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By NASA
5 Min Read Cassiopeia A, Then the Cosmos: 25 Years of Chandra X-ray Science
By Rick Smith
On Aug. 26, 1999, NASA’s Chandra X-ray Observatory opened its powerful telescopic eye in orbit and captured its awe-inspiring “first light” images of Cassiopeia A, a supernova remnant roughly 11,000 light-years from Earth. That first observation was far more detailed than anything seen by previous X-ray telescopes, even revealing – for the first time ever – a neutron star left in the wake of the colossal stellar detonation.
Those revelations came as no surprise to Chandra project scientist Martin Weisskopf, who led Chandra’s development at NASA’s Marshall Space Flight Center in Huntsville, Alabama. “When you build instrumentation that’s 10 times more sensitive than anything that was done before, you’re bound to discover something new and exciting,” he said. “Every step forward was a giant step forward.”
Twenty-five years later, Chandra has repeated that seminal moment of discovery again and again, delivering – to date – nearly 25,000 detailed observations of neutron stars, quasars, supernova remnants, black holes, galaxy clusters, and other highly energetic objects and events, some as far away as 13 billion light-years from Earth.
Chandra has further helped scientists gain tangible evidence of dark matter and dark energy, documented the first electromagnetic events tied to gravitational waves in space, and most recently aided the search for habitable exoplanets – all vital tools for understanding the vast, interrelated mechanisms of the universe we live in.
NASA’s Chandra X-ray Observatory has observed Cassiopeia A for more than 2 million total seconds since its “first light ” images of the supernova remnant on Aug. 26, 1999. Cas A is some 11,000 light-years from Earth. Chandra X-rays are depicted in blue and composited with infrared images from NASA’s James Webb Space Telescope in orange and white.Credits: X-ray: NASA/CXC/SAO; Infrared: NASA/ESA/CSA/STScI/D. Milisavljevic (Purdue Univ.), I. De Looze (University of Ghent), T. Temim (Princeton Univ.); Image Processing: NASA/CXC/SAO/J. Schmidt, K. Arcand, and J. Major “Chandra’s first image of Cas A provided stunning demonstration of Chandra’s exquisite X-ray mirrors, but it simultaneously revealed things we had not known about young supernova remnants,” said Pat Slane, director of the CXC (Chandra X-ray Center) housed at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts. “In a blink, Chandra not only revealed the neutron star in Cas A; it also taught us that young neutron stars can be significantly more modest in their output than what previously had been understood. Throughout its 25 years in space, Chandra has deepened our understanding of fundamental astrophysics, while also greatly broadening our view of the universe.”
To mark Chandra’s silver anniversary, NASA and CXC have shared 25 of its most breathtaking images and debuted a new video, “Eye on the Cosmos.”
Chandra often is used in conjunction with other space telescopes that observe the cosmos in different parts of the electromagnetic spectrum, and with other high-energy missions such as ESA’s (European Space Agency’s) XMM-Newton; NASA’s Swift, NuSTAR (Nuclear Spectroscopic Telescope Array), and IXPE (Imaging X-ray Polarization Explorer) imagers, and NASA’s NICER (Neutron Star Interior Composition Explorer) X-ray observatory, which studies high-energy phenomena from its vantage point aboard the International Space Station.
Chandra remains a unique, global science resource, with a robust data archive that will continue to serve the science community for many years.
“NASA’s project science team has always strived to conduct Chandra science as equitably as possible by having the world science community collectively decide how best to use the observatory’s many tremendous capabilities,” said Douglas Swartz, a USRA (Universities Space Research Association) principal research scientist on the Chandra project science team.
These images were released to commemorate the 25th anniversary of Chandra. They represent the wide range of objects that the telescope has observed over its quarter century of observations. X-rays are an especially penetrating type of light that reveals extremely hot objects and very energetic physical processes. The images range from supernova remnants, like Cassiopeia A, to star-formation regions like the Orion Nebula, to the region at the center of the Milky Way. This montage also contains objects beyond our own Galaxy including other galaxies and galaxy clusters.X-ray: NASA/CXC/UMass/Q.D. Wang; “Chandra will continue to serve the astrophysics community long after its mission ends,” said Andrew Schnell, acting Chandra program manager at Marshall. “Perhaps its greatest discovery hasn’t been discovered yet. It’s just sitting there in our data archive, waiting for someone to ask the right question and use the data to answer it. It could be somebody who hasn’t even been born yet.”
That archive is impressive indeed. To date, Chandra has delivered more than 70 trillion bytes of raw data. More than 5,000 unique principal investigators and some 3,500 undergraduate and graduate students around the world have conducted research based on Chandra’s observations. Its findings have helped earn more than 700 PhDs and resulted in more than 11,000 published papers, with half a million total citations.
Weisskopf is now an emeritus researcher who still keeps office hours every weekday despite having retired from NASA in 2022. He said the work remains as stimulating now as it was 25 years ago, waiting breathlessly for those “first light” images.
NASA’s Chandra X-ray Observatory data, seen here in violet and white, is joined with that of NASA’s Hubble Space Telescope (red, green, and blue) and Imaging X-ray Polarimetry Explorer (purple) to show off the eerie beauty of the Crab Nebula. The nebula is the result of a bright supernova explosion first witnessed and documented in 1054 A.D.X-ray: (Chandra) NASA/CXC/SAO, (IXPE) NASA/MSFC; Optical: NASA/ESA/STScI; Image Processing: NASA/CXC/SAO/J. Schmidt, K. Arcand, and L. Frattare “We’re always trying to put ourselves out of business with the next bit of scientific understanding,” he said. “But these amazing discoveries have demonstrated how much NASA’s astrophysics missions still have to teach us.”
The universe keeps turning – and Chandra’s watchful eye endures.
More about Chandra
Chandra, managed for NASA by Marshall in partnership with the CXC, is one of NASA’s Great Observatories, along with the Hubble Space Telescope and the now-retired Spitzer Space Telescope and Compton Gamma Ray Observatory. It was first proposed to NASA in 1976 by Riccardo Giacconi, recipient of the 2002 Nobel Prize for Physics based on his contributions to X-ray astronomy, and Harvey Tananbaum, who would later become the first director of the Chandra X-ray Center. Chandra was named in honor of the late Nobel laureate Subrahmanyan Chandrasekhar, who earned the Nobel Prize in Physics in 1983 for his work explaining the structure and evolution of stars.
Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://cxc.harvard.edu
News Media Contact
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov
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Last Updated Aug 26, 2024 Related Terms
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By European Space Agency
Video: 00:09:15 ESA’s Jupiter Icy Moons Explorer (Juice) returns to Earth on 19–20 August 2024, to complete the world's first Lunar-Earth gravity assist. Flight controllers will guide the spacecraft past the Moon and then Earth itself, ‘braking’ the spacecraft. This manoeuvre may seem counterintuitive but will allow Juice to take a shortcut via Venus on it's way to Jupiter.
Juice has already travelled more than 1000 million km to the giant planet but it still has a long way to go even though Jupiter is on average ‘just’ 800 million km away from Earth. Join us as we explain why Juice's journey to Jupiter is taking sooo long.
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By NASA
On July 23, 1999, space shuttle Columbia took to the skies on its 26th trip into space, to deliver its heaviest payload ever – the Chandra X-ray Observatory. The STS-93 crew included Commander Eileen M. Collins, the first woman to command a space shuttle mission, Pilot Jeffrey S. Ashby, and Mission Specialists Catherine “Cady” G. Coleman, Steven A. Hawley, and Michel A. Tognini of the French Space Agency (CNES). On the mission’s first day, they deployed Chandra, the most powerful X-ray telescope. With a planned five-year lifetime, Chandra continues its observations after a quarter century. For the next four days, the astronauts worked on twenty secondary middeck payloads and conducted Earth observations. The successful five-day mission ended with a night landing.
Left: The STS-93 crew patch. Middle: Official photo of the STS-93 crew of Eileen M. Collins, left, Steven A. Hawley, Jeffrey S. Ashby, Michel A. Tognini of France, and Catherine “Cady” G. Coleman. Right: The patch for the Chandra X-ray Observatory.
Tognini, selected by CNES in 1985 and a member of NASA’s class of 1995, received the first assignment to STS-93 in November 1997. He previously flew aboard Mir as a cosmonaut researcher, spending 14 days aboard the station in 1992. On March 5, 1998, First Lady Hilary R. Clinton announced Collins’ assignment as the first woman space shuttle commander in a ceremony at the White House together with President William J. “Bill” Clinton. NASA announced the rest of the crew the same day. For Collins, selected in the class of 1990, STS-93 represented her third space mission, having previously served as pilot on STS-63 and STS-84. Ashby, a member of the class of 1994, made his first flight aboard STS-93, while Coleman, selected in 1992, made her second flight, having flown before on STS-73. Hawley made his fifth flight, having previously served as a mission specialist on STS-41D, STS-61C, STS-31, and STS-82. He has the distinction of making the last flight by any member of his class of 1978, more than 21 years after his selection.
Left: Schematic of the Chandra X-ray Observatory showing its major components. Right: Diagram of the trajectory Chandra took to achieve its final operational 64-hour orbit around the Earth – IUS refers to the two burns of the Inertial Upper Stage and IPS to the five burns of Chandra’s Integral Propulsion System.
Because the Earth’s atmosphere absorbs X-ray radiation emitted by cosmic sources, scientists first came up with the idea of a space-based X-ray telescope in the 1970s. NASA launched its first X-ray telescope called Einstein in 1978, but scientists needed a more powerful instrument, and they proposed the Advanced X-ray Astrophysics Facility (AXAF). After a major redesign of the telescope in 1992, in 1998 NASA renamed AXAF the Chandra X-ray Observatory after Indian American Nobel Prize-winning theoretical physicist Subrahmanyan Chandrasekhar who made significant contributions to our knowledge about stars, stellar evolution, and black holes. Chandra, the third of NASA’s four Great Observatories, can detect X-ray sources 100 times fainter than any previous X-ray telescope. At 50,162 pounds including the Inertial Upper Stage (IUS) it used to achieve its operational orbit, Chandra remains the heaviest payload ever launched by the space shuttle, and at 57 feet long, it took up nearly the entire length of the payload bay. It has far exceeded its expected five-year lifetime, still returning valuable science after 25 years.
Left: The STS-93 crew during the Terminal Countdown Demonstration Test. Middle: The Chandra X-ray Observatory loaded into Columbia’s payload bay. Right: Liftoff of Columbia on the STS-93 mission carrying the Chandra X-ray Observatory and the first woman shuttle commander.
Columbia returned to KSC following its previous flight, the STS-90 Neurolab mission, in May 1998. Workers in KSC’s Orbiter Processing Facility (OPF) serviced the orbiter and removed the previous payload. With all four orbiters at KSC at the same time, workers temporarily stowed Columbia in the Vehicle Assembly Building (VAB), returning it to the OPF for final preflight processing on April 15, 1999. Rollover of Columbia from the OPF to the VAB took place on June 2, where workers mated it with an external tank and two solid rocket boosters. Following integrated testing, the stack rolled out to Launch Pad 39B on June 7. The crew participated in the Terminal Countdown Demonstration Test on June 24. Workers placed Chandra in Columbia’s payload bay three days later.
On July 23, 1994, Columbia thundered into the night sky from KSC’s Launch Pad 39B to begin the STS-93 mission. Two previous launch attempts on July 20 and 22 resulted in scrubs due to a faulty sensor and bad weather, respectively. As Columbia rose into the sky, for the first time in shuttle history a woman sat in the commander’s seat. Far below, problems arose that could have led to a catastrophic abort scenario. During the engine ignition sequence, a gold pin in Columbia’s right engine came loose, ejected with great force by the rapid flow of hot gases, and struck the engine’s nozzle, punching holes in three of its hydrogen cooling tubes. Although small, the hydrogen leak caused the engine’s controller to increase the flow of oxidizer, making the engine run hotter than normal. Meanwhile, a short-circuit knocked out the center engine’s digital control unit (DCU) and the right engine’s backup DCU. Both engines continued powered flight without a redundant DCU, with a failure in either causing a catastrophic abort. Although this did not occur, the higher than expected oxidizer usage led to main engine cutoff occurring 1.5 seconds early, leaving Columbia in a lower than planned orbit. The shuttle’s Orbiter Maneuvering System engines made up for the deficit. The harrowing events of the powered flight prompted Ascent Flight Director John P. Shannon to comment, “Yikes! We don’t need any more of these.”
Left: Eileen M. Collins, the first woman shuttle commander, shortly after reaching orbit. Right: First time space flyer STS-93 Pilot Jeffrey S. Ashby, shortly after reaching space.
After reaching orbit, the crew opened the payload bay doors and deployed the shuttle’s radiators, and removed their bulky launch and entry suits, stowing them for the remainder of the flight. The astronauts prepared for the mission’s primary objective, deployment of Chandra, and also began activating some of the middeck experiments.
Left: The Chandra X-ray Observatory in Columbia’s payload bay shortly after reaching orbit. Middle: Chandra raised to the deployment angle. Right: Chandra departs Columbia.
Coleman had prime responsibility for deploying Chandra. After initial checkout of the telescope by ground teams, the astronauts tilted Chandra and the IUS to an angle of 29 degrees. After additional checks, they tilted it up to the release angle of 58 degrees. A little over seven hours after launch, Coleman deployed the Chandra/IUS stack. Collins and Ashby flew Columbia to a safe distance, and about an hour after deployment, the IUS fired its first stage engine for about two minutes, followed by a two-minute burn of the second stage. This placed Chandra in a temporary elliptical Earth orbit with a high point of 37,200 miles. After separation of the IUS, Chandra used its own propulsion system over the next 10 days to raise its altitude to 6,214 miles by 86,992 miles, its operational orbit, circling the Earth every 64 hours. For the next four days of the mission, the astronauts operated about 20 middeck experiments, including a technology demonstration of a treadmill vibration isolation system planned for the International Space Station.
Left: Michel A. Tognini works with the Commercial Generic Bioprocessing Apparatus. Middle: Jeffrey S. Ashby checks the status of the Space Tissue Lab experiment. Right: Catherine G. Coleman harvests plants from the Plant Growth in Microgravity experiment.
Left: Catherine G. Coleman, left, and Michel A. Tognini pose near the Lightweight Flexible Solar Array Hinge technology demonstration experiment. Middle: Stephen A. Hawley checks the status of the Micro Electromechanical Systems experiment. Right: Tognini places samples of the Biological Research in Canisters experiment into a gaseous nitrogen freezer.
Left: Eileen M. Collins runs on the Treadmill Vibration Isolation System. Middle: Stephen A. Hawley, left, and Michel A. Tognini operate the Southwest Ultraviolet Imaging System instrument. Right: Inflight photograph of the STS-93 crew.
A selection of the STS-93 crew Earth observation photographs. Left: Laguna Verde in Chile. Middle left: Sunrise over the Mozambique Channel. Middle right: Darling River and lakes in Australia. Right: The Society Islands of Bora Bora, Tahaa, and Raiatea.
Left: Eileen M. Collins prepares to bring Columbia home. Middle: Columbia streaks through the skies over NASA’s Johnson Space Center in Houston during reentry. Right: Collins guides Columbia to a smooth touchdown on the Shuttle Landing Facility at NASA’s Kennedy Space Center in Florida.
Left: Three holes visible in the hydrogen cooling tubes of Columbia’s right main engine, seen after landing. Middle: The STS-93 crew pose in front of Columbia on the Shuttle Landing Facility at NASA’s Kennedy Space Center in Florida. Right: Eileen M. Collins addresses the crowd at Houston’s Ellington Field during the welcome home ceremony for the STS-93 crew, as Vice President Albert “Al” A. Gore and other dignitaries listen.
At the end of five days, the astronauts finished the last of the experiments and prepared for the return to Earth. On July 28, they closed Columbia’s payload bay doors, donned their launch and entry suits, and strapped themselves into their seats for entry and landing. Collins piloted Columbia to a smooth landing on KSC’s Shuttle Landing Facility, completing the 12th night landing of the shuttle program. The crew had flown 80 orbits around the Earth in 4 days, 22 hours, and 50 minutes. Columbia wouldn’t fly again until March 2002, the STS-109 Hubble Servicing Mission-3B. A postflight investigation into the cause of the short on ascent that led to two DCUs failing revealed a wire with frayed insulation, likely caused by workers inadvertently stepping on it, that rubbed against a burred screw head that had likely been there since Columbia’s manufacture. The incident resulted in significant changes to ground processes during shuttle inspections and repairs. With regard to the pin ejected during engine ignition that damaged the hydrogen cooling tubes, investigators found that those pins never passed any acceptance testing. Since STS-93 marked the last flight of that generation of main engines, newer engines incorporated a different configuration, requiring no design or other changes.
Enjoy the crew narrate a video about the STS-93 mission. Read Hawley’s recollections of the STS-93 mission in his oral history with the JSC History Office.
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By NASA
5 Min Read 25 Years On, Chandra Highlights Legacy of NASA Engineering Ingenuity
By Rick Smith
“The art of aerospace engineering is a matter of seeing around corners,” said NASA thermal analyst Jodi Turk. In the case of NASA’s Chandra X-ray Observatory, marking its 25th anniversary in space this year, some of those corners proved to be as far as 80,000 miles away and a quarter-century in the future.
Turk is part of a dedicated team of engineers, designers, test technicians, and analysts at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Together with partners outside and across the agency, including the Chandra Operations Control Center in Burlington, Massachusetts, they keep the spacecraft flying, enabling Chandra’s ongoing studies of black holes, supernovae, dark matter, and more – and deepening our understanding of the origin and evolution of the cosmos.
Engineers in the X-ray Calibration Facility – now the world-class X-ray & Cryogenic Facility – at NASA’s Marshall Space Flight Center in Huntsville, Alabama, integrate the Chandra X-ray Observatory’s High Resolution Camera with the mirror assembly inside a 24-foot-diameter vacuum chamber, in this photo taken March 16, 1997. Chandra was launched July 23, 1999, aboard space shuttle Columbia.NASA “Everything Chandra has shown us over the last 25 years – the formation of galaxies and super star clusters, the behavior and evolution of supermassive black holes, proof of dark matter and gravitational wave events, the viability of habitable exoplanets – has been fascinating,” said retired NASA astrophysicist Martin Weisskopf, who led Chandra scientific development at Marshall beginning in the late 1970s. “Chandra has opened new windows in astrophysics that we’d hardly begun to imagine in the years prior to launch.”
Following extensive development and testing by a contract team managed and led by Marshall, Chandra was lifted to space aboard the space shuttle Columbia on July 23, 1999. Marshall has continued to manage the program for NASA ever since.
“How much technology from 1999 is still in use today?” said Chandra researcher Douglas Swartz. “We don’t use the same camera equipment, computers, or phones from that era. But one technological success – Chandra – is still going strong, and still so powerful that it can read a stop sign from 12 miles away.”
That lasting value is no accident. During early concept development, Chandra – known prior to launch as the Advanced X-ray Astrophysics Facility – was intended to be a 15-year, serviceable mission like that of NASA’s Hubble Space Telescope, enabling periodic upgrades by visiting astronauts.
But in the early 1990s, as NASA laid plans to build the International Space Station in orbit, the new X-ray observatory’s budget was revised. A new, elliptical orbit would carry Chandra a third of the way to the Moon, or roughly 80,000 miles from Earth at apogee. That meant a shorter mission life – five years – and no periodic servicing.
The Chandra X-Ray Observatory, the longest cargo ever carried to space aboard the space shuttle, seen in Columbia’s payload bay prior to being tilted upward for release and deployment on July 23, 1999.NASA The engineering design team at Marshall, its contractors, and the mission support team at the Smithsonian Astrophysical Observatory revised their plan, minimizing the impact to Chandra’s science. In doing so, they enabled a long-running science mission so successful that it would capture the imagination of the nation and lead NASA to extend its duration past that initial five-year period.
“There was a lot of excitement and a lot of challenges – but we met them and conquered them,” said Marshall project engineer David Hood, who joined the Chandra development effort in 1988.
“The field of high-powered X-ray astronomy was still so relatively young, it wasn’t just a matter of building a revolutionary observatory,” Weisskopf said. “First, we had to build the tools necessary to test, analyze, and refine the hardware.”
Marshall renovated and expanded its X-ray Calibration Facility – now known as the X-ray & Cryogenic Facility – to calibrate Chandra’s instruments and conduct space-like environment testing of sensitive hardware. That work would, years later, pave the way for Marshall testing of advanced mirror optics for NASA’s James Webb Space Telescope.
On July 23, 1999, the Chandra X-Ray Observatory is released from space shuttle Columbia’s payload bay. Twenty-five years later, Chandra continues to make valuable discoveries about high-energy sources and phenomena across the universe.NASA “Marshall has a proven history of designing for long-term excellence and extending our lifespan margins,” Turk said. “Our missions often tend to last well past their end date.”
Chandra is a case in point. The team has automated some of Chandra’s operations for efficiency. They also closely monitor key elements of the spacecraft, such as its thermal protection system, which have degraded as anticipated over time, due to the punishing effects of the space environment.
“Chandra’s still a workhorse, but one that needs gentler handling,” Turk said. The team met that challenge by meticulously modeling and tracking Chandra’s position and behavior in orbit and paying close attention to radiation, changes in momentum, and other obstacles. They have also employed creative approaches, making use of data from sensors on the spacecraft in new ways.
Acting project manager Andrew Schnell, who leads the Chandra team at Marshall, said the mission’s length means the spacecraft is now overseen by numerous “third-generation engineers” such as Turk. He said they’re just as dedicated and driven as their senior counterparts, who helped deliver Chandra to launch 25 years ago.
An artist’s illustration depicting NASA’s Chandra X-ray Observatory in flight, with a vivid star field behind it. Chandra’s solar panels are deployed and its camera “eye” open on the cosmos.NASA The work also provides a one-of-a-kind teaching opportunity, Turk said. “Troubleshooting Chandra has taught us how to find alternate solutions for everything from an interrupted sensor reading to aging thermocouples, helping us more accurately diagnose issues with other flight hardware and informing design and planning for future missions,” she said.
Well-informed, practically trained engineers and scientists are foundational to productive teams, Hood said – a fact so crucial to Chandra’s success that its project leads and support engineers documented the experience in a paper titled, “Lessons We Learned Designing and Building the Chandra Telescope.”
“Former program manager Fred Wojtalik said it best: ‘Teams win,’” Hood said. “The most important person on any team is the person doing their work to the best of their ability, with enthusiasm and pride. That’s why I’m confident Chandra’s still got some good years ahead of her. Because that foundation has never changed.”
As Chandra turns the corner on its silver anniversary, the team on the ground is ready for whatever fresh challenge comes next.
Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://cxc.harvard.edu
Media Contact:
Jonathan Deal / Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
jonathan.e.deal@nasa.gov / lane.e.figueroa@nasa.gov
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