316
Output Specification:
Quantization
SNR
No. of gains
:
:
:
10-bit
>512
One
Indian Remote Sensing Missions & Payloads – A glance
13-7
Compatibility
:
LSTTL
13.5.1.9 Data Handling
The imaging modes/profiles are new this mission so as to use the imaging time
more efficiently with respect to the coverage.. The payload consists of two 12K
element linear CCDs. The video data is quantised to 10 bits. The total data rate per
ports of the CCD works out to be 336MBPS. The video data at this rate from the 8
ports of the CCD video processor electronics required to be formatted and
transmitted to the ground by DH system through the X-band carrier. The video data
is also to be suitably encrypted and additionally stored in a SSR for later playback
and transmission. CCD1 data is to be transmitted through the main DH chain and the
CCD2 data is to be transmitted through the redundant DH chain.
13.5.1.10 Data Interface Package
Data Interface Package receives eight ports of data each at 4.2 Mpixels/sec
from Payload Electronics. Each port data bus is 10 bits parallel. The JPEG like
compression system requires data in a 8x8 block form. There is also a requirement to
bypass the compression and transmit the original data in bypass.
Electrical Specifications
No. of input ports
Port data rate
Port data format
No. Of Pixels/Port
:
:
:
:
8 ( 4I + 4Q)
4.2M words/Sec
10 bit parallel
1504 (2 prescan+1500 Valid video+2 post
Integration time
Output data to DCS
:
:
~ 365.71μsec.
2 ports, LVDS, 10 bit parallel @ 17.5
Output data to BDH
Power
:
:
2 ports, TTL 10 bit parallel @ 5.25 MBPS
~ 10W
scan)
MBPS
The order in which video pixels of each port are coming out from payload is as
shown below:
Odd Ports
Port1: Prescan 19 &20,, Pixel#1, #3,……,#2997, #2999, post scans 1&2
Port2: Prescan 19 &20,Pixel#3001, #3003,……,#5997, #5999 post scans1&2
Port3: Prescan 19 &20,, Pixel#8999, #8997,……,#6003, #6001, post scans1&2
Port4: Prescan 19 &20, Pixel#11999, #11997,……,#9003, #9001, post scans1&2
Even Ports
Port5: Prescan 19 &20, Pixel#2, #4,……,#2998, #3000, post scans1&2
Port6: Prescan 19 &20, Pixel#3002, #3004,……,#5998, #6000, post scans1&2
Indian Remote Sensing Missions & Payloads – A glance
13-8
Port7: Prescan 19 &20,Pixel#9000, #8998,……,#6004, #6002, post scans1&2
Port8: Prescan 19 &20,Pixel#12000, #11998,……,#9004, #9002, post scans1&2
13.5.1.11 Imaging Pattern of Cartosat-2 satellites
The imaging modes of Cartosat-2 series employs step and stare method to get
required along track resolution. Based on the requirement different size imaging
strips are imaged.
Figure 13.2 Image pattern of Cartosat-2
Indian Remote Sensing Missions & Payloads – A glance
13-9
Indian Remote Sensing Missions & Payloads – A glance
13-10
14 IMS-1 (TWSAT)
14.1 Introduction
IMS-1 (earlier it was called as TWSAT) is the first micro satellite fabricated
for remote sensing application purpose.( Other microsatellites are Rohini, SROSS,
HAMSAT). These satellites can be launched mounted on the EB of PSLV with no
additional cost for launch. The redundant philosophy is not implemented in IMS-1
bus
14.2 Mission Objective
 To build, launch, and operate a 3 axis stabilized remote sensing micro
satellite for launch, onboard PSLV, as auxiliary satellite, providing easy
access of remote sensing data to the educational institutions, research
organizations, and government agencies in the developing countries. The
spacecraft bus is developed as a versatile Micro Satellite bus in order to
carry in future, a number of different payloads without significant changes in
the bus.
 To develop low cost user terminals that can be used by users in Universities
or Institutions of developing countries to receive the payload data.
 The Hyper-spectral imager being flown in Chandrayaan-1 is also being flown
in IMS-1 to evaluate and validate the payload.
14.3 Orbit Details
Altitude
Inclination
Orbit
Eccentricity
Local time
Orbits/day
Repeat cycle
Period
Path to Path separation
638 Km
97.94 º
Polar Sun Synchronous
0.001
09. 44 AM (descending node)
14
369 orbits in 25 days
97minutes
108.6 km
14.4 Salient Features of Spacecraft
Mechanical systems: IMS-1 is designed with Aluminum Honeycomb
sandwich panels as a Cuboid structure with a bottom deck, top deck and four cross
ribs in a staggered fashion connecting the top and bottom deck. This configuration
Indian Remote Sensing Missions & Payloads – A glance
14.1
generates a central core to house the fuel tank, thruster and plumbing while
transferring the loads effectively to the interface ring. Payloads are mounted on the
top deck.
The electronic packages are mounted
on the four cross ribs / cover panels for
mounting external appendages like antennas
etc, forming the cuboid. The structure is a
cuboid of size 552 x 600 x 600 mm. The
overall size of spacecraft with stowed solar
panel is 604 x 980 x 1129 (h) mm. IBL-298
interface ring interfaces with PSLV.
Thermal System: Thermal control is achieved
by passive means using semi-active elements
like paints, MLI, OSR and thermal tapes.
However, provision is made for heaters
wherever necessary. Thermistors, Platinum
Resistance
Temperature
sensors
and
Thermocouples are used for temperature
monitoring at required locations of IMS-1.
The temperature sensor data is processed in
BMU for heater control and telemetry to
ground.
Data Handling System: The Payload consists of 4 band multi-spectral CCD camera
(MxT) and 64 bands HYSI payload. Either MX data or HYSI data will be recorded
and transmitted at a time. The BDH consists of P/L interface unit, Data Compression,
RS coding and formatting unit. TheCompression ratio is 3.401:1 for MXT Payload
and no compression for HYSI P/L data. Compressed, RS encoded and formatted data
is stored in SSR @ 10.66Mbps and simultaneously played back @ 8 Mbps in
compression mode for MXT Payload. In compression bypass mode RS encoded,
formatted data is stored in SSR @ 32 Mbps and simultaneously played back @
8Mbps for MX. The transmission time required is 1.33 times (10.66Mbps / 8 Mbps)
the imaging time in compression mode for MX. The transmission time required is 4
(32 Mbps / 8 Mbps) times the imaging time in compression bypass mode for MX.
The playback data @ 8Mbps is differential encoded in BDH before transmission to
RF Transmitter. Data transmission is S band BPSK.
Solid State recorder: A Solid State Recorder of 16 GB is configured to meet the
mission requirement. The data from the payloads are formatted and a single stream is
Indian Remote Sensing Missions & Payloads – A glance
14.2
input to SSR. The basic operating modes of the SSR are Normal, Diagnostics, BER
or Self Test.
RF Systems: A standard S-band (RF) TTC system supported by global network of
ISTRAC will be used for Telemetry, Telecommand of IMS-1. To minimize the
transmitted power and bandwidth and thereby cost of user terminals, it is designed
that Payload and Telemetry data transmission as well as Telecommand reception are
in S-band. A single Telemetry / Data transmitter is used for TM (4Kbps) / Payload
data (8 Mbps). The transmitter will have RF output power of 5W for payload data
transmission and 100 mW for telemetry data transmission. The modulation scheme is
PCM / BPSK for both Payload and Telemetry. Payload data will be transmitted
through a separate data transmission antenna with higher gain (+3dBi) and telemetry
data will be transmitted through TTC antenna (0dBi). The common TM / DATA
transmitter output will be switched between the TTC antenna and DATA antenna
using a coaxial switch. A filter is used in the data transmission path to restrict the out
of band emission. IMS-1 also has on-board a miniature SPS which is used for
generating accurate position and velocity parameters used for onboard orbit
determination.
Power Systems: Power system is designed to meet the requirements of a
micro satellite. IMS-1 Power system supports a nominal load of 72W, peak load of
132W during MxT Payload and peak load of 120 W during HySi-T Payload
operation. Power system is based on a single bus of 28 – 33V. The solar array
consists of two wings, each having one panel of 0.810m x 0.720m. In order to meet
the higher specific power requirements, Triple Junction Solar cells are used for power
generation.. To meet the powering requirements of new packaging concept, involving
cards (instead of packages) for different subsystems, common DC / DC converters
are used. Additionally, a new centralized power switching and distribution scheme is
used for switching and distributing the outputs of DC/DCs & Raw Bus, to different
user systems. This reduces the total number of DC/DC converter requirements.
BMU & Attitude and Orbit control system: The Bus Management Unit
(BMU) executes the attitude and orbit control functions like TM, TC, and attitude
orientation and orbit maintenance of the spacecraft to the required accuracies. Apart
from this, the BMU does the 3-axis auto acquisition and control from the moment of
injection into the orbit and puts the spacecraft in safe mode sun pointing orientation
in the case of contingency.
The AOCS specifications are:
Pointing accuracy
: 0.1 deg (3)
Drift Rate
: 5.0 X 10-04 ° / sec.
Indian Remote Sensing Missions & Payloads – A glance
14.3
Four heads of 4  Sun sensor, a miniature tri-axial magnetometer, a single
head Star Sensor and Inertial Reference unit (2 DTGs) are used for attitude sensing.
In Magnetometer, for one axis, a MEMS sensor is used in place of conventional
sensor. There are four Micro Reaction Wheels with 0.36Nms angular momentum
arranged in tetrahedron configuration for attitude control and two magnetic torquers
of dipole moment of 9 Am2 along Roll and pitch axis used during detumbling. A
monopropellant Reaction control System comprising a fuel tank with 3.5 kg fuel and
one 1N thruster is planned for orbit correction.
Parameter
Structure
Thermal
Components
Temp. Range
Mechanism
Solar Panel
Power
Solar Array
Battery
Electronics
Telemetry/dat
a transmission
Communication
Telecommand
BMU
(AOCE+TM/TC)
Attitude/Orbit
sensors
IMS-1 (TWSAT)
Aluminum Honeycomb sandwich based Cuboid
structure with a bottom deck, top deck and four
cross ribs in a staggered fashion connecting the
top and bottom deck.
Passive control using tapes , OSR, MLI
Blankets and semi-active/active control using
proportionate temperature controller and heaters
20+5 deg.C range for imaging sensors electrooptics
0 to 40 deg.C for electronic packages
Paraffin based actuator for solar panel
deployment mechanism.
The solar array consists of two wings, each
having one panel of 0.810m x 0.720m. Multijunction cells, 206 watts @ the end of 2 years.
Nominal load :72W, peak load of 132W
Li-ion, 10.5 AH, 8S x 7P, one battery
Power system is based on a single bus of 28 –
33V.
A single Telemetry / Data transmitter is used for
TM (4Kbps) / Payload data (8 Mbps). The
transmitter will have RF output power of 5W
for payload data transmission and 100 mW for
telemetry data transmission.
The modulation scheme is PCM / BPSK for
both Payload and Telemetry
Modulation scheme is FM//FSK/PCM.
Star sensor(1), 4 PI sun sensors(4), Dynamically
Tuned Gyros (DTG)(2), Magnetometer, (Y)
Mems (R&P) normal, SPS for orbit
determination
Indian Remote Sensing Missions & Payloads – A glance
14.4
Attitude
control
0.36 NMS, 0.018 Nm RW (4) mounted in
tetrahedral configuration, Magnetic torquers(2),
Orbit Control
Hydrazine thrusters (1 one Newton) 3.5 Kg Fuel
MX, HYSI
87 kg
Payloads
Mass
14.5 Payloads:
Payload system consists of two Payloads, namely Multi Spectral Camera and
Hyper Spectral Camera
14.5.1 Multi Spectral Camera
The Mx-T is a four-band
multi spectral camera with
modular configuration having
individual
optics,
detector
assembly
and
Electronics
separately for each band. The four
bands selected for the instrument
are identical to the previous IRS
missions. The camera operates in a
push broom scanning mode to
image the earth. The Payload will
be used for the purpose of natural
resource
management
like
Agriculture, Forest coverage and deforestation, urban infrastructure development,
land use as well as disaster management.The major challenge in the design and
development of camera has been to minimize size, weight and power and realization
in shortest time.
14.5.1.1 Payload Configuration
The TWSAT camera is configured to be a highly compact, low weight
camera commensurate with the overall mission requirements of developing a low
cost and lightweight micro-satellite.
The camera, which operates in push broom mode, is multispectral with four
bands in the visible and near infra red (VNIR) spanning 0.45 microns to 0.86 micron.
The spectral bands, viz., Band 1 (0.45 to 0.52 micron), Band 2 (0.52 to 0.59 micron),
Band 3 (0.62 to 0.68 micron) and Band 4 (0.77 to 0.86 micron) are identical to the
Indian Remote Sensing Missions & Payloads – A glance
14.5
ones used in the previous IRS missions. The nominal ground resolution is 36.87
meters from an altitude of about 638 km.
All the four bands are nadir viewing with the linear detector array being used
to image the scene in across track direction of the satellite motion.
The TWSAT camera has a modular configuration with each of the four
spectral bands having its individual optics, detector and associated electronics.
14.5.1.2 Multi Spectral Camera Specifications
Ground Resolution
Altitude
Swath
Spectral Band
:
Integration time
Camera SWR (at Nyquist frequency)
(%) (TWSAT: 70lp/mm)
:
:
:
Saturation Radiance (mW/cm2/str/m) :
SNR (at Saturation radiance)
Quantization (bits)
Data Rate
No of ports
Detector
Pixels per port Active
Pixel size
Size
(EOM) mm
Camera Weight (kg)
Power (W)
:
:
:
:
:
:
:
:
:
:
36.87m
:
636.18 km
151 Km
B1 (0.45 – 0.52 m)
B2 (0.52 – 0.59 m)
B3 (0.62 – 0.68 m)
B4 (0.77 – 0.86m)
5.23 ms
:
B1: 20
B2: 20
B3: 20
B4: 10
B1:55
B2:53
B3:47
B4:31.5
>400
10
32 Mbps
4
4 K Elements Linear CCD
1024
7 x 7 Micron
300.2 x 151.7 x 227
5.905 kg
10.4W (Four Bands)
160 mA @ 5.6V (Single
Band)
90mA @ 18.7V (Single
Band)
14.5.1.3 Description

The major subsystems of the Mx-T payload are
Optics (Lens assemblies)

Detector Head Assemblies
Indian Remote Sensing Missions & Payloads – A glance
14.6

Camera Electronics

Mechanical System
Optics: The collecting optics for each of the spectral bands is an eightelement lens assembly with a thermal filter at the front and a band pass filter (to
select the respective spectral range) at the rear. The optics is f/5 operating at a spatial
frequency of 70 lp/mm over a field of view (fov) of ± 7 degrees.
The optical configuration consists of a multi-element lens assembly with a
thermal filter at the front and a band pass filter at the rear end. All the lens elements
have spherical surface profiles. The last element is a plane parallel glass window with
a band pass filter coating. The choice of two types of glass for elements ensures that
the focus does not change appreciably within operating temperature of 2010C.
Figure 14.1 Optical Schematic of Mx
14.5.1.4 Detector Head Assembly:
Each of the four bands has a separate and identical detector head assembly
(DHA), which essentially consists of a 4k linear array CCD (sc 3925a) with a pixel
size of 7 micron x 7 micron, a PCB and mechanical housing. The detector is
indigenously developed and qualified.
SC 3925A, 4096 elements 7X7 micron linear CCD, manufactured
indigenously by SCL, Chandigarh, is used.
At each output channel, signal corresponding to 16 dummy pixels (6
isolation pixels + 4 dark pixel + 6 isolation pixels) arrives first, followed by the
signal from sensitive 1024 pixels. After the 16 dummy pixel outputs, signal
Indian Remote Sensing Missions & Payloads – A glance
14.7
corresponding to end photosensitive pixels is delivered (pixel # 1 for Vos1, pixel #2 for
Vos2, pixel # 4095 for Vos3 and pixel # 4096 for Vos4). These output signals can be
processed to reconstruct the image.
All four bands have the same detector type. These devices have been source
screened and qualified by the manufacturer, the SCL.
14.5.2 Hyper Spectral Camera
Hyper spectral imager (HySI-T) is the other payload in TWSAT. The Hyperspectral imager being flown in Chandrayaan-1 is also being flown in TWSAT to
evaluate and validate the payload.
Inclusion
of
Hyperspectral imager in TWSAT will
enhance the mission capability.
The data from this instrument will
be useful for ocean and
atmospheric studies.
Hyper-spectral Imager is
already being developed for
Chandrayaan-1 using Lens, wedge
filter, active pixel detector,
miniaturized camera electronics
etc. Same configuration is used for
TWSAT hyper-spectral imager.
Necessary changes have been
carried out in camera electronics
FPGA logic design to match the TWSAT configuration and data rate. HySI-T will be
an independent chain in TWSAT. Considering the transmittable data rate limits and
power availability of spacecraft, it is planned to have either the multi-spectral or
hyper-spectral payload operation at a time.
14.5.2.1 Specifications
Spectral range
No of bands
Spectral separation
Ground track velocity
Spatial resolution
Along track sampling interval
Swath
Bandwidth
:
:
:
:
:
:
:
:
Indian Remote Sensing Missions & Payloads – A glance
400-950nm
64 fixed
8 nm
6.9302 Km/s
505.6m
543.6m
129.5Km
<15nm
14.8
MTF
SNR at saturation
No. of gains
No. of exposure settings
Clock input (BRC)
WLS period
Digitization
Data rate
Data type
Power
:
:
>0.2
:
>400 - 1500
:
1
:
8
:
16MHz
:
78.45ms
:
16 bit
:
4.0Mbps
:
16 bit serial
0.8W (176mA @ 3.8V, 25mA
@5.6V)
Weight
:
4 kg
14.5.2.2 Description




The major subsystems of the HySI-T payload are
Optics (Lens assemblies)
Detector Head Assemblies
Camera Electronics
Mechanical System
Optics: The collecting optics for HySI-T is a multi-element lens assembly
with a thermal filter at the front. Effective focal length and F/No. are 62.5mm and 4
respectively.
Detector: A custom built area array with 512 rows and 256 columns based
on active pixel technology with inbuilt 12 bit digitiser is used in HySI-T.
Spectral separation: Spectral separation is done using a wedge filter. The
wedge filter is an interference filter with varying thickness along one dimension so
that the spectral content transmitted through it varies in that direction. Thus when
placed in front of the area array, all pixels in a given row will receive irradiance from
same spectral (but different spatial) region. The pixels along a given column will
receive irradiance from different spectral as well as different spatial regions. This
arrangement of spectral dispersion results in spectral sampling at 1nm intervals and
bandwidth of 8 nm for each row at system level.
Camera Electronics: Camera Electronics is designed around area array
active pixel detector. It receives the 12 bit, 512 bands parallel data from detector.
These 512 bands of over sampled data is processed to 64 bands and given to Base
band data handling system. As the data is distributed in multiple integration times,
the data from detector is stored. Real time data storage is incorporated in camera
electronics.
Indian Remote Sensing Missions & Payloads – A glance
14.9
Mechanical System: Camera structure is designed to hold various
components like lens assembly, detector head assembly, hood etc. CE and power
supply are in separate trays which are stacked together and mounted behind the
camera.
Power System: HySI-T camera requires 3.8V and 5.6V power supplies and
is similar to HySI Chandrayaan-1. Detector is powered though a filter which is part
of power distribution system.
Figure 14.2 Spectral scanning and swath coverage of HySI
Indian Remote Sensing Missions & Payloads – A glance
14.10
15 CHANDRAYAAN-1
15.1 Introduction
Chandrayaan-1 is the first Indian planetary exploration mission that
performed remote sensing observation of the Moon to enhance our understanding
about its origin and evolution. Chandrayaan-1 was launched successfully on October
22, 2008 from SDSC SHAR, Sriharikota. The spacecraft was orbiting around the
Moon at a height of 100 km from the lunar surface for chemical, mineralogical and
photo-geologic mapping of the Moon. The spacecraft carries 11 scientific instruments
built in India, USA, UK, Germany, Sweden and Bulgaria.
After the successful completion of all the major mission objectives, the orbit
has been raised to 200 km during May 2009.
15.2 Mission Objectives
Mission Objectives of Chandrayaan-1 are as follows


To realise the mission goal of harnessing the science payloads, lunar
craft and the launch vehicle with suitable ground support systems
including Deep Space Network station.
To realise the integration and testing, launching and achieving lunar
polar orbit of about 100 km, in-orbit operation of experiments,
communication/ telecommand, telemetry data reception, quick look
data and archival for scientific investigation by identified group of
scientists.
15.3 Orbit Details
Chandrayaan-1 Mission sequence and Final orbit are shown in following
picture
Table 15.1 Orbit Details
Mission
Orbit
Launch Date
Weight
Launch Site
Launch Vehicle
Remote Sensing, Planetary Science
100 km x 100 km : Lunar Orbit
22 October 2008
1380 kg (Mass at lift off)
SDSC, SHAR, Sriharikota
PSLV - C11
Indian Remote Sensing Missions & Payloads – A glance
15.1
15.4 Salient features of Satellite
The spacecraft design is
adopted from flight proven Indian
Remote Sensing Satellite bus
coupled with suitable modifications
specific to the lunar mission. Apart
from the solar array, TTC and data
transmission, that are specific to the
lunar mission, other aspects of
system design have flight heritage.
However, some changes specific to
lunar mission is also incorporated.
These include extending the thrust
cylinder and having an upper
payload deck to accommodate Moon Impact Probe(MIP) and few other payloads.
Additionally, Chandrayaan-1 had a canted solar array since the orbit around the
Moon is inertially fixed resulting in large variation in solar incidence angle. There is
a need to have a gimbaled high gain antenna system for downloading the payload
data to the Indian Deep Space Network (IDSN).
The spacecraft is a cuboids in shape of approximately 1.50 m side, with a
liftoff mass of about 1.380 ton with bus element accounting for about 0.4 ton,
payload about 0.1 ton and propellant about 0.8 ton. At lunar orbit it will be about
0.6 ton. This is a three-axis stabilized spacecraft generating about 750 W of peak
Indian Remote Sensing Missions & Payloads – A glance
15.2
power using canted single sided solar array and supported by a Li-Ion battery for
eclipse operations. The spacecraft used bipropellant system to carry it from EPO
through lunar orbit, including orbit and attitude maintenance in lunar orbit. The
propulsion system carried required propellant for a mission life of two years, with
adequate margin. The TTC communication is in the S-band. The scientific payload
data that stored in a solid-state recorder is later played back and down linked in Xband through 20 MHz bandwidth by a steerable antenna pointing at DSN.
Table 15.2 Salient feature of Chandrayaan -1
Parameter
Structure
Thermal
Components
Temp. Range
Mechanism
DGA Drive
Power
Solar Array
Deployment
Solar Array
Battery
Electronics
TCR
Telemetry
HK 2 Kbps/ 1 Kbps/ 0.5 Kbps (command
selectable)
CCDS compatible TC system 125 bps
Telecommand
BMU
Attitude/Orbit
sensors
CASS/ Star sensor(2),DTGs
Attitude control
4 reaction Wheels mounted in tetrahedral ,
Bipropellant thrusters
Accuracy: +/- 0.05 deg.
Drift rate 3 x 10-4 deg/sec
Bipropellant system 440 N LAM orbit rising,
8 nos. of 22 N thrusters canted along –ve roll
direction. 815 Kg Fuel Loaded
QPSK, 2x 8.4 Mbps
Orbit Control
Data Handling
Sada Hold down and Drive Mechanism
709 watts, Multi junction MTJ , 3.87 m2
Solar Array
27 AH Li ion, 28-42 volt
Communication
(AOCE+TM/TC)
Chandrayaan-1
Cuboid, 1.5m x 1.3 m x 1.56m , aluminum
honeycomb panels
Passive control using tapes , OSR, MLI
Blankets and semi-active/active control using
proportionate temperature controller and
heaters, Detector cooling via heat pipe
Electronics packages ~ 0 to 40 deg. C
Battery 0 to 20 Deg. C
RADOM – 20 to 50 deg. C
HEX -10 to 0 Deg. C
DGA Mechanism
Indian Remote Sensing Missions & Payloads – A glance
15.3
Mass (Kg)
1380
15.5 Payloads
There are 11 instruments on chandrayaan-1. Among them five are from
India and six are from other space agencies.
Sl.No
Payload
Description
Organisation &
Country
Scientific Payloads from India
1
Terrain Mapping
Camera (TMC)
camera in the panchromatic band SAC,
having 5m spatial resolution and 40 India
km swath, to prepare a high resolution
atlas of moon
ISRO,
2
Hyper Spectral
Imager (HySI)
imager operating in 400-900nm band SAC,
with a spectral resolution of 15nm and India
spatial resolution of 80 m with a
swath of 40 km, for mineralogical
mapping
ISRO,
3
Lunar Laser Ranging
Instrument (LLRI)
for determining accurate altitude of LEOS,ISRO,I
the spacecraft above the lunar surface ndia
for topographical mapping
4
High Energy X - ray
Spectrometer (HEX)
with a ground spatial resolution of ISAC,PRL,
approximately 20 km, for measuring India
210Pb, 222Rn degassing, U, Th etc
5
Moon Impact
Probe(MIP)
payload for exploration of the moon VSSC, ISRO,
from close range and impacting on the India
moon
Scientific Payloads from abroad
1
Chandrayaan-I X-ray
Spectrometer (CIXS)
X-ray spectrometer
2
Near Infrared
Spectrometer (SIR - 2)
Ihttp://www.cbk.waw.pl/teledetekcja/ Max-Planck
chandrayan/sir2ang.htmlnvestigations Institute,
of the process of basin, Maria and Lindau,
crater formation on the Moon
Indian Remote Sensing Missions & Payloads – A glance
Rutherford
Appleton
Laboratory
(RAL)& ISAC
15.4
3
Sub keV Atom
Reflecting Analyzer
(SARA)
for imaging the Moon surface using Swedish
low energy neutral atoms as Institute
of
diagnostics in the energy range 10eV- Space Physics
2keV
4
Miniature Synthetic
Aperture Radar (Mini
SAR)
for detection of water ice in the
permanently shadowed regions on the
Lunar poles up to a depth of a few
meters
(NASA)
Developed by
JHU/APL and
NAWC
5
Moon Mineralogy
Mapper (M3)
spectrometer for characterization and
mapping lunar surface mineralogy in
the context of lunar geologic
evolution
(NASA)
Brown
University and
JPL.
6
Radiation Dose
Monitor (RADOM)
To qualitatively and quantitatively Bulgarian
characterize, in terms of particle Academy
flux, dose rate and deposited energy Sciences
spectrum,
the
radiation
environment in near moon space
15.5.1 Terrain Mapping Cameara(TMC)
The terrain mapping stereo camera (TMC) in the 500–850 nm band with
three linear array detectors for nadir, fore and aft viewing and has a swath of 20 km.
It provide 3D image of the lunar surface with a ground resolution of 5 m with base to
height ratio of one.
Figure 15.1 Terrain mapping Camera
Scientific Objective:
The aim of TMC is to map topography of both near and far side of the Moon
Indian Remote Sensing Missions & Payloads – A glance
15.5
of
and prepare a 3-dimensional atlas with high spatial and elevation resolution of 5 m.
Such high resolution mapping of complete lunar surface will help to understand the
evolution processes and allow detailed study of regions of scientific interests. The
digital elevation model available from TMC would improve upon the existing
knowledge of Lunar Topography.
Figure 15.2 Optical Schematic and View angles of TMC
Payload Configuration Details:
The TMC images in the panchromatic spectral region of 0.5 to 0.85 µm, with
a spatial/ ground resolution of 5 m and swath coverage of 20 km. The camera is
configured for imaging in the push broom mode, with three linear 4k element
detectors in the image plane for fore, nadir and aft views, along the ground track of
the satellite. The fore and aft view angles are ±25º respectively w.r.t. Nadir.
TMC measures the solar radiation reflected / scattered from the Moon’s
surface. The dynamic range of reflected signal is quite large and is represented by the
two extreme targets – fresh crust rocks and mature mare soil.
TMC uses Linear Active Pixel Sensor (APS) detector with in-built digitizer.
Single refractive optics covers the total field of view for the three detectors. The
optics is designed as a single unit catering to the wide field of view (FOV)
requirement in the direction along the ground track. The incident beams from the fore
(+25°) and aft (-25°) directions are directed on to the focusing optics, using mirrors.
Modular camera electronics for each detector is custom designed for the system
requirements using FPGA. The data rate is of the order of 50 Mbps. The dimension
of TMC payload is 370 mm x 220 mm x 414 mm and mass is 6.3 kg.
Indian Remote Sensing Missions & Payloads – A glance
15.6
15.5.2 Hyper spectral imager (HySI)
The hyper spectral imager for mineralogical mapping is
operating in the 400–950 nm range employing a wedge filter
coupled to an area array detector. It has 64 continuous channels
with a spectral resolution better than 15 nm and a spatial (pixel)
resolution of 80 m with a swath of 20 km
Scientific Objective:
To obtain spectroscopic data for mineralogical mapping of
the lunar surface. The data from this instrument help in improving the available
information on mineral composition of the surface of Moon. Also, the study of data
in deep crater regions/central peaks, which represents lower crust or upper mantle
material, helps in understanding the mineralogical composition of Moon’s interior.
Payload Configuration Details:
The uniqueness of the HySI is in its capability of mapping the lunar surface
in 64 contiguous bands in the VNIR, the spectral range of 0.4-0.95 µm region with a
spectral resolution of better than 15 nm and spatial resolution of 80 m, with swath
coverage of 20 km. HySI collects the Sun’s reflected light from the Moon’s surface
through a tele-centric refractive optics and focus on to an APS area detector for this
purpose. The dispersion is achieved by using a wedge filter so as to reduce the weight
and compactness of the system compared to using a prism / grating.
Figure 15.3 Optical Ray trace of HySI
The wedge filter is an interference filter with varying thickness along one
dimension so that the transmitted spectral range varies in that direction. The wedge
filter is placed in close proximity to an area detector. Thus, different pixels in a row
of the detector will be receiving irradiance from the same spectral region but different
Indian Remote Sensing Missions & Payloads – A glance
15.7
spatial regions in the across track direction. In the column direction of the detector,
different rows will receive irradiance of different spectral as well as spatial regions in
the along track direction. The full spectrum of a target is obtained by acquiring image
data in push broom mode, as the satellite moves along the column direction of the
detector. An Active Pixel Sensor (APS) area array detector with built-in digitizer
maps the spectral bands. The payload mass is 2.5 kg and its size is 275 mm x 255
mm x 205 mm.
Figure 15.4 Mapping Scheme of HySI
15.5.3
Lunar laser ranging instrument (LLRI)
The LLRI employs an Nd–Yag laser with
energy 10 mJ and employ a 20 cm optics
receiver coupled to a Si–APD (Avalanche
Photo Diode). It is operating at 10 Hz
(5 ns pulse) and can provide a vertical
resolution better than 5 m. The LLRI and
TMC provide complementary data for
generating a topographic map of the
Moon and the LLRI, in particular, provide
the first such data set for the polar region
at higher than 80° latitude.
Indian Remote Sensing Missions & Payloads – A glance
15.8
Figure 15.5: Laser pulse roundtrip - illustration
Payload Configuration Details:
LLRI works on the time-Of-Flight (TOF) principle. In this method, a
coherent pulse of light from a high power laser is directed towards the target whose
range is to be measured. A fraction of the light is scattered back in the direction of
the laser source where an optical receiver collects it and focuses it on to a
photoelectric detector. By accurately measuring the roundtrip travel time of the laser
pulse, highly accurate range/spot elevation measurements can be made.
LLRI consists of a 10 mJ Nd:YAG laser with 1064 nm wave source
operating at 10 Hz pulse repetition mode. The reflected laser pulse from the lunar
surface is collected by a 200 mm Ritchey-Chrétien Optical receiver and focused on
to a Silicon Avalanche Photodetector. The output of the detector is amplified and
threshold detected for generating range information to an accuracy <5m. Four
constant fraction discriminators provide the slope information in addition to range
information. The different modes of operation of LLRI and the range computations
from the detector output are controlled and computed by a FPGA based electronics.
The processed outputs of LLRI are used for generating high accuracy lunar
topography. The payload mass is 11.37 kg with base plate.
Indian Remote Sensing Missions & Payloads – A glance
15.9
Figure 15.6: Block Schematic of LLRI
15.5.4
High energy X– γ ray spectrometer (HEX)
The high-energy X–γ ray (30–270 keV) spectrometer (HEX) employs
CdZnTe solid-state detectors and has a suitable collimator providing an effective
spatial resolution of 40 km in the low energy region (<60 keV). It employs a CsI
anticoincidence system for reducing back-ground and is primarily intended for the
study of volatile transport on Moon using the
46.5 keV γ ray line from 210Pb decay as tracer. 210Pb
is a decay product of volatile 222Rn and both belong
to the 238U decay series. The instrument has a
detection threshold of <30 keV and a resolution of
better than 10% at 60 keV. This instrument is to infer
compositional characteristics of lunar terrain from a
study of the continuum background in this energy
range as well as low resolution Th and U mapping of
terrains enriched in these elements
The High-Energy X-ray spectrometer covers the hard X-ray region from 30
keV to 270 keV. This is the first experiment to carry out spectral studies of planetary
Indian Remote Sensing Missions & Payloads – A glance
15.10
surface at hard X-ray energies using good energy resolution detectors. The High
Energy X-ray (HEX) experiment is designed primarily to study the emission of low
energy (30-270 keV) natural gamma-rays from the lunar surface due to 238U and
232
Th and their decay chain nuclides.
15.5.5 Moon impact probe (MIP)
In addition to the primary scientific payloads, an impactor carrying a high
sensitive mass spectrometer, a video camera and a radar altimeter was included in
this mission. The impact probe of 35 kg mass was attached at the top deck of the
main orbiter. The impactor was released at the beginning of the mission after
reaching 100 x 100 km lunar polar orbit and allowed to impact in a predetermined
location on the lunar surface.
During the descent phase, it is spin-stabilized. The total flying time from
release to impact on Moon was around 25 minutes. Apart from the video imaging of
the landing site, the onboard mass spectrometer tried to detect possible presence of
trace gases in the lunar exosphere.
The primary objective is to demonstrate the technologies required for landing
the probe at a desired location on the Moon and to qualify some of the technologies
related to future soft landing missions.
Payload Configuration Details:
There were three instruments on the Moon Impact Probe
Radar Altimeter – for measurement of altitude of the Moon Impact Probe and for
qualifying technologies for future landing missions. This is operating at 4.3 GHz ±
100 MHz.
Video Imaging System – for acquiring images of the surface of the Moon during the
descent at a close range. The video imaging system consists of analog CCD camera.
Mass Spectrometer – for measuring the constituents of tenuous lunar atmosphere
during descent. This instrument is based on a state-of-the-art, commercially available
Quadrupole mass spectrometer with a mass resolution of 0.5 amu and sensitivities to
partial pressure of the order of 10-14 torr.
The dimension of the impact probe is 375 mm x 375 mm x 470 mm
MIP System Configuration
The Moon Impact Probe (MIP) essentially made up of honeycomb structure,
which housed all the subsystems and instruments. In addition to the instruments, it
comprised of, the separation system, the de-boost spin and de-spin motors, the
avionics system and thermal control system. The avionics system supported the
Indian Remote Sensing Missions & Payloads – A glance
15.11
payloads and provided communication link between MIP and the main orbiter, from
separation to impact and provided a database useful for future soft landing.
Figure 15.7 Impact Probe Mission Profile
15.5.6 Chandrayaan Imaging X-ray Spectrometer (CIXS)
Two
options
were
considered for detection of low
energy (1–10 keV) fluorescence Xrays from lunar surface; use of a
thermoelectrically cooled X-ray
CCD (LEX) or of a swept-charge
X-ray detector (SCD) array. The
final choice was SCD and CIXS, a
modified version of D-CIXS
instrument on board SMART-1,
proposed by RAL, UK, and
supported by ESA was selected in
place of LEX.
This collimated LEX had a field of view of ∼30 km and aimed to provide
detail chemical mapping of the lunar surface for the elements, Mg, Al and Si and also
for Ca, Ti and Fe during solar flare times. An X-ray solar monitor (XSM) is a part of
this payload and will continuously monitor the solar X-ray flux essential for
analyzing the data on fluorescence X-rays to infer absolute elemental abundance.
Indian Remote Sensing Missions & Payloads – A glance
15.12
CIXS is collaborative payload between ISRO and RAL with a group of ISRO
scientists and engineers involved in various aspects of payload design and fabrication
and detector characterization.
Scientific Objective:
The primary goal of the CIXS instrument is to carry out high quality X-ray
spectroscopic mapping of the Moon, in order to constrain solutions to key questions
on the origin and evolution of the Moon. CIXS used X-ray fluorescence spectrometry
(1.0-10 keV) to measure the elemental abundance, and map the distribution, of the
three main rock forming elements: Mg, Al and Si. During periods of enhanced solar
activity (solar flares) events, it was planned to determine the abundance of minor
elements such as Ca, Ti and Fe on the surface of the Moon.
Payload Configuration Details:
The instrument utilised technologically innovative Swept Charge Device (SCD) Xray sensors, which were mounted behind low profile gold/copper collimators and
aluminium/polycarbonate thin film filters. The system had the virtue of providing
superior X-ray detection, spectroscopic and spatial measurement capabilities, while
also operating at near room temperature. A deployable proton shield protects the
SCDs during passages through the Earth’s radiation belts, and from major particle
events in the lunar orbit. In order to record the incident solar X-ray flux at the Moon,
which is needed to derive absolute lunar elemental surface abundances, CIXS also
includes an X-ray Solar Monitor.
The XSM sensor unit:
The X-ray Solar Monitor (XSM) was provided through collaboration
between Rutherford Appleton Laboratory (RAL) and University of Helsinki. With its
wide field-of-view of ±
52
degrees,
XSM
provides observation of
the
solar
X-ray
spectrum from 1-20
keV with good energy
resolution
(<
250
[email protected] keV) and fast
spectral sampling at 16
s intervals. The onboard solar monitor acting in real time will greatly enhance the
capability of CIXS to determine absolute elemental abundances as well as their
ratios. The total mass of CIXS and XSM is 5.2 kg.
Indian Remote Sensing Missions & Payloads – A glance
15.13
Heritage:
The CIXS instrument was primarily based on the D-CIXS instrument on the
ESA SMART-1 mission. The hardware was developed at the Rutherford Appleton
Laboratory, UK in collaboration with the ISRO Satellite Centre, Bangalore, and
exhibits significant improvements over the instrument flown on SMART-1.
15.5.7 Near infrared spectrometer (SIR-2)
SIR-2 is an upgraded, compact,
monolithic grating, near infrared point
spectrometer based on SIR flown on board
ESA's SMART-1 mission and covered the
wavelength region 0.9–2.4 μm. The instrument
has a spectral resolution of 6 nm. It is a linear
CCD array based instrument with a resolution
of ∼80 m per pixel.
Scientific Objectives:
SIR-2 is to address the surface-related aspects of lunar science in the
following broad categories:
 Analyse the lunar surface in various geological/mineralogical and
topographical units;
 Study the vertical variation in composition of crust;
 Investigate the process of basin Maria and crater formation on the Moon;
Indian Remote Sensing Missions & Payloads – A glance
15.14


Explore “Space Weathering” processes of the lunar surface;
Survey mineral lunar resources for future landing sites and exploration.
The determination of the chemical composition of a planet’s crust and mantle
is one of the important goals of planetary research. Diagnostic absorption bands of
various minerals and ices are located in the near-IR range, thus making near-infrared
measurements of rocks, particularly, suitable for identifying minerals.
Payload Configuration:
SIR-2 is a grating NIR point spectrometer working in the 0.93-2.4 microns
wavelength range with 6 nm spectral resolution. It collects the Sun’s light reflected
by the Moon with the help of a main and a secondary mirror. This light is fed through
an optical fiber to the instrument’s sensor head, where it is reflected off a dispersion
grating. The dispersed light reaches a detector, which consists of a row of
photosensitive pixels that measure the intensity as a function of wavelength and
produces an electronic signal, which is read out and processed by the experiment’s
electronics. The mass of the instrument is 3.3 kg and the instrument unit dimension is
260 mm x 171 mm x 143 mm.
15.5.8
Sub-keV Atom Reflecting Analyzer (SARA)
The SARA payload consists of two major subsystems, Chandrayaan-1 low
energy neutral atom (CENA) and solar wind monitor (SWIM). CENA detects neutral
atom sputtered from the lunar surface by solar wind ions. The CENA sensor has an
energy range of 10 eV to 2 keV with an energy resolution of ∼50% and can resolve
groups of elements such as H, O, Na/Mg group, K/Ca group and Fe. SWIM is a
simple ion mass analyzer consisting of a sensor and an energy analyzer that provides
information on the energy and mass of the incident solar wind ions. Space Physics
Laboratory, Thiruvananthapuram, is responsible for developing the data processing
unit.
Sub keV Atom Reflecting Analyser (SARA)
Indian Remote Sensing Missions & Payloads – A glance
15.15
Scientific Objectives: SARA will image the Moon surface using low energy
neutral atoms as diagnostics in the energy range 10 eV - 3.2 keV to address the
following scientific objectives:




Imaging the Moon’s surface composition including the permanently shadowed
areas and volatile rich areas
Imaging the solar wind-surface interaction
Imaging the lunar surface magnetic anomalies
Studies of space weathering
The Moon does not possess a magnetosphere and atmosphere. Therefore, the
solar wind ions directly impinge on the lunar surface, resulting in sputtering and
backscattering. The kick-off and neutralized solar wind particles leave the surface
mostly as neutral atoms. The notable part of the atoms has energy exceeding the
escape energy and thus, such atoms propagate along ballistic trajectories. The SARA
instrument is designed to detect such atoms with sufficient angular and mass
resolution to address the above scientific objectives. SARA is the first-ever energetic
neutral atom imaging mass spectrometer. Payload Configuration Details: The SARA
instrument consists of neutral atom sensor CENA (Chandrayaan-1 Energetic Neutrals
Analyzer), solar wind monitor SWIM and DPU (Data Processing Unit). CENA and
SWIM interface with DPU, which in turn interfaces with the spacecraft. The masses
of CENA, SWIM and DPU are 2 kg, 0.5 kg and 2 kg respectively, totaling the SARA
mass as 4.5 kg.
Indian Remote Sensing Missions & Payloads – A glance
15.16
The functional blocks of CENA are shown in above figure: Low-energy
neutral atoms enter through an electrostatic charged particle deflector (1), which
sweeps away ambient charged particles by a static electric field. The incoming low
energy neutral atoms are converted to positive ions on an ionization surface (2), and
then passed through an electrostatic analyzer of a specific (“wave”) shape that
provides energy analysis and effectively blocks photons (3). Particles finally enter the
detection section (4) where they are reflected at grazing incidence from a start surface
towards one of several stop micro channel plate (MCP) detectors. Secondary
electrons generated at the start surface and the stop pulses from the stop MCP
detectors preserve the direction and the velocity of the incident particle. SWIM is an
ion mass analyzer, optimized to provide monitoring of the precipitating ions. Ions
first enter the deflector, which provides selection on the azimuth angle, following a
cylindrical electrostatic analyzer. Exiting the analyzer the ions are post-accelerated
up to 1 keV and enter the time-of-flight cell, where their velocity is determined by
the same principle (surface reflection), as in the CENA instrument.
15.5.9 Miniature synthetic aperture radar (MINI-SAR)
Multifunction miniature radar consisting of SAR, altimeter, scatterometer
and radiometer operating at 2.5 GHz will explore the permanently shadowed areas
near lunar poles to look for signature of water ice. The mini-SAR system will
transmit right circular polarization (RCP) and receive both left circular polarization
(LCP) and RCP. The SAR system has a nominal resolution of 150 m per pixel with
8 km swath.
Figure 15.8: Miniature Synthetic Aperture Radar (Mini-SAR)
Scientific Objectives: To detect water ice in the permanently shadowed
regions on the Lunar poles, upto a depth of a few meters. Although returned lunar
Indian Remote Sensing Missions & Payloads – A glance
15.17
samples (from earlier missions) show the Moon to be extremely dry, recent research
suggest that water-ice may exist in the Polar Regions. Because its axis of rotation is
perpendicular to the ecliptic plane, the poles of the Moon contain areas that never
receive light and are permanently dark. This results in the creation of “cold traps”,
zones that, because they are never illuminated by the sun, may be as cold as 50–70oK.
Cometary debris and meteorites containing water-bearing minerals constantly
bombard the Moon. Most of this water is lost to space, but, if a water molecule finds
its way into a cold trap, it remains there forever – no physical process is known that
can remove it. Over geological time, significant quantities of water could accumulate.
An onboard SAR at suitable incidence would allow viewing of all permanently
shadowed areas on the Moon, regardless of whether sunlight is available or the angle
is not satisfactory. The radar would observe these areas at incidence angle near 45
degrees, recording echoes in both orthogonal senses of received polarization,
allowing ice to be optimally distinguished from dry lunar surface. The Mini-SAR
radar system can operate as an altimeter/scatterometer, radiometer, and as a synthetic
aperture radar imager. Payload Configuration Details: The Mini-SAR system will
transmit Right Circular Polarization (RCP) and receive, both Left Circular
polarization (LCP) and RCP. In scatterometer mode, the system will measure the
RCP and LCP response in the altimetry footprint, along the nadir ground track. In
radiometer mode, the system will measure the surface RF emissivity, allowing
determination of the near normal incidence Fresnel reflectivity. Meter-scale surface
roughness and circular polarization ratio (CPR) will also be determined for this
footprint. This allows the characterization of the radar and physical properties of the
lunar surface (e.g., dielectric constant, porosity) for a network of points. When
directed off nadir, the radar system will image a swath parallel to the orbital track by
delay/Doppler methods (SAR mode) in both RCP and LCP. The synthetic aperture
radar system works at a frequency 2.38 GHz, with a resolution of 75 m per pixel
from 100 km orbit and its mass is 8.77 kg.
15.5.10 Radiation dose monitor (RADOM)
RADOM is a miniature
spectrometer–dosimeter that uses a
semiconductor detector and measure
the deposited energy from primary and
secondary particles using a 256
channel pulse analyzer. The deposited
energy spectrum can then be converted
to deposited dose and incident flux of
charged particles on the silicon
detector.
Indian Remote Sensing Missions & Payloads – A glance
15.18
Scientific Objectives:
RADOM will qualitatively and quantitatively characterise the radiation
environment in near lunar space, in terms of particle flux, dose rate and deposited
energy spectrum.
The specific objectives are to
Measure the particle flux, deposited energy spectrum, accumulated
radiation dose rates in Lunar orbit;
Provide an estimate of the radiation dose around the Moon at different
altitudes and latitudes;
Study the radiation hazards during the Moon exploration. Data obtained
will be used for the evaluation of the radiation environment and the
radiation shielding requirements of future manned Moon missions.
Radiation exposure of crew members on future manned space flight had been
recognised as an important factor for the planning and designing of such missions.
Indeed, the effects of ionising radiation on crew health, performance and life
expectancy are a limitation to the duration of man’s sojourn in space. Predicting the
effects of radiation on humans during a long-duration space mission requires i)
accurate knowledge and modeling of the space radiation environment, ii) calculation
of primary and secondary particle transport through shielding materials and through
the human body, and iii) assessment of the biological effects of the dose.
The general purpose of RADOM is to study the radiation hazards during the
Moon exploration. Data obtained will be used for the evaluation of radiation
environment and radiation shielding requirements for future manned lunar missions.
Payload Configuration Details:
RADOM is a miniature spectrometer-dosimeter containing one
semiconductor detector of 0.3 mm thickness, one charge-sensitive preamplifier and
two micro controllers. The detector weighs 139.8 mg. Pulse analysis technique is
used for obtaining the deposited energy spectrum, which is further converted to the
deposited dose and flux in the silicon detector. The exposure time for one spectrum is
fixed at 30 s. The RADOM spectrometer will measure the spectrum of the deposited
energy from primary and secondary particles in 256 channels. RADOM mass is 160
g.
Indian Remote Sensing Missions & Payloads – A glance
15.19
15.5.11 Moon mineral mapper (MMM)
The MMM (M3) is a high throughput push broom imaging spectrometer
operating in 0.7–3.0 μm range with high spatial (70 m per pixel) and spectral (10 nm
sampling) resolution. It will have a swath of 40 km. It uses a 2D HgCdTe detector
array for measuring reflected solar energy in the above wavelength range.
High-resolution compositional maps by Moon Mineralogy Mapper will
improve the understanding of the early evolution of a differentiated planetary body
and provide a high-resolution assessment of lunar resources.
Scientific Objectives:
The primary Science goal of M3 is to characterize and map lunar surface
mineralogy in the context of lunar geologic evolution. This translates into several
sub-topics relating to understanding the highland crust, basaltic volcanism, impact
craters, and potential volatiles. The primary exploration goal is to assess and map
lunar mineral resources at high spatial resolution to support planning for future,
targeted missions. These M3 goals translate directly into the following requirements:

Accurate measurement of diagnostic absorption features of rocks and
minerals;

High spectral resolution for deconvolution into mineral components;

High spatial resolution for assessment geologic context and active processes;
Payload Configuration Details:
The M3 scientific instrument is a high throughput pushbroom imaging
spectrometer, operating in 0.7 to 3.0 µm range. It measures solar reflected energy,
using a two-dimensional HgCdTe detector array featuring.
Sampling
: 10 nanometers
Indian Remote Sensing Missions & Payloads – A glance
15.20
Spatial resolution
: 70 m/pixel [from 100 km orbit]
Field of View
: 40 km [from 100 km orbit]
Mass
: 8.2 kg
The spectral range 0.7 to 2.6 µm captures the absorption bands for the most
important lunar minerals. In addition, the spectral range 2.5 to 3.0 µm is critical for
detection of possible volatiles near the lunar poles. The presence of small amounts of
OH or H2O can be unambiguously identified from fundamental absorptions that
occur near 3000 nm. M3 measurements are obtained for 640 cross track spatial
elements and 261 spectral elements. This translates to 70 m/pixel spatial resolution
and 10 nm spectral resolutions (continuous) from a nominal 100 km polar orbit for
Chandrayaan-1. The M3 FOV is 40 km in order to allow contiguous orbit-to-orbit
measurements at the equator that will minimize lighting condition variations.
Indian Remote Sensing Missions & Payloads – A glance
15.21
Chandrayaan-1: Summary
Scientific Objectives:
Simultaneous chemical, mineralogical
and photogeologic mapping of the
whole moon in visible, near infrared,
low and high energy X-rays with high
spatial resolution
Scientific Payloads
Terrain Mapping Camera-TMC
Hyper Spectral Imager-HySI
Lunar Laser ranging Instrument-LLRI
Low Energy X-ray Spectrometer-LEX
Solar X-ray Monitor- SXM
High Energy X-ray /-ray Spectrometer-HEX
Payload Weight
55kg (Including 10kg Announcement of
Opportunity payload)
Launcher
Polar Satellite Launch Vehicle-PSLV-XL
Mission Strategy
Elliptic Parking Orbit. Trans Lunar Injection.
Lunar Orbit Insertion
Lunar Orbit
100 X 100 km Circular Polar
Operational Life Time
Two Years
Spacecraft
Cuboid shape, 1.5 m side, 3-axis stabilized
Spacecraft Mass
Dry mass-440kg, Initial Lunar Orbit Mass with
propellant-524kg
Communication System
S-Band uplink for telecommand, S-Band
downlink for telemetry, X-Band for Payload data
reception
Deep
Space
Network Location : Bangalore, Fully steerable dual feed
(DSN) Station
32m-dia antenna
Mission Control Centre
Location : Bangalore-responsible for all
spacecraft operations, running of ground
infrastructure
National Science Data Act as repository of scientific data Centre (NSDC)
Centre (NSDC)
from
experiments
conducted
on-board
Chandrayaan-1
Indian Remote Sensing Missions & Payloads – A glance
15.22
Indian Remote Sensing Missions & Payloads – A glance
15.23
Indian Remote Sensing Missions & Payloads – A glance
15.24
Indian Remote Sensing Missions & Payloads – A glance
15.25
Water mapping of moon from M3 Payload
Indian Remote Sensing Missions & Payloads – A glance
15.26
16 OCEANSAT-2
16.1 Introduction
Oceansat-2 spacecraft provides continuation of services of IRS-P4 with
enhanced application areas. Oceansat-2 is a 3-axis stabilized spacecraft basically
derived from I-1.5K IRS bus with proven mainframe systems.
Oceansat-2 carries three payloads - Ocean Colour Monitor (OCM-2), Kuband Scatterometer and Radio Occultation Sounder for Atmosphere (ROSA). OCM
is a multi-spectral optical camera, providing ocean colour data with repetivity of two
days. It provides a ground IFOV of 360 m in across track and 246 m in along track
directions covering a swath of 1420 Km. The camera can be tilted by  20  with
respect to nadir in the along-track direction to avoid sun glint from sea surface.
The Ku band pencil beam scatterometer is an active microwave sensor for
measurement of wind speed and wind direction. It consists of a parabolic dish
antenna of 1m diameter that is continuously rotated at 20.5 rpm using a scan
mechanism with the scan axis along the +Yaw axis. This antenna is arrested during
launch and released in orbit for the operations.
The ROSA is a GPS Receiver for atmospheric sounding by radio occultation.
The GPS receiver determines position, velocity and time using GPS signals. Besides,
ROSA receives RF signals from the ‘rising’ GPS satellites near Earth’s horizon
through its occultation antenna and from the excess phase delay and Doppler
measurements, atmospheric parameters (Temperature, humidity, pressure) can be
derived.
During operational phase of the spacecraft, Scatterometer and ROSA
payloads are continuously ON and OCM will be switched ON during sun-lit passes
over oceans as per user requirements.
16.2 Mission Objective
The mission objectives of Oceansat-2 are




To design, develop, launch and operate a state of art 3 axis body
stabilized satellite providing ocean based remote sensing services to the
user communities
To develop remote sensing capabilities with respect to Ocean resources
To establish ground segment to receive and process the payload data.
To develop related algorithms and data products
Indian Remote Sensing Missions & Payloads – A glance
16.1

To serve in well established application areas and also to ensure the
mission utility.
16.3 Orbit details
Type
Altitude (Km)
Inclination (Deg)
Period (Min)
Local Time
Repeat Cycle
Distance between adjacent traces
Distance between successive ground
track
Ground Track Velocity
SSPO
720
98.28
99.31
12.00 Noon + 10 min
2 Days
1382 Km.
2764 Km
6.7818 Km/s
16.4 Salient features of Oceansat-2
Indian Remote Sensing Missions & Payloads – A glance
16.2
16.5 Payloads
There are two main payloads in
Oceansat-2, namely, an Ocean Colour
Monitor (OCM) and Ku-band Pencil beam
Scatterometer. In addition, a piggy-back
payload called the Radio Occultation Sounder
for the Atmosphere (ROSA) developed by
the Italian Space Agency will also be flown
on-board Oceansat-2. While the OCM
provides data on the bio-physical properties
of
global
oceans
like
Chlorophyll
concentration, suspended sediments, algal
blooms etc., the Scatterometer provides data
from which the surface Wind velocity (both
speed and direction) over ocean surface will
be derived. ROSA is an atmospheric sounder
and provides data on Temperature and
Humidity profiles in the troposphere as well as space weather.
A brief description of these payloads is given in the following paragraphs.
16.5.1 OCEAN COLOR MONITOR
The Ocean Color Monitor (OCM) is a solid state CCD camera and operates
in eight narrow spectral bands with 360m along-track and 243m across-track ground
resolution covering a swath of 1420Km from 720Km altitude. All the eight bands are
Indian Remote Sensing Missions & Payloads – A glance
16.3
in Visible and Near Infrared region having spectral bands between 0.4µm and
0.885µm. Since the local time of pass for Oceansat-2 is 12noon, provision is made to
tilt the Electro-Optics module about the Pitch axis by ±20º with reference to nadir to
avoid the sun glint from sea surface. During launch the EO Module will be held by
hold-down mechanism, which will be released in-orbit using a pyro cutter.
The OCM payload consists of the following systems
Electro-Optics Module (EOM)
Payload Electronics (PLE)
Power converters and regulators (OPC / OPR)
16.5.1.1 Specifications of OCM
IGFOV
:
360m (Across track)
GSD
:
252m (Along track)
Swath
:
>1420Km
Repetivity
:
2 days
Quantisation
:
12 bits
SNR @ saturation
:
> 512
Spectral bands (missions)
Band-1
0.402-0.422
Band-5
Band-2
0.433-0.453
Band-6
Band-3
0.480-0.500
Band-7
Band-4
0.500-0.520
Band-8
Saturation Radiance (mW/cm2/sr/μm) @ max exposure
Band-1
35.5
Band-5
Band-2
28.5
Band-6
Band-3
22.8
Band-7
Band-4
25.7
Band-8
Integration time
:
34.75ms
Detector
:
CCD191A
Number of pixels
:
Total
6000
Used 3730
Video readout rate /port
:
86.6KHz
Data rate / band
:
2.08Mbits/s
Total Data rate generated
:
16.64Mbits/ s
Band-to-band registration
:
<+ 0.25 Pixel
Camera MTF
:
>0.2
(@ Nyquist frequency)
Indian Remote Sensing Missions & Payloads – A glance
0.545-0.565
0.610-0.630
0.725-0.755
0.845-0.885
22.4
18.1
9.0
17.2
16.4
Size (mm) E-O module
Weight (Kg)
EO module
Camera
Power (Regulated)
Imaging mode
Calibration mode
:
Roll
Pitch
Yaw
701
527
420
:
:
64
78 (w/o power modules)
:
:
130W
132W
16.5.1.2 Electro-Optics Module (EOM)
The EO Module consists of imaging lens assemblies, EOM Structure,
Detector head assembly; Detector electronics and payload tilt mechanism
Optical system
It consists of eight spectral bands in visible and near infrared region having
spectral bands between 0.4µm and 0.885µm with 20nm band width for bands B1 to
B6 30nm bandwidth for band B7 and 40nm bandwidth for B8. Each band consists of
its own imaging Lens assembly and a linear array detector (CCD). The optical
system consists of 10 refractive lens elements, a thermal filter in front and
interference filter. To cover the wide field-of-view (+ 43º), the first lens element is
realized with parabolic surface.
A “tele-centric” optical system is selected to
provide minimum distortion, uniformity of illumination and good MTF over the wide
field angle.
Transmission of the lens is improved by providing anti-reflection coating.
The band pass function is achieved by using an interferential filter located after the
lenses, at the end of the objectives. This filter has two substrates, each one having
two faces coated.
16.5.1.3 Optical system specification
Equivalent focal length (EFL) (mm)
F-number
Field of View
Clear working distance (mm)
Distortion
MTF(@ 50 lp/mm)
Indian Remote Sensing Missions & Payloads – A glance
:
:
:
:
:
:
:
20.0±0.1
0.3 for B1 & B2
0.5 for B3 to B8
± 43º (86º total)
>16
< ±0.02%
> 0.6
16.5
16.5.1.4 EOM structure
The main structure of EO module is made out of single block of Al. Alloy
6061 material. This material is selected for its matching coefficient of thermal
expansion, which helps in maintaining the separation between the lens focal plane
and detector within ± 2.0μ over a temperature variation of 15 ± 2º C. Four thermal
covers fitted on the EOM will cover the EO module on +ve Yaw, -Ve Yaw, +ve pitch
and –ve pitch direction. Thermal cover is black painted on its inside surfaces and
covered by MLI blanket outside. Auto-control heaters are mounted on the inside
surface of thermal cover. Lens side and detector side thermal covers have one cutout
for viewing and wire harness. A common hood with a slit aperture is placed in front
of each row of the lenses. These hoods limit the Field of View of the lenses to ±45º
in pitch-yaw plane and ±2º in roll-yaw plane w.r.t the optical axis. The interface for
the Tilt mechanism gimbal shaft is provided on the Pitch axis sides of EOM. The
EOM is held-down at an angle of –23º in the launch configuration.
16.5.1.5 OCM Electronics
The OCM electronics is modular and satisfies the mission goal that no single
point failure shall lead to non-availability of two or more bands data. It has separate
electronics for each band without any redundancy. But cross coupling exists between
camera electronics and BDH.
OCM Electronics can be functionally divided into following three portions



Detector Head Assembly
Detector Electronics
Video processing Electronics
16.5.1.6 Detector head assembly
A 6000 element of 7 x 10μm pixel size linear arrays CCD (CCD191A same
as that used in IRS-P4) is used as detector. Out of 6000 active pixels available in the
CCD, 3730 central pixels are used for imaging. For the dark current estimation and
subtraction from video data, 150 pixels on either edge of the CCD are used.
Each band lens assembly has different back focal length. Suitable spacers are
used to place the Detector in the focal plane. Considering the variation of the focal
length with reference to temperature the most matching material is found to be
aluminum. However CCD is made out of ceramic, which has very low coefficient of
Thermal Expansion (CTE). Hence Invar material is chosen for CCD Holder.
Thermal stability among these two dissimilar materials will be achieved by using a
dowel screw at one end and free screw at other end. Two LED holders are located on
Indian Remote Sensing Missions & Payloads – A glance
16.6
the detector head. Each LED holder would accommodate two LEDs used for onboard calibration.
16.5.1.7 Calibration
Four LEDs of type HP 1N6092 are mounted on the detector mount. Their
optical axis is at 71º from the normal due to the limited space between the detector
and the imaging optics. In view of this large angle, the LEDs illuminate a larger
photosensitive area compared to the imaging mode in the lateral direction of the
detector array. Sixteen distinct calibration levels will be set using digitally altered
exposure time method. The signal range coverage would be about 70% of the full
range. The expected non-uniformity of the illumination using calibration LEDs is
better than ± 50% with respect to the array mean calibration count.
16.5.2 Ku-BAND SCATTEROMETER
16.5.2.1 Introduction
The main objective of the Scatterometer Payload onboard OCEANSAT-2 is
to gather the information about the near surface winds over oceans at a global level
which form a very important input to the global weather forecasting system.
The near surface wind mostly modulates the capillary waves on the ocean
surface whose wave length is of the order of centimeters. Previous missions carried
Scatterometers operating in both C-band and Ku-band frequencies. The examples of
the C-band Scatterometer are ERS-1 & 2, and the recent Advanced Scatterometer
(ASCAT) onboard METOP satellite. Ku-band missions include SeaSAT, NSCAT
and SeaWinds Scatterometer on QuickScat and ADEOS-II satellites. Looking at the
already established sensitivity of the Ku-Band frequencies to the wind vector and the
wide applications and significant research being carried out using the data from
NSCAT and SeaWinds and the available primary allocation, Ku-band was chosen for
the Oceansat-2 mission.
Indian Remote Sensing Missions & Payloads – A glance
16.7
Figure 16.1 Scatterometer
Characteristics of System
Parameter
Inner beam
Satellite Altitude
720Km
Principal Axis Pointing angle
46o
Frequency
13.515625GHz
Wavelength
0.0221965m
Wind Speed
4 – 24m/s with accuracy of 10 % or 2 m/s
whichever is higher
Wind direction
0 – 360ºwith accuracy of 20º deg.
Swath (qualified)
1400Km
Polarization
HH
Indian Remote Sensing Missions & Payloads – A glance
Outer beam
VV
16.8
Parameter
Inner beam
Outer beam
Basic Sigma naught cell (Center)
26Km x 6.8Km
31Km x 5.8Km
Kp over Basic sigma naught Cell
1.32-3.49 over 5
cells around beam
centre
1.89-3.02 over 5
cells around beam
centre
without error (24m/s cross wind)
0.28-0.3 over 5 cells
around beam centre
0.3-0.33 over 5 cells
around beam centre
Slant Range(Km) 1208
1031
1208
One Way 3dB Foot Print
Az(Km)xEl(Km)
26 X 46
31 X 65
Along Track Spacing (Km)
19.7
19.7
Along Scan Spacing (Km)
16.3
21
Across Scan Overlap ( Varies with
28% to 48%
29% to 71%
41%
34%
-0.25 Deg Pointing Error (KHz)
± 455.69
± 510.54
0.00 Deg Pointing Error (KHz)
± 457.86
± 512.47
+0.25 º Pointing Error (KHz)
± 460.03
± 514.38
Earth Rotation Doppler (Equator)
± 29KHz
± 31KHz
4m Cross Wind (Qualified)
-31.3
-29.8
24m Up Wind (Qualified)
-10.9
-12.4
without error (4 m/s cross wind)
Kp over Basic sigma naught Cell
Azimuth position )
Along Scan Overlap
Cell Center Doppler (Excluding
Earth rotation)
σ0Parameters (dB)
Antenna Specifications
Antenna Diameter
1m
Angular Separation of Feeds
6.76º
Peak Gain
39.5dBi
Beam width (Al. Scan. X Ac. Scan)
1.47º x 1.67º
Transmitter Specifications
Transmit Power
100W
Transmit Duty Cycle
27%
Indian Remote Sensing Missions & Payloads – A glance
16.9
Parameter
Inner beam
Outer beam
Transmit PRF for system(
Nominal ) Transmit PulseWidth
193Hz
Transmit Modulation
LFM
Transmit Chirp Bandwidth
400KHz
Receiver Specifications
Receiver Type
Single Channel Output on IF of
15.625MHz
O/P Bandwidth
15.625MHz ±800KHz
Gain control (controlled by 6-bit
gain control telecommand)
45dB to 109dB
1.35ms
Receiver Pathloss (dB)
Noise figure (dB)
3
Input Noise Power
3
Receiver output
-109dBm over 1600KHz bandwidth
500m V p-p across 50 Ω resistance
Antenna Sub-System
The 1 mtr dia antenna reflector is a prime focal parabolic dish with a focal
length of 0.4 meter. The vertex of the dish is offset from the mounting interface by
180 mm (approx.). The reflector dish is fixed at a tilt of 460 about the + yaw axis in
the yaw-wave-guide plane. In the launch condition, the reflector assembly is rotated
by 300 clockwise, about the yaw axis (when viewed from the positive yaw axis).
Three CFRP tubes (called Spars) support the feed horns of the antenna. The waveguide is to be routed along one of the three Feed Support tubes. Two feed horns are
used for generating the two beams (Outer & Inner) with different polarizations at
specified look angles. The Antenna is attached to the Scatterometer scan mechanism
to mechanically spin the parabolic reflector along with the feeds around scan axis
coinciding with the +ve yaw axis of the satellite. The rear side of the antenna is white
painted and the feed assembly is covered with MLI blanket as per the Thermal
design.
Indian Remote Sensing Missions & Payloads – A glance
16.10
Figure 16.2 Scatterometer Swath coverage
Specifications of Scatterometer antenna reflector
Diameter of dish
:1000mm
Outer diameter of dish
:1014mm (max. permitted)
Focal length
:400mm
Shape
:Axis-symmetric paraboloid
Angle of tilt (With respect to spin axis) : 46.0 + 0.010
RMS error
:0.1mm
Mass
:<10Kg
No. of feed support tubes (FST)
:3
Diameter of FST
:20mm (max. permitted)
Feed bracket mass
:0.4Kg
Feed adjustment (along reflector axis) :+ 10mm
16.5.2.2 Dual Channel Wave guide Rotary Joint
Space qualified dual channel microwave rotary joint for Ku-band has been
developed in-house for pencil beam scanning scatterometer payload onboard
Oceansat-2 after performing electrical, mechanical, thermal and environmental
qualifications. The conical scanning is effected by mechanically rotating the
scatterometer antenna about the yaw axis at 20.5 rpm using a scan mechanism. The
two feeds of the reflector antenna for scatterometer payload are fed with microwave
signal through the dual channel rotary joint. The stationary part of the joint is
mounted to the satellite deck through waveguide plumbing. The specifications of the
Rotary joint are given below.
Indian Remote Sensing Missions & Payloads – A glance
16.11
Specifications for the Dual Channel Rotary Joint
Frequency
:
13.515625GHz
Bandwidth
:
± 25MHz
Return Loss (max)
:
Ch1: >19dB
Ch2: >19dB
Insertion loss (max)
Isolation
Insertion loss – variation
within a single scan
Peak power
EMI/EMC Results
:
Ch1: 0.35dB
Ch2: 0.35dB
:
40dB
:
Ch1: ± 0.05dB
Ch2 : ±0.05dB
:
Peak 140W, 34%DC
:
67 dB μVolt/m
Test type – RE102 MIL-STD 461 E
16.5.2.3 SCATTEROMETER SCAN MECHANISM (SSM)
The Scatterometer Scan Mechanism is used to rotate the Antenna reflector
along with its Feeds and waveguide assembly and Rotary joint at a constant rate of
20.5rpm. It consists of a brushless DC motor and its Drive Electronics.
The functional requirements of Scatterometer Scan Mechanism are

To provide necessary mechanical interface and rotate antenna, feed
system, which weighs 10Kg, at 20.5 rpm about the precision axis of
rotation with scan stability of 0.1%.
 Provide necessary mechanical interface for microwave rotary joint stator
& rotor part
 To accommodate the rotary joint stator part.
 Provide accurate scanning position information with accuracy of 0.01º
on interrogation at PRF
 Provide mechanical interface to payload deck.
 Define scatterometer relative orientation and position w. r. to payload
reference frame/bus reference frame.
 Precise static and dynamic balancing of rotating parts.
 Provide redundancy in drive motor, angular sensor and control
electronics.
The SSM consists of a precision bearing unit with static reservoir, brushless
DC outer rotating drive motor assembly, optical encoder assembly, cube assembly
(both in stator part and rotor part) for optical alignment, housing, motor rotor
housing, hollow central shaft and balancing arms.
Indian Remote Sensing Missions & Payloads – A glance
16.12
Bearing Unit Assembly
The mechanism is outer rotating one. SSM consists of precision bearing unit
assembly, which includes static central shaft that locates inner race of face to face
mounted two pairs of duplex angular contact ball bearings. Outer races are axially
supported by a single housing. Static reservoirs using nylasint are provided at both
bearing pairs. This forms the bearing unit assembly. The criticality is the designing
and achieving of labyrinth seal so as to avoid lubricant leakage as well as sufficient
clearance between stator and rotor.
Encoder Assembly
Custom built 17 bit absolute optical encoder is used as angle sensor. It
consists of three parts such as encoder rotor, encoder stator, and electronics on stator
part. Configuration design ensures proper axial gap between stator and rotor disk of
encoder.
The C.G. offset and cross inertia of scatterometer rotor has to be balanced for
static and dynamic balancing. Balancing provisions are provided in rotating parts in
two balancing planes sufficiently apart. Locations are identified in other two
orthogonal directions for minor cross inertia unbalance correction. Static & dynamic
balancing of QM SSM with antenna has been done using 4 component Kistler
dynamometer. The residual unbalance and the location of unbalance w. r. t. scan start
are obtained. S/C level drift rate performance analysis has been carried out using the
above values and the results are satisfactory.
Pennzane lubricant oil with its matching grease (Rheolube 2000/ MAPLUB)
is used for SSM. To ensure lubricant availability, the amount of oil that will be lost
by evaporation over the mission life is compared to the oil quantity available in the
bearings. The rate of lubricant mass loss per unit surface area of oil is calculated to be
4.0mg/ cm2/year. For 200m radial gap between stationary shaft and rotating retainer,
by providing a labyrinth passage estimated opening is 1cm2 on each side of the
bearings. Hence the expected loss from each bearing during the 5 year life is only
56mg. Oil retained by each bearing cage is more than 450mg. Hence, factor of safety
= 450 / 56 = 8.
16.5.3 ROSA (Radio Occultation Sounder for the Atmosphere)
16.5.3.1 Introduction
The ROSA Receiver is a GPS Receiver for space borne applications,
specifically conceived for atmospheric sounding by radio occultation, which is able
to determine position, velocity and time using GPS signals.
Indian Remote Sensing Missions & Payloads – A glance
16.13
The ROSA, besides providing real-time navigation data, is able to accurately
measure pseudo ranges and integrated carrier phase (raw data), to be later processed
on ground for scientific purposes.
The ROSA processes the received GPS signals in both the L1 and L2
frequency bands, allowing compensation of ionospheric delays. A codeless tracking
scheme is included, in order to process the encrypted P(Y) signals transmitted in the
L2 frequency band.
The instrument is equipped with one hemispherical-coverage antenna that is
mounted with bore-sight direction equal to the Zenith direction and is used to track
the GPS signals for navigation purpose and for Precise Orbit Determination (POD).
In addition, a directive Velocity antenna is mounted on the Oceansat-2 spacecraft.
This antenna is oriented in such a way to be able to track signal from GPS satellites
in Earth occultation (rising).
Sixteen (4 AGGA chips) dual-frequency channels are available in the ROSA
Receiver, and can be freely assigned to any combination of satellites. ROSA is
provided with a MIL-STD-1553 communication interface over which telecommand,
telemetry and measurement data are exchanged. The Receiver digital section is based
on an ADSP 21020 processor and four AGGA-2a channels ASIC.
16.5.3.2 Main elements of ROSA Payload
Zenith pointing Hemispherical Antenna and LNA:
Signals from this antenna can reach (through the RF/IF section) all the
Receiver AGGA-2a HW channels. GPS signals received by this antenna are used to
produce raw data measurements that are post-processed on ground for Atmospheric
Sounding purposes and they are used also to compute the on-board real-time
navigation and time solutions.
Velocity Antenna and LNA: This antenna is used only for Atmospheric Sounding
applications to produce raw data measurements from satellites that are rising behind
the Earth horizon. The Antenna is composed by two linear arrays, each pointing to a
semi-plane (Velocity-Left, Velocity-Right). The RF/IF paths coming from Velocity
arrays are connected to all AGGA-2a chips.
RF/IF sections: Five RF/IF sections (one for each antenna path) compose the
Receiver front-end and include filtering and down conversion for the L1 and L2
frequencies. A 10 MHz reference OCXO oscillator is used in the frequency
synthesizer from which all the Local Oscillators, and also clocks used internally to
the Receiver, are derived.
Indian Remote Sensing Missions & Payloads – A glance
16.14
Digital Section: This section includes the Signal Processing HW(AGGA-2a
channels), the CPU Module that controls via SW all the Receiver functions and the
Communication Module that handles communication with the external Host (Onboard Computer or Test Equipment). Four AGGA-2a chips are mounted on ROSA,
each AGGA being composed of 4 complex (12 single) channels.
Power Management: ON/OFF commands are required from spacecraft to switch
ON/OFF ROSA receiver. These commands issued by the Spacecraft and to execute
these commands DC/DC Converter provides the secondary voltages to the Receiver,
starting from the Spacecraft primary line.
16.5.3.3 Navigation Antenna
The Navigation Antenna is dedicated to acquire the GNSS signals to
determine with precision the orbit of the satellite where there is installed the ROSA
Instrument.
The navigation solution, from which depends the orbit determination, is
fundamental in this application, because the position’s knowledge in the time is
essential to trace all the occultation events during the observation phase of the
Instrument. Its main features are summarized by the following information.
Specifications:
Frequency range
:
VSWR
Gain
:
:
Polarisation
Radiation Pattern
:
:
Weight
:
L1 1560 L2  1212 - 1242MHz
1.5:1
-5dBic at Zenith
4dBic at 5° elevation above the
horizon
RHCP
Omni-directional - Azimuth
Hemispherical - Vertical
0.23Kg
Indian Remote Sensing Missions & Payloads – A glance
16.15
16.5.3.4 Radio Occultation Antenna
The Radio Occultation Antenna is a special Antenna designed and developed
for this application. Its main purpose is to acquire and amplify the signal from the
high atmospheric layers (ideally up to 600Km) to ground earth surface (ideally 0Km).
The major part of the gain of this Antenna (about 12dB) is concentrated on angle of
view of the lower atmospheric layers (under 100Km) where the signal is weaker due
to the atmospheric absorption, refractivity, and multipath effects.
The main functional and performance features of this Antenna could be
summarized in the following information:
Frequency bands: The R.O. antenna shall operate in two L frequency bands:
L1 = 1565.19 - 1613.86MHz & L2 = 1217.37 – 1256.36MHz
VSWR:
Polarisation: Circular Right Hand Polarisation is requested for both L1 and
L2 frequency band.
Axial Ratio: The 3.5dB value can be considered only in the baseline
coverage region; outside the axial ratio will be limited as much as possible.
Gain inside the baseline coverage region: The minimum value of 12dBi for
both L1 & L2 bands is critical related to the requested antenna dimension.
Gain inside the extended coverage region: The constraint of the minimum
gain of -3dBi in the extended coverage reduces the minimum gain value of the
baseline coverage region.
Azimuth Gain Ripple: The antenna gain ripple shall not vary by more than
2dB for any azimuth variation inside the baseline coverage region (0-100Km). For
the extended region the gain ripple will be minimized.
Functional Description
The main operations are:
 The ROSA Receiver performs the following main operations:
o
Allocates HW channels to GPS satellites
o
Receives L1/L2 C/A and P signals from GPS satellites
o
and decodes data
Indian Remote Sensing Missions & Payloads – A glance
16.16
o
message and recovers Navigation Data from each received GPS
satellite
When at least 4 GPS satellites are in view, performs position, time
and velocity calculation based on a Least Squares algorithm
(ECEFSPS solution)

In parallel, performs Filtered Navigation Solution (ECINKF solution); the
Kalman filtered solution is able to propagate the solution also in absence of
GPS measurements

information of each acquired GPS satellite with respect to the Receiver
platform, maintains a tracking list of visible satellites and performs
occultation events prediction

For observation events, when Carrier Lock is not possible, performs OpenLoop high-rate sampling of raw observables for carrier reconstruction on
ground

Monitors and maintains Receiver Health & Status
Indian
Indian Remote Sensing Missions & Payloads – A glance
16.17
OCM - Gujarat
SCATTERMETER - World
Indian Remote Sensing Missions & Payloads – A glance
16.18
Indian Remote Sensing Missions & Payloads – A glance
16.19
17 RESOURCESAT-2
17.1 Introduction
Resourcesat-2 is a follow on mission to provide service continuity to the
Resourcesat-1 users. Hence Resourcesat-2 payload systems were conceived around
IRS-P6 with certain improvements in payload electronics. Resourcesat- 2 spacecraft
is configured with improved features like 70 Km Mx data, Enhanced SSR memory,
new data handling system, 10/8 channels SPS, indigenously developed star sensor,
AOCE with Mil-1553 interfaces. Apart from Resourcesat -1 payloads, a new payload
called Hosted Indian payload from COMDEV, Canada for automatic identification of
ship was also flown.
17.2 Mission Objective
Mission objective of Resourcesat-2 are


To provide continued remote sensing data services on an operational basis for
integrated land and water resource management at a micro level with enhanced
multispectral/ spatial coverage and stereo imaging.
To further carryout studies in advanced areas of user applications like improved
crop discrimination, crop yield, crop stress, and pest / decease surveillance and
disaster management etc.
17.3 Orbital Parameters
Table 17.1 Orbit details of Resourcesat-2
Sl.No
1
2
3
4
5
6
7
Parameter
Orbit
Altitude
Inclination
Eccentricity
Period
Local Time
Repetivity Cycle
8
Distance between adjacent
Traces
Off Nadir coverage +/- 26 deg
Distance between successive
9
10
Resourcesat-2
Polar sun synchronous circular
817 Km
98.69 deg
0.0004
101.35 minutes
10.30 A.M
341 Orbits
24 days for LISS-3
5 days for AWiFS
5 days Revisit (LISS-4)
117.5 Km
398 Km (for LISS-4)
2820 Km
Indian Remote Sensing Missions & Payloads – A glance
17.1
Sl.No
11
Parameter
Ground tracks
Ground Trace velocity
Resourcesat-2
6.65 Km/s
17.4 Salient features of Spacecraft
Figure 17.1 Stowed view of Resourcesat-2
17.5 Payloads
Resourcesat-2 payload system consists of Four Payloads namely
1.
2.
3.
4.
Linear Imaging Self Scanning Sensor-4 (LISS-4)
Linear Imaging Self Scanning Sensor-3 (LISS-3)
Advanced Wide Field Sensors (AWiFS)
HIP
Indian Remote Sensing Missions & Payloads – A glance
17.2
17.5.1 Linear Imaging Self Scanning Sensor (LISS-4)
17.5.1.1 Introduction
LISS4 is a high resolution multi-spectral camera with three spectral bands
namely B2, B3 and B4 similar to those of LISS 3* and AWiFS camera. This camera
operates in three spectral bands B2 (0.52-0.59 µm), B3 (0.62-0.68 µm) and B4 (0.770.86 µm). The ground resolution of LISS-4 will be 5.8 m with the swath of 70 Km
from an altitude of 817 Km.
The three spectral bands are realized using field-splitting technique near the
focal plane. The final selection of the spectral bands is achieved by using appropriate
band pass filters in front of the detectors.
17.5.1.2 LISS-4 Specifications
Optical system
Type
telescope
Focal length
F-Number
Spectral Bands
:
Off
axis
unobscured
980 mm
4.0
B2
B3
B4
:
:
:
:
:
:
Field of view (FOV)
Across track
Along track
Telescope MTF
Optical Efficiency
:
:
:
:
+ 2.5º
+0.4º & -0.6º
>40% at 70 lp/mm
0.6
three-mirror
(0.52-0.59 µm),
(0.62-0.68 µm)
(0.77-0.86 µm)
Detector (CCD)
No. of pixels
: 12000
Pixel size
: 7 µm x 7 µm
No. of output ports
: 8
Separation between
Odd - Even rows
: 35 µ (5 scan lines)
System
IGFOV (m)
Across Track : 5.83
Along Track : 5.82
Swath (Km)
: 70.0 (Mono &Mx mode)
Integration time (ms)
: 0.8777142Quantization
10 bits (7 bits transmission to BDH after DPCM)
SNR (at saturation)
: >128
SWR (%)
: >20
Indian Remote Sensing Missions & Payloads – A glance
:
17.3
BBR (Pixel)
: + 0.25
Saturation radiance (mW/cm2/Sr/µm)
: B2 53
B3 47
B4 31.5
Raw Bus Power (W) @37V
Imaging Mode
Calibration Mode
Size (P x R x Y) (mm)
Weight (Kg)
EO Module
Camera
:
:
126(All Bands)
: 127.7 (All Bands)
742 x 596 x 888
:
:
95
104
17.5.1.3 System configuration
Electro optical module (EOM)
The Electro optical module (EOM) of LISS-4 consists of three mirror
assemblies, focal plane splitter optics and Detector Head Assembly (DHA) at
specified locations. The telescope is a three mirror off-axis reflective system (similar
to IRS-1C/1D PAN telescope).
Optical System
The optical system of LISS-4 consists of three mirrors unobscured off-axis
telescope (an off-axis concave hyperboloid primary mirror, a convex spherical
secondary mirror, and an off axis concave oblate ellipsoid tertiary mirror), focal
plane splitter assembly, and band-pass filters. A 245 mm diameter primary mirror
collects the radiation from earth and reflects it on the secondary mirror. The beam
reflected from secondary mirror falls on to tertiary mirror, which focuses the beam on
to the detector. Three focal planes are realized by splitting the field in the along track
direction using an isosceles reflecting prism with a slot. The beam corresponding to
B3 is transmitted through the slot while the B2 and B4 are reflected by prism sides.
The placement of band pass interference filter in front of CCD ensures the selection
of required band.
The telescope has an effective focal length of 980 mm and covers a field of
view of + 2.5º in across track and + 0.4º and -0.6º in the along track directions.
Detector Head Assemblies (DHA)
LISS-4 payload has three detector head assemblies (DHA) corresponding to
B2, B3 and B4 respectively. LISS-4 DHA for Resoucesat-2 is identical to
Indian Remote Sensing Missions & Payloads – A glance
17.4
Resoucesat-1 in terms of interfaces and basic philosophy, but has been realized with
reduced size and number of components. Also improvement has been carried out in
thermal interface.
Each DHA consists of
 12K linear array CCD
 Bias voltage generating circuits
 Clock driver circuits
 Heaters and thermistors for thermal control
 LEDs for On-board Calibration
The 12K element linear CCDs of Thomson make (TH31543) are used for
each spectral band. Each CCD has a pixel size of 7 µm x 7 µm. The Odd and Even
pixel rows are arranged in a staggered mode separated by 35 µ (equal to 5 scan lines).
Each CCD gives analog data on eight output ports - four for odd pixels and four for
even pixels. Each port provides data for 1520 pixels including 20 pre-scan/ white
reference pixels. CCD has in-built anti-blooming and integration control.
DHA receives +18.3 V DC regulated voltage from power package and
generates various bias voltages required for CCD operations using series regulator.
DHA receives clock signals at a TTL levels from timing and control logic circuits of
Camera Electronics (PLE12/13/14) and conditions them to suitable voltage levels and
drives the required capacitive loads of CCD using clock driver circuits. CCD requires
a total of 16 clocks for its operation.
Video data obtained from eight video ports are given to video processor
circuit (PLE12/13/14 of camera electronics).
Each band DHA consists of two identical PCBs and each PCB caters to
electrical requirements of four ports. DHA also receives +5.6 V regulated DC voltage
from spacecraft to be applied to heaters to maintain CCD temperature.
The CCD temperature increases considerably whenever DHA is powered. In
order to control the temperature excursion in the CCD, heaters are placed near the
CCD, which are switched ON whenever DHA is switched OFF and vice versa. This
ensures minimum change in CCD temperature at any time. CCD temperature needs
to be maintained within 202 ºC, hence DHA is cooled. To achieve temperature
control, control heaters are provided on the DHA. This is realized using a copper
braid whose ends are terminated with copper blocks. A compensatory heater of 1.8 W
(equal to CCD dissipation) is switched ON and OFF as complementary to LISS-4
OFF and ON respectively.
Indian Remote Sensing Missions & Payloads – A glance
17.5
17.5.2
Linear Imaging Self Scanning Sensor (LISS-3*)
17.5.2.1 Introduction:
The LISS-3* Camera is a medium resolution multi-spectral camera operating
in four spectral bands - B2, B3, B4 in Visible - Near infrared Range (VNIR) and B5
in Short Wave Infrared Range (SWIR) . This camera is similar to the LISS-3* of
Resoucesat-1. LISS-3* will have four spectral bands with independent optical
assemblies and a linear array detector for each channel providing identical IGFOV of
23.5 m. All bands will provide 100% albedo coverage with 1023 levels of
quantization.
The SWIR band is designed using a new custom built 6000 element Indium
Gallium Arsenide (InGaAs) CCD. Based on the experience of IRS-1C/1D in-orbit
performance, certain improvements have been incorporated in the LISS-3* design.
LISS-3* SWIR band has improved performance in terms of resolution with 23.5 m
compared to 70 m in IRS-1C/1D. The focal length of the SWIR band is modified to
meet the improved resolution.
17.5.2.2 LISS3* Specifications:
Optics
EFL (mm)
F-No
FOV (deg)
:
B2, B3 & B4
347.50.3
B5
451.750.3
:
:
<4.5
+5
<4.5
+5
0.52-0.59
0.62-0.68
0.77- 0.86
1.55 -1.70
:
:
:
6000
7 x 10
Si
6000
13 x 13
InGaAs
:
:
::
:
:
23.5
22.0
141
3.32
10
23.5
22.11
141
3.32
7
Spectral bands (µm)
B2 :
B3 :
B4 :
CCD
No. of Pixels
Pixel size (µm)
Detector
System
IGFOV (m)
Along track sampling (m)
Swath
(km)
Integration time (ms)
Quantization bits
Indian Remote Sensing Missions & Payloads – A glance
17.6
SNR (at saturation)
SWR (%)
BBR (Pixel)
Saturation radiance
(mW/cm2/Sr/µm)
:
B2 :
B3 :
B4 :
:
B2 :
B3 :
B4 :
Regulated Power (W)
Imaging Mode
Calibration Mode
:
Temperature Controller (TC)
Raw Bus Power
Imaging Mode
Calibration Mode
Size (PxRxY) (mm)
Weight (Kg)
EO Module
Camera
>128
>30
>30
>20
+ 0.25
53
47
31.5
>128
>20
+ 0.25
7.5
: 29.44(VNIR), 4.78(SWIR) (w/o TC)
31.15 (VNIR), 4.87 (SWIR) (w/o TC)
: 2.3
:
:
:
72.4 (All Bands)
74.9 (All Bands)
493x470.5x626.31
:
:
73.2
74.9
17.5.2.3 System Configuration
Each band has individual optics, DHA and camera electronics (CE). Four
identical DHAs, one each per band forms part of the EO module. The major
constituents of the payload are described below.
Optics:
The LISS-3* camera uses refractive optics for all four spectral bands. The
collecting optics consists of 8 refractive lens elements with the interference filter and
the thermal filter. The optical configuration consists of a multi-element lens
assembly. All the lens elements have spherical surface profile. Lenses of all four
bands are developed by LEOS.
Detectors:
VNIR bands, have 6000 elements devices (CCD 191A) with a pixel size of
10 µX7 µ on a pixel pitch of 10 µ with two video output ports. SWIR band, has 6000
element staggered array device with a pixel size of 13 µX13 µ on a pixel pitch of 13
µ and line pitch of 26 µ with two video output ports
Detector Head Assembly for VNIR:
Indian Remote Sensing Missions & Payloads – A glance
17.7
DHA houses linear array CCD-detector, PCB, onboard calibration LEDs and
mechanical mount. LISS 3* will have three VNIR band DHAs.
Description of CCD 191A Device:
The CCD 191A has 6000 photosensitive elements each of size 10µm along
the array and 7 µm perpendicular to array length. The device has two video output
ports and packaged in a custom build 40 pin DIP ceramic package. CCD 191A is
fabricated using advanced n-channel isoplanner buried channel technology.
The photosensitive elements accumulate charges during integration period.
These accumulated charges are transferred to two analog shift register using transfer
clocks. Analog shift register transport these charge packets sequentially, with the help
of 2-phase shift clocks, to charge amplifier where charge to voltage conversion takes
place and three levels analog voltage signal is available on each port. The true video
information is carried out by taking difference of reference level and video level.
Both the ports start with 10 prescan reference pixels followed by 3000 photoresponsive pixels. The ports here correspond to the even and odd pixels respectively.
 Anti-Blooming control
In order to take care of the super saturation problems seen in IRS-1C/1D inorbit, Anti-blooming control (ABC) feature of CCD191A is incorporated in the
VNIR bands of LISS3*. This feature is used to arrest the Raw-Bus current increase
when camera is exposed to higher illumination compared to its saturation settings.
The ABC is implemented by proper setting of ‘Integration Control’ bias voltage (VIC)
available on the CCD pin and is adjusted by trimming the bleeder resistors in the bias
supply circuit in the DE package. .
Onboard Calibration:
Calibration assembly consists of LED wired on PCB and mounted on LED
holders. Four LEDs connected in series mounted on LED-holder. Two such holders
one on each side of CCD are mounted on DHA plate/flange. All LEDs are connected
in series. A DC current of 161mA is passing through LEDs. Calibration levels are
generated using exposure control feature of the CCD.
Onboard calibration is to be carried out using 8 LEDs (02 sets of 4 LEDs)
covering the complete array. LED profile depends on the LED mounting geometry.
16 levels will be generated using integration control feature. The LED intensity is
expected to vary with temperature.
Mechanical Mount:
Indian Remote Sensing Missions & Payloads – A glance
17.8
The PCB is mounted on the mechanical mount made from lnvar and back
cover of aluminium. The calibration LED assembly is also mounted on the same
mount.
Detector Head Assembly for SWIR:
The detectors used for SWIR channels in RS-1/2 are of type TH31906. This
detector uses modular approach. Each module contains 600 photodiodes arranged in
staggered fashion and CMOS multiplexers on either side of the array for even and
odd pixels readout. A total of 10 such modules are butted together to form a linear
array of 6000 pixels. Two consecutive pixels are lost at each splice due to
butting.Photosensitive area of each pixelis13 µmX13 µm with 13 µm pitch along the
length of the array. The odd and even lines of the staggered configuration are
separated by 26 µm. the photodiodes and CMOS MUX are glued on a 2 mm thick cofired ceramic plate.
The photodiodes in TH31906 are operated under near zero bias condition.
This is ensured by placing a suitable resistance between VREF and ADJREF pins.
In order to avoid reflections from the focal plane which manifests itself as
ghost image after re-reflection from interference filter which is part of camera optics,
most of the focal plane is masked and 1 mm wide and 83 mm long slit which is 1mm
above the surface of photodiode die exposes photodiodes to the incident radiation.
But reflections from the edges of this slit cause some extra illumination in few of the
pixels. In order to avoid this, two external slits of appropriate dimensions are placed
near optics exit so that the edges of the slit on mask are properly shadowed.
17.5.3 Advanced Wide field sensor (AWiFS)
17.5.3.1 Introduction
The Advanced Wide Field Sensor (AWiFS) camera will be catering to the
high temporal resolution requirement of RS-2 mission with revisit period of 5 days. It
has IGFOV of 70m from an altitude of 817 Km. The AWiFS camera consists of four
spectral bands, three in the visible and in near IR (VNIR B2, B3 and B4) and one in
the short wave infrared (SWIR B5) similar to AWiFS of Resoucesat-1.
AWIFS is configured as a set of two identical camera modules i.e. AWIFS-A
&AWIFS-B. Each camera consists of four lens assemblies, detectors and associated
electronics pertaining to the four spectral bands B2, B3, B4 and B5. The two cameras
are combined to generate the required field of vie commensurate with the desired
swath. The imaging concept is based on push broom scanning that uses a linear array
CCD placed in the focal plane of the optics. The 4 spectral bands are realized using
independent refractive optical assemblies. To generate the required swath along with
Indian Remote Sensing Missions & Payloads – A glance
17.9
the desired overlap of 150+20 pixels, the two EO modules will be mounted on the
spacecraft deck such that they are squinted with respect to nadir by 11.84º. The field
of view of each lens assembly is  12.5º. In nutshell, total field coverage of 47.94º is
shared equally by two optical heads for each of the four bands.
AWiFS Specifications
B2, B3 & B4
Optics
EFL (mm)
F-No
FOV (deg)
Spectral bands (µm)
:
139.5 + 0.15
: <5.0
: +12.5
B2 :
B3 :
B4 :
B5
181.35 + 0.2
<5.0
+ 12.5
0.52-0.59
0.62-0.68
0.77- 0.86
1.55-1.70
CCD
No. of Pixels
:
6000
6000
Pixel size (µm)
:
7 x 10
13 x 13
Detector
:
Si
InGaAs
System
IGFOV (m)
Across track
Along Track
56 (@ nadir),
70(off-nadir)
: 66
Swath (km)
:
740
740
Integration time (ms)
:
9.96
9.96
Quantisation (Bits)
:
: 12(MLG)
SNR (at saturation)
56 (nadir)
70(off-nadir)
66
:
12(MLG)
> 512
> 512
SWR (%)
:
BBR (Pixel)
:
B2
30
B3
30
B4
20
+ 0.25
Radiance @ Saturation (mW/cm2/Sr/um)
B2 : 53
B3 : 47
B4 : 31.5
Indian Remote Sensing Missions & Payloads – A glance
20
+ 0.25
7.5
17.10
Calibration levels
: 16
6 non-zero
Regulated Power (W)
Imaging Mode
: 47.16(VNIR), 8.31(SWIR) (w/o TC)
Calibration Mode
: 48.81 (VNIR), 8.554 (SWIR) (w/o TC)
Temperature Controller (TC) :
4.6 (SWIRTC)
Raw Bus Power (@37V)
Imaging Mode
: 124.1(All Band AWiFS-A&B)
Calibration Mode
: 126.7(All Band AWiFS-A&B)
Size (PxRxY) (mm)
AWiFS A
AWiFS B
Weight (Kg)
EO Module
Camera
:
:
471 x 410 x 316
418 x 410 x 316
:
:
28(AWiFS A), 25.5 (AWiFS B)
55.8(AWiFS A + AWiFS B)
17.5.3.2 System Configuration
Each band has individual optics, DHA and camera electronics (CE). Four
identical DHAs, one each per band forms part of the EO module. The major
constituents of the payload are geven below.
Optics:
The optics of AWiFS camera consists of two optical heads (two lens
assemblies) for each of the four spectral bands to cover the full swath. Each lens
assembly comprises a Thermal Filter, interference Filter, and 8 lens elements. In view
of the required geometric/radiometric performance, f/5 system is employed for both
VNIR and SWIR bands. All the lens elements have spherical surface profiles. The
optics for the same is being developed at LEOS.
Detectors:
For the 3 VNIR bands, 6000 elements devices (CCD191A) with a pixel size
of 10 µX7 µ on a pixel pitch of 10 µ with two video output ports is used. For the
SWIR band, a 6000 element staggered array device with a pixel size of 13 µ X 13 µ
on a pixel pitch of 13 µ and line pitch of 26 µ with two video output ports is used.
Detector Head Assembly for VNIR:
DHA houses linear array CCD-detector, PCB, onboard calibration assembly
and mechanical mount. AWiFS-A & B will have three VNIR band DHAs.
Onboard Calibration Assembly:
Calibration assembly consists of LED wired on PCB and mounted on LED
holders. Four LEDs connected in series mounted on LED-holder. Two such holders
Indian Remote Sensing Missions & Payloads – A glance
17.11
one on each side of CCD are mounted on DHA plate/flange. All LEDs are connected
in series. A DC current of 161 mA is passing through LEDs. Calibration levels are
generated using exposure control feature of the CCD.
Mechanical Mount:
The PCB is mounted on the mechanical mount made from lnvar and back
cover of aluminium. The calibration LED assembly is also mounted on the same
mount.
Detector Head Assembly for SWIR:
The detectors used for SWIR channels in RS-1/2 are of type TH31906. This
detector uses modular approach. Each module contains 600 photodiodes arranged in
staggered fashion and CMOS multiplexers on either side of the array for even and
odd pixels readout. A total of 10 such modules are butted together to form a linear
array of 6000 pixels. Two consecutive pixels are lost at each splice due to butting.
Photosensitive area of each pixelis13µmX13µm with 13µm pitch along the length of
the array. The odd and even lines of the staggered configuration are separated by
26µm. the photodiodes and CMOS MUX are glued on a 2mm thick co-fired ceramic
plate. Electrical interconnections are provided by either gold coated tracks or wires.
The photodiodes in TH31906 are operated under near zero bias condition.
This is ensured by placing a suitable resistance between VREF and ADJREF pins.
In order to avoid reflections from the focal plane which manifests itself as
ghost image after re-reflection from interference filter which is part of camera optics,
most of the focal plane is masked and 1mm wide and 83mm long slit which is 1mm
above the surface of photodiode die exposes photodiodes to the incident radiation.
But reflections from the edges of this slit cause some extra illumination in few of the
pixels. In order to avoid this, two external slits of appropriate dimensions are placed
near optics exit so that the edges of the slit on mask are properly shadowed.
Camera Electronics:
Each camera and detector have independent camera electronics to cater to
various functional and performance requirements. AWiFS-A accommodates
hardware for Detector 1 of all bands and similarly AWiFS-B covers hardware for
Detector 2 of all bands. In RS-2, all four bands use Multi Linear Gain (MLG)
technique to provide 12 bit performance retaining 10 bit hardware interface. RS-2
camera electronics (CE) hardware is realized using passive SMDs, FPGAs, double
sided or multi-layered PCBs and tray packaging. This has resulted in improvements
with respect to size, weight and power. Similar approach has been adopted for SWIR
electronics.
Indian Remote Sensing Missions & Payloads – A glance
17.12
VNIR:
Camera electronics is custom designed for Resourcesat-2 AWiFS camera. The
system is configured to meet the functional and performance requirements with
minimum hardware complexity. The salient features of AWiFS (VNIR) camera
electronics are
 Separate camera electronics for each detector
 Separate detector-drive electronics for each detector
 Separate timing logic for each detector without redundancy(like in
Resoucesat-1)
 Cross coupling of BRC and WLS
 Hot redundancy for data and telemetry
The electronic system design of Resourcesat-2 maximally uses the
subsystems and circuit blocks designed and developed for Resourcesat-1, thereby
improving reliability. Camera electronics is modular for each detector. The functional
blocks of camera electronics consists of
 Bias generator
 Clock driver
 Cal LED Driver
 Video Processing Electronics
 Timing and Calibration Logic
 Telemetry and Telecommand Interface
Bias generator:
Bias generator circuit consist of linear regulators and capacitor multiplier
filters, which provides 4 regulated low noise bias voltages for detector operation. The
circuit also incorporates short circuit protection for VDD. The circuit configuration is
same as that used in OCM.
Clock Drivers:
Detector electronics receives 9 clocks from payload electronics package for
its operation in phased read out mode. Clock driver translate these TTL signals to
MOS level with adequate capability to drive capacitive loads for realizing fast
rise/fall times. The high level required by photo gate, transfer and reset clocks are
typically 15 V and 10 V for transport and integration control clocks. Accordingly,
two linear regulators are used to generate low noise supply voltages required for 15 V
and 10 V.
CAL LED Driver:
Indian Remote Sensing Missions & Payloads – A glance
17.13
Calibration requires a light source in front of the CCD. IRS payloads uses
solid-state LED based source. To drive LEDs a low noise constant current is
generated. A regulator ie wired with LEDs in the feedback loop. The output gain
resistors and the current deciding resistor at the inverting input of the error amplifier
control the required current.
17.5.4 HIP (Hosted Indian Payload)
17.5.4.1 Introduction:
The Automatic Identification System (AIS) Payload flown in Resourcesat-2 as an
experimental payload for ship surveillance in VHF band to derive the position, speed,
start point and end point of ships. The VHF antenna which is provided by CMG,
ISAC consists of four orthogonally polarized monopole antennas (one is left hand
circular polarized and another right hand circular polarized), placed at the edges of
EP-01 panel, receive data from ships which may have horizontal or vertical
movement because of sea tides. The data received from ships is stored in the onboard
memory (4 GB) and it is transmitted through QPSK modulated S-Band carrier (2280
MHz) to ISTRAC and Canadian stations. VHF data (160-162 MHz) is uplinked to
AIS payload at 2.5 Mbps and stored in onboard memory of 4 GB which can
simultaneously record and playback the data.
The AIS is a shipboard broadcast system. The AIS will improve security by
increasing the Coast Guard’s awareness of vessels in the maritime domain, especially
vessels approaching ports. The AIS corroborates and provides identification and
position of vessels not always possible through voice radio communication or radar
alone.
Ships can be identified anywhere in the Oceans/seas by receiving AIS
signals. Unidentified ships, which can pose threat to security, can be figured out by
spotting all the ships through radar network and isolating the unidentifiable ships
near coastal zones.
AIS antennae Operate in the VHF maritime band (160 -162 MHz)
standardized digital communication protocols. Each station transmits and receives
over two radio channels to avoid interference problems. Transmissions use 9.6 Kb
GMSK/FM modulation uses Self-Organizing Time Division Multiple Access
(SOTDMA) technology to meet this high broadcast rate and ensure reliable ship-toship operation. Each station determines its own transmission schedule (slot), based
upon data link traffic history and knowledge of future actions by other stations.
 The data received from satellite is processed offline at Bangalore and
Canada.
Indian Remote Sensing Missions & Payloads – A glance
17.14
 COMDEV agreed to provide ships data, processed at Bangalore and
Canada, for Indian region and Indian ships data throughout the world to
ISRO.
17.5.4.2 Mission Objectives:
The mission Objectives of the AIS program are as follows:
 Collect samples of AIS ship transmissions over the Indian Area of Interest
within the limits imposed by the mission constraints (power, availability of
ground stations)
 Collect samples of AIS ship transmissions over other parts of the globe
within the limits imposed by the mission constraints (power, availability of
ground stations)
The current system has been optimized using two ground stations, one in
Bangalore and one in northern Canada
17.5.4.3 Payload Description
The AIS payload is designed to perform AIS signal receive, store and
forward functions covering the two AIS frequencies of 161.975 MHz and 162.025
MHz.
The payload is comprised of
 Two AIS Receive antennas, circular polarization (one left handed, one
right handed).
 Two RF cables between the AIS antennas and the AIS Receiver.
 An AIS Receiver provided by COMDEV that provides the power
conditioning, RF front end, digital control, data storage, data
conditioning and data transmission to the S-Band downlink
 ISRO’s cables to carry the AIS data signal from the AIS Receiver to the
S Band Transmitter.
 An S Band Transmitter provided by ISRO, 16 Mbps QPSK (the
transmitter will receive two signals at 8Mbps each, used as I and Q
signals for the modulation).
 An S Band Antenna provided by ISRO
Indian Remote Sensing Missions & Payloads – A glance
17.15
Indian Remote Sensing Missions & Payloads – A glance
17.16
Indian Remote Sensing Missions & Payloads – A glance
17.17
Indian Remote Sensing Missions & Payloads – A glance
17.18
18 YOUTHSAT
18.1 Introduction
The Youthsat is the second small satellite fabricated by ISAC. Youthsat
carried three payloads namely SOLRAD, LiVHySI and RaBIT. The remote sensing
data from this micro satellite is used for scientific studies like research of solar flare
activity, mapping of Total Electron Content (TEC) of the ionosphere and measuring
airglow of the earth’s atmosphere.
18.2 Mission Objective


Mission Objectives of Youthsat are
To build, launch and operate 3 axis stabilized Micro satellite for launch onboard PSLV as an auxiliary satellite with scientific payloads that are useful for
observing solar flares and also for study of their impact on atmosphere.
To involve the youth consisting of students, research scholars etc., for the
development and use of payloads mentioned above, in order to inculcate interest
and participation in space related activities and also to participate in the data
analysis.
18.3 Orbital Parameters
Orbital parameters of Youthsat is as given below.
Local Time
Altitude (Km)
Semi Major Axis (Km)
Inclination (Deg)
Orbits/Cycle
Orbit/Day
Repetivity
Period (Min)
Ground track velocity (Km/s)
10.30 AM
817
7195.11
98.69
341
14.22
24 Days
101.35
6.65
18.4 Payloads
Youthsat is second in the Indian Mini Satellite -1 Series carrying three
payloads namely SOLRAD, LiVHySI and RaBIT.

SOLRAD by Moscow University (Solar Radiation Experiment)

RaBIT by SPL-VSSC (Radio Beacon for Ionosphere Tomography)

LiVHySI by VSSC & SAC (Limb Viewing Hyper Spectral Imager)
Indian Remote Sensing Missions & Payloads – A glance
18.1
18.4.1 SOLRAD Payload
SOLRAD (Solar Radiation Experiment) is a co-operative joint scientific
mission between India and Russia with participation of youth from both the
countries. The payload is developed with an aim to inculcate interest in the youth in
space research and space technology.
Scientific goals: SOLRAD instrument is designed in SINP/MSU to study
time variations of solar x-ray and gamma-ray flux and spectra as well as the
variations of the flux of charged particles generated in the Sun or in the Earth
vicinity. Astrophysical gamma-ray bursts and some variable sources can be also
studied.
SOLRAD experiment will provide the measurements in the range:
•
X-rays and gammas 0.02-10 MeV
•
Electrons 0.3-3.0 MeV
•
Protons 3-100 MeV, Alphas 5 - 24 MeV/nucl., nuclei of C, N, O
group 6 - 15 MeV/nucl.
The goal is research of solar flare activity by measuring temporal and
spectral parameters of solar flare X-rays and gamma rays as well as of charge particle
(electron and protons) fluxes in the Earth Polar cap regions which are sensitive to
solar flare activity. The scientific objectives are met with an X-ray and Gamma ray
detector – spectrometer system using a NaI(TI) / Cs(TI) phoswich unit and a charged
particle detector system using a silicon detector telescope unit. SOLRAD payload
consists of two modules namely detector module and electronics module. The
Detector module consists of two independent units: Detector Unit for Electrons
(DUE) and Detector Unit for X-rays and Gamma (DUXG). Based on the scientific
objective, SOLRAD payload has to be pointing towards Sun during Sun Pointing
period of the orbit.
Figure 18.1 Detector Box
Figure 18.2 Information Box
Indian Remote Sensing Missions & Payloads – A glance
18.2
The phenomena to be studied with SOLRAD particle detector are:
 SEP events and solar charged particle penetration boundaries in the Earth’s
magnetosphere during geomagnetic disturbances;
 Dynamics of the relativistic electron fluxes in the Earth’s magnetosphere;
 Energetic particle precipitation under the Earth’s radiation belts (at low and high
latitudes).
 The phenomena to be studied with SOLRAD x-ray and gamma detector are:
 Solar flares: fast x-ray and Gamma-ray flux variations
 Solar flares: thermal and non-thermal part of X-ray and gamma-ray spectra
 Solar flares: gamma-ray lines
 Astrophysical gamma-ray bursts (GRB)
 X-ray binaries, pulsars, SGR, etc
SOLRAD payload is always kept ON throughout the time in the orbit
irrespective of the attitude geometry. SOLRAD payload data is stored in its internal
memory. SOLRAD payload has a provision onboard to store the last 20 sessions
payload data, which can be played back on requirement by issuing a SOLRAD multi
data command appropriately. The estimated data volume is 100 Mbytes/day.
18.4.2 RaBIT Payload
Scientific Objectives: In the recent years it has become clear that the
understanding of the ionosphere is central to the design of many modern
communication, navigation and positioning systems. In the past, ionospheric studies
have been confined to traditional areas of broadcast and radio communication. With
the increasing use of satellites for navigation and positioning (GPS, GLONASS, etc.),
characterizing and modeling of the ionosphere (its spatial and temporal variability)
has become extremely important. This is because the position accuracy achievable
from navigation satellites is largely affected by the intervening ionosphere. The
range error is directly proportional to the total electron content (TEC) along the ray
path. The equatorial ionosphere with its inter-related unique features like equatorial
ionization anomaly (EIA), equatorial spread F (ESF), poses additional challenges due
to their highly dynamical nature and large spatial and temporal variability which are
not yet well quantified even for quiet conditions. The geomagnetic storms
significantly alter the background ionospheric and thermospheric structure, energetic
and dynamics and as a consequence modify the major equatorial ionospheric
processes.
The morphological features of the equatorial ionosphere are well understood,
but its day-to-day variability still remains enigmatic. These facts highlight the need
for a comprehensive understanding of the complex processes of the ionosphereIndian Remote Sensing Missions & Payloads – A glance
18.3
thermosphere system including its response to the various external forcing so as to
reach a level of predictive capability. One of the most important aspects still to be
understood is the temporal and spatial variability in electron density distribution
during space weather events. It has been established from the Indian Coherent Radio
Beacon Experiment (CRABEX) program, using dual band coherent transmissions
from Low Earth Orbiting Satellites (LEOS) that the tomographic techniques are very
effective and useful in investigating the large-scale structures over low and equatorial
latitudes, like equatorial ionization anomaly (EIA), equatorial spread F (ESF), their
temporal and spatial variability, their inter relationship and response to space weather
effects.
The main objective of RaBIT payload(Radio Beacon for Ionosphere
Tomography) is to measure the Total electron content (TEC) of the Ionosphere. The
position accuracy achievable from navigation satellites is largely affected by the
intervening ionosphere. The range error is directly proportional to the total electron
content along the ray path. It is understood that ionospheric TEC measurement
simultaneously along a latitudinal chain of receivers could be used for tomographic
imaging, i.e., for obtaining the latitude –altitude distribution of electron density of the
ionosphere. RaBIT payload being an RF payload, it does not have any interface with
Base Band Data handling system. RaBIT payload has to be on the earth-viewing side.
The scientific objectives of RaBIT payload are:




To study the structure and dynamics of equatorial ionosphere over the Indian
region using tomographic technique.
To study the coupling between high and low latitudes during space weather
events.
To study the ionospheric effects of various solar and geophysical factors.
Transcontinental studies of the ionosphere in Russia and India during different
seasons and local time intervals
Ionospheric tomography: Ionospheric tomography is a powerful tool to
address the spatial variability of the ionosphere. The advantage of tomography
technique is that it can give a snapshot picture of the latitude-altitude variation of the
ionosphere, using data from a chain of simple, inexpensive ground receivers, by
recording coherent beacon signals from a low-earth orbiting satellite. The primary
data for the tomographic inversion is the line of sight TECs estimated along a number
of ray paths from a chain of ground receivers aligned along the same longitude.
These TECs are then inverted to obtain the electron density distribution as a function
of latitude and altitude over a given longitude. The schematic geometry of the CIT is
shown in the figure below. In the simple case the ionosphere is replaced by pixels of
appropriate size and electron density within each pixel is assumed to be a constant
(piecewise constant).
Indian Remote Sensing Missions & Payloads – A glance
18.4
Then mathematically, ionospheric tomography problem reduces to
Y  Ax  E
Where Y is the observed TEC data, x is a the unknown electron densities, and
A is the geometry matrix, which describes the relationship between the received TEC
data and the electron densities on each ray path (the length of the ray in the
corresponding pixel). Thus the electron density in each pixel is obtained as x = A-1
Y. In practice the inverse of the large geometry matrix is estimated by either
truncated Singular Value Decomposition technique or Algebraic Reconstruction
Technique.
Working Principle: The basic data for ionospheric tomography is the line of sight
TEC (STEC). The STEC is obtained by Differential Doppler technique. Here the
measured data, is the relative phase between 150 and 400 MHz, is proportional to the
relative slant TEC (STEC) along the propagation path of the signal as
(1)
  C D x STEC
Where,  is measured in radians, STEC is in m-2 and CD = 1.6132 x 10-15 for
NNSS satellites (Leitinger, 1994). Since the phase measurements are accurate to <
5when the receiver is at locked condition, and the data sampling is at 50 Hz, these
observations yield accurate estimates of the relative TEC, with errors < 0.05%.
Estimation of TEC: The ground receiver measures the phase difference between the
incoming signals, and the TEC is estimated by the method of Differential Doppler
method. Here, based on the phase or frequency shift measurements which results
from the changes in optical path length P =  n ds: where n is the refractive index and
is a measure of electron density, Ne.
Indian Remote Sensing Missions & Payloads – A glance
18.5
RaBIT Electronics: The purpose of RaBIT is to measure the Total Electron Content
(TEC) of Ionosphere. RaBIT will generate two phase coherent frequencies, 150MHz
and 400MHz. The relative phase of 150MHz with respect to 400MHz is proportional
to the slant relative TEC along the line of sight. The basic source is a coaxial
resonator oscillator (CRO) at 1200MHz. This is phase locked using an integer PLL.
The reference to the PLL is a Temperature compensated Oven Controlled Crystal
Oscillator (TC-OCXO). A clock distribution IC with programmable internal
frequency divider generates two coherent frequencies viz, 400MHz, and 150MHz.
An 8-bit microcontroller is used to program the PLL and to issue a synchronization
command for synchronizing 400MHz and 150MHz signals. These outputs are filtered
using in-house made band pass filters, which improve the signal quality. For
improving return loss, attenuator pads are used at both the outputs, before and after
amplification. The amplifiers are realized using Monolithic Microwave Integrated
Circuits (MMIC). The final stage in each chain consists of a power amplifier, which
enhances the power to 1.58 Watts. The entire circuitry works with a single 3.3V
power supply. This power is derived onboard using a hybrid DC/DC converter with
built in EMI filter. The 150MHz and 400MHz signals are combined using a lumped
element frequency combiner to get nominal output power of 1W.
Antenna systems: RaBIT antenna is a deployable antenna. The deployable antenna
system consists of (i) Boom assembly, (ii) Dipole sub assembly, (iii) UHF and VHF
reflectors, (iv) Retention and release mechanism and (v) Deployment and locking
mechanism. The major subassemblies of the system are detailed below:
Boom Assembly: The deployable antenna system consists of a centrally
positioned boom to which all subsystems are assembled. The boom assembly consists
of two parts viz a conical lower part and a cylindrical upper part assembled using a
lap joint at the center. The base of the boom is assembled to satellite deck. The top of
the boom provides interface for mounting TTC antenna. Boom assembly is the
central structural element of the antenna system. It provides the structural interface
for various elements of the system. Dipole sub assemblies and reflector are attached
to the boom assembly through specially designed hinges.
Dipole sub Assembly: The dipole sub assembly consists of tubes (OD 12
mm, WT 1mm) made of brass. Two dipoles sub assemblies are symmetrically
attached to the top of the boom at diametrically opposite locations. Each dipole sub
assembly is made of two brass tubes that is assembled using TRAP holder made of
GFRP material to enable the system to work for dual frequency. The dipole sub
assembly is electrically insulated from boom. The dipole tubes are bonded to TRAP
holder using Hysol 9394. The trap holder houses the LC circuit which enables the
antenna to work for dual frequencies.
Indian Remote Sensing Missions & Payloads – A glance
18.6
UHF Reflector & VHF Reflector: The UHL reflector is made with rod made
of Brass to meet the inertial constraint to avoid collision during deployment. The
VHF reflector is made with tube made of Al alloy. The UHF reflector is a brass rod
with OD 12 mm and the VHF reflector is an Al alloy tube with OD 12 mm. The UHF
&VHF reflectors are positioned at a distance of 170mm and 425mm from dipole sub
assembly respectively.
Retention and release Mechanism: In order to meet the envelope constraints, the
dipole and reflectors are stowed during the ascent phase of the mission and deployed
after injection of satellite into the orbit. The stowed dipole and reflectors are held in
position using rope made of Nylon 6. The Nylon rope, either ends are attached to the
strain gauged load links through bowline. The rope is finally assembled to the boom
through a bracket at two locations. The antenna elements are preloaded against the
boom by tightening the rope. The tension in the rope is controlled using preload bolts
and monitored using the strain gauged load links. The rope is also touching the
heating wire (SS 304 wire of dia 0.25 mm) routed through a block made of
Machinable glass ceramic. The release of the antenna elements are achieved by
fusing the rope using the heating wire. Two sets of heating wire are provided on the
block to improve system reliability.
Deployment mechanism: The deployment mechanism moves the dipole and
reflectors on release from the stowed configuration to the final position. Torsion
springs are mounted at the hinge joint of dipole and reflectors to give necessary
energy for deployment and also the necessary preload at the deployed condition.
Indian Remote Sensing Missions & Payloads – A glance
18.7
Indian Block of Stations:
Station
Lat. (°N)
Long. (°E)
Trivandrum
8.5
77.0
Bangalore
13
77.6
Hyderabad
17.8
78.0
Bhopal
23.2
77.2
Delhi
28.6
77.2
Russian Block of Stations:
Station
Lat. (°N)
Norilsk
69.2
Turukhansk
65.46
Tomsk
56.3
Long. (°E)
88.6
87.56
84.55
18.4.3 LiVHySI Payload
In recent years the need for a comprehensive understanding of the complex
processes of the ionosphere-thermosphere system, including its response to the
various external forgings so as to reach a level of predictive capability, has been felt.
As is known, the information regarding the thermosphere can be obtained through
atmospheric emissions known as ‘Airglow’ while ionosphere variability’s can be
studied through radio wave propagation characteristics. As a consequence,
simultaneous measurements of (i) airglow emission intensity from the menopause
(height region around 90 km), ionosphere-thermosphere and, (ii) electron density
distribution would provide important insight into the generation mechanisms and
evolution of these processes. In this context, the combination of LiVHySI and RaBIT
would provide excellent simultaneous measurements of neutral and plasma
parameters respectively, complementing each other and also the solar radiation
measurements through SOLRAD. Both these Indian experiments are the first of its
kind indigenously built experiments onboard an Indian satellite.
The terrestrial upper atmosphere i.e. about 80 km to 1000 km is a closely
coupled two component system where the neutrals (thermosphere) and plasma
Indian Remote Sensing Missions & Payloads – A glance
18.8
(ionosphere) coexist with linkages to magnetosphere higher above and the lower
atmosphere below.
Figure 18.3: Exploded view of LiVHySI
This region consists of ionized matter (ionosphere) and neutral matter
(thermosphere in the form of atoms and molecules). This part of the earth’s
atmosphere responds sensitively the solar radiation and wind reaching the earth
through the interplanetary space. This region is controlled primarily by the solar EUV
radiation through atmospheric heating, photo dissociation and photo ionization of the
atmospheric species. The electrons and ions constitute the electrically conducting
ionosphere with the neutral atmosphere (thermosphere) dominating the background.
Indian Remote Sensing Missions & Payloads – A glance
18.9
The state of thermosphere-ionosphere region at any given time and location
is determined not only by chemistry but also by the transport through neutral winds,
electric fields and field-aligned plasma diffusion. For instance, solar wind–
magnetosphere interactions cause significant changes in the energies of this region
over high latitudes. Over low and equatorial latitudes, the scenario is even more
complicated as the energetic and dynamics is affected not only by the direct solar
forcing but also by the non local forcing from the high latitudes and the atmosphere
lower below it.
Figure 18.4 A typical product of LiVHySI
The individual constituents of the atmosphere whether they are atomic and
molecular in nature play important role in the process of upper atmospheric energy
balance. The lifetime of most of these species, to a large extent, are controlled by the
photochemical processes involving them. A number of the atmospheric species get
excited and undergo specific spectral transitions as a result of these processes.
Consequently, atomic and molecular emissions occur depending on the lifetime of
the meta stable state and the timescale of the ongoing quenching reactions. These
atmospheric emissions are known as the `Airglow’. The broad classification of the
airglow phenomenon is day glow, nightglow or twilight glow depending on the time
of the day it is being observed. Twilight glow can also be termed as the day glow as
seen from the night sky. The phenomenon of excitation and de-excitation over the
polar-regions is known as Aurora. Though, the variations in the airglow intensity
would primarily be caused by the changing relative contribution of the various
chemical channels causing the particular excitation, transport effects would also
modulate the observed airglow intensity at any given time. As a consequence, these
airglow emissions thus serve as a perfect tracer for the processes occurring in the
Indian Remote Sensing Missions & Payloads – A glance
18.10
altitude regions from which they emanate. LiVHySI is a wedge filter based
instrument that is capable of making simultaneous measurements of the intensity of
many airglow emissions at different wavelengths, emanating within 80-600km
altitude region within the limb of earth. The airglow emissions that are of interest to
us are listed here giving details of the emitting species and corresponding
wavelengths.
Wavelength(λ in nm)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
First negative band of N2427.8
NI 520.0
OI 557.7
NaI 589.0
OI 630.0
OI 636.4
OH 731.6
OII 732.0
OH 740.2
O2 762.0
OI 777.4
OI 844.6
O2 864.5
Emission
Altitude Type
of
Range(km)
emission
120-250
Band
100-220
Atomic
90-120 & 150-200
Atomic
90-100
Atomic
160-500
Atomic
160-500
Atomic
80-98
Band
100-200
Atomic
80-98
Band
80-100
Band
250-350
Atomic
250-350
Atomic
100-200
Band
Payload Operating Principle:
The ‘Limb Viewing Hyper Spectral Imager’ referenced to as LiVHySI would
be continuously imaging the earth’s limb along the meridian between ~ 80-600 km as
it moves in the polar orbit. As mentioned earlier, the atmosphere in this altitude
region is emanating a range of prominent airglow emissions at different wavelengths
maximizing at different heights. The details of these emissions have been given in
Table above. Further, the signals coming from the limb of earth would be spectrally
dispersed only along the altitude while spatial variability that could exist horizontally
would be time averaged depending upon the temporal resolution of the proposed
measurements, since the satellite is moving with a velocity of ~8-10 km/s. In this
context, the 256 pixels side of the detector would be aligned vertically (Yaw axis)
along the altitude axis, while the 512 pixel side i.e. wavelength side of the detector
would be employed horizontally (Band 1 is along +Roll side, Band 512 is along –
Roll side). In this configuration, the imaged airglow emissions would not only
provide the altitudinal distribution of the emitting species but also give us an insight
Indian Remote Sensing Missions & Payloads – A glance
18.11
into the physical, chemical and transport processes operating at different altitude
regimes of upper atmosphere.
The main objective of the instrument is to perform airglow measurements in
the Earth’s upper atmosphere (80 to 600 km) in a spectral range of 450 nm to 950
nm. The observations would be carried out in the earth’s limb viewing mode with a
range of about 3172 km from a LEO sun-synchronous polar orbital platform (altitude
of 817 km). Sensor Development Area (SEDA) at Space Applications Centre has
developed this Hyper-spectral Imager as a part of scientific payload onboard
Youthsat. This instrument has taken the advantage of the design and development of
similar instrument hardware that was developed at SAC and used in Chandrayan-1
and IMS-1 missions.
FOV of LiVHySI
Limb of earth
V_
Altitude
(Emissions
to
be
spectrally
dispersed)
satellite
LiVHySI
airglow
Spatially
averaged
Global coverage of air glow measurements is required to generate the
required database to study and understand various aspects of the space weather. This
is possible by satellite based observations. The Earth’s Limb viewing geometry is
chosen because it provides a number of advantages as compared to the nadir viewing
geometry. The horizontal line of sight through the Earth’s limb contains up to sixty
times more emitting material than a corresponding nadir view, providing greater
sensitivity for measurement of tenuous species. The combination of the spherical
geometry of the Earth’s atmosphere and the exponential decrease of gas density with
altitude provides data heavily weighted around the tangent point altitude of viewing
and also provides high vertical resolution. Further, the background viewed by the
Indian Remote Sensing Missions & Payloads – A glance
18.12
instrument is cold blackness of the space, which reduces the dark signal and noise
and hence simplifies data interpretation.
This imaging spectrometer is based on a wedge filter as a dispersive element
placed very close to an Active Pixel sensor (APS) area array which in turn is placed
at the focal plane of F#2, f = 80 mm telecentric lens system. The principal advantages
of wedge spectrometer approach are its relative simplicity, lack of complex aft optics,
a compact and easily ruggedized instrument design, uncomplicated layout that results
in minimal sensor integration and test time, reduced cost and delay time.
The estimated radiometric performance of the proposed instrument is < 50
Rayleighs at noise floor through the signal integration for 10 seconds. The pixel
projection turns out to be 2 km/pixel at a range of about 3172 km with altitude
coverage of 80 km to about 600 km and horizontal swath of 1024 km from a
spacecraft altitude of 817 km. The spectral sampling distance is 1.1 nm. The
observations could be carried out only during the eclipse due to the constraints
imposed by the observational modes of other on-board SOLRAD payload.
The subsystems of the LiVHySI P/L are:

Optics (f/2, f=80mm, telecentric lens)

Wedge filter

APS (Active Pixel Sensor) & its Temp. Controller

Camera electronics

Power supply

EOM structure
Payload subsystems are detailed below:
Optics: The imaging system for LiVHySI consists of a collecting optics, a wedge
filter, an APS area array and the associated electronics. The optical design consists of
a single lens assembly. This optical design utilizes eight lenses, consisting of four
types of Schott glasses. A telecentric design, in which the principal ray at all the field
angles, is parallel to the optical axis, ensures that the angle of incidence on the band
pass filter is nearly the same for all the wavelengths. Keeping the angle of incidence
close to normal to the filter reduces the complexity of filter coating.
Detector head Assembly: LiVHySI DHA (Limb Viewing Detector Head Assembly)
of Youthsat consists of512*256 elements Silicon based Area array Active Pixel
Sensor (improved version of the sensor used in Chandrayaan-1 and IMS-1). Desired
system sensitivity is achieved by fast optics and integrating the sensor for long
duration. The sensor temperature is maintained with tight tolerance (21 ± 0.1C)
using heater and thermistor in close loop to minimize dark signal variation. The DHA
responds to optical radiation covering spectral region from 450nm to 950 nm. Wedge
filter is placed very close to the sensor array for obtaining spectral separation (512
spectral bands) along the row direction.
Indian Remote Sensing Missions & Payloads – A glance
18.13
Thermal: The sensor temperature is maintained with tight tolerance (21 ± 0.1C)
using heater and thermistor in close loop. The temperature control system consists of
two number of thermo foil heaters (type: MINCO HK5537R26.1L12E, 26.1ohm,
20W/inch, 12.7mm dia. Circular patch) and two numbers of thermistors (type:
YSI44906/44907,one for the control loop and one for temperature monitoring). These
components are mounted directly on back surface of the APS.
Camera Electronics - Limb viewing hyper-spectral imager (LiVHySI) consists
oftwo trays stacked together.
1. Camera Electronics Main tray (PLE21)
2. Temperature Controller tray (PLE22)
CE configuration is similar to IMS-1-HySI with changes carried out in FPGA
logic design to meet LiVHySI configuration requirements. In addition, a temperature
controller is added as a part of CE to minimize dark signal accumulated due to large
integration time.
Following are the main changes in Youthsat-LiVHySI CE w.r.to IMS-1
Camera Electronics.

All 512 bands data is transmitted as compared to 64 bands in IMS-1

WLS from BDH is with minimum 8 skips as compared to IMS-1

No TC/TM interface

All dark pixels included in the data format from CE to BDH without
change in data rate

12 LSB’s out of 16 bit output data represent valid data with 4 MSB’s
stuffed to logic “1”
Indian Remote Sensing Missions & Payloads – A glance
18.14
Indian Remote Sensing Missions & Payloads – A glance
18.15
19 MEGHA-TROPIQUES
19.1 Introduction
Megha-Tropiques is an Indo-French Joint Satellite Mission for studying the
water cycle and energy exchanges in the tropics. In the early 1990s, France wanted a
‘Tropiques' satellite while India wanted a ‘Climatsat' satellite. They merged the two
ideas, resulting in a joint venture Megha-Tropiques. The name chosen for the
satellite, Megha-Tropiques, reflected the mission's goals. ‘Megha,' the Sanskrit word
for clouds, underscoring a key focus of the satellite, and the French word ‘Tropiques'
denoting its concentration on the tropical region.
The main objective of this mission is to understand the life cycle of convective
systems that influence the tropical weather and climate and their role in associated
energy and moisture budget of the atmosphere in tropical regions. Megha-Tropiques
provides scientific data on the contribution of the water cycle to the tropical
atmosphere, with information on condensed water in clouds, water vapour in the
atmosphere, precipitation, and evaporation.
The scientific goal of the mission is to study the impact of this water cycle on
the atmosphere, the oceans and climate variability.
19.2 Mission Objective
The main objective of the Megha-Tropiques mission is to study the
convective systems that influence the tropical weather and climate. The tropical
region is the domain of monsoons, tropical cyclones. It is also characterized by large
intra seasonal inter annual variations, which may lead to catastrophic events such as
droughts or floods. Any change in the energy and water budget of the land-oceanatmosphere system in the tropics has an influence on global climate.
Objectives can be stated briefly as given below.

To provide simultaneous measurements of several elements of the atmosphere
water cycle, water vapour, clouds, condensed water in clouds, precipitation
and evaporation.

To measure the corresponding radiative budget at the top of the atmosphere

To ensure high temporal sampling in order to characterize the life cycle of the
convective systems and to obtain significant statistics
Indian Remote Sensing Missions & Payloads – A glance
19.1
19.3 Orbital Parameters
Table 19.1: Orbital Parameters of Megha trophique
Orbit
Altitude (km)
Inclination (deg)
Orbit Plane regression
Apparent Sun Angle
Orbit perigee
Distance between successive
orbit (km)
Orbital Period(min)
Number of period/day
Launch vehicle
Near circular/ equator
865.5.Km
20 Deg
6.01 deg/day
52 days/Cycle
within +/- 10 km
2892
101.91
14.13
PSLV-C18
Figure 19.1 One day orbit pattern of Megha tropiques
Figure 19.2: 3.5 day Orbit patterns of Megha tropiques
Indian Remote Sensing Missions & Payloads – A glance
19.2
Figure 19.3 Orbital pattern of Megha Trophiques
The Megha Tropiques satellite can be divided into two main parts 1. Main
Bus and 2 PIM(Payload Interface Module.
Indian Remote Sensing Missions & Payloads – A glance
19.3
Figure 19.4 Stowed configuration of Megha tropiques
19.4 Payloads
Megha-Tropiques satellite carried 4 scientific passive instruments, ie :
MADRAS: (Microwave Analysis and Detection of Rain and Atmospheric
Structures) A multi–channel self-calibrating microwave imager mainly aimed at
studying precipitation and cloud properties.
SAPHIR: (Soundeur Atmospherique du profil d’Humidite Interopicale par
Radiometric) A microwave instrument used to retrieve water vapour vertical profiles.
SCARAB: (Scanner for Radiation Budget) An optical radiometer devoted to
the measurement of outgoing radiative fluxes at the top of the atmosphere.
ROSA: (Radio Occultation Sounder for Atmosphere Payload) A GPS
Receiver specifically conceived for atmospheric sounding by radio occultation,
which is able to determine position, velocity, and time using GPS signals.
Combining the information from these different payloads, the following
parameters can be derived: size of convective cells, cloud cover, water vapour
profiles, deep cloud water content, rain rate, cloud ice content and radiative fluxes,
humidity content at the top of the atmosphere.
Indian Remote Sensing Missions & Payloads – A glance
19.4
19.4.1 Microwave Analysis and Detection of Rain and Atmospheric Structures
(MADRAS)
The MADRAS instrument is a 9 channel
self-calibrating microwave imager. The payload is
jointly developed by ISRO and CNES. The payload
scans the Earth +/65 deg, with onboard angle of
+45.05 deg in the along track direction. The rotating
part of MADRAS has a mass of about 100 kg.
MADRAS is nominally a scanning payload. A
stationary mode is defined for the payload, where
the MADRAS is pointed a specific angle (within +/65 deg) continuously. IISU, SAC and ISAC have
developed the MSM/MCE, MBE-R/MBE-S and
HDRM components of MADRAS respectively,
whereas MARFEQ-A & B have been developed by CNES.
The MADRAS RF front-end consisting of the entire RF units from 18 GHz – 157
GHz including the antenna, feed cluster, and on-board calibration is designated as
MARFEQ (MADRAS RF Equipment).
MARFEQ-A is the mobile part of MADRAS. It includes a structure supporting the
main reflector associated to the horns located at the focal point of the parabola.
Behind each horn one or several receivers allows the detection of the RF signals






Main Reflector made from a CFRP dish (projected diameter 650 mm),
Feed Cluster and Front Ends Assembly constituted by aluminum RF elements
with their supporting structure and thermal hardware
Back Ends, Low Frequency Receivers and Interface Electronic Unit,
Related waveguides, coaxial cables and harness,
CFRP structure which supports the above elements and their thermal hardware
and which interfaces with the Scan Mechanism Rotating part through a titanium
cylinder and with the Hold Down and Release Mechanism through 6 titanium
integrated fittings.
MBE(R) will be accommodated on the lower part of MARFEQ-A Deck.
MARFEQ B is mounted on the fixed part of the instrument. It allows the calibration
of the receivers at each rotation. It is constituted of a mirror allowing a cold
Indian Remote Sensing Missions & Payloads – A glance
19.5
calibration and a black body allowing the hot calibration. This equipment contains
only accurate thermistors to measure the physical temperature of the black-body.
The MARFEQ fixed part (MARFEQ-B) consists of:



Cold Calibration Reflector made from a CFRP dish (projected diameter
285mm),
Hot Calibration Target
Aluminum structure which supports the above elements and interfaces with
the Scan Mechanism fixed part.
Hold Down and Release Mechanism (HDRM)
This is necessary to protect MSM bearings from launch loads, since the rotating
elements of MADRAS high. The mechanism will rigidly hold the MARFEQ at six
locations. Once the spacecraft is in orbit, the mechanism will release the MARFEQ,
to enable scanning. MSM, MCW and MCE form MADRAS Mechanism and
Momentum Compensation System (MMCS). MMCS has four modes of operation,
viz.
 Run-up mode
 Scanning mode
 Pointing mode
 Run down mode.
MADRAS Momentum Compensation System (MMCS)
MMCS as a part of MADRAS payload consists of three elements such as;
MADRAS Scan Mechanism (MSM) : Scan Mechanism consisting of
precision angular contact ball bearing assembly, Diaphragm assembly for hold down
compliance, drive motor, optical encoder, PSTD for transfer of power and signal
from and to Marfeq A/MBE(R) and MBE (S). The nominal speed of the mechanism
is 24.14 rpm with scan stability of +/- 0.1%.
Momentum Compensating Wheel (MCW): Momentum Compensating
Wheel MCW consists of precision ball bearing assembly, flywheel, brushless iron
less DC motor in a hermetically sealed casing. The MCW (Momentum Compensative
Wheel) generates counter momentum such that the residual momentum is very small
and tolerable by the spacecraft. MCW consists of a wheel with a low mass but high
rotational speed to generated compensative momentum.
MADRAS Control Electronics (MCE): The MADRAS Control Electronics
(MCE) containing all the electronic functions as management of the MSM, MCW,
commutation electronics, power supply, mechanisms command and control, interface
with MBE.
Indian Remote Sensing Missions & Payloads – A glance
19.6
MCE (MSM and Momentum Compensating Electronics) is an integrated
control electronics package for MSM. Rotating mass of the payload (100kg)
generates a large momentum about its axis of rotation, which can destabilize the
platform.
Payload Characteristics
MADRAS channel definitions
Channel
No.
Frequency
Polarization
Pixel
size
Bandwidth
Science Parameters
M1
18.7 GHz
H+V
40 km
100 MHz
Rain above oceans
M2
M3
23.8 GHz
36.5 GHz
V
H+V
40 km
40 km
200 MHz
500 MHz
M4
89 GHz
H+V
10 km
1350 MHz
M5
157 GHz
H+V
6 km
1350 MHz
Integrated water vapour
Liquid water in clouds, rain
above sea
Convective rain areas over land
and sea
Ice at cloud tops
Figure 19.5: View from –ve pitch
Scan type
constant speed
Onboard look angle (w.r.t. Nadir)
Incidence angle
Maximum scan angle (cross track)
Scan mechanism speed
:
Conical
:
:
:
:
45.05
53.5
65
24.14 rpm
Indian Remote Sensing Missions & Payloads – A glance
scanning
at
19.7
Dwell time (Channel wise)
36.5 GHz)
 144.84 /sec
 2.4855 sec/revolution
 0.4023 cycles/sec =
0.4023 Hz.
:
16.8 millisec (18.7, 23.8,
:
:
:
Swath
Dynamic range of radiometer
Brightness temperature
Scan mechanism stability
4.2 millsec (89 GHz)
2.5 millisec (157 GHz)
1700 km
3 K to 320 K
0.1% of the rate
:
:
Data rate: The total data rate of MADRAS is 33.858 Kbps.
Type of data
Science TM
Size
5248 words
Rate
2.48sec
Figure 19.6 MADRAS Swath coverage pattern
19.4.2 SAPHIR (Soundeur Atmospherique du Profil d’Humidite Intertropicale
par Radiometrie) Payload
SAPHIR is a Microwave instrument for the retrieval of water vapour vertical
profiles and scanning millimeter wave humidity sounder. It scans the Earth in a nadir
plane symmetrically with respect to the local vertical with a scan angle of 42.96
deg. It uses narrow channels close to a water vapour absorption band at a frequency
of 183 GHz. Six channels would allow to retrieve information about six atmospheric
layers from the Earth surface up to 12 km height. The horizontal resolution is 10 km.
The 6 channels are in the range of 183.31 0.2, 1.1, 2.8, 4.2, 6.8, 11.0 (GHz).
Indian Remote Sensing Missions & Payloads – A glance
19.8
The instrument is composed of two packages linked by a dedicated harness.
The packages are
The RF Unit (6 Passive microwave channels) contains the antenna, the frontend,
IF processor, the scanning with the shroud and the calibration target.
The Electronic unit (EU) containing all the electronic functions as management of
the equipment, power supply, mechanisms command and control interface with
satellite processor.
Following are highlights of its operation. Scans Earth’s atmosphere and switches
between the calibration sources of cold sky and hot target
 During each scan period the antenna performs one complete rotation in order
to scan the Earth over an angle of +/- 42.96 deg and performs hot and cold
calibration
 During Earth scanning of +/- 42.96 deg, in nominal mode the angular speed
is constant and equal to 103.5 degree/sec.
 During the rest of scan period, in order to optimize the time dedicated to
Earth’s atmosphere measurements, the motor will produce half part of the
time a constant and maximum acceleration and on the other half part of the
time a constant maximum deceleration. The current values of acceleration
and deceleration [20] are 1666 deg/sec2 and 1666 deg/sec2.
Figure 19.7 Schematic of SAPHIR Payload
SAPHIR channel definitions and characteristics
Channels
Req.
Goal
S1
Central
nominal Nominal
frequencies (GHz) Bandwidth
(MHz)
183.31 ± 0.2
200
2 K
1 K
S2
183.31 ± 1.1
1.5 K
0.7 K
350
Indian Remote Sensing Missions & Payloads – A glance
19.9
S3
183.31 ± 2.8
500
1.5 K
0.7 K
S4
183.31 ± 4.2
700
1.3 K
0.6 K
S5
183.31 ± 6.8
1200
1.3 K
0.6 K
S6
183.31 ± 11
2000
1.0 K
0.5 K
Figure 19.8 Payload Interface Module
Scan type
:
Cross track scanning at constant
Polarisation
Incidence angle
Maximum scan angle
(cross track)
Scan mechanism speed
:
:
Variable along swath
Variable along swath
:
:
 42.96
36.63 rpm
 219.78 /sec
1.638 sec/revolution
 0.6105 Hz
:
:
:
:
103.5 /sec
6.406 msec
1705 km
10 km
4 K to 313 K
speed
Scan rate during
Earth viewing phase
Dwell time
Swath
Nadir spatial resolution
Brightness temperature Range:
Data rate:
The total data rate of SAPHIR is 12.487 Kbps. The different kinds of data
coming to BDH from SAPHIR instrument are given in the table below.
Indian Remote Sensing Missions & Payloads – A glance
19.10
Type of data
Science TM
Aux data
Size
1216 words
64 words
Rate
1.64 sec
19.6 sec
19.4.3 ScaRaB (Scanner for Radiation Budget) Payload
Radiometer devoted to the measurement of outgoing radiative fluxes at the
top of the atmosphere. Measures radiation fluxes in four channels in the range of 0.5
to 0.7m, 0.2 to 4 m, 0.2 to 50 m and 10.5 to 12.5 m spectral bands; in Visible,
Solar, Total and IR Windows. It consists of (a) Optical Sensor Module (including
scanner and calibration devices) and (b) Electronic Module.
The optical sensor module (OSM) can be divided in two parts
 A rotating part with mechanism, four detectors, two choppers, an internal
electronics and a filter wheel.
 The external structure, with the casing, the two feet and the calibration
module (CalM) formed by three black body simulators and a lamp.
The Electronic Module (EM) containing all the electronic functions as
management of the equipment, power supply, mechanisms command and control
interface with satellite processor.
Following are the highlights of its operation.
 During each scan period the rotor performs one complete rotation in order to
scan the Earth over an angle of +/- 48.91° and performs calibration on cold
space.
 Produce part of time some acceleration and part of time some deceleration.
The total duration for one full scan is 6 sec.
19.4.3.1 Scanning sequence in nominal mode
Function
Angle
Typical Duration
Type
movement
Earth/Atmosphere
Scanning
Switching period
-48.91 to +48.91
51Xte = 3.1875 sec
Constant speed
+48.91 to -74.35
30Xte = 1.875 sec
Stop on space view
-74.35
6Xte = 0.375 sec
Acceleration/
Deceleration
Stop(fixed
Indian Remote Sensing Missions & Payloads – A glance
19.11
of
position)
Switching period
-74.35 to -48.91
Total Period
9Xte = 0.5625 sec
Acceleration/
Deceleration
96*te = 6 sec
In the background of the discussion above on the working of payloads, it is
evident that the payloads’ scanning are asynchronous. Further SAPHIR has
acceleration and deceleration before it scans the Earth portion. Similarly in case of
SCARAB, in addition to acceleration and deceleration, it stops to view deep space for
a finite amount of time. This is likely to cause disturbance on the platform with
impact on spacecraft control and eventually Data Products Generation. During this
exercises, it emerged that platform rates achievable are of the order 10-2deg/sec.
Figure 19.9: Scarab Scanning lines and Overlap
ScaRaB channel definitions and characteristics
Channels
Wavelength
Radiometric
(Noise)
Resolution Signal Dynamics
(Max.)
Sc1
– 0.5 to 0.7 m
Visible
Sc2 – Solar 0.2 to 4 m
Sc3 – Total 0.2 to 50 m
< 1 W.m-2.sr-1
120 W.m-2.sr-1
< 0.5 W.m-2.sr-1
425 W.m-2.sr-1
< 0.5 W.m-2.sr-1
500 W.m-2.sr-1
Sc4 – IR 10.5 to 12.5 m
Window
< 0.5 W.m-2.sr-1
30 W.m-2.sr-1
Indian Remote Sensing Missions & Payloads – A glance
19.12
Scan type
:
Cross track scanning at constant
Scan Angle (across track)
Scan mechanism speed
:
:
 48.91
10 rpm  60 /sec
 6 sec/revolution
 0.17 Hz
62.5 msec
2242 km
40 km
speed
Dwell time
:
Swath
:
Nominal nadir spatial resolution :
Data rate:
The total data rate of SCARAB is 853.333 Kbps. The different kinds of
SCARAB data coming to BDH are given in the table below.
Type of data
Science TM
Aux data
19.4.4
Size
256 words
64 words
Rate
6 sec
6 sec
ROSA
The ROSA is a 16-channel dual-frequency GPS (Global Positioning System)
receiver for space borne applications, specifically used for atmospheric sounding by
radio occultation and determines position, velocity and time using GPS signals. The
ROSA processes the received GPS signals in both the L1 and L2 frequency bands,
allowing compensation of ionospheric delays. A codeless tracking scheme is
included, in order to process the encrypted P(Y) signals transmitted in the L2
frequency band.
The ROSA, besides providing real-time navigation data, is able to accurately
measure pseudo-ranges and integrated carrier phase (raw data), to be later processed
on ground for the scientific purposes of retrieval of atmospheric parameters such as
Humidity, Pressure and Temperature profiles between 0 and 100 km height above the
Earth surface. These profiles can be used in meteorological and climatologic forecast
with a vertical resolution much higher than that obtainable with measurement based
upon microwaves or infrared techniques.
ROSA payload on Megha-Tropiques will supplement / complement the
mission objectives for the atmospheric studies. ROSA on Megha-Tropiques
spacecraft has a fore and an aft antenna facilitating occultation measurements in both
velocity and anti-velocity directions of the spacecraft thus allowing a large number of
observations. The Navigation antenna looking along the spacecraft’s zenith direction
facilitates the precise orbit determination (POD).
Indian Remote Sensing Missions & Payloads – A glance
19.13
GPS ROSA, raw data and the products are generated at ISSDC Bangalore
and are also archived for further use by application scientists.
ROSA Specifications
Features
Specification
Dual Frequency operation:
Receiving Frequencies:
L1 [1575.42 MHz] C/A-Code signal
L1 [1575.42 MHz] P-Code signal
L2 [1227.60 MHz] P-Code signal
Bandwidth:
10 MHz nominal
16 Dual-Frequency channels.
Allocating channels to POD or Occultation is managed
automatically only by onboard software in order to optimally
share the hardware resources (channels).
Number of
Channels:
Dual-Frequency
Navigation/POD:
1 Hz sampling data rate (for both code phase and carrier
phase)
Carrier Phase measurements for Occultation/space weather
channels:
(a) Observation (Close loop): 1 Hz, 10 Hz and 50 Hz
sampling data rate depending on altitude of the tangent
point.
(b) Occultation (open loop): 100 Hz sampling data rate
only in lower troposphere.
Pseudo range:< 50 cm
Carrier phase:< 5 mm
Bending angle: Better than 1 µrad
Measurement rate:
Measurement accuracy:
On-board POD software with
Satellite positioning accuracy:
Receiver Power consumption:
< 30 metre (Real-time 3D-3 solution)
Receiver operating voltage:
+28V to +42V DC (37 V nominal)
Navigation input signal levels:
L1-CA: -127 dBm (minimum)
L1-P: -130 dBm (minimum)
L2-P: -133 dBm (minimum)
Radio Occultation input signal
range:
L1-CA: -130 dBm to -142 dBm, -132 dBm (nominal)
L1-P: -133 dBm to -145 dBm, -135 dBm (nominal)
L2-P: -136 dBm to -148 dBm, -138 dBm (nominal)
Interfaces
platform:
House-Keeping Telemetry, Telecommand and Science
Telemetry interface: Mil-Std-1553B
Science Telemetry format: Space Packet as per CCSDS
133.0-B-1
Pulse Per Second (PPS) signal interface: RS-422
Number of PPS output signals:2
with
satellite
45 Watts (Operating Mode)
Indian Remote Sensing Missions & Payloads – A glance
19.14
Receiver Mass:
9.2 kg
Receiver Dimension:
290.6 mm x 334.6 mm x 207.7 mm
Receiver
operating -10 C to +45 C
temperature:
The total data rate of ROSA varies from 11.264 Kbps to 113.664 Kbps.
Type of data
Navigation and Observation data
Size
704 to 7104 words
Rate
1 sec
Dual-Frequency ROSA antenna specifications
Features
Specification
FOV (Field of View):
Azimuth FOV (referred to orbital plane):  30
Elevation FOV (referred to local zenith)
 Baseline coverage region:
116.7 to
118.3
 Extended coverage region:
90 to 116.7
Gain inside the coverage region:
 12 dBi for both L1 and L2 band
Gain inside the extended coverage region:
 -3 dBi for both the L1 and L2 band
Right Hand Circular Polarization (RHCP)
Antenna Gain:
Polarization:
VSWR:
Mass:
Dimensions:
Operating temperature:
1.4:1
2.5 kg
1050 mm x 280 mm x 80mm
(Single panel patch array)
-80 C to +100 C
Dual-Frequency Navigation/POD antenna specifications
Features
Specification
FOV (Field of View):
 75 (referred to local zenith)
Antenna Gain:
5 dBi (at zenith)
4 dBi (at 5 elevation above the horizon)
Polarization:
Right Hand Circular Polarization (RHCP)
VSWR:
1.5:1
Mass:
0.138 kg
Dimensions:
127 mm x 49 mm
Operating temperature:
-70 C to +80 C
Indian Remote Sensing Missions & Payloads – A glance
19.15
Indian Remote Sensing Missions & Payloads – A glance
19.16
Indian Remote Sensing Missions & Payloads – A glance
19.17
20 RISAT-1
20.1 Introduction
RISAT is the first microwave satellite designed and fabricated by ISRO. This
mission will facilitate data collection in day/night and in all weather conditions.
20.2 Mission Objective




To Develop a multimode, agile SAR payload operating in ScanSAR, Strip and
spot modes to provide images with coarse, fine and high spatial resolutions
respectively
To develop and operate a compatible satellite to meet the mission
requirements operating in three axis stabilized mode in 536.38 km circular
sun synchronous orbit.
To establish ground segment to receive and process SAR data.
To develop related algorithms and data products to serve in well established
application area and also to enhance the mission utility.
20.3 Orbital Parameters
The guiding parameter for the orbit selection for RISAT is achieving a
global coverage in a systematic way for a given swath. In interferometric applications
modes, the presence of atomic oxygen and atmospheric drag has also been kept in
view.
Sl.No
Parameters
ScanSAR
Mode
Medium
Resolution
Mode
STRIP
MAP
Mode
Interferomete
r Mode
1
Altitude(Km)
536.38
536.38
536.65
526.9
2
Inclination
97.554o
97.554o
97.555o
97.52o
3
Repeat cycle
377 orbits
in 25 Days
377 orbits in
25 Days
2096
orbits in
139 Days
136 orbits in
13 Days
4
Orbit Period
95.4907
95.4907
95.542
95.294
(Minutes)
Indian Remote Sensing Missions & Payloads – A glance
20.1
5
Path-to-path
Distance(Km)
212.6
106.3
19.12
294.7
6
Swath (Km)
223
115
25
25
7
Local Time: 6.00- Hrs +/- 5 min (Descending)
Figure 20.1 Stowed view of RISAT
20.4 Payload
20.4.1 SAR Payload
The C-Band Synthetic Aperture Radar (SAR) is the payload of RISAT.
Radar backscattering depends upon the sensor parameters such as frequency,
polarization and incidence angle, dielectric constant roughness and geometry of the
target. In RISAT, SAR Payload will be operating in C-band (5.35 GHz) with both
co-and cross- polarization, which will meet most of the resource applications and also
Indian Remote Sensing Missions & Payloads – A glance
20.2
enable achieving high resolution capability. The SAR payload is based on active
phased array antenna technology, which will provide multimode capability.
20.4.1.1 Modes of Operation
The proposed SAR will operate in the following basic modes:
Fine Resolution strip map Mode-1 (FRS-1): This is the conventional mode of
SAR. In this the orientation of the antenna beam is fixed with respect to flight path so
that a strip of constant swath (25 Km) is illuminated along the flight direction. The
indented resolution is 3m for FRS-1 mode.
Coarse Resolution ScanSAR Mode (CRS): The scanSAR mode allows increasing
the swath. This is achieved by periodically stepping the antenna beam to the
neighboring subswaths(in range direction). In the CRS mode of RISAT there will be
12 beams. These results, total swath in CRS mode would be 223 km. the resolution
offered in this mode will be 50 m.
Medium Resolution Stripmap Mode-2 (FRS-2): This is a 6 beam scanSAR mode,
similar to the CRS mode, providing a resolution of 25 m over a swath of 115 km.
Fine resolution Stripmap Mode-2(FRS-2): This mode has quad polarization
capability. Philosophically, this mode is a hybrid strip map and scanSAR. In this case
the beam orientation is kept fixed with respect to the flight path and a strip of
constant swath width is covered. Part of the aperture time the beam polarisation is
switched from V-transmit to H-transmit, and vice-versa. Hence, this mode would be
used for polarimetry, as we can have all the four combinations of polarization viz.
VV, VH, HH,HV.
High Resolution Spotlight Mode (HRS): In the spotlight mode, the antenna beam is
oriented continuously to illuminate a particular spot on the ground. This method
increases the target aperture time which results in improved azimuth resolution (1m)
The improved resolution is obtained at the cost of azimuth coverage.
Circular Polarimetric Modes (C-HRS, C-FRS-1, C-FRS-2, C-MRS, C-CRS): All
the modes mentioned above can be operated in hybrid-circular polarization. This is
achieved by transmitting H & V polarized signals simultaneously but with a relative
phase-shift of 90o. Hence, the transmit signal is in circular polarization and the
receive signal is in linear (Dual-pol) – this makes it a hybrid-circular polarisation
operation. To keep the average power-requirements same as the original
specifications, the pulse-width is reduced to half.
Indian Remote Sensing Missions & Payloads – A glance
20.3
Major Mission Parameters for Space borne High Resolution SAR
Altitude
Orbit
P/L operating frequency
Polarisation
536 Km
Sun Synchronous (6 A.M/6 PM equatorial crossing)
C-Band
Single/Dual/Quad-polarisation
Hybrid circular polarimetry
(Transmit circular, receive linear)
Microstrip Active antenna 6m x 2m
43.1 dBi
64 on each side of the flight track (Total 128)
SSR with 240 GBits
288 pairs
per 10 W (Ave.)
Antenna
Peak Gain
Total no. Beams
On board storage
No. of TR Modules
Transmitter power
TRM
Antenna peak power
Average DC Input Power
Range Compression
Pulse Width
Antenna Roll Bias(deg)
Range Coverage(Km)
Look Angle (Deg
Incidence Angle
Doppler BW (Hz)
PRF(Hz)
Worst
o (dB) Considering
both
qualified
and
unqualified regions (100 km
– 700km)
Swath
Slant range resolution(m)
Ground
range
resolution(m)
Azimuth Resolution(m)
Chirp bandwidth(MHz)
2.88 kW
3.92 kW
On Ground
20 micro sec/10 microsec ( 10 microsec for circular
polarization)
36
107 - 659
11.28 – 49.09
12.25 – 55.02
2532.23
FRS-1/FRS-2/ MRS/CRS
HRS
2800-3200
3000-7000
-16.81 @ 25 Km
-15.82
25/25/115/223
2/4/8/8
FRS1: 9.4 – 2.4
FRS2: 18.8 – 4.9
MRS: 37.7-9.8
CRS: 37.7.9.8
3/9/21-23/41-55
75/37.5/18.75/18.75
Indian Remote Sensing Missions & Payloads – A glance
10
0.7
3.3-0.85
1
225
20.4
83.3/41.67/20.83/20.83
Sampling frequency(MHz)
Data Window (micros)@ 63-184 (@30km Swath)
nominal earth radius of
6371 km
4864-21504/2560No. Of complex samples
12288/1280-6144/12806144
Onboard BAQ(6/5/4/3/2
Data Compression
bits)
6 BAQ
Data
Rate
(Mbps)
Single pol. 176-744/-/44-213/44-213
Dual Pol.
352-1488/-/88-426/88-426
Quad pol.
-/1756-744/-/Worst-case
Range [email protected] Km
Ambiguity(in
dB)
@ [email protected] km
[email protected] Km
nominal PRF
Worst
case
Azimuth -21.47
Ambiguity (in dB) @
Nominal PRF
250
80-165(@10km Swath
19072-41344
3 – bit BAQ
3 BAQ(For
azimuth)
490 – 744
980-1488
100km
[email protected]
-25.20
Active Antenna specifications of C- Band SAR
Frequency
Antenna Type
Antenna Size
Antenna Gain
Antenna Bandwidth
C-band
Printed Antenna
6m (Along Flight) x 2m (Cross Flight)
43.1 dBi
0.5 dB over 225 MHz bandwidth around center
frequency
Azimuth
Elevation
Side Lobe Level
- 15 dB
- 18 dB
Cross polarization level Better than – 23 dB
Phase Tracking
Relative gain and phase Gain Tracking
6 deg rms
tracking
between 0.5 dB rms
radiating arrays of 24
elements
288, each with 10 W peak power
No. of TR Modules
2.88 kW
Peak Power
Indian Remote Sensing Missions & Payloads – A glance
20.5
Avg. Output power
Average
DC
Input
Power
(to
Active
antenna)
TR Module Output
tracking
TR Module Receive
path Tracking
Gain/Phase
Quantisation
TR Module Bandwidth
213 W (with duty cycle of 7 %)
3.672 kW
Loss/Noise Figure
O/P Power Tracking
0.5 dB rms
Gain
0.5 dB rms
Gain
6 bits
0.5 dB over 225 MHz
frequency
Tx loss
Rx loss
No. of Antenna Beams
0.3 dB
128
0.3 dB
Indian Remote Sensing Missions & Payloads – A glance
Phase Tracking
6 deg rms
Phase
6 deg rms
Phase
6 Bits
bandwidth around centre
Mismatch
Loss
0.6 dB
Noise
Figure
3.5 dB
20.6
Indian Remote Sensing Missions & Payloads – A glance
20.7
Glossary
Absorption:
The process by which radiant energy is absorbed and converted into other
forms of energy. This occurs when radiation impinging on a molecule
excites its internal energy and causes changes in its electronic, vibrational,
and/or rotational states.
Across-track scanner : A remote-sensing tool with an oscillating mirror that moves back
and forth across a satellite's direction of travel, creating scan line strips that
are contiguous or that overlap slightly, thereby producing an image.
Active Sensor: A sensor that generates its own electromagnetic energy to illuminate the
target, usually within the microwave wavebands. RADAR is an example of
such a system.
Additive primary colors: Blue, green and Red.
Aerosol -
A mixture of fine liquid or solid particles suspended in a gas or air. Or
suspended particles like dust in atmosphere
Airglow:
A nighttime glow from the upper atmosphere, occurring over middle and
low altitudes, due to the emission of light from various atoms, molecules
and ions.
Albedo:
The ratio of the light reflected by a planet to that received by it
Altimeter:
Instrument for measuring altitudes or elevations with respect to a reference
level, usually mean sea level.
Altitude:
The height or vertical elevation of a point above a reference surface.
Altitude measurements are usually based on a given reference datum, such
as mean sea level.
Angle of ascending node The angle between the ascending node and the x axis. Also
referred to as the right ascension of the ascending node.
Angular Field of View: Angle subtended by remote sensing system/detector.
Angular resolving power: Minimum separation between two resolvable targets,
expressed as angular separation.
Antenna:
Device that transmits and receives microwave energy.
Aperture:
Opening in the remote sensing system that admits electromagnetic
radiation to the film/detector
Apogee:
The point in an orbit farthest from the Earth.
Indian Remote Sensing Missions & Payloads – A glance
1
Argument of Perigee: The angular distance between the ascending node and the point of
perigee.
Artefact:
A feature on an image which is produced by the optics of the system or by
digital image processing.
Ascending node The point where the satellite crosses the equatorial plane going north.
Aspect ratio: The ratio of horizontal scale to vertical scale for printing or display.
Atmospheric windows: Wavelength interval within which the atmosphere readily
transmits electromagnetic radiation.
Attitude:
Angular orientation of a remote sensing system with respect to a
geographic reference system.
Azimuth:
Geographic orientation of the line given as an angle measured in degrees
clockwise from north.
Band:
A sub division within an electromagnetic region.
Binning:
is the combination of intensities of adjacent pixels into in image with a
resulting lower spatial resolution.
Bitmap:
An image format in which one or more bits represent each pixel on the
screen. The number of bits per pixel determines the shades of gray or
number of colors that a bitmap can represent. Bitmap files generally have
the extension .bmp.
Blackbody :
Hypothetical body that absorbs and emits electromagnetic radiation in all
parts of the electromagnetic spectrum so that
1) all incident radiation is completely absorbed;
2) The maximum possible emission takes place in all wavelengths of the
EM spectrum.
Brightness temperature: is a measure of the intensity of radiation thermally emitted by
an object, given in units of temperature because there is a correlation
between the intensity of the radiation emitted and physical temperature of
the radiating body which is given by the Stefan-Boltzmann law.
Calibration:
The process of comparing measurements, made by an instrument, with a
standard.
Cartography: The organization, design, collection and reproduction of geographic
information on various formats to generate maps.
Indian Remote Sensing Missions & Payloads – A glance
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CCD (Charge Coupled Devices): A light sensitive solid-state detector sensitive solidstate detector that generates a voltage which is proportional to the intensity
of illumination. Arrays of CCDs make up pushbroom scanners.
Chromatic aberration - Aberration caused by the dispersive effects of refracting optical
systems. Because light rays of different wavelengths (colors) bend by
different amounts as they pass through dielectric media, each wavelength
will converge to a slightly different focal point. This means that it is
impossible to focus rays from a polychromatic source accurately. This
prove problematic in large refracting telescopes.
Contrast: good image contrast is desirable for viewing low contrast objects such as the
lunar surface and planets. newtonian and catadioptric telescopes have
secondary (or diagonal) mirrors that obstruct a small percentage of light
from the primary mirror. light scattering and diffraction from such
obstructions can cause a reduction in image contrast. it is commonly
believed that image contrast is severely reduced with newtonians or
catadioptrics because of this obstruction, but this is not the case. this would
only be true if more than 25% of the primary mirror's surface area was
obstructed by the secondary.
DEM (Digital Elevation Model): Represents a topographic surface using a continuous
array of elevation values, referenced to a common datum. DEMs are used
typically to represent terrain relief.
Detector:
Component of a remote sensing system that converts electromagnetic
radiation into a electrical signal.
Dichroic Mirror: A special type of interference filter, which reflects a specific part of the
color spectrum.
Digital Image processing: Computer manipulation of digital images.
Digital Number(DN): Value assigned to a pixel in a digital image
Digitisation:
Process of converting an analog display into a digital display
Dispersion:
Is the phenomenon by which light the bending or refraction of light is
dependent on its wavelength or frequency in a certain medium. This occurs
because some frequencies are closer to the resonant frequencies of atoms
in the medium, causing them to be propagated more effectively. This
accounts for the dispersion of white light into a spectrum as it passes
through a prism.
Distortion:
On an image, changes in shape and position of objects with respect to their
true shape and position.
Indian Remote Sensing Missions & Payloads – A glance
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Doppler effect: The phenomenon of apparent change in frequency, with the relative
motion of the source and the observer.
Dwell time:
Time required in an image between areas with different tones.
Dynamic range: of the CCD is defined as the ratio of the full well capacity to the signal to
noise ratio SNR.
Effective focal length: Distance between principal plane and the focal plane
Electromagnetic spectrum: The electromagnetic spectrum is the range of all possible
electromagnetic radiation.
Enhancement-Process of altering the appearance of an image so that the interpreter can
extract more information.
Equatorial Orbit: An orbit that lies at any altitude above the Equator, i.e. has an
inclination of 0 degrees
Indian Remote Sensing Missions & Payloads – A glance
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False color composition (FCC): The selection of set of image bands whereby terrestrial
features are not portrayed in their natural colors
Field Of View: the range of angle that is scanned or sensed by a system in degrees
Fill factor:
Fill factor of Pixel is the active area for the conversion of incoming
photons.
F-number:
Representation of the speed of a lens determined by the focal length
divided by diameter of the lens. Smaller numbers indicate faster lenses.
Full well capacity: Is the maximum number of electrons which one pixel can contain
before its saturation.
GCP (Ground Control Point)
Ground control: Refers to points on the surface of the earth with known coordinates as
represented by some geographic grid reference system. The location of
ground control points can be represented on maps and other cartographic
products, and can serve as reference points with which to rectify the scale
and accuracy of cartographic products to the actual area on the ground that
is represented. Ground control points are classified according to their
horizontal and vertical accuracy
Geographical information system (GIS): a system for capturing, storing, checking,
integrating, manipulating, analyzing and displaying data (such as geocoded
images) which are spatially referenced to the earth
Geoid :
The figure that represents the irregular spheroidal shape of the earth is
called the geoid.
Geostationary Orbit: A Geosynchronous Orbit having zero inclination so that the
spacecraft hangs motionless with respect to a point on the planet below.
Geosynchronous Orbit: A direct, circular, low-inclination orbit around Earth having a
period of 23 hours 56 minutes 4 seconds and a corresponding altitude of
35,784 km (22,240 miles, or 5.6 Earth radii).
Geosynchronous orbit: An orbit in which the satellite’s orbital period is identical to the
orbital period of the Earth.
Grey Scale:
A calibrated sequence of grey tones ranging from black to white.
Ground sampling distance (GSD): GSD is defined as the distance moved on the ground
during the integration period of the detector line array of an imaging
instrument.
Ground Segment :The part of an earth observation mission comprising data reception
processing archiving and distribution facilities
Indian Remote Sensing Missions & Payloads – A glance
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Ground track: Refers to the vertical projection of the actual flight path of a satellite onto
the surface of the Earth.
Histogram:
A graph showing the distribution of values in a set of data. Individual
values are displayed along a horizontal axis, and the frequency of their
occurrence is displayed along a vertical axis.
Hyper spectral: More spectral bands (Minimum 20 Spectral band)
Image Processing: Encompasses all the various operations which can be applied to
photographic or image data. These include, but are not limited to image
compression, image restoration, image enhancement, preprocessing,
quantization, spatial filtering and other image pattern recognition
techniques.
Image:
pictorial representation of a scene recorded by a remote sensing system.
Inclination:
The angular distance of the orbital plane from the equatorial plane of the
planet, stated in degrees.
Instantaneous Field of View (IFOV): A term denoting the angular resolution of a single
detector element.
Instantaneous Geometrical Field of View (IGFOV): The projection size of a pixel on
ground specified in length.
Integration Time: The time period allocated for the radiative measurement of the
instantaneous area of observation by the detector of a sensor.
Interpretation: The process in which a person extracts information from an image.
Irradiance: The radiative energy per unit time(power) impinging on a surface normalized
by the surface area, and is specified in watt per square meter(W/m2)
Isotherm:
Contour line connecting points of equal temperature.
Isotropy (the opposite of anisotropy) is the property of being independent of direction.
Isotropic radiation has the same intensity regardless of the direction of
measurement, and an isotropic field exerts the same action regardless of
how the test particle is oriented.
JPEG2000 (Joint Photographic Experts Group): An updated version of JPEG which
offers more efficient compression of images and can use both lossless and
lossy compression algorithms. The lossless compression method makes
JPEG2000 images very useful in GIS applications.
Langmuir probe: An instrument employed to measure the current-voltage characteristics
of plasma in order to determine plasma density.
Indian Remote Sensing Missions & Payloads – A glance
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Lens:
A lens is any refracting device (corresponding to a discontinuity in a
medium) that rearranges the distribution of transmitted energy. Lens do not
have to be transparent to light, but can instead be used to redirect X-rays or
microwaves. The most useful lenses have spherical surfaces and act to
focus light rays to a point near the lens
Limb Occultation sounding: A horizon-looking observation technique that uses a distant
object sun, Star, or a sensor on another satellite in a different earth orbit as
a source to observe the signal on its path through the atmosphere that is
essentially tangential to the Earth’s Surface
Low Earth Orbit: The lowest altitude a spacecraft must achieve to orbit the Earth.
Map Base: A map depicting background reference information such as landforms, roads,
landmarks, and political boundaries, onto which other, thematic
information is placed. A basemap is used for locational reference and often
includes a geodetic control network as part of its structure.
Map Cadastral: is a comprehensive register of the metes-and-bounds real property of a
country. A cadastre commonly includes details of the ownership, the
tenure, the precise location, the dimensions and the value of individual
parcel of land
Map Contour: A topographic map that uses contour lines to portray relief. Contour lines
join points of equal elevation or simply lines on any other isomorphic map
(such as temperature isolines on a weather map) that identify levels of a
parameter at specified, discrete intervals.
Map Thematic: The application specific maps. Example: road ways, pipelines, soil types,
vegetation types and water distributions
Map Units:
The coordinate units in which the geographic data are presented, such as
inches, feet, or meters or degrees, minutes and seconds.
Map, Isopleth (isoline): A map displaying the distribution of an attribute in terms of lines
connecting points of equal value. Examples include contour maps and
weather maps depicting lines of temperature or precipitation changes.
Metrology:
is the interdisciplinary scientific study of the atmosphere
Microwave:
Region of the electromagnetic spectrum in the wavelength range from 0.1
to 30 cm.
MID-INFRARED (MIR): The range of wavelengths from 8 to 14 micrometres dominated
by emission of thermally generated radiation from materials; also known
as thermal infrared.
Indian Remote Sensing Missions & Payloads – A glance
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Modulation Transfer Function(MTF): A function measuring the reduction in contrast
from object
Mosaic: A technique whereby multiple satellite images are digitally joined, while
correcting for systematic changes in radiometry and geometry thus creating
a 'seamless' image product.
Nadir:
Point on the ground directly in line with the remote sensing system and the
center of the earth.
Nodal period: The time required to make a complete orbit. For a polar orbiting sun
synchronous satellite the nodal period is 102 minutes.
Occultation : An alignment of two bodies with the observer such that the nearer body
prevents the light form the farther body from reaching the observer
Optical axis: is an imaginary line that defines the path along which light propagates
through the system
Orbit:
Path of a satellite around a body such as the earth, under the influence of
gravity.
Orthoimage : An image derived from a conventional perspective image by simple or
differential rectification so that image displacements caused by sensor tilt
and relief of terrain are removed.
Panchromatic channel: A channel of a sensor detector system covering the entire visible
part of the electromagnetic spectrum
Parallax:
A change in position of the object, as viewed through an instrument, if the
viewing eye is moved. Parallax correction is especially important for a
riflescope.
Passive remote sensing: Remote sensing of energy naturally reflected or radiated by the
target (Terrain)
Period:
The length of time required for a satellite to complete one orbit.
Photogrammetry: Science or art of obtaining reliable measurements or information from
photographs or other sensing systems.
Pitch:
Rotation of a satellite/aircraft about the horizontal axis normal to its
longitudinal axis that causes a nose-up r nose down attitude.
Polar Orbit: An orbit that passes close to the poles, thereby enabling a satellite to pass
over most of the surface of the earth, except the immediate vicinity of the
poles themselves.
Pre-processing: it a process of radiometric correction and geometric correction
Indian Remote Sensing Missions & Payloads – A glance
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Prism: is a transparent optical element with flat, polished surfaces that refract light. The
exact angles between the surfaces depend on the application. The
traditional geometrical shape is that of a triangular prism with a triangular
base and rectangular sides, and in colloquial use "prism" usually refers to
this type.
Quantum efficiency: QE is defined as the percentage of the generated electronic charges
by the incoming photos.
Radiometric resolution: capability of the sensor to differentiate the smallest change in the
spectral reflectance/emittance between various targets
Raster Data: Machine-readable data that represent values usually stored for maps or
images and organized sequentially by rows and columns. Each "cell" must
be rectangular but not necessarily square, as with grid data.
Reflection:
When a light ray is incident on an interface between two media, some
portion of the light ray will usually remain in the incident medium, tracing
a path such that the angle of the incident ray with respect to the normal is
equal to the angle of the reflected ray with respect to the normal.
Moreover, the incident and reflected rays, as well as the normal to the
surface, all lie in the same plane.
Refraction:
When a light ray is incident on an interface between two media, some
portion of the light ray will usually be transmitted into the second medium.
If the speed of light in the transmitting medium is different to the incident
medium, this causes the light ray to change direction. This phenomenon is
called refraction. The amount of refraction is determined by the ratio is the
speed of lights in the two media, and the angle of the incident ray as given
by Snell's Law.
Remote sensing: sensing of earth’s surface from space by making use of the properties of
electromagnetic wave emitted, reflected or diffracted by the sensed object
or Technique of acquiring information about an area or an object from a
distance without being in physical contact with the object.
Repetivity:
The frequency with which given scene can be imaged. Depends on orbit
characteristics and swath.
Roll:
Rotation of an Aircraft/satellite that causes a wing-up or wing-down
attitude
Scale:
The relationship between a distance on a map and the corresponding
distance on the earth. Often used in the form 1:24,000, which means that
one unit of measurement on the map equals 24,000 of the same units on the
earth's surface.
Indian Remote Sensing Missions & Payloads – A glance
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Sensor: An instrument, usually consisting of optics, detectors, and electronics, that collects
radiation and converts it into some other form suitable for obtaining
information.
Spatial resolution: the capability of sensor to discriminate the smallest object on the
ground. The ability of the sensors to image closely spaced objects so that
they are distinguishable as separate objects.
Spectral Band: An interval in the electromagnetic spectrum defined by two wavelengths,
two frequencies, or two wave numbers.
Spectral resolution: the spectral band width with which the data is collected
Spectrometer: Device for measuring intensity of radiation radiated or reflected by a
material as a function of wavelength.
Stefan-Boltzmann law-States that radiant flux of a blackbody is equal to the temperature
to the fourth power times the Stefan-Boltzmann constant.
Step and stare: Step is to impart the initial bias to spacecraft to make the camera look
ahead of the sub-satellite point.
Sun Synchronous Orbit: An Earth satellite orbit in which the orbital plane is near polar
and the altitude is such that a satellite will always pass over a specific
place on earth at the same local sun time and at fixed time intervals
Telescope (from the Greek tele = 'far' and skopein = 'to look or see'; teleskopos = 'farseeing') is an instrument designed for the observation of remote objects.
Temporal resolution: The capability to view the same target, under similar conditions at
regular intervals.
UV:
Ultraviolet region of the electromagnetic spectrum, ranging in wavelength
from 0.01 to 0.4 microns.
Wien's displacement law-Describes the shift of the radiant power peak to shorter
wavelengths as temperature increases.
Yaw:
Rotation of an aircraft /satellite about its vertical axis (Nadir)
Indian Remote Sensing Missions & Payloads – A glance
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Acronyms
BPSK
Binary Phase Shift Keying
4 Pi SS
4 Pi Sun Sensor
BRC
Bit Rate Clock
ADC
Analog to Digital Converter
Attitude Determination and
Control Subsystem
Ampere Hour
Assembly Integration &
Testing
Aluminium alloy
Attitude and Orbit Control
Electronics
Attitude and Orbit Control
System
Avalanche Photo Detector
CAN
CART
OSAT
CBT
Controller Area Network
CCD
Charge Coupled Device
CCGA
Ceramic Column Grid Array
ADCS
AH
AIT
Al
AOCE
AOCS
APD
APS
ASIC
ASLV
Active Pixel Sensor
Application Specific
Integrated Circuit
Augmented Satellite Launch
Vehicle
Cartographic Satellite
C-Band Transponder
CCL
Closed Control Loop
Consultative Committee for
CCSDS
Space Data Systems
CDR
Critical Design Review
Carbon Fibre Reinforced
CFRP
Plastic
CGP
Central Grounding Point
CIP
Command Interface Port
CMG
COTS
Control Moment Gyro
Complementary Metal Oxide
Semiconductor
Configuration Management
Review Board
Centre National d’Etudes des
Spatiales
Commercial - Off –The- Shelf
CP
Circular Polarized (RCP, LCP)
CMOS
ATC
Auto Temperature Control
ATE
Automated Test Equipment
ATJ
Advanced Triple Junction
AWiFS
BAPT
A
BBR
Advanced Wide Field Sensor
Bearing and Power Transfer
Assembly
Band-To-Band Registration
CPM
Charge Particle Monitor
BCD
Binary Coded Decimal
CPSK
Coherent Phase Shift Keying
BDH
Baseband Data Handling
CRC
BDR
Base-line Design Review
Be
Beryllium
BER
Bit Error Rate
CTF
Cyclic Redundancy Code
Coefficient of Thermal
Expansion
Contrast Transfer Function
BFL
Back Focal Length
CVD
Chemical Vapor Deposition
BMU
Bus Management Unit
CZT
Cadmium Zink Telluride
BOL
Beginning of Life
dB
Decibel
CMRB
CNES
CTE
Indian Remote Sensing Missions & Payloads – A glance
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DCU
Data Compression Unit
EMC
Electromagnetic Compatibility
DDR
Detailed Design Review
EMI
Electromagnetic Interference
DE
Detector Electronics
EOL
End of Life
DEC
Decoder
EOM
Electro-Optical Module
DFT
Discrete Fourier Transform
EOS
Earth Observation System
DFU
Data Formatting Unit
ESD
Electro Static Discharge
DGA
Dual Gimbal Antenna (DGA)
FCC
False Color Composite
DH
FD
Flange Distance
FM
Frequency Modulation
FM
Flight Model
DMA
Data handling
Dual Inline Package/Data
Interface Package
Direct Memory Access
FOG
Fiber Optic Gyro
DMSS
Dynamic Multi Star Simulator
FOV
Field of View
DN
Digital Number
FPA
DP
FRR
Focal Plane Arrays
Field Programmable Gate
Array
Flight Readiness Review
FSK
Frequency Shift Keying
G/T
Gain/Temperature
Gbps
Giga Bits Per Second
GCP
Ground Control Point
DSER
Data Products
Differential Pulse Code
Modulation
Differential Phase Shifting
Keying
Data Quality Evaluation
Dynamic Random Access
Memory
Deserializer
GMT
Greenwich Mean Time
DSN
Deep Space Network
Global Positioning System
DSP
Digital Signal Processing
GPS
GSLV
DSS
EDAC
Digital Sun Sensor
Dynamically Tuned
Gyroscope
Error Detection and Correction
EED
DIP
DPCM
DPSK
DQE
DRAM
FPGA
HEX
Geo-Synchronous Satellite
Launch Vehicle
High Energy X-ray Payload
HILS
Hardware In-Loop Simulation
HK
House Keeping
Electro Explosive Device
HMC
Hybrid Microwave Circuit
EFL
Effective Focal Length
HR
High Resolution
EID
Electrical Interface Document
Effective Isotropic Radiated
Power
Engineering Model
HRMX
High Resolution Multispectral
Hyper spectral imaging
instrument
DTG
EIRP
EM
HySI
IC
Indian Remote Sensing Missions & Payloads – A glance
Integrated Circuit
2
IFOV
Instantaneous Field Of View
Instantaneous Geometric Field
Of View
Integrated Information
Management System
ISRO Inertial Systems Unit
Information Management
System
LCD
Liquid Crystal Display
LED
Light Emitting Diodes
LENA
Low Energy Neutral Atom
LEO
IMS
INCOI
S
InGaAs
Indian Micro Satellite
Indian National Committee for
Ocean Information Services
Indium Gallium Arsenic
Li-ion
IOC
Integrated Optic Chip
IR
Infra-Red
Indian Remote Sensing
Satellites
Inertial Reference Unit
International Society for
Photogrammetry and Remote
Sensing
Indian Space Research
Organisation
International Space Station
Indian Space Science Data
Centre
Indian Scientific Satellite
Project
Integrated Spacecraft Testing
ISRO Telemetry Tracking and
Command Network
International Telephone &
Telegraph
Joint Photographic experts
group
Kelvin
Large area Xenon Filled
Proportional counter
Low Earth Orbit
Laboratory for Electro Optics
Systems
Left Hand Circular
Polarisation
Lithium ion
Linear Imaging Self-Scanning
Sensor
Lunar Laser Ranging
Instrument
Low Noise Amplifier
IGFOV
IIMS
IISU
IMS
IRS
IRU
ISPRS
ISRO
ISS
ISSDC
ISSP
IST
ISTRA
C
ITT
JPEG
K
LAXP
C
LEOS
LHCP
LISS
LLRI
LNA
LO
LOCO
LPSC
LTC
LVDS
LWIR
M3
MADR
AS
Mbps
Local Oscillator
Low Complexity Lossless
Compression
Liquid Propulsion Systems
Centre
Light Transfer Characteristics
Low Voltage Differential
Signaling
Long Wave Infrared
Moon Mineralogy Mapper
Microwave Analysis and
Detection of Rain and
Atmospheric Structures
Mega Bits Per Second
MCT
Mercury Cadmium Telluride
MEO
MEOS
S
MHD
MSS
Medium Earth Orbit
Monocular Electro-Optical
Stereo Scanner
Multiple Head Dynamic multi
star simulator
MI
Moment of Inertia
Indian Remote Sensing Missions & Payloads – A glance
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MID
MILSTD
MIP
Mechanical Interface
Document
PAN
Panchromatic
PCB
Printed Circuit Board
Military Standard
PCM
Pulse Code Modulation
PDR
Preliminary Design Review
PEB
Project Executive Board
PFZ
Potential Fishing Zone
PID
PINFE
T
PIU
Parameter Identification
Positive Intrinsic Field effect
Transistor
Payload Interface Unit
PLE
Payload Electronics
PLL
Phased lock loop
PM
Phase Modulation
PMB
Moon Impact Probe
MIR
Medium wave Infra-Red
MLI
Multi-Layer Insulation
MMU
Mission Management Unit
Multispectral Opto-electronic
Scanner
MOS
MRB
Material Review Board
MRR
MTC
Mission Readiness Review
Multi-frequency Scanning
Microwave Radiometer
Magnetic Torquer Coil
MTF
Modulation Transfer Function
MX
Multispectral
NDC
NRSC Data Centre
PMT
Project Management Board
Programme Management
Office
Photo Multiplier Tube
NI-Cd
Nickel Cadmium Batteries
PPC
Payload Power Converter
NIR
Near Infra Red
PPC
Pointed Proportional Counter
Nm
Newton Metre
PPR
Payload Power Regulator
NMS
PrEB
OBC
Newton Metre Second
National Remote Sensing
Centre
On-Board
Controller/Computer
OBT
On-Board Time
OCM
Ocean Colour Monitor
PSK
Programme Executive Board
Programme Management
Board
Photo Response NonUniformity
Programmable Read Only
Memory
Phase shift keying
OCP
PSLV
Polar Satellite Launch Vehicle
PSR
Pre-Shipment Review
QPSK
Quadrature Phase shift keying
OSR
Over Current Protection
Onboard Software In Loop
Simulation
Optical Solar Reflector
Pitch axis
PAA
Phased Array Antenna
R
RADO
M
Roll axis
P
MSMR
NRSC
OILS
PMO
PrMB
PRNU
PROM
Indian Remote Sensing Missions & Payloads – A glance
Radiation Dose Monitor
4
RAM
Random Access Memory
SiC
Silicon Carbide
RCS
Reaction Control System
SLV
Satellite Launch Vehicle
RF
Radio Frequency
Right Hand Circular
Polarization
Radar Imaging Satellite
SNR
Signal to Noise Ratio
SOC
System On Chip
SPS
Satellite Positioning System
SPSS
Solar Panel Sun Sensor
SRC
SS
Standing Review Committee
Stretched Rohini Satellite
Series
Star Sensor
SSM
Scanning Sky Monitor
SSPA
Solid State Power Amplifier
SSPO
Sun Synchronous Polar Orbit
RTX
Reduced Instruction Set
Computing
Read Only Memory
Radio Occultation for
Sounding of Atmosphere
Reed-Solomon, Receive/send
Regenerative Thermal
Oxidizer
Receive/Transmit
SSR
Solid State Recorder
RW
Reaction Wheel
SSRB
Subsystem Review Board
Rx
Receiver
SST
Sea Surface Temperature
S/N
Signal-to-Noise Ratio
SWIR
Short Wave Infrared
SAA
Sun Aspect Angle
SWR
Square Wave Response
SAC
Space Application Centre
SXT
Soft X-ray imaging Telescope
SADA
Solar Array Drive Assembly
Satellite Microwave
Radiometer
TC
TM
Telecommand
Temperature Controlled
Crystal Oscillator
Time Delay Integration
Technology Experimental
Satellite
Tata Institute of Fundamental
Research
Telemetry
Spacecraft Control Centre
TMC
Terrain Mapping Camera
SCD
Swept Charge Device
TSG
SEO
Satellite for Earth Observation
SER
SGCM
G
Serializer
Single Gimbal Control
Moment Gyro
Thermal Systems Group
Telemetry Tracking and
Command
Traveling Wave Tube
Amplifier
Transmitter
RHCP
RISAT
RISC
ROM
ROSA
RS
RTO
SAMIR
SAR
SARA
SARA
L
SCC
Synthetic Aperture Radar
Sub KeV Atom Reflective
Analyzer
Satellite for Argos and Altika
SROSS
TCXO
TDI
TES
TIFR
TTC
TWTA
Tx
Indian Remote Sensing Missions & Payloads – A glance
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UHF
Ultra high Frequency
USB
VNIR
Universal Serial Bus
United Technologies
Microelectronics Center
Ultra Violet
Ultra Violet Imaging
Telescope
Very high speed Hardware
Description Language
Very High Frequency
Very High Resolution
Radiometer
Visible and Near InfraRed
VSSC
VSSG
CMG
WDE
Vikram Sarabhai Space Centre
Variable Speed Single Gimbal
Control Moment Gyro
Wheel Drive Electronics
WiFS
Wide Field Sensor
XSM
X-ray Sky Monitor
Y
Yaw Axis
UTMC
UV
UVIT
VHDL
VHF
VHRR
Indian Remote Sensing Missions & Payloads – A glance
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References
1. S. Dhawan, ‘The Indian Space Programme’ Presented at the thirteenth
International Symposium on space technology and science (ISTS) Held at
Tokyo During June 28-July 3, 1982.
2. U.R.Rao ‘An Overview of the ‘Aryabhata’ Project’ Proc. Indian Acad. Sci.
Vol. C1 No.3 Nov 1978 pp 117-133.
3. U.R.Rao et Al ‘ The X ray astronomy experiment’ Proc. Indian Acad. Sci.
Vol. C1 No.3 Nov 1978 pp 331-343.
4. S Prakash Jet.al ‘The Aeronomy Experiment’ Proc. Indian Acad. Sci. Vol.
C1 No.3 Nov 1978 pp 321-329.
5. MVK Appa Rao et al. ‘An experiment to detect energetic neutrons and
gamma rays from the sun’ Proc. Indian Acad. Sci. Vol. C1 No.3 Nov 1978
pp 313-319.
6. U.R.Rao. Remote sensing for National Development, Current Science Vol.
61 Nos 3 & $ 25 August 1991
7. U.R.Rao Space for Sustainable Development Journal of Spacecraft
Technology Vol. 5, No.1, Jan. 1995
8. U.R.Rao, K.Kasthurirangan and V.R.Katti. Bhaskara I and II – The
experimental Earth Observation Satellite, Proceedings of the indo-soviet
symposium on space research – Bangalore 1983
9.
T.K.Alex, Attitude sensor systems in Aryabhata and Bhaskara Satellites
Proceedings of the indo-soviet symposium on space research – Bangalore
1983
10. K Kasturirangan, et. al. The Indian EO Programme National and Global
Drivers Acta Astronautica Vol 48, No.5-12, pp. 799-808, 2001
11. K.Kasturirangan and K.R. Sridharamurthy ‘ISRO spacecraft technology
evolution’ Sadhana Vol. 12 , Part 3 March 1988 pp. 251-288
12. S. Kalyanaraman, K. Thyagarajan, R.N. Tyagi & M. Venkata Rao “ Three
Years of Mission Performance - IRS-lA” Journal of Spacecraft Technology.
13. S. Kalyanaraman and R.K.Rajangam IRS-1C Spacecraft Configuration,
Technology and Realisation Aspects, ‘ Journal of Spacecraft Technology
Vol. %, No.2, July 1995.
Indian Remote Sensing Missions & Payloads – A glance
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14. S.Kalyanaraman et.al IRS-1C ‘Mission Operation System ‘,Journal of
Spacecraft Technology Vol.5, No.2, July 1995.
15. K.Thyagarajan, IRS-P3 Remote sensing Mission Acta Asrronaurica. Vol. 39,
No. 9-12, PP. 711-716, 1996
16. M. Ramakrishna Sharma, Nagesh Upadhyaya, N, Sitarama Murthy, C.N
Umapathy and E. Vasantha, The processing electronics system for the
pointed mode Operation of IXAE on the Indian Satellite IRS-P3 IEEE
Transactions on Nuclear science Vol 46 No. 1 Feb 1999
17. R.N.Tyagi, ‘IRS-P4 Mission’ Current Science Vol. 77 No.8 25 October
1999.
18. K.S.V. Seshadri, Mukund Rao B, V. Jayaraman, K. Thyagarajan, K.R.
Sridhara Murthi Resourcesat-1:Aglobal multi-observation mission for
resources monitoring, Acta Astronautica 57 (2005) 534 – 539
19. V.Koteswara Rao, P.C.Agrawal, P.Sreekumar, K.Thyagarajan The scientific
objectives of the ASTROSAT mission of ISRO, Acta Astronautica 65 (2009)
6–17.
20. Configuration Data Books of Remote Sensing spacecrafts
21. Internet sources
Indian Remote Sensing Missions & Payloads – A glance
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Indian Remote Sensing Missions & Payloads – A glance
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