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    • By NASA
      “Trying to do stellar observations from Earth is like trying to do birdwatching from the bottom of a lake.” James B. Odom, Hubble Program Manager 1983-1990.

      The third servicing mission to the Hubble Space Telescope, placed in orbit in 1990, occurred during the STS-103 mission in December 1999. During the mission, originally planned for June 2000 but accelerated by six months following unexpected failures of the telescope’s attitude control gyroscopes, the astronauts restored the facility to full functionality. During their eight-day mission that featured the first space shuttle crew to spend Christmas in space, the seven-member U.S. and European crew rendezvoused with and captured Hubble, and four astronauts in rotating teams of two conducted three lengthy and complex spacewalks to service and upgrade the telescope. They redeployed the telescope with greater capabilities than ever before to continue its mission to help scientists unlock the secrets of the universe.
      Schematic showing the Hubble Space Telescope’s major components. Workers inspect the Hubble Space Telescope’s 94-inch diameter primary mirror prior to assembly. Astronauts release the Hubble Space Telescope in April 1990 during the STS-31 mission. The discovery after the Hubble Space Telescope’s launch in 1990 that its primary mirror suffered from a flaw called spherical aberration disappointed scientists who could not obtain the sharp images they had expected. But thanks to the Hubble’s built-in feature of on-orbit servicing, NASA devised a plan to correct the telescope’s optics during the first planned repair mission in 1993. A second servicing mission in 1997 upgraded the telescope’s capabilities until the next mission planned for three years later. But after three of the telescope’s six gyroscopes failed in 1997, 1998, and 1999, mission rules dictated a call up mission in case additional gyroscope failures sent Hubble into a safe mode. NASA elected to move up some of the servicing tasks from the third mission, splitting it into missions 3A and 3B, planning to fly 3A in October 1999 on Discovery’s STS-103 mission primarily to replace the failed gyroscopes. Delays to the shuttle fleet resulting from anomalies during the launch of STS-93 in July 1993 slipped STS-103 first into November and ultimately into December. Technical issues with Discovery itself pushed the launch date to mid-December, and raised concerns about having a shuttle in orbit during the Y2K transition. Once the launch had slipped to Dec. 19, mission planners cut the mission from 10 to eight days, deleting one of the four spacewalks, to ensure a return before the end of the calendar year. The servicing mission couldn’t come soon enough, as a fourth gyroscope failed aboard Hubble in mid-November, with Discovery already poised on the launch pad to prepare for STS-103. Controllers placed Hubble in a safe mode until the astronauts arrived.
      The STS-103 crew of C. Michael Foale, left, Claude Nicollier, Scott J. Kelly, Curtis L. Brown, Jean-François A. Clervoy, John M. Grunsfeld, and Steven L. Smith. The STS-103 crew patch. The mission patch for the Hubble Servicing Mission-3A. To execute the third Hubble Servicing Mission, in July 1998 NASA selected an experienced four-person team to carry out a record-breaking six spacewalks on the flight then planned for June 2000. The spacewalkers included Mission Specialists Steven L. Smith serving as payload commander, John M. Grunsfeld, C. Michael Foale, and European Space Agency (ESA) astronaut Claude Nicollier from Switzerland. The addition in March 1999 of Commander Curtis L. Brown, Pilot Scott J. Kelly, and Mission Specialist ESA astronaut Jean-François A. Clervoy of France rounded out the highly experienced crew with 18 previous spaceflights among them. Brown earned the distinction as only the fifth person to fly in space six times. For Kelly, STS-103 marked his first spaceflight. Smith, Clervoy, and Grunsfeld each had flown two previous missions, Foale four including a long-duration mission aboard Mir, and Nicollier three. Smith participated in three spacewalks during the second Hubble Servicing Mission and Nicollier served as the Remote Manipulator System (RMS) or robotic arm operator during the first.
      The STS-103 crew at the traditional prelaunch breakfast at NASA’s Kennedy Space Center in Florida. Suited up, the STS-103 astronauts leave crew quarters for the trip to Launch Pad 39B. Space shuttle Discovery on Launch Pad 39B, awaiting launch. Discovery arrived back to KSC at the end of the STS-96 mission on June 6, 1999, and workers towed it to the Orbiter Processing Facility the same day to begin readying it for STS-103. The vehicle rolled over to the Vehicle Assembly Building on Nov. 4, where workers mated it with its external tank and twin solid rocket boosters, before rolling the stack out to Launch Pad 39B on Nov. 13.
      Liftoff of space shuttle Discovery on the STS-103 Hubble Space Telescope servicing mission 3A. The Hubble Space Telescope as Discovery approaches. The STS-103 crew berthing the Hubble into the payload bay. Beginning its 27th trip into space, Discovery lifted off from Launch Pad 39B at 7:50 p.m. EST on Dec. 19 to fix the ailing space telescope. Two days later, Brown and Kelly maneuvered Discovery to within range of Hubble so Clervoy operating the 50-foot-long RMS could grapple the telescope and berth it into the payload bay.
      During the first spacewalk, astronauts John M. Grunsfeld, left, and Steven L. Smith replacing one of the Rate Sensor Units containing two gyroscopes. Smith gives a thumbs up with his image reflected in the Hubble Space Telescope. Smith and Grunsfeld conducted the mission’s first spacewalk on Dec. 22, the flight’s fourth day in space. The duo, aided by Clervoy operating the RMS from inside Discovery, completed two of mission’s highest priority objectives. They replaced the failed gyroscopes, installing three new Rate Sensor Units, each containing two gyroscopes, to return control to the ailing telescope. They also installed six Voltage/Temperature Improvement Kits to prevent the telescope’s batteries from overheating as they aged. The excursion lasted eight hours 15 minutes, at the time the second longest spacewalk.
      During the second spacewalk, astronauts C. Michael Foale, left, and Claude Nicollier during the changeout of the fine guidance sensor. Foale at the end of the Remote Manipulator System services the Hubble Space Telescope. The next day, Nicollier and Foale conducted the mission’s second spacewalk. The main task for this excursion involved installing a new computer aboard Hubble, replacing the original 1970s vintage unit. The new radiation-hardened system ran 20 times faster and carried six times more memory while using one-third the electrical power. They also installed a fine guidance sensor before concluding the eight-hour 10-minute spacewalk.
      Astronauts Steven L. Smith, left, and John M. Grunsfeld begin their servicing activities during the third spacewalk. At the end of the third and final spacewalk, Grunsfeld, left, and Smith provide closing comments about the work the mission accomplished to service the Hubble Space Telescope. Smith and Grunsfeld ventured outside for a second time to complete the flight’s third and final spacewalk on Dec. 24, the first spacewalk conducted on Christmas Eve day. First, they replaced an old reel-to-reel tape recorder with a solid state unit providing a 10-fold increase in recording capability and replaced a failed data transmitter. They installed seven new covers on Hubble’s electronics bay doors for added protection of the telescope’s insulation. This third spacewalk lasted eight hours eight minutes.
      The first space shuttle crew to celebrate Christmas in space, the STS-103 astronauts pose wearing Santa hats. The Hubble Space Telescope shortly after the STS-103 crew released it. The next day, the STS-103 astronauts earned the distinction as the first space shuttle crew to spend Christmas Day in space. Clervoy grappled Hubble, lifted it out of the payload bay and released it to continue its mission. Hubble Space Telescope Program Manager John H. Campbell said after the release, “The spacecraft is being guided by its new gyros under the control of its brand new computer. [It] is now orbiting freely and is in fantastic shape.” After deploying Hubble, the astronauts enjoyed a well-deserved Christmas dinner, with Clervoy providing French delicacies. The crew spent Dec. 26 readying Discovery for its return to Earth, including testing its reaction control system thrusters and aerodynamic surfaces and stowing unneeded gear.
      Astronauts Steven L. Smith, left, Claude Nicollier, and John M. Grunsfeld complete their fluid loading protocol and put on their launch and entry suits prior to reentry. Space shuttle Discovery makes a perfect night landing at NASA’s Kennedy Space Center in Florida. The crew welcome home ceremony at Ellington Field in Houston. On Dec. 27, the astronauts donned their launch and entry suits and prepared for the return to Earth. They closed the payload bay doors and fired Discovery’s engines to bring them out of orbit. Just before landing, Kelly lowered the craft’s landing gear and Brown guided Discovery to a smooth night landing at KSC, concluding a flight of seven days, 23 hours, 11 minutes. They circled the Earth 119 times. The flight marked Discovery’s last solo flight as all its subsequent missions docked with the International Space Station. Workers at KSC began readying it for its next mission, STS-92 in October 2000.

      The Hubble Space Telescope continues to operate today, far exceeding the five-year life extension expected from the last of the servicing missions in 2009. Joined in space by the James Webb Space Telescope in 2021, the two instruments together continue to image the skies across a broad range of the electromagnetic spectrum to provide scientists with the tools to gain unprecedented insights into the universe and its formation.

      Watch the STS-103 crew narrate a video of their Hubble servicing mission.
      View the full article
    • By NASA
      Hubble Space Telescope Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts News Hubble News Hubble News Archive Social Media Media Resources Multimedia Multimedia Images Videos Sonifications Podcasts E-books Online Activities Lithographs Fact Sheets Glossary Posters Hubble on the NASA App More 35th Anniversary 2 min read
      Hubble Spies a Cosmic Eye
      This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 2566. ESA/Hubble & NASA, D. Thilker This NASA/ESA Hubble Space Telescope image features the spiral galaxy NGC 2566, which sits 76 million light-years away in the constellation Puppis. A prominent bar of stars stretches across the center of this galaxy, and spiral arms emerge from each end of the bar. Because NGC 2566 appears tilted from our perspective, its disk takes on an almond shape, giving the galaxy the appearance of a cosmic eye.
      As NGC 2566 appears to gaze at us, astronomers gaze right back, using Hubble to survey the galaxy’s star clusters and star-forming regions. The Hubble data are especially valuable for studying stars that are just a few million years old; these stars are bright at the ultraviolet and visible wavelengths to which Hubble is sensitive. Using these data, researchers can measure the ages of NGC 2566’s stars, which helps piece together the timeline of the galaxy’s star formation and the exchange of gas between star-forming clouds and the stars themselves.
      Hubble regularly teams up with other astronomical observatories to examine objects like NGC 2566, including the NASA/ESA/CSA James Webb Space Telescope. Webb data complements Hubble’s by going beyond the infrared wavelengths of light Hubble can see, better defining areas of warm, glowing dust. At even longer wavelengths, the Atacama Large Millimeter/submillimeter Array (ALMA) of 66 radio telescopes that work together can capture detailed images of the clouds of gas and dust in which stars form. Together, Hubble, Webb, and ALMA provide an overview of the formation, lives, and deaths of stars in galaxies across the universe.
      Explore More

      How does Hubble work with other telescopes?


      Hubble’s Galaxies


      Galaxy Details and Mergers


      Hubble Focus E-Book: Galaxies through Space and Time

      Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
      Claire Andreoli (claire.andreoli@nasa.gov)
      NASA’s Goddard Space Flight Center, Greenbelt, MD
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      Last Updated Dec 19, 2024 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
      Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Hubble Space Telescope Spiral Galaxies Keep Exploring Discover More Topics From NASA
      Hubble Space Telescope


      Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.


      Hubble’s Partners in Science



      Hubble’s Night Sky Challenge



      Hubble’s Galaxies


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    • By NASA
      A rendering of Firefly’s Blue Ghost lunar lander and a rover developed for the company’s third mission to the Moon as part of NASA’s CLPS (Commercial Lunar Payload Services) initiative.Credit: Firefly Aerospace NASA continues to advance its campaign to explore more of the Moon than ever before, awarding Firefly Aerospace $179 million to deliver six experiments to the lunar surface. This fourth task order for Firefly will target landing in the Gruithuisen Domes on the near side of the Moon in 2028.
      As part of the agency’s broader Artemis campaign, Firefly will deliver a group of science experiments and technology demonstrations under NASA’s CLPS initiative, or Commercial Lunar Payload Services, to these lunar domes, an area of ancient lava flows, to better understand planetary processes and evolution. Through CLPS, NASA is furthering our understanding of the Moon’s environment and helping prepare for future human missions to the lunar surface, as part of the agency’s Moon to Mars exploration approach. 
      “The CLPS initiative carries out U.S. scientific and technical studies on the surface of the Moon by robot explorers. As NASA prepares for future human exploration of the Moon, the CLPS initiative continues to support a growing lunar economy with American companies,” said Joel Kearns, deputy associate administrator for exploration, Science Mission Directorate, NASA Headquarters in Washington. “Understanding the formation of the Gruithuisen Domes, as well as the ancient lava flows surrounding the landing site, will help the U.S. answer important questions about the lunar surface.”
      Firefly’s first lunar delivery is scheduled to launch no earlier than mid-January 2025 and will land near a volcanic feature called Mons Latreille within Mare Crisium, on the northeast quadrant of the Moon’s near side. Firefly’s second lunar mission includes two task orders: a lunar orbit drop-off of a satellite combined with a delivery to the lunar surface on the far side and a delivery of a lunar orbital calibration source, scheduled in 2026.
      This new delivery in 2028 will send payloads to the Gruithuisen Domes and the nearby Sinus Viscositatus. The Gruithuisen Domes have long been suspected to be formed by a magma rich in silica, similar in composition to granite. Granitic rocks form easily on Earth due to plate tectonics and oceans of water. The Moon lacks these key ingredients, so lunar scientists have been left to wonder how these domes formed and evolved over time. For the first time, as part of this task order, NASA also has contracted to provide “mobility,” or roving, for some of the scientific instruments on the lunar surface after landing. This will enable new types of U.S. scientific investigations from CLPS.
      “Firefly will deliver six instruments to understand the landing site and surrounding vicinity,” said Chris Culbert, manager of the CLPS initiative at NASA’s Johnson Space Center in Houston. “These instruments will study geologic processes and lunar regolith, test solar cells, and characterize the neutron radiation environment, supplying invaluable information as NASA works to establish a long-term presence on the Moon.”
      The instruments, collectively expected to be about 215 pounds (97 kilograms) in mass, include: 
      Lunar Vulkan Imaging and Spectroscopy Explorer, which consists of two stationary and three mobile instruments, will study rocks and regoliths on the summit of one of the domes to determine their origin and better understand geologic processes of early planetary bodies. The principal investigator is Dr. Kerri Donaldson Hanna of the University of Central Florida, Orlando. Heimdall is a flexible camera system that will be used to take pictures of the landing site from above the horizon to the ground directly below the lander. The principal investigator is Dr. R. Aileen Yingst of the Planetary Science Institute, Tucson, Arizona. Sample Acquisition, Morphology Filtering, and Probing of Lunar Regolith is a robotic arm that will collect samples of lunar regolith and use a robotic scoop to filter and isolate particles of different sizes. The sampling technology will use a flight spare from the Mars Exploration Rover project. The principal investigator is Sean Dougherty of Maxar Technologies, Westminster, Colorado. Low-frequency Radio Observations from the Near Side Lunar Surface is designed to observe the Moon’s surface environment in radio frequencies, to determine whether natural and human-generated activity near the surface interferes with science. The project is headed up by Natchimuthuk Gopalswamy of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.  Photovoltaic Investigation on the Lunar Surface will carry a set of the latest solar cells for a technology demonstration of light-to-electricity power conversion for future missions. The experiment will also collect data on the electrical charging environment of the lunar surface using a small array of solar cells. The principal investigator is Jeremiah McNatt from NASA’s Glenn Research Center in Cleveland. Neutron Measurements at the Lunar Surface is a neutron spectrometer that will characterize the surface neutron radiation environment, monitor hydrogen, and provide constraints on elemental composition. The principal investigator is Dr. Heidi Haviland of NASA’s Marshall Spaceflight Center in Huntsville, Alabama. Through the CLPS initiative, NASA purchases lunar landing and surface operations services from American companies. The agency uses CLPS to send scientific instruments and technology demonstrations to advance capabilities for science, exploration, or commercial development of the Moon. By supporting a robust cadence of lunar deliveries, NASA will continue to enable a growing lunar economy while leveraging the entrepreneurial innovation of the commercial space industry. Two upcoming CLPS flights scheduled to launch in early 2025 will deliver NASA payloads to the Moon’s near side and south polar region, respectively.
      Learn more about CLPS and Artemis at:
      https://www.nasa.gov/clps
      -end-
      Alise Fisher
      Headquarters, Washington
      202-358-2546
      alise.m.fisher@nasa.gov
      Natalia Riusech / Nilufar Ramji    
      Johnson Space Center, Houston
      281-483-5111
      natalia.s.riusech@nasa.gov / nilufar.ramji@nasa.gov
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      Last Updated Dec 18, 2024 LocationNASA Headquarters Related Terms
      Commercial Lunar Payload Services (CLPS) Artemis View the full article
    • By NASA
      4 Min Read NASA Finds ‘Sideways’ Black Hole Using Legacy Data, New Techniques
      Image showing the structure of galaxy NGC 5084, with data from the Chandra X-ray Observatory overlaid on a visible-light image of the galaxy. Chandra’s data, shown in purple, revealed four plumes of hot gas emanating from a supermassive black hole rotating “tipped over” at the galaxy’s core. Credits: X-ray: NASA/CXC, A. S. Borlaff, P. Marcum et al.; Optical full image: M. Pugh, B. Diaz; Image Processing: NASA/USRA/L. Proudfit NASA researchers have discovered a perplexing case of a black hole that appears to be “tipped over,” rotating in an unexpected direction relative to the galaxy surrounding it. That galaxy, called NGC 5084, has been known for years, but the sideways secret of its central black hole lay hidden in old data archives. The discovery was made possible by new image analysis techniques developed at NASA’s Ames Research Center in California’s Silicon Valley to take a fresh look at archival data from the agency’s Chandra X-ray Observatory.
      Using the new methods, astronomers at Ames unexpectedly found four long plumes of plasma – hot, charged gas – emanating from NGC 5084. One pair of plumes extends above and below the plane of the galaxy. A surprising second pair, forming an “X” shape with the first, lies in the galaxy plane itself. Hot gas plumes are not often spotted in galaxies, and typically only one or two are present.
      The method revealing such unexpected characteristics for galaxy NGC 5084 was developed by Ames research scientist Alejandro Serrano Borlaff and colleagues to detect low-brightness X-ray emissions in data from the world’s most powerful X-ray telescope. What they saw in the Chandra data seemed so strange that they immediately looked to confirm it, digging into the data archives of other telescopes and requesting new observations from two powerful ground-based observatories.
      Hubble Space Telescope image of galaxy NGC 5084’s core. A dark, vertical line near the center shows the curve of a dusty disk orbiting the core, whose presence suggests a supermassive black hole within. The disk and black hole share the same orientation, fully tipped over from the horizontal orientation of the galaxy.NASA/STScI, M. A. Malkan, B. Boizelle, A.S. Borlaff. HST WFPC2, WFC3/IR/UVIS.  The surprising second set of plumes was a strong clue this galaxy housed a supermassive black hole, but there could have been other explanations. Archived data from NASA’s Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile then revealed another quirk of NGC 5084: a small, dusty, inner disk turning about the center of the galaxy. This, too, suggested the presence of a black hole there, and, surprisingly, it rotates at a 90-degree angle to the rotation of the galaxy overall; the disk and black hole are, in a sense, lying on their sides.
      The follow-up analyses of NGC 5084 allowed the researchers to examine the same galaxy using a broad swath of the electromagnetic spectrum – from visible light, seen by Hubble, to longer wavelengths observed by ALMA and the Expanded Very Large Array of the National Radio Astronomy Observatory near Socorro, New Mexico.
      “It was like seeing a crime scene with multiple types of light,” said Borlaff, who is also the first author on the paper reporting the discovery. “Putting all the pictures together revealed that NGC 5084 has changed a lot in its recent past.”
      It was like seeing a crime scene with multiple types of light.
      Alejandro Serrano Borlaff
      NASA Research Scientist
      “Detecting two pairs of X-ray plumes in one galaxy is exceptional,” added Pamela Marcum, an astrophysicist at Ames and co-author on the discovery. “The combination of their unusual, cross-shaped structure and the ‘tipped-over,’ dusty disk gives us unique insights into this galaxy’s history.”
      Typically, astronomers expect the X-ray energy emitted from large galaxies to be distributed evenly in a generally sphere-like shape. When it’s not, such as when concentrated into a set of X-ray plumes, they know a major event has, at some point, disturbed the galaxy.
      Possible dramatic moments in its history that could explain NGC 5084’s toppled black hole and double set of plumes include a collision with another galaxy and the formation of a chimney of superheated gas breaking out of the top and bottom of the galactic plane.
      More studies will be needed to determine what event or events led to the current strange structure of this galaxy. But it is already clear that the never-before-seen architecture of NGC 5084 was only discovered thanks to archival data – some almost three decades old – combined with novel analysis techniques.
      The paper presenting this research was published Dec. 18 in The Astrophysical Journal. The image analysis method developed by the team – called Selective Amplification of Ultra Noisy Astronomical Signal, or SAUNAS – was described in The Astrophysical Journal in May 2024.
      For news media:
      Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.
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      Last Updated Dec 18, 2024 Related Terms
      Black Holes Ames Research Center Ames Research Center's Science Directorate Astrophysics Chandra X-Ray Observatory Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research General Hubble Space Telescope Marshall Astrophysics Marshall Science Research & Projects Marshall Space Flight Center Missions NASA Centers & Facilities Science & Research Supermassive Black Holes The Universe Explore More
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    • By NASA
      X-rays are radiated by matter hotter than one million Kelvin, and high-resolution X-ray spectroscopy can tell us about the composition of the matter and how fast and in what direction it is moving. Quantum calorimeters are opening this new window on the Universe. First promised four decades ago, the quantum-calorimeter era of X-ray astronomy has finally dawned.
      Photo of the XRISM/Resolve quantum-calorimeter array in its storage container prior to integration into the instrument. The 6×6 array, 5 mm on a side, consists of independent detectors – each one a thermally isolated silicon thermistor with a HgTe absorber. The spectrometer consisting of this detector and other essential technologies separates astrophysical X-ray spectra into about 2400 resolution elements, which can be thought of as X-ray colors.NASA GSFC A quantum calorimeter is a device that makes precise measurements of energy quanta by measuring the temperature change that occurs when a quantum of energy is deposited in an absorber with low heat capacity. The absorber is attached to a thermometer that is somewhat decoupled from a heat sink so that the sensor can heat up and then cool back down again. To reduce thermodynamic noise and the heat capacity of the sensor, operation at temperatures less than 0.1 K is required. 
      The idea for thermal measurement of small amounts of energy occurred in several places in the world independently when scientists observed pulses in the readout of low-temperature thermometers and infrared detectors. They attributed these spurious signals to passing cosmic-ray particles, and considered optimizing detectors for sensitive measurement of the energy of particles and photons.
      The idea to develop such sensors for X-ray astronomy was conceived at Goddard Space Flight Center in 1982 when X-ray astronomers were considering instruments to propose for NASA’s planned Advanced X-ray Astrophysics Facility (AXAF). In a fateful conversation, infrared astronomer Harvey Moseley suggested thermal detection could offer substantial improvement over existing solid-state detectors. Using Goddard internal research and development funding, development advanced sufficiently to justify, just two years later, proposing a quantum-calorimeter X-ray Spectrometer (XRS) for inclusion on AXAF. Despite its technical immaturity at the time, the revolutionary potential of the XRS was acknowledged, and the proposal was accepted.
      The AXAF design evolved over the subsequent years, however, and the XRS was eliminated from its complement of instruments. After discussions between NASA and the Japanese Institute of Space and Astronautical Science (ISAS), a new XRS was included in the instrument suite of the Japanese Astro-E X-ray observatory. Astro-E launched in 2000 but did not reach orbit due to an anomaly in the first stage of the rocket. Astro-E2, a rebuild of Astro-E, was successfully placed in orbit in 2005 and renamed Suzaku, but the XRS instrument ceased operation before observations started due to loss of the liquid helium, an essential part of the detector cooling system, caused by a faulty storage system.
      A redesigned mission, Astro-H, that included a quantum-calorimeter instrument with a redundant cooling system was successfully launched in 2016 and renamed Hitomi. Hitomi’s Soft X-ray Spectrometer (SXS) obtained high resolution spectra of the Perseus cluster of galaxies and a few other sources before a problem with the attitude control system caused the mission to be lost roughly one month after launch. Even so, Hitomi was the first orbiting observatory to obtain a scientific result using X-ray quantum calorimeters. The spectacular Perseus spectrum generated by the SXS motivated yet another attempt to implement a spaceborne quantum-calorimeter spectrometer.
      The X-ray Imaging and Spectroscopy Mission (XRISM) was launched in September 2023, with the spectrometer aboard renamed Resolve to represent not only its function but also the resolve of the U.S./Japan collaboration to study the Universe through the window of this new capability. XRISM has been operating well in orbit for over a year.  
      Development of the Sensor Technology
      Development of the sensor technology employed in Resolve began four decades ago. Note that an X-ray quantum-calorimeter spectrometer requires more than the sensor technology. Other technologies, such as the coolers that provide a
      The sensors used from XRS through Resolve were all based on silicon-thermistor thermometers and mercury telluride (HgTe) X-ray absorbers. They used arrays consisting of 32 to 36 pixels, each of which was an independent quantum calorimeter.  Between Astro-E and Astro-E2, a new method of making the thermistor was developed that significantly reduced its low-frequency noise. Other fabrication advances made it possible to make reproducible connections between absorbers and thermistors and to fit each thermistor and its thermal isolation under its X-ray absorber, making square arrays feasible.
      Through a Small Business Innovation Research (SBIR) contract executed after the Astro-E2 mission, EPIR Technologies Inc. reduced the specific heat of the HgTe absorbers. Additional improvements made to the cooler of the detector heat sink allowed operation at a lower temperature, which further reduced the specific heat. Together, these changes enabled the pixel width to be increased from 0.64 mm to 0.83 mm while still achieving a lower heat capacity, and thus improving the energy resolution. From Astro-E through Astro-H, the energy resolution for X-rays of energy around 6000 eV improved from 11 eV, to 5.5 eV, to 4 eV. No changes to the array design were made between Astro-H and XRISM.
      Resolve detector scientist Caroline Kilbourne installing the flight Resolve quantum-calorimeter array into the assembly that provides its electrical, thermal, and mechanical interfaces.NASA GSFC Over the same period, other approaches to quantum-calorimeter arrays optimized for the needs of future missions were developed. The use of superconducting transition-edge sensors (TES) instead of silicon (Si) thermistors led to improved energy resolution, more pixels per array, and multiplexing (a technique that allows multiple signals to be carried on a single wire). Quantum-calorimeter arrays with thousands of pixels are now standard, such as in the NASA contribution to the future European New Advanced Telescope for High-ENergy Astrophysics (newAthena) mission. And quantum calorimeters using paramagnetic thermometers — which unlike TES and Si thermistors require no dissipation of heat in the thermometer for it to be read out — combined with high-density wiring are a promising route for realizing even larger arrays. (See Astrophysics Technology Highlight on these latest developments.)
      The Resolve instrument aboard XRISM (X-ray Imaging and Spectroscopy Mission) captured data from the center of galaxy NGC 4151, where a supermassive black hole is slowly consuming material from the surrounding accretion disk. The resulting spectrum reveals the presence of iron in the peak around 6.5 keV and the dips around 7 keV, light thousands of times more energetic that what our eyes can see. Background: An image of NGC 4151 constructed from a combination of X-ray, optical, and radio light.Spectrum: JAXA/NASA/XRISM Resolve. Background: X-rays, NASA/CXC/CfA/J.Wang et al.; optical, Isaac Newton Group of Telescopes, La Palma/Jacobus Kapteyn Telescope; radio, NSF/NRAO/VLA Results from Resolve
      So, what is Resolve revealing about the Universe? Through spectroscopy alone, Resolve allows us to construct images of complex environments where collections of gas and dust with various attributes exist, emitting and absorbing X-rays at energies characteristic of their various compositions, velocities, and temperatures. For example, in the middle of the galaxy known as NCG 4151 (see figure above), matter spiraling into the central massive black hole forms a circular structure that is flat near the black hole, more donut-shaped further out, and, according to the Resolve data, a bit lumpy. Matter near the black hole is heated up to X-ray-emitting temperatures and irradiates the matter in the circular structure. The Resolve spectrum has a bright narrow emission line (peak) from neutral iron atoms that must be coming from colder matter in the circular structure, because hotter material would be ionized, and would have a different emission signature. Nonetheless, the shape of the iron line needs three components to describe it, each coming from a different lump in the circular structure. The presence of absorption lines (dips) in the spectrum provides further detail about the structure of the infalling matter.
      A second example is the detection of X-ray emission by Resolve from the debris of stars that have exploded, such as N132D (see figure below), that will improve our understanding of the explosion mechanism and how the elements produced in stars get distributed, and allow us to infer the type of star each was before ending in a supernova. Elements are identified by their characteristic emission lines, and shifts of those lines via the Doppler effect tell us how fast the material is moving.
      XRISM’s Resolve instrument captured data from supernova remnant N132D in the Large Magellanic Cloud to create the most detailed X-ray spectrum of the object ever made. The spectrum reveals peaks associated with silicon, sulfur, argon, calcium, and iron. Inset at right is an image of N132D captured by XRISM’s Xtend instrument.JAXA/NASA/XRISM Resolve and Xtend These results are just the beginning. The rich Resolve data sets are identifying complex velocity structures, rare elements, and multiple temperature components in a diverse ensemble of cosmic objects. Welcome to the quantum calorimeter era! Stay tuned for more revelations!
      Project Leads: Dr. Caroline Kilbourne, NASA Goddard Space Flight Center (GSFC), for silicon-thermistor quantum calorimeter development from Astro-E2 through XRISM and early TES development. Foundational and other essential leadership provided by Dr. Harvey Moseley, Dr. John Mather, Dr. Richard Kelley, Dr. Andrew Szymkowiak, Mr. Brent Mott, Dr. F. Scott Porter, Ms. Christine Jhabvala, Dr. James Chervenak (GSFC at the time of the work) and Dr. Dan McCammon (U. Wisconsin).
      Sponsoring Organizations and Programs:  The NASA Headquarters Astrophysics Division sponsored the projects, missions, and other efforts that culminated in the development of the Resolve instrument.
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