Small Spacecraft Design and On-orbit
SSC14-XII-9
Small Spacecraft Design and On-orbit Performance for the IRIS Mission
Gary Kushner, Brett Allard, Chris Hoffmann, Alan Title
Lockheed Martin, Space Systems Company, STAR Labs
Palo Alto, Ca; 650-424-2310
[email protected]
ABSTRACT
In June 2013, the Interference Region Imaging Spectrograph (IRIS) launched from Vandenberg AFB for a two year
solar observing science investigation to study the interface of the solar photosphere to the corona. IRIS is a NASA
Small Explorers mission that is in a sun-synchronous, low-Earth orbit. It is obtaining high-resolution images and
spectra of the chromosphere and transition region that, combined with advanced computer models, will explore how
matter, light, and energy move from the sun’s 6,000 K surface to its million K outer atmosphere, the corona. This
paper describes the design, development, and test of the 183 kg observatory along with a summary of the on-orbit
performance. IRIS was designed and built at the Lockheed Martin Space Systems STAR Labs in Palo Alto, Calif.,
with support from the company’s Civil Space line of business and major partners Smithsonian Astrophysical
Observatory and Montana State University. NASA Ames is responsible for mission operations and the ground data
system. The Norwegian Space Agency provides the primary ground station at Svalbard, Norway with scientific
modeling performed by the University of Oslo. The science data is managed by the SDO Joint Science Operations
Center, run by Stanford University and Lockheed Martin.
distribution. The instrument, spacecraft, and ground
data system were developed, tested, and prepared for
launch over a 44 month period. Along with the
hardware development, scientific models and data
analysis tools were developed in preparation for dealing
with the complex IRIS data set.
INTRODUCTION
IRIS is a NASA Small Explorer (SMEX) mission that
was launched on June 27, 2013 in a dusk-dawn sunsynchronous, polar, low earth orbit. The goal of the
IRIS mission is to understand the connection and
energy transfer between the 6000K visible surface (the
photosphere), the 10,000K Chromosphere, and the
1,500,000K corona. The mission consists of a UV
telescope and imaging spectrograph, a small spacecraft
bus, the mission operations and ground data system,
and the science investigation. The program is led by
the Principal Investigator, Dr. Alan Title, of the
Lockheed Martin (LM) Space System Company STAR
Labs. The mission was selected and operated out of
NASA’s Science Mission Directorate Heliophysics
Division with oversight by the Explorers office at
NASA Goddard Space Flight Center. Lockheed Martin
was responsible for managing the mission including the
instrument and the spacecraft development; instrument
development support was provided by the Smithsonian
Astronomical Observatory and Montana State
University. NASA Ames Research Center developed
and manages the mission operations center and the
ground data system with ground network contributions
from the Norwegian Space Center (NSC), European
Space Agency (ESA), and NASA’s Near Earth
Network (NEN). The University of Oslo provides
scientific modeling support and Stanford University
provides scientific data processing, archiving, and
Kushner, et. al.
IRIS is the latest in a long line of successful NASA
SMEX missions. The satellites usually range from
100kg to 300kg in total mass and operate in low earth
orbit, placing them in the “small” satellite category
following the generally accepted range of satellites
from picosatellite (up to 1kg), nanosatellites (up to
10kg), microsatellite ( up to 100kg) to small satellites
(up to 500kg). A goal of the SMEX program is to
provide relatively frequent access to space for
heliophysics and astrophysics research programs. The
procurement and selection of NASA SMEX missions
are similar to other NASA missions such as Explorer
and Discovery in that they are selected in response to an
Announcement of Opportunity (AO) and go through a
two step down select process. From a development
perspective, some of the distinguishing characteristics
of the SMEX program are the classification as an
enhanced Class D mission, the two year on-orbit life
time, the use of single string (non-redundant) systems, a
reduced level of program oversight, and the schedule,
cost, and launch vehicle constraints. Other, general
characteristics of SMEX and small satellite missions
are: testing of the flight hardware is performed to
proto-qualification levels, a small tightly-coupled
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several band pass filters to allow for multiple
wavelength imaging. The slit passes a 0.33 arcsec x
175 arcsec area of the sun to the spectrograph3 prism
where it is split into two optical paths corresponding to
the Far Ultraviolet (FUV) and Near Ultraviolet (NUV)
bandpasses listed in table 1. The slit also includes two
development team, early definition and control of
program requirements, reuse of existing design as much
as possible (evolutionary design versus revolutionary
design), a robust risk management process, and a
streamlined set of development and management
processes. This paper will cover the science enabled by
this small, but powerful observatory, describe the onorbit performance of the observatory, and describe the
technical aspects of the mission and how it was
developed considering the budget, schedule, and
programmatic constraints.
Table 1: IRIS Bandpasses
OBSERVATORY
The mission concept is shown in figure 1. As noted,
the observatory flies in a sun-synchronous polar orbit
allowing the instrument to be pointed at the sun at all
times. The instrument is described in DePontieu1 and
summarized as follows. A schematic of the instrument
is provided in figure 2. The Cassegrain telescope2 has
a primary mirror with a dielectric coating that reflects
the UV portion of the solar radiation onto the secondary
mirror and allows the visible and infrared radiation to
pass through the primary mirror onto an absorbing back
plate with the heat radiated into space. The secondary
mirror has three actuators that allow it to be tilted about
two axes and translated along the optical axis to allow
for focus adjustment, removal of small observatory
motions, and for scanning of the image on the
spectrograph. The light reflects off the secondary
mirror onto the spectrograph’s slit jaw aperture. The
majority of the aperture is reflective and directs light to
the Slit Jaw Imager (SJI) channel providing 175 x 175
arcsec2 images of the sun. This channel also includes
Parameter
Requirement
Bandpasses:
images and spectra
Spectrograph
temperature range of
plasma emissions
Imager
temperature
range
of
plasma
emissions
FUV: 1332 to 1406Å
NUV: 2785 to 2835Å
10,000K
−
10,000,000K
10,000K − 60,000K
fiducial marks that allow the slit jaw images and the
spectral images to be aligned. A reflective diffraction
grating disperses the light into its constituent
wavelengths onto the three Charge Coupled Devices
(CCDs). The spectrograph is designed to reimage the
portion of the sun under study onto the CCD at each
spectral position. This allows for simultaneous imaging
of the sun at multiple UV wavelengths. The image of
the sun can be scanned across the slit to provide for a
130 arcsec x 170 arcsec field of view. The scan speed
and step size can be adjusted based on the phenomena
Figure 1 IRIS Mission Concept
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Figure 2 Instrument Schematic
support and launch vehicle interface. The ACS uses a
magnetometer, coarse and digital sun sensors, star
trackers, and the instrument guide telescope for attitude
determination and fine pointing knowledge while the
reaction wheels and magnetic torque rods provide
pointing and momentum control.
An Integrated
Avionics Unit (IAU) contains both the C&DH and EPS
subsystems; power is supplied by deployed solar arrays
and stored in a lithium-ion battery. Communications is
handled by an S-Band transponder and science data
transfer is via an X-Band transmitter with
corresponding antennas.
under study with a baseline spectral cadence of 3s per
step and image cadence of 5s per image. In addition to
these small field scans, the entire observatory can be
slewed to any position on the sun including off-limb.
With this capability, the science team programs the
observatory to carry out scientific observations focusing
on one specific solar region or a sequence of such
observations including the ability to construct a full
image mosaic of the sun.
The spacecraft architecture was based on similar,
larger scale spacecraft developed at LM. See figure 3
for a schematic of the spacecraft bus. The spacecraft
was designed for the IRIS mission, but can be extended
to support a variety of heliophysics, astrophysics, and
earth observing payloads. For IRIS, the primary drivers
were to support the instrument’s high resolution
imaging and spectral requirements and ability to point
to any region of the sun. The other critical drivers were
acquisition of the sun upon reaching orbit and fault
detection and management to enable a high level of
autonomous operations. Cost, schedule, and volumetric
constraints impacted the selection of the bus structure
and components. The spacecraft includes the following
subsystems: electrical power generation, storage, and
distribution (EPS), attitude determination and control
(ACS), command and data handling (C&DH),
communications, and the bus structure for instrument
Kushner, et. al.
MISSION DEVELOPMENT
As noted above, the cost, schedule, and size constraints
were part of all design trades. The result was to use
existing hardware and software designs as much as
possible and to use commercially supplied components
where feasible. Single string systems and subsystems
were used throughout the observatory. The observatory
was designed for autonomous on-orbit operations with
minimal human support from the ground. Flight spares,
brassboards, and engineering units were kept to a
minimum. Deferral of subsystem testing was carried
out to streamline the integration and test effort, and
qualification by similarity was used for components
with flight heritage. A small core team was responsible
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for the design, development, integration, test, launch,
and on-orbit checkout of the observatory. See figure 4
for a picture of the completed observatory.
The instrument design was based on prior missions
such as the Atmospheric Imaging Assembly4 (AIA),
Helioseismic Magnetic Imager5 (HMI), Transition
Region And Coronal Explorer6 (TRACE), and Hinode7;
trades were carried out to balance the IRIS mission
requirements against the available capability. For
example, initial optical analyses indicated a telescope
aperture of approximately 30cm would meet all mission
requirements with some margin. It was determined that
the existing AIA 20cm telescope would meet the
threshold requirements for IRIS with significant cost
and schedule savings, thus it was selected. Other
examples of design reuse include the guide telescope,
the telescope and spectrograph mechanisms including
the shutters, filter wheel, and focus mechanisms, the
secondary mirror mount with actuators, the
spectrograph optics mounts8 (from NIRCAM) the
instrument electronics, and the instrument flight
software. Additional instrument features that saved
cost and schedule was the use of existing AIA flight
spare camera electronics boxes and a the procurement
of a catalog CCD that required only slight
modifications for use in IRIS; all four focal planes were
designed to use this one CCD type. For the instrument,
the primary new technology was the development of the
spectrograph optical system and several new electronics
Kushner, et. al.
boards. A limited structural model was built to aid in
development of the spectrograph assembly and
alignment operations. Except for the qualification of
the optics mounts by type, no other structural model or
engineering models were fabricated. For the electronics
subsystem, brassboard electronics boards were
developed for verifying the new power and limb tracker
boards and to populate an instrument electronics test
bed to support software testing and checkout. Life
testing of mechanisms was not performed; they were
qualified by similarity to mechanisms flown and tested
on prior missions. For the instrument, the only flight
spares were for several critical optics, for several
electronics components, and for two camera electronics
boards with high ESD sensitivity. See Kushner9 for
further discussion on the design and test philosophy.
For the spacecraft, prior missions and design studies
were used for reference in the design of the IRIS
spacecraft bus. The LM team designed the spacecraft
architecture including the bus structure, the harness and
interconnects, the Multi-layer Insulation (MLI)
blanketing, the ACS flight software, the fault
management scheme, and the Electrical Ground
Support equipment (EGSE).
The solar arrays,
deployment mechanisms, and EGSE were developed in
house. The majority of the spacecraft components were
procured from vendors with a majority being catalog
items such as the reaction wheel assemblies, torque
rods, Integrated Avionics Unit (IAU) (which consisted
Figure 3 Spacecraft Schematic
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Figure 4 IRIS Observatory with Solar Arrays Deployed
traditional flight development program would have a
progressive level of flight qualification and acceptance
testing as components are developed and integrated into
higher levels of assembly. On an enhanced Class D
mission such as IRIS, all flight acceptance tests are
performed, but the program has the ability to trade at
what level the tests are carried out, as long as all
subsystems are exposed to the required test
environments at some time in the test flow. The
majority of the vendor supplied hardware was
acceptance tested prior to delivery to LM. One
exception was the telescope assembly for which the
thermal vacuum, vibration, and Electromagnetic
Interference,
Electromagnetic
Compatibility
(EMI/EMC) tests were deferred to higher levels of
assembly. For the instrument, vibration testing was
deferred to the observatory level due to the complexity
of replicating the mounting to the spacecraft and to
reduce the risk of over test. However, extensive
thermal vacuum and optical performance testing was
performed at the instrument level due to the new
spectrograph design and the complexity of optical
stimulation at the observatory level. Instrument level
EMI/EMC testing was deferred to the observatory level
to ensure all electrical interfaces were tested in the most
flight like configuration. For the spacecraft, vibration,
thermal vacuum, and EMI/EMC tests were all deferred
to the observatory level. The decision as to which level
of integration to carry out the environmental and
acceptance testing was based on balancing schedule,
of the C&DH and EPS subsystems), the coarse and
digital sun sensors, the magnetometer, and the star
trackers. The flight and test batteries were spares from
the GRAIL program. The S-Band and X-Band RF
communications units were vendor developed to meet
the system requirements and size constraints of the IRIS
spacecraft structure. Cost and schedule saving features
included the design of a gyro-less ACS system enabled
by the use of the fine pointing signal from the
instrument guide telescope and the use of auto
generated ACS code from the Simulink system model10.
The only engineering units procured for the spacecraft
development were two IAU engineering models used
for development and test of the spacecraft and ACS
software. The communications vendor developed
engineering units for the X- and S- band units to aid in
their development, but they were not contract
deliverables. A Reaction Wheel Assembly (RWA)
engineering unit was loaned from the GRAIL program
to aid in an anomaly investigation, but was not
transferred to the IRIS program and the magnetometer
vendor loaned an engineering unit for system and
model validation. No spacecraft flight spares were
procured. The architecture was single string with some
limited redundancy from the use of 4 RWAs (can
operate in degraded mode with 3) and the star tracker
and magnetometer electronics units.
The assembly, integration, and test operations were also
planned with cost, schedule, and risk in mind. The
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A common ground system EGSE operating system,
ITOS12, was selected for the instrument, spacecraft, and
mission operations systems. This allowed test scripts
and display screens developed during subassembly
integration and test to be migrated to the system level
testing and to the MOC. EGSE imaging and analysis
routines from AIA and HMI were ported for use on
IRIS. The spacecraft EGSE was developed for the IRIS
program with a few components such as the Solar
Array Simulators and RF test equipment made available
from prior programs. The optical stimulus GSE – used
for performance testing of the instrument throughout
integration and test - was based on the AIA stimulus
system including use of a spare telescope tube. In
addition, a set of company processes and procedures
were tailored to meet the scope and pace of the mission.
test complexity, and risk with many of the decisions
reducing the overall risk to the mission.
The Mission Operations System (MOS) and Ground
Data System (GDS) were developed by NASA Ames
Research Center (ARC). The Mission Operations
Center (MOC)11 is housed and staffed by NASA Ames
personnel. The GDS is supported by NASA’s NEN and
the Norwegian Space Center (NSC) with ground
stations in Svalbard, Alaska, and Wallops Island. The
observatory operates autonomously with one command
pass during nominal working days (5 days per week).
Science team members prepare observation timelines
that include pointing targets, scans and slews, and
coordinated observation sequences with other missions
and observatories. The timelines are prepared the day
prior to the command load and cover weekends and
holidays.
The science data is downlinked via 13
ground station passes per day (7 days per week). The
MOC is staffed for the command passes with lights out
operation the remainder of the time. The data from
each ground station pass is transferred autonomously
using standard internet protocol. The observatory has a
fault management system that monitors subsystem
telemetry points and determines if immediate action is
required or if alerts are to be sent to the ground. The
team has a health and safety web page viewable by all
team members and an Alert Notification System on the
ground that monitors telemetry and sends out text
messages if any program parameters go out of range.
IRIS generates more than 45 Gb of science data per
day. The data is transferred from the NASA MOC to
the Solar Dynamics Observatory (SDO) Science
Operations Center at Stanford where preliminary
processing is performed. The Quicklook data is
typically available on an open access basis to the
science community within 6 hours of receipt on the
ground. Calibrated data is available 7 days after receipt
on the ground.
The assembly, test, and integration of the observatory
and subsystems proceeded well, but IRIS did have its
share of developmental anomalies and issues. See
Kushner9 for several representative examples.
MISSION TIMELINE
The program received contract authorization to start in
September of 2009. All the major program reviews
were held in calendar year 2010 with the System
Requirements Review (SRR) in January, Preliminary
Design Review (PDR) in May, and Critical Design
Review (CDR) in December. These formal reviews
included the instrument, spacecraft, and MOS/GDS
with subsystem peer reviews held prior to each major
review. Subsystems that were qualified on prior
missions were not formally reviewed. In addition,
designs that were complete and accepted at the PDR
were not re-reviewed at the CDR. The instrument and
spacecraft were developed, assembled, integrated, and
tested in parallel.
The instrument spectrograph
structure was received in Sept 2011; the optics,
mechanisms, and focal planes were installed and
aligned over a period of 5 months. The spectrograph
was completed and a spectrograph level thermal
vacuum test and optical calibration test were performed
and completed by April 2012. In parallel, the telescope
assembly was assembled, integrated, and tested at the
Smithsonian Astrophysical Observatory (SAO) with
delivery to LM in December of 2011. The telescope
and spectrograph were integrated in May 2012 with the
instrument level thermal vacuum testing completed in
July 2012. The spacecraft structure was received in
September 2011 with subassemblies installed as they
arrived including: torque rods in September 2011, the
IAU and star trackers in December 2011, and the
RWAs in March 2012. The spacecraft bus was vacuum
baked in June 2012 and ready for mechanical
integration with the instrument in July 2012. The
remaining critical subsystem, the RF communication
Throughout design, development, integration, and test,
the instrument, spacecraft, MOS/GDS, and science
teams were integrated and co-located as much as
possible.
Many personnel who worked on the
instrument and spacecraft subsystems and components
were part of the program from design phase to launch
and on-orbit checkout. This was an important part of
the program as it ensured: continuity of knowledge
from design to test, that subsystem test scripts could be
modified and carried into observatory test, and that
anomaly and root cause investigations could be carried
out in a timely manner. This also enabled team
members to cross-train on other subsystems allowing
the relatively small team to carry out the environmental,
comprehensive and functional tests, launch operations,
and on-orbit checkout and calibration.
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currently operating within specification and the science
continues to exceed level one requirements. The
observatory operates and executes the science timelines
autonomously with the MOC uploading commands via
S-Band once per day, five days a week. The science
team develops the timelines based on recent active
areas and regions of interest and based on
collaborations with other missions and observatories;
the timelines are loaded between one and three days
before execution. The science data is transmitted to the
ground via X-Band using ground stations at Svalbard,
Alaska, and Wallops. The data is transmitted via
internet protocol to the MOC and then to Stanford for
archiving, processing, and distribution to the science
community.
units, were installed during the observatory
environmental test flow. The instrument and spacecraft
were mechanically integrated in August 2012 and the
first comprehensive performance test was completed in
November 2012. Observatory environmental testing
was then performed from November 2012 through
March 2013. Testing included random vibration,
separation shock, EMI/EMC, RF compatibility testing
with NEN, thermal vacuum and thermal balance
testing, deployment testing, and mass properties
measurements.
Random vibration testing was
performed instead of acoustic testing due to the
relatively small size and low surface area of the
observatory. Separation shock testing was performed
using pyrotechnic actuators with a simulated rocket
section.
Functional and performance tests were
performed throughout the environmental test program.
The observatory shipped to the launch site at
Vandenberg Air Force Base on April 15, 2013. Various
tests and checkouts were performed at the integration
site with the observatory mated to the Orbital Science
Corp. Pegasus ™ rocket on May 29, 2013. After
several launch simulations and functional tests, the
rocket was mated to the L1011 aircraft on June 19,
2013 with takeoff and launch on June 27, 2013.
The technical performance on-orbit has met or
exceeded the program requirements. Details of the on
orbit ACS performance is provided in Van Bezooijen14.
During nominal science operations, the x and y axis
(pitch and yaw) pointing accuracy has been better than
0.5 arcsec which is an order of magnitude better than
the requirements. The peak to peak roll error is 7.7
arcsec which translates to a line of sight error on the
sun to less than 0.05 arcsec. While there are periodic
disturbances from the large filter wheel in the
instrument and from RWA momentum unloading, these
motions are corrected by the instrument’s image
stabilization system. Housekeeping data is transmitted
to the ground along with the science data and
subsystem trends are monitored by the operations team.
All systems are operating nominally with the RWAs
showing a minor change in drag indicating possible
IRIS was launched on June 27, 2013 and obtained a
near perfect orbit of 620 x 670 km allowing for the
maximum time of eclipse free viewing13.
See
Vanbezooijen14 for description of the detumble, sun
acquisition, and fine pointing performance of the
observatory and the ACS system. For the next 20 days,
the telescope door remained closed to allow for
outgassing of internal components prior to exposure to
solar radiation. During these 20 days, the pointing of
the observatory was optimized and on-board systems
were functionally tested. On July 17, 2013, the
telescope door was opened and first light obtained. On
July 28, 2013, IRIS completed the engineering
checkout phase and the science phase was begun.
About 30 days were then spent calibrating the
telescope, the spectrograph, and the pointing and
slewing operations and numerous operational sequences
and timelines were exercised. In September, the
observatory achieved full scientific readiness and in
October, the science data was made available to the
scientific community and public. On December 1, 2013
NASA declared that IRIS met its Mission Success
Criteria.
Table 2. Key Performance Data
Parameter
Orbit
Eclipse-free Observing
(EFT)
Mass (kg)
Power (W)
Field of View
SCIENCE AND ON-ORBIT PERFORMANCE
Since the opening of the telescope door on July 17,
2013, IRIS has been collecting over 45 Gb a day of
images and spectra from the photosphere out to the
corona. The science and technical performance of the
observatory has been excellent. All systems are
Kushner, et. al.
Resolution
Science Data Link
On-board storage
Data Volume
7
Performance
620 x 670 km
7 months per year
183 kg observatory
87 kg instrument
96 kg spacecraft
365W
Solar
beginning of
Array
life
175 x 175 arcsec2 Imager
0.33 x 175 arcsec2 Spect Slit
130 x 175 arcsec2 Spect
Scan
0.4” NUV
0.33” FUV
32 Mbps
6 Gbyte
> 45 Gbit/day
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bearing seating and the primary mirror running several
degrees warmer than planned due to higher than
modeled thermal absorption, but both are within
operating specifications. The data downlink timelines
had to be adjusted to accommodate the X-band
radiating pattern being different than that modeled.
There have been two star tracker software loads to
optimize its performance in the presence of glint,
reflected from the Earth’s surface. There has been one
spacecraft FSW load to correct a timing bug in the
C&DH code, an end-of-year ephemeris propagation
error in ACS, and to enhance the ACS code to provide
latency information of star tracker attitude solutions.
The optical and science performance of the observatory
is described in DePontieu1. The performance and
alignment of the optical system is excellent with
calibrations performed to remove orbital and thermal
variations. The FUV channels have a spatial resolution
of 0.33 arcsec and a spectral resolution of 26mA and
the NUV channels have a spatial resolution of 0.4
arcsec and a spectral resolution of 53mA. The spectral
Figure 5 Coronal Mass Ejection Images from the Slit Jaw Imager
On May 9, 2014 IRIS observed its first CME. The four panels show the evolution of the CME as
captured in the SJI channel; the sequence starts in the top left panel and progresses from frame ad. Images cover a 175 arcsec x 175 arcsec area of the sun. The central line is the 0.33 arcsec wide
spectrograph slit.
Kushner, et. al.
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Figure 6 Sample NUV Spectra
the density, the height of the observed material, the
velocity (from the Doppler shift), and the relative
motion of the material. Figure 7 shows a series of these
recombined slit images at multiple wavelengths from a
relatively quiescent part of the sun. At the top left of
each panel is a plot of the Magnesium II line in the
NUV channel. Below the spectral line plot is the
wavelength of the composite image shown and the
velocity of the material. To the right of the spectral line
plot is the reconstructed image from the scanned slit
images. The horizontal line is from the fiducial mark
on the entrance slit. As one views each panel, it is
evident that different heights/layers of the
chromosphere/photosphere become visible as one
changes wavelength.
resolution allows for a velocity resolution of less than 1
km/s. The instrument can achieve overall temporal
resolution as low as 1.5s.
A summary of the science investigation is provided in
Title15. Table 2 lists a few of the key performance
parameters. Over the past year, IRIS has carried out
greater than 5000 orbits of solar observations including
long observations of active regions and studies of:
coronal holes, solar plage, solar flares, emergence of
filaments, spicules, coronal rain, and other solar
features. Recently, IRIS observed its first Coronal
Mass Ejection (CME)16. There have been several
CMEs during the past year, but, due to the small field
of view, IRIS must be pointed at the location when the
CME occurs as finally happened on May 9, 2014.
Images taken from the slit jaw imager channel are
shown figure 5. The full movie of the CME is available
at16 showing the spatial and temporal resolution of
IRIS. The horizontal line across the image is the
entrance slit for the spectrograph. All of the IRIS slit
jaw movies and images are available to the scientific
community and the public17.
The high resolution images and spectra from IRIS
greatly complement data gathered from other missions
and ground observatories including AIA, HMI, Hinode,
THEMIS, BBSO, and the SST. An example is the
massive X-Flare observed simultaneously by IRIS,
AIA, HMI, Hinode, and RHESSI on March 29, 2014.
IRIS has participated in coordinated observing
campaigns with each of these observatories adding
spatial and spectral information on the interactions
within the interface region.
In addition to the slit jaw images, the spectrograph
produces images of the 0.33 arcsec slit in each spectral
band. An example of a spectral image from the NUV
channel is provided in figure 6. As the slit is scanned
across the field of view, a series of these spectral
images of are captured. When the series of slit images
are combined, composite solar images from the scanned
field of view can be created simultaneously for each
wavelength band. With the spectral data, information
on the plasma can be obtained such as the temperature,
Kushner, et. al.
CONCLUSION
IRIS is a very good example of a small, rapidly
developed, relatively inexpensive program that
produces ground breaking data that is exceeding the
expectations of the international scientific community.
Key to this accomplishment has been the use of
existing, proven designs when feasible, inclusion of
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Figure 7. Combined Spectral Images
ground station passes were contributed by NASA
NEN, ESA, and NSC, and NASA ARC contributed
millions of CPU cycles in support of the modeling
program.
commercially available hardware when appropriate, a
set of streamlined systems engineering and
management processes, a small, core team responsible
for the mission from requirements definition, through
design and test, to launch and on-orbit checkout, and
flexibility in defining a test program that includes
deferral and combining of tests while meeting the
program’s risk management goals. IRIS has been on
orbit for a little over one year and continues to produce
high resolution images and spectra of the sun
contributing to the study of the complex region between
the photosphere and the corona.
References
1.
De Pontieu, B., The Interface Region Imaging
Spectrograph (IRIS), Solar Physics, July 2014,
Volume 289, Issue 7, pp 2733-2779,
2.
Podgorski, W.A., 2012, “Design, performance
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Acknowledgments
IRIS was funded by the NASA Science Mission
Directorate Heliophysics division and managed by the
Explorers Program at NASA GSFC under contract
NNG09FA40C. Although a relatively small program,
many people contributed to IRIS’s success including
personnel at LM, NASA ARC, NASA GSFC, NASA
HQ, SAO, MSU, HAO, UCB, NSO, and UiO.
Hardware was contributed or loaned from the GRAIL
program at JPL and the SDO program by NASA GSFC,
Kushner, et. al.
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28th Annual AIAA/USU
Conference on Small Satellites
5.
Scherrer, P., et al., “the Helioseismic and
Magnetic Imager (HMI) Investigation for the
Solar Dynamics Observatory (SDO),” Solar Phys
(2012) 275:207-227.
6.
Handy, B., “The transition region and coronal
explorer,” Solar Phys (1999) 187:229-260.
7.
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Hinode Mission: An Overview,” Solar Phys
(2008) 249:167-196.
8.
Weingrod, I., et al., “Design of bipod flexure
mounts for the IRIS spectrometer,” Proc. SPIE
8836, (2013).
9.
Kushner, G., “The IRIS Mission – Development
of the Observatory and Ground Systems,”
Aerospace Conference, 2014 IEEE in publication
10.
http://www.mathworks.com/company/user_storie
s/Lockheed-Martin-Space-Systems-DevelopsGNC-System-for-IRIS-Satellite-with-ModelBased-Design.html?by=company
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Ames Multi Mission Operations Center
http://www.nasa.gov/centers/ames/engineering/fa
cilities_mmoc.html
12.
Integrated Test and Operations System (ITOS),
http://itos.gsfc.nasa.gov/index.php
13.
Hametz, Mark E., “ A Combined Spacecraft and
Launch Vehicle Systems Approach to Mission
Design for the IRIS Mission” The 24th
International Symposium on Space Flight
Dynamics (ISSFD), Laurel, MD May 2014.
https://dnnpro.outer.jhuapl.edu/Portals/35/ISSFD
24_Paper_Release/ISSFD24_Paper_S174_Hametz.pdf
14.
Van Bezooijen, R., “Flight Performance of the
IRIS Attitude Control System”, GNC 2014, 9th
International ESA conference on Guidance
Navigation, and Control Systems – in
publication.
15.
Title, A., “The IRIS Mission – Science
Investigation”, Aerospace Conference, 2014
IEEE in publication
16.
http://www.nasa.gov/content/goddard/a-first-fornasas-iris-observing-a-gigantic-eruption-of-solarmaterial/
17.
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http://www.lmsal.com/hek/hcr?cmd=viewrecent-events&instrument=iris
Kushner, et. al.
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28th Annual AIAA/USU
Conference on Small Satellites
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