B

Astrophysics Science Division Missions

The committee requested data on several NASA astrophysics missions. These included the Astro-H (now the Hitomi), Kepler/K2, Nuclear Spectroscopic Telescope Array (NuSTAR), Wide-Field Infrared Survey Explorer (WISE), Galaxy Evolution Explorer (GALEX), Swift Gamma-Ray Burst (Swift), James Webb Space Telescope (JWST), and Fermi Gamma-Ray Space Telescope (Fermi).

ASTRO-H

The Hitomi mission (formerly Astro-H) is a joint program between NASA and the Japan Aerospace Exploration Agency (JAXA). Launched in February 2016, the new Hitomi program’s goal was to seek insights on evolutionary characteristics of some of the universe’s largest structures, behavior of matter in gravity fields, black hole spins, internal structures of neutron stars, and the physics of particle jets. For Astro-H, Key Decision Point C (KDP-C) was in June 2010 and launch was in February 2016. Astro-H was lost before it completed commissioning.

Scientific Productivity

The Astro-H Soft X-ray Spectrometer (SXS) was a cryogenic instrument, operating at 0.05 Kelvin (K). Achieving this temperature requires feed-forward technology. There are many future missions that will require sub-K technology. These include cryocoolers, to get down to 1 to 4 K, and solid-state magnetic refrigerators, to get to <0.1 K.

The Astro-H microcalorimeter array works by sensing electromagnetic radiation as heat, similar to infrared (IR) detector technology. In fact, the X-ray calorimeter array on Astro-H would have made a very sensitive IR bolometer if it were configured for this application. The spacecraft also used very thin-film optical blocking filters, which have general applicability throughout X-ray and ultraviolet astronomy.

Impact on the Current and Future Health of the Relevant Scientific Communities

The spacecraft flew a detector array that was developed for the Astro-E2 (Suzaku) mission. The spacecraft also used spare electrical components. Critical capabilities were created and maintained at Goddard Space Flight

Center (GSFC) in the areas of microcalorimeter fabrication and applications, low-temperature systems technology, high-spectral-resolution X-ray calibration technology, and atomic physics as applied to X-ray astronomy.

Astro-H was a JAXA-led mission, with JAXA providing the project, spacecraft, launch, operations, three instruments, and part of the SXS. NASA provided key elements of the SXS (detector array, adiabatic demagnetization refrigerators, aperture, electronics) and soft X-ray telescopes for two missions, as well as the science pipeline for the SXS.

Astro-H technology will enable future international missions including the Astro-H recovery mission and the European Space Agency (ESA) Advanced Telescope for High-Energy Astrophysics (ATHENA) mission, utilizing the X-ray Integral Field Unit instrument.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Astro-H carried the first calorimeter detector that accumulated scientific data of astronomical objects, such as the Perseus cluster of galaxies. These calorimeters are the detectors of the future, and more advanced versions will be key elements of any major mission. They are in the baseline instrument package (to which NASA is contributing) for ATHENA, an ESA L1 (“Large” class) mission. A calorimeter is also in the baseline design for a large strategic NASA X-ray mission, X-ray Surveyor. The development of the Astro-H calorimeter, funded by NASA, has created a team that leads the field in this technology.

Conclusions

Hitomi was a short-lived mission that demonstrated the power of an X-ray calorimeter for addressing astrophysical problems. The construction of the calorimeter detector helped NASA to advance this critical technology, which will be a vital instrument on any large X-ray mission of the future.

KEPLER/K2

Kepler is a mission that uses the transit method to find Earth-like planets around Sun-like stars. When Earth passes in front of the Sun, as seen by a distant observer located in the plane of the ecliptic, a reduction in flux by 80 parts per million would be seen. This dip lasts for several hours and recurs every year. At least three, and preferably four, such transits must be seen to be sure one is seeing a planet instead of random glitches. In addition, less than 1 percent of distant observers will be situated where these transits can be seen. Thus, Kepler set out to obtain simultaneous photometry with 10 parts per million accuracy on more than 150,000 stars with continuous coverage for 4 years. It succeeded in this prime mission but then experienced a second reaction wheel failure, leading to a degraded attitude control capability. An extended mission, known as K2, is currently ongoing and is working around this difficulty by observing a field for about 80 days and then moving on to a new field. While this mission is unable to detect orbital periods longer than about 30 days, it can still find planets in the habitable zone around low-luminosity stars. Since the number of stars observed by K2 is larger than the number observed by the prime Kepler mission, a larger variety of stellar types can be targeted, including red dwarfs and X-ray binaries like Sco X-1.

Scientific Productivity

Kepler has been an extremely productive mission. Through 2016, over 2,000 papers using Kepler or K2 data have been published.

Impact on the Current and Future Health of the Relevant Scientific Communities

The Kepler mission has contributed to an explosion of the exoplanet community in astrophysics, to the point that it seems like astrophysics has become “all exoplanets all the time.” Public interest in exoplanet research is very

high, which encourages students to study science, technology, engineering, and mathematics fields and Congress to continue to fund NASA. The techniques developed for Kepler that allow highly precise wide-field photometry have been widely adopted throughout the exoplanet community and will certainly be used in the upcoming Transiting Exoplanet Survey Satellite, which will extend K2-like observing cadences to the entire sky.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

There was, intentionally, little new technology developed for the Kepler mission. Off-the-shelf technology was used to the greatest extent possible to keep costs low. The only exception was in the development of the focal plane. While all the parts were essentially off-the-shelf, or built using existing processes, there was a need to extend certain practices: the coating of the sapphire field-flattener lenses required a complex custom technique to provide the consistent, required bandpass.

Although the Kepler mission did not use existing flight spares from other missions, it took significant advantage of technology and designs that already existed. The list includes fully off-the-shelf components and software (e.g., thrusters, star trackers, solid-state recorders) as well as system designs that needed only marginal Kepler-specific alterations (e.g., spacecraft bus, spacecraft operating system software).

Conclusions

Kepler has been a highly successful mission that has contributed substantially to the development of the field of exoplanets.

NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY

The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first orbiting telescope with focusing optics for a hard X-ray light (3 to 80 kiloelectron volts [keV]). First launched in March 2012, the prime mission was originally scheduled for 2 years but is now operating in extended phase. The current extended phase also includes a guest investigator program, and the spacecraft and instruments continue to operate nominally. The Senior Review of Astrophysics panel highly regarded the program in their 2014 and 2016 reviews.

The NuSTAR telescope also includes hybrid X-ray detectors that utilize CdZnTe sensors, which are segmented into 32 × 32 pixels with a 13 × 13 field of view. In addition to its positional sensitivity, it records the energy and arrival times of photons.

Scientific Productivity

NuSTAR has investigated a variety of high-energy astrophysical issues, such as detecting nuclear line emission from Ti in young supernova remnants; revealing supermassive black holes (active galactic nuclei) that are mostly hidden by large quantities of absorbing gas; showing the emission from the halos around black holes, where the light is bent by the gravity within the system; and resolving a significant fraction of the hard X-ray background. It maintains an active community and a strong publication rate.

Impact on the Current and Future Health of the Relevant Scientific Communities

The NuSTAR mission will have a positive impact on the current and future health of the astrophysics scientific communities. Some of the primary examples include the development and maintenance of the capabilities for the X-ray detectors (Caltech), the mirror production (Columbia), and contributions to maintaining the mission operations center at University of California, Berkeley, and its Space Sciences Lab.

Also, the maturation of technology, including the imaging in the hard X-ray band, can be infused for future missions. Other developments include the extendible mast, the adjustment mechanism, and the metrology system that will be used to help develop future Small Explorer (SMEX) X-ray polarimeter missions.

The mirrors, coatings, and detectors were developed through the suborbital program. NuSTAR adapted the deployable mast from the Shuttle Radar Topography mission. It used flight spares from the Lunar Reconnaissance Orbiter (LRO; transceiver) as well as some miscellaneous electronic flight parts. The spacecraft was commercial off-the-shelf.

The NuSTAR mission was also an international collaborative effort with Denmark’s contribution of optics coatings and pipeline software and the Italian Space Agency’s contribution of the Malindi ground station.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

This was the first hard X-ray telescope with focusing optics, a technology developed in part for this mission. Another contribution is the development of multilayer technologies for the optics, which extend the reflectivity to higher energies. The improvement in optics has led to an enormous improvement in sensitivity. The successful demonstration of this technology can naturally lead to higher quality optics with greater collecting area for future missions.

Conclusions

This Explorer-class mission demonstrated the exciting science possible with focusing hard X-ray optics and efficient detectors. There is considerable room for improvement in somewhat larger missions, given the relatively modest collecting area of NuSTAR, as well as improvement in multilayer technology. The user base is significant and active and should increase if a subsequent mission is developed.

WIDE-FIELD INFRARED SURVEY EXPLORER

The Wide-Field Infrared Survey Explorer (WISE) was launched on December 14, 2009, to scan the entire sky in infrared bands. The three primary goals were to find the most luminous galaxies in the universe, to locate the closest stars to the Sun, and to discover and characterize asteroids. The Planetary Science Division of NASA funded a Near-Earth Object WISE (NEOWISE) add-on, which ran a special data processing pipeline. The WISE astrometric data on asteroids became available within a few days of observation and enabled ground-based followup. The project was then temporarily decommissioned in February 2011 and reactivated in September 2013 as NEOWISE-Reactivation (NEOWISE-R) with Planetary Science Division funding. This new mission focused its attention on scanning for near-Earth objects, producing only the single-frame images and source detections useful for moving objects. NEOWISE-R continues to survey the sky in 2017.

Scientific Productivity

The scientific productivity of the WISE mission was substantial and provides many opportunities for development and research in the future. With over 7 years of flight, the returned science was vast and beneficial for researchers. The results of the mission included photographs taken of over 750 million objects, such as remote hyperluminous infrared galaxies, nearby low-luminosity cool brown dwarfs, and over 150,000 asteroids during the first year of the mission. Over 2,000 refereed publications have used WISE data.

The WISE mission provided a critical platform for the development of new technologies. These new technological developments for the WISE spacecraft include the following: a 96-gigabyte (GB) flash memory card by SEAKR, the WISE Ku-band transmitter that was based on Fermi and supports a much higher data rate at 100 megabits per second, and the WISE Ku-band high-grain antenna that provides an evolved design from the model used in many commercial satellites. The technology development conducted for the WISE payload includes the following: the cryogenic readout for the WISE 1024 × 1024 Si:As detector arrays that provides more resources to detect longwave IR, which maintains competition and potentially lowers the cost of future missions; the 5-micron 1024 × 1024 HgCde detectors, which could also benefit future Near-Earth Object Camera (NEOCam) missions; and the WISE advanced telescope design developed by L-3 SSG-Tinsley, which utilizes lower cost materials

such as aluminum diamond-turned mirrors that could benefit future mission proposals like NEOCam and Field Investigations to Enable Solar System Science and Exploration.

Impact on the Current and Future Health of the Relevant Scientific Communities

The WISE mission will have a positive impact on future missions through continual technology development and by providing a “heritage” of instruments used. This includes the WISE spacecraft, which was originally based on Ball Aerospace’s RS200-bus and software package. This package originated from the 2005 Deep Impact mission’s Impactor spacecraft and the 2007 Orbital Express mission’s NEXTSat spacecraft.

The payload component of the WISE mission will also be used as part of a larger line of payload technology development. The current system was developed and evolved from the Space Dynamic Laboratory for the Wide-Field Infrared Explorer (WIRE) satellite. Before the WISE mission, WIRE was developed with a solid hydrogen cryostat under Lockheed Martin. The two short-wavelength detectors were also developed from a model used under the JWST (built by Teledyne). In addition to the shortwave detectors, the long-wavelength detectors originated from a smaller format used in Spitzer’s Multiband Imaging Photometer and Infrared Spectrograph instruments. These heritage developments decrease the risks and vulnerabilities that may come with testing new technology.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

WISE played a critical role in continuing many mission capabilities from other programs. This includes, but is not limited to, maintaining the Earth-orbiting mission operations capabilities from JPL; the science data processing and archiving capabilities from the Infrared Processing and Analysis Center at Caltech; and the expertise on solar system small bodies, brown dwarfs, galaxy clusters, and active galactic nuclei from both institutions.

Conclusions

WISE provided orders of magnitude improvements in the sensitivity of all-sky surveys in the mid-infrared, being hundreds of times more sensitive than the Infrared Astronomical Satellite at 12 and 22 microns, and hundreds of thousands times more sensitive than the Diffuse Infrared Background Experiment at 3.4 and 4.6 microns. By observing the whole sky, WISE automatically provided data for almost all astronomical research programs, leading to a large number of papers using WISE data.

WISE achieved its prime objectives. It discovered the third and fourth closest star systems to the Sun, a brown dwarf binary at 2-parsec (pc) distance, and the coldest known brown dwarf at 2.3-pc distance. WISE discovered a class of hot dust-obscured galaxies with luminosities up to 400 trillion solar luminosities.

GALAXY EVOLUTION EXPLORER

Launched in 2003 the Galaxy Evolution Explorer (GALEX) is a small Explorer (SMEX)-class mission with the purpose of studying the origins of star formation in galaxies. By observing low-redshift galaxies in the ultraviolet (UV), GALEX provided an important reference set for studies of high-redshift galaxies where the rest-frame ultraviolet was redshifted in the visible. GALEX had two wide-field ultraviolet detectors: the near ultraviolet (NUV) and the far ultraviolet (FUV). The planned program for the 29-month prime mission included a targeted Nearby Galaxy Survey and three levels of untargeted surveys: a Deep Imaging Survey (DIS), a Medium Imaging Survey (MIS), and an All-Sky Imaging Survey (AIS). GALEX was extended by more than one NASA Senior Review panel but was finally decommissioned on June 28, 2013. The FUV detector failed 6 years after launch. The UV detectors could be damaged by looking at bright stars, so the AIS was not actually all-sky, avoiding the galactic plane and bright stars at higher galactic latitudes. During the latter part of the extended mission, observations of the galactic plane and brighter stars were undertaken.

Scientific Productivity

GALEX data have been used in at least 750 papers. In addition, the data archive is available at the Barbara A. Mikulski Archive for Space Telescopes and can provide data on sources discovered at other wavelengths. The untargeted GALEX surveys have led to serendipitous discoveries like the long “comet” tail nebulosity being shed by Mira Ceti.

Impact on the Current and Future Health of the Relevant Scientific Communities

GALEX was a SMEX mission that ran on a very constrained budget. Thus, grants for guest investigators did not have a significant impact on the community. However, GALEX collected a large amount of data that still have value, and proposals to mine this archive can be submitted through the Astrophysical Data Program.

Conclusions

GALEX was a very productive SMEX mission. It was fully operational for more than twice its design lifetime and continued to provide useful NUV data for 4 additional years. Its archive covers most of the sky (except when limited by bright stars) and is the UV-equivalent of the Palomar Sky Survey.

SWIFT GAMMA-RAY BURST

Launched in 2004 the Swift Gamma-Ray Burst mission (Swift) is classified as a MIDEX mission. Swift includes a hard X-ray and gamma-ray burst detector (large field of view), a pointed soft X-ray telescope, and a pointed UV-optical telescope (larger field of view than the Hubble Space Telescope [HST] by approximately 20 times). The primary goals of the Swift missions were to determine the origin of gamma-ray bursts (GRBs), to classify GRBs and search for new types, to determine how the burst evolves and interacts with the surroundings, to use GRBs to study the early universe, and to perform the first sensitive hard X-ray survey of the sky.

Scientific Productivity

The team rewrote the control software so that it could easily accept targets of opportunity from the outside (rather than being triggered internally). This allowed the team to interface with other ground- and space-based observatories. This leads to a natural synergy with other observatories when investigating astrophysical phenomena.

The team also opened up the telescope to a user community to perform any observations that the satellite was capable of. During the past 12 years, observations of transient objects have gained in importance, so these modifications transformed the telescope from a narrow focus to a much broader set of science.

Its ranking has been #1 of 11 in the 2008 Senior Review (SR), #4 of 11 in the 2010 SR, the best Explorer mission in the 2012 SR, #1 of 9 in the 2014 SR, and #1-2 of 6 in the 2016 SR. The high rankings reflect the adaptability to new science, which has led to an impressive set of discoveries. The budget has decreased from approximately $10 million per year to approximately $6 million per year. This is less than the team needs to run the observatory without risk, for which it has been criticized. Most of the cost is in full-time equivalents (FTEs), and the team has sold guaranteed time for cash in order to hire FTEs, a mutually beneficial arrangement.

Impact on the Current and Future Health of the Relevant Scientific Communities

Swift has made significant strides in the field of gamma-ray bursters, but its primary mission has become much broader. It responds to outbursts of many different types of astronomical objects (e.g., tidal disruption events) and is the leading space observatory for time-domain astronomy. Its importance in the area of time-domain astronomy will continue, even with significant new ground-based efforts. Swift covers wavebands not possible from the ground, and it responds extremely rapidly from its own triggers. In addition, the UV telescope is the best

operating wide-field-of-view UV telescope, with a field of view 6 times that of the Wide-Field Camera (WFC) 3 on the Hubble. Overall, it offers a unique set of capabilities.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Swift was the first operating mission to employ CdZnTe detectors in an orbiting mission. This detector technology was used for the Burst Alert Telescope, and it offered some significant advantages over previous detectors. It has demonstrated both excellent performance and longevity without significant degradation. The other new aspect of this mission was its rapid response time, about 1 minute from the time of the burst alert to the pointing of its X-ray and UV-optical telescope. This high-speed repointing and stabilization system has proven to be extremely reliable and of low risk. A third contribution is by flight software redevelopment after launch, which greatly improved flexibility for target acquisition and reduced costs. This shows that critical software can be modified on a large scale.

Conclusions

This Explorer mission delivered on its original scientific promise, unraveling the mysteries of gamma-ray bursts and, in the process, demonstrating the viability of a new detector and a fast-response pointing system. Several years after the launch, the Swift team rewrote the flight software, allowing it to better respond to transient events, including targets of opportunity that are triggered by ground requests. These capabilities have transformed the mission, giving it greatly improved scientific breadth, from which it continues to be a high-value NASA asset, as judged from several NASA Astrophysics Senior Reviews.

JAMES WEBB SPACE TELESCOPE

The 2000 astronomy and astrophysics decadal survey ranked the James Webb Space Telescope (JWST) as the highest priority space astronomy recommendation. It was recognized as the successor to the HST and a continuation of the Great Observatories program.

JWST undertook an intensive technology development period following the selection of the prime contractor in 2002. According to the Independent Comprehensive Review Panel (ICRP) called for by Congress, these developments took longer and consequently cost more than forecast during formulation. The ICRP found,

Following a rebaselining of the program in 2011, the program has met its technical milestones, schedule, and budget. Although it is widely recognized that the final testing and integration phase of the project is a major challenge, the project remains on track for launch in 2018.

Scientific Productivity

JWST has not yet been commissioned. The confirmation date was March 9, 2009.

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¹ James Webb Space Telescope (JWST) Independent Comprehensive Review Panel (ICRP), “Final Report” October 29, 2010, https://www.nasa.gov/pdf/499224main_JWST-ICRP_Report-FINAL.pdf.

Impact on the Current and Future Health of the Relevant Scientific Communities

JWST did not use any flight spares from previous missions. No specific hardware technology from prior astrophysics missions was used.

JWST is a partnership among NASA, ESA, and the Canadian Space Agency (CSA). ESA is providing the design, optical benches, filters, and dispersive optical elements for two science instruments (Near Infrared Spectrograph and Mid-Infrared Instrument); an Ariane 5 launch from Kourou with standard launch services; and 15 FTEs at the Space Telescope Science Institute (STScI) during mission operations. CSA is providing the Fine Guidance Sensor, one science instrument (they share opposite sides of one optical bench), and 5 FTEs at the STScI during operations.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Detector technology developed for JWST is being used in the NASA contribution to the Euclid mission. The Wide-Field Infrared Survey Telescope (WFIRST) mission is studying whether components of the cryocooler system would be applicable for that mission. The cryogenic Application-Specific Integrated Circuit developed by JWST was actually used in the final servicing mission of Hubble. Also, several components of the community-facing software developed by the STScI for JWST are now being used for Hubble.

JWST developed numerous facilities for its construction and testing. The most significant and longest lasting of these were the improvements at the GSFC Space Environment Simulator (SES) and the Johnson Space Center Chamber A facility. Smaller improvements were made at the Marshall Space Flight Center’s X-ray and Cryogenic Facility. Most of these improvements were related to the mission’s cryogenic and cleanliness requirements. Additionally, GSFC acquired two very large shaker table systems that could be useful for ambient testing of future missions. NASA does not track whether its industry partners maintained their JWST-specific facilities and hardware after they had finished using them. With the selection of STScI as the operations center for JWST, NASA has ensured that that capability, developed initially for Hubble, will exist should Hubble cease operations.

Conclusions

There have been many lessons learned from the JWST experience. The ICRP report stressed that agency managers plan for project reserves in the years needed and that inadequacy of reserves early in the program was a major factor in the bow wave of cost increases. The ICRP also highlighted the need for unimpeded, transparent communications at all levels to ensure that risks and budget problems are well understood.

FERMI GAMMA-RAY SPACE TELESCOPE

The Fermi Gamma-Ray Space Telescope (Fermi) is the only observatory sensitive to cosmic gamma rays that employs two instruments. The primary instrument is the Large-Area Telescope (LAT), which has a wide field-of-view pair conversion device and is sensitive to gamma rays with energies between 20 megaelectron volts (MeV) and >300 gigaelectron volts (GeV); photon energies, arrival times, and directions are recorded. The other instrument is a Gamma-Ray Burst Monitor, operating in the energy range between 8 keV and 40 MeV. These two instruments have modest angular resolution but observe most of the visible sky continuously. This makes it different from most observatories, which operate in “pointed” mode. For point sources, it measures spectral properties as a function of time, making it the premier time-domain observatory at these high energies. For extended sources that do not vary (e.g., Fermi bubbles), it accumulates photons in every orbit.

Fermi was a joint NASA and Department of Energy (DOE) collaboration, along with institutions in France, Germany, Japan, Italy, and Sweden. It was launched June 11, 2008, and has been working without degradation since full science deployment in August 2008. The 5-year prime phase ended in 2013, and it continues to operate in extended phase, following successful evaluations by the Senior Review panels.

Fermi is the highest energy orbiting observatory, with the photons detected coming from compact objects

(active galactic nuclei, pulsars, neutron stars), explosive events (supernova remnants, gamma-ray bursts), and a few other potential or observed phenomena (dark matter decay, pulsar wind nebulae, terrestrial gamma-ray flashes). It has surveyed the sky, addressing the nature of the gamma-ray background and making the surprise discovery of giant bubbles of plasma extending from the center of the Galaxy, which probably were created by the supermassive black hole at the center.

Fermi has significant synergies with other missions and ground-based observatories, most prominently at high energies in the radio regime, and with optical ground-based efforts, such as surveys. It may contribute to the Laser Interferometer Gravitational-Wave Observatory (LIGO) detections. There is an active ground-based community involved in the data (mainly from the LAT) and publishing at a rate of about 300 to 350 papers per year. It has led to more than 200 Ph.D. dissertations.

Impact on the Current and Future Health of the Relevant Scientific Communities

The overall concept of the Fermi-LAT pair conversion telescope was directly derived from previous pair conversion telescopes (Energetic Gamma Ray Experiment Telescope [EGRET], Cosmic Origins Spectrograph [COS]-B, etc.). The optimization of the Fermi-LAT design was based on lessons learned from EGRET. Design of the micrometeoroid shield on Fermi-LAT was directly derived from the design developed for EGRET onboard the Compton Gamma-Ray Observatory (CGRO). The LAT benefited enormously from the efforts in particle physics to develop silicon strip detectors at an affordable cost and in a manner that allows large-scale integration.

Fermi is an international and interagency partnership, supported by NASA and DOE in the United States and by agencies in France, Germany, Italy, Japan, and Sweden.

International hardware contributions and roles include the following:

• Sweden provides and acceptance-tests the CsI crystals for the Fermi-LAT calorimeter.
• France designs and fabricates the calorimeter mechanical housing.
• Italy assembles and tests the Fermi-LAT tracker towers.
• Japan purchases and acceptance-tests Si-strip detectors for the Fermi-LAT tracker.
• Germany provides Fermi Gamma-Ray Burst Monitor detectors.

Fermi uses DOE (Stanford Linear Accelerator Center [SLAC]), French (Lyon), and Italian (Bologna) computing resources. The bulk of the processing is done on the high-throughput computing facility at SLAC. Additional high-throughput resources from the Computing Center of the National Institute of Nuclear Physics and Particle Physics in France and GRID-based supercomputers in Italy are used as needed.

Contributions to Development and Demonstration of Technology Applicable to Future Missions

Fermi pioneered the use of Mock Data Challenges and detailed detector simulations in NASA missions. These techniques have been adopted by missions such as the Laser Interferometer Space Antenna.

The Fermi-LAT tracker was the first large-scale silicon detector placed on a space mission. The technology development and lessons learned from the Fermi-LAT silicon tracker design and construction have a direct impact on reducing risk for future medium-energy gamma-ray mission concepts such as the All-Sky Medium Energy Gamma-Ray Observatory (United States) and eASTROGAM (ESA), both of which include large silicon strip trackers.

Science data processing for Fermi-LAT is complex and computer-intensive, and it requires handling of large data sets (5 terabytes per week). The pipeline infrastructure developed for Fermi-LAT to process data using approximately 1,000 CPUs, track all data products and processes, and seamlessly utilize international supercomputing resources has been adapted for use on the Large Synoptic Survey Telescope. Since launch, there have been a number of improvements in the data processing software that have led to considerable noise reduction and improved sensitivity.

Conclusions

Fermi is unusual for the astrophysics division in that it was a joint project, mainly with the DOE, at a cost that would be in the range of a probe ($500 million to $1 billion). It was not competed in the same way as an established Announcement of Opportunity line (e.g., Explorer), so it may be considered a strategic mission. The LAT on Fermi is the only orbiting instrument capable of detecting photons at energies up to about 100 GeV with good sensitivity (GRB detectors have much lower sensitivity). It has made a variety of unique scientific contributions, carried forward by an active scientific community, with most publications from guest observers.