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30 Years Ago: STS-61, the First Hubble Servicing Mission


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“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 discovery after its launch that the Hubble Space Telescope’s primary mirror suffered from a flaw 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. The agency assigned one of its most experienced crews to undertake the complex tasks, naming Richard O. Covey, Kenneth D. Bowersox, Kathryn C. Thornton, Claude Nicollier of the European Space Agency, Jeffrey A. Hoffman, F. Story Musgrave, and Thomas D. Akers to the STS-61 first Hubble Servicing Mission. The first all veteran crew since the STS-26 return to flight mission in 1988 had a cumulative 16 previous missions among them and all had previous spacewalking experience. During their 11-day flight in December 1993, they repaired the telescope during an unprecedented five spacewalks in a single space shuttle mission, rendering it more capable than originally designed.

The STS-61 crew of Kenneth D. Bowersox, sitting left, Kathryn C. Thornton, F. Story Musgrave, and Claude Nicollier of the European Space Agency; Richard O. Covey, standing left, Jeffrey A. Hoffman, and Thomas D. Akers The STS-61 crew patch Endeavour rolls over from Launch Pad 39A to 39B at NASA’s Kennedy Space Center in Florida
Left: The STS-61 crew of Kenneth D. Bowersox, sitting left, Kathryn C. Thornton, F. Story Musgrave, and Claude Nicollier of the European Space Agency; Richard O. Covey, standing left, Jeffrey A. Hoffman, and Thomas D. Akers. Middle: The STS-61 crew patch. Right: Endeavour rolls over from Launch Pad 39A to 39B at NASA’s Kennedy Space Center in Florida.

The first Hubble servicing mission proved to be one of the most complex up to that time. With that in mind, on March 16, 1992, NASA named Musgrave, an astronaut since 1967 and a veteran of four previous missions including conducting the first spacewalk of the shuttle era, as the payload commander and one of the four spacewalkers for STS-61. On Aug. 28, NASA named Hoffman, Akers, and Thornton as the other three spacewalkers who in teams of two would carry out the five spacewalks on alternating days. Finally, on Dec. 3, NASA named Covey, Bowersox, and Nicollier as the commander, pilot, and flight engineer, respectively, for the mission. Nicollier also served as the prime operator of the Remote Manipulator System (RMS), or robotic arm, with Bowersox as his backup. The seven-person crew trained intensely for the next year preparing for the complex tasks ahead, including simulating the spacewalks at the Neutral Buoyancy Simulator at NASA’s Marshall Space Flight Center in Huntsville, Alabama, and the Weightless Environment Training Facility at NASA’s Johnson Space Center in Houston. Meanwhile, at NASA’s Kennedy Space Center in Florida, workers prepared space shuttle Endeavour for its fifth journey into space. They rolled the shuttle, assembled with its external tank and solid rocket booster, to Launch Pad 39A on Oct. 28. However, following a wind storm on Oct. 30 that contaminated the payload changeout room with sandy grit, managers decided to move Endeavour to neighboring Pad B on Nov. 15, in only the second roll around in shuttle history.

Schematic of 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
Left: Schematic of the Hubble Space Telescope’s major components. Middle: Workers inspect the Hubble Space Telescope’s 94-inch diameter primary mirror prior to assembly. Right: Astronauts release the Hubble Space Telescope in April 1990 during the STS-31 mission.

The first concrete plan for placing an optical telescope in space, above the obscuring and distorting effects of the Earth’s atmosphere, originated with Princeton University astronomer Lyman S. Spitzer in 1946. In 1972, NASA first proposed a plan to launch a Large Space Telescope (LST) and five years later Congress approved the funding. As envisioned, the LST would contain a 94-inch diameter primary mirror and launch on the space shuttle, then still under development, in 1983. With an expected on-orbit lifetime of 15 years, the LST’s instruments would make observations primarily in the visible and ultraviolet parts of the electromagnetic spectrum. In 1983, managers abandoned the original plan to use the space shuttle to return the telescope to Earth for refurbishment and relaunch in favor of in-orbit maintenance and upgrades by astronauts during spacewalks in the shuttle’s payload bay. The same year, NASA renamed the LST after astronomer Edwin P. Hubble and set the launch for October 1986. The Challenger accident in January 1986 delayed the launch of the Hubble Space Telescope until April 24, 1990, during Discovery’s STS-31 mission. The shuttle flew to an unusually high 380-mile orbit to ensure that Hubble would operate above as much of the Earth’s atmosphere as possible. After initial on-orbit activation and checkout of the telescope’s systems, it was time for the much-anticipated “first light” images. The initial images, however, puzzled scientists as they showed stars not as single well-focused points of light but as blurred and fuzzy. Investigators learned that the telescope’s primary mirror suffered from a production error, its edges too flat by 0.003 mm, resulting in an optical problem called spherical aberration. While this significantly degraded the capability of several of Hubble’s instruments to return exceptionally detailed photographs, the telescope still produced some good images. NASA put in place a plan to fix the Hubble’s optical problems without resorting to repairing the mirror. With the spherical aberration well-defined, engineers designed a set of mirrors that astronauts could place aboard Hubble during the previously planned first servicing mission.

Liftoff of space shuttle Endeavour on the STS-61 mission to repair the Hubble Space Telescope The Hubble Space Telescope as seen from Endeavour during the rendezvous, with the end of the Remote Manipulator System (RMS), or robotic arm, visible at lower right On the shuttle’s flight deck, European Space Agency astronaut Claude Nicollier operates the RMS to grapple Hubble
Left: Liftoff of space shuttle Endeavour on the STS-61 mission to repair the Hubble Space Telescope. Middle: The Hubble Space Telescope as seen from Endeavour during the rendezvous, with the end of the Remote Manipulator System (RMS), or robotic arm, visible at lower right. Right: On the shuttle’s flight deck, European Space Agency astronaut Claude Nicollier operates the RMS to grapple Hubble.

Planning for the first servicing mission to Hubble began in 1988, two years before the launch of the telescope. With the post-launch discovery of spherical aberration, the scope of the first servicing mission changed dramatically. The primary goal now focused on correcting the telescope’s optics to ensure that its onboard instruments could function as planned. Engineers developed the Corrective Optics Space telescope Axial Replacement (COSTAR), a tool to correct Hubble’s blurry vision, consisting of five pairs of corrective mirrors placed in front of the Faint Object Camera, the Faint Object Spectrograph, and the Goddard High Resolution Spectrograph (GHRS) instruments. Installing COSTAR required the removal of the High-Speed Photometer, the sacrifice of one instrument outweighed by the saving of the other three. The astronauts also replaced the original Wide Field Planetary Camera (WFPC) with the more advanced WFPC2 to improve the telescope’s ultraviolet performance. The WFPC2 carried its own corrective optics. The astronauts also replaced fuses and the telescope’s two solar arrays, one of which imparted vibrations that prevented precise pointing. On Dec. 2, 1993, space shuttle Endeavour lifted off from Pad 39B at 4:27 a.m. EST, after a one-day weather delay. Following insertion into an unusually high 360-mile orbit to reach Hubble, the astronauts began their initial on-orbit operations by opening the payload bay doors. The next day, Covey and Bowersox performed several engine burns as part of the rendezvous maneuvers. The astronauts checked out the rendezvous radar, the Ku-band antenna, the Canadian-built Remote Manipulator System (RMS) or robotic arm, and the spacesuits, and reduced the pressure inside the shuttle from 14.7 pounds per square inch (psi) to 10.2 psi in preparation for the upcoming spacewalks to reduce the pre-breathe time required to prevent decompression sickness or the bends.

Endeavour approach to the Hubble Space Telescope Hubble secured onto its flight support structure in Endeavour’s payload bay The STS-61 crew poses on Endeavour’s flight deck, with Hubble visible through the windows
Left: Endeavour continues its approach to the Hubble Space Telescope. Middle: Hubble secured onto its flight support structure in Endeavour’s payload bay. Right: The STS-61 crew poses on Endeavour’s flight deck, with Hubble visible through the windows.

On the third day, Covey brought Endeavour to within 30 feet of Hubble so Nicollier could grapple it with the RMS. Covey radioed Houston, “Endeavour has a firm handshake with Mr. Hubble’s telescope.” Nicollier berthed the giant telescope onto its turntable-like Flight Support System (FSS) in the shuttle’s payload bay. Nicollier then used the RMS cameras to perform an inspection of Hubble.

European Space Agency astronaut Claude Nicollier operates the shuttle’s Remote Manipulator System (RMS) or robotic arm in support of the spacewalks Astronaut F. Story Musgrave works on the Hubble Musgrave releases bolts on the replacement solar arrays
First spacewalk. Left: European Space Agency astronaut Claude Nicollier operates the shuttle’s Remote Manipulator System (RMS) or robotic arm in support of the spacewalks. Middle: Astronaut F. Story Musgrave works on the Hubble. Right: Near the end of the first spacewalk, Musgrave releases bolts on the replacement solar arrays.

With Nicollier operating the RMS as he did for all five spacewalks, Hoffman and Musgrave conducted the mission’s first excursion on flight day four. They replaced two sets of Rate Sensing Units that contain gyroscopes to orient the telescope and replaced electrical control units and fuse plugs, providing the telescope with six healthy gyroscopes. Musgrave and Hoffman prepared for the next day’s spacewalk by loosening bolts on the replacement solar arrays, stored in the forward part of the payload bay. The pair spent 7 hours and 54 minutes outside on this first spacewalk. The ground commanded the two existing solar arrays on the telescope to retract, and while one did so the second one did not due to a bent support rod.

Astronaut Kathryn C. Thornton, on the end of the Remote Manipulator System, releases Hubble’s old solar array that failed to retract properly The solar array drifting away from space shuttle Endeavour Thornton disconnects Hubble’s retracted solar array
Second spacewalk. Left: Astronaut Kathryn C. Thornton, on the end of the Remote Manipulator System, releases Hubble’s old solar array that failed to retract properly. Middle: The solar array drifting away from space shuttle Endeavour. Right: Thornton disconnects Hubble’s retracted solar array.

On flight day five, Thornton and Akers stepped outside for the mission’s second spacewalk, lasting 6 hours 36 minutes. The primary tasks revolved around replacing the telescope’s two solar arrays. First, they disconnected the array that would not retract as planned, working only at night since the array generated electricity when exposed to sunlight. With Thornton on the end of the RMS, she released the partially open array as Nicollier pulled her away. Bowersox fired thrusters to separate from the array, the plumes impinging on it causing it to flap like a giant bird. Thornton and Akers then connected one of the new arrays, rotated the telescope on its FSS, disconnected the other array, stowing it in the payload bay for return to Earth, and replaced it with a new one.

Astronauts Jeffrey A. Hoffman, left, and F. Story Musgrave have removed the old Wide Field Planetary Camera (WFPC) from Hubble, the black rectangle at upper left shows its former location With European Space Agency astronaut Claude Nicollier operating the Remote Manipulator System from inside the shuttle, Hoffman guides the new WFPC2 into position, with Musgrave ready to assist Musgrave, left, and Hoffman have installed WFPC2, the white triangle in the middle of the telescope, with Hoffman about to pick up WFPC1 temporarily stowed on the side of the payload bay and place it in its permanent location for return to Earth
Third spacewalk. Left: Astronauts Jeffrey A. Hoffman, left, and F. Story Musgrave have removed the old Wide Field Planetary Camera (WFPC) from Hubble, the black rectangle at upper left shows its former location. Middle: With European Space Agency astronaut Claude Nicollier operating the Remote Manipulator System from inside the shuttle, Hoffman guides the new WFPC2 into position, with Musgrave ready to assist. Right: Musgrave, left, and Hoffman have installed WFPC2, the white triangle in the middle of the telescope, with Hoffman about to pick up WFPC1 temporarily stowed on the side of the payload bay and place it in its permanent location for return to Earth.

On the sixth day, Hoffman and Musgrave took their turn outside for the mission’s third spacewalk. Their primary task involved the replacement of the original WFPC with the more advance WFPC2 instrument. With Nicollier controlling the RMS, Hoffman removed the WFPC1 from the telescope and temporarily stowed it on the side of the payload bay. He then removed WFPC2 from its stowage location and he and Musgrave installed it into the telescope. After stowing WFPC1 in the payload bay for return to Earth, Hoffman replaced two magnetometers, essentially compasses the telescope uses to determine its orientation in space. This third spacewalk lasted 6 hours 47 minutes.

Astronaut Kathryn C. Thornton works in shuttle Endeavour’s payload bay European Space Agency astronaut Claude Nicollier controlling the Remote Manipulator System, Thornton, top, removes the Corrective Optics Space telescope Axial Replacement (COSTAR) from its storage location Astronaut Thomas D. Akers, inside the Hubble Space Telescope prepares to install the COSTAR
Fourth spacewalk. Left: Astronaut Kathryn C. Thornton works in shuttle Endeavour’s payload bay. Middle: With European Space Agency astronaut Claude Nicollier controlling the Remote Manipulator System, Thornton, top, removes the Corrective Optics Space telescope Axial Replacement (COSTAR) from its storage location. Right: Astronaut Thomas D. Akers, inside the Hubble Space Telescope prepares to install the COSTAR.

For Akers and Thornton, the primary tasks of the fourth spacewalk on the mission’s seventh day focused on the removal of the HSP instrument and replacing it with the COSTAR system to correct the telescope’s optics. Akers opened the telescope’s shroud doors and with Thornton removed the HSP, temporarily stowing it on the side of the payload bay. Nicollier then maneuvered the RMS with Thornton to pick up COSTAR from its storage location and translate them to Hubble where Akers awaited to help with the installation. After closing the door and stowing the HSP, and installing an electronics package with additional computer memory, Akers and Thornton finished the 6-hour 50-minut spacewalk.

Remote Manipulator System operator European Space Agency astronaut Claude Nicollier translates Jeffrey A. Hoffman and F. Story Musgrave to the top of the Hubble Space Telescope The second of two solar arrays unfurls as Hoffman and Musgrave continue working Hoffman celebrates the first Hannukah in space, with a spinning dreidel floating nearby
Fifth spacewalk. Left: Remote Manipulator System operator European Space Agency astronaut Claude Nicollier translates Jeffrey A. Hoffman and F. Story Musgrave to the top of the Hubble Space Telescope. Middle: The second of two solar arrays unfurls as Hoffman and Musgrave continue working. Right: Hoffman celebrates the first Hannukah in space, with a spinning dreidel floating nearby.

On the morning of the eighth day, Bowersox used Endeavour’s thrusters to slightly raise and circularize Hubble’s orbit. Hoffman and Musgrave stepped outside for the mission’s fifth and final spacewalk. When the two newly installed solar arrays failed to deploy after ground commanding, they manually deployed them, and the arrays unfurled without incident. They next replaced the solar array drive electronics and fitted an electronic connection box on the GHRS instrument. Hoffman and Musgrave’s final task involved installing covers, manufactured by Bowersox and Nicollier on board the shuttle, on the telescope’s magnetometers. The final spacewalk lasted 7 hours 21 minutes, bringing the mission’s total spacewalk time to 35 hours 28 minutes. Once back inside Endeavour, Hoffman celebrated the first Hanukkah in space during a televised broadcast, displaying a traveling menorah, unlit of course, and a spinning dreidel.

European Space Agency astronaut Claude Nicollier grapples the Hubble Space Telescope, with its high-gain antenna deployed, just prior to release Hubble slowly drifts away from Endeavour A distant view of Hubble, right, with a crescent Moon
Left: European Space Agency astronaut Claude Nicollier grapples the Hubble Space Telescope, with its high-gain antenna deployed, just prior to release. Middle: After its release, Hubble slowly drifts away from Endeavour. Right: A distant view of Hubble, right, with a crescent Moon.

On flight day nine, Nicollier grappled Hubble with the RMS for the final time and lifted it above the payload bay. Ground controllers commanded its aperture door to open, and Nicollier released the telescope. Bowersox fired Endeavour’s thrusters to slowly back away from the telescope. The next day, the astronauts enjoyed a well-deserved day of rest. They returned the shuttle’s cabin pressure to 14.7 psi and tidied up the spacecraft. On the mission’s 11th day, Covey and Bowersox tested Endeavour’s flight control surfaces and practiced touchdowns using a laptop computer, all in preparation for deorbit, entry, and landing the following day.

Astronaut Richard O. Covey guides Endeavour to a landing at NASA’s Kennedy Space Center (KSC) in Florida Workers at KSC continue to safe Endeavour following its landing Images of M100 galactic nucleus before, left, and after the first servicing mission showing the improved optical qualities
Left: Astronaut Richard O. Covey guides Endeavour to a landing at NASA’s Kennedy Space Center (KSC) in Florida. Middle: Workers at KSC continue to safe Endeavour following its landing. Right: Images of M100 galactic nucleus before, left, and after the first servicing mission showing the improved optical qualities.

On Dec. 13, 1993, their 12th and final day in space, the astronauts donned their pressure suits and prepared for the return to Earth. Due to predicted worsening weather conditions at KSC, Mission Control elected to bring them home one orbit earlier than planned. Covey guided Endeavour to a smooth landing at night at KSC, concluding a flight of 10 days, 19 hours, 59 minutes. They circled the Earth 163 times. Within a month, new images from Hubble indicated the repairs returned the telescope to its expected capabilities, providing astronomers with a unique observation platform. The lessons learned from planning and executing the complex series of spacewalks, with extensive coordination with teams on the ground, proved highly useful not only for future Hubble servicing mission but also for the difficult spacewalks required to assemble and maintain the International Space Station.

Timeline of the Hubble Space Telescope’s instruments and their replacements during servicing missions Hubble as it appeared after its release during the final servicing mission in 2009
Left: Timeline of the Hubble Space Telescope’s instruments and their replacements during servicing missions. Right: Hubble as it appeared after its release during the final servicing mission in 2009.

Although the STS-61 crew’s work left the Hubble Space Telescope in better condition than originally designed, over the years it required additional servicing to ensure it met its expected 15-year on-orbit life. Four additional shuttle crews serviced the telescope between 1997 and 2009, and today it carries a suite of instruments far more advanced than its original complement. During the five servicing missions, 16 space walking astronauts conducted 23 spacewalks totaling more than 165 hours, or just under 7 days, to make repairs or improvements to the telescope’s capabilities. To summarize the discoveries made by scientists using data from the Hubble Space Telescope is well beyond the scope of this article. Suffice it to say that during its more than 30 years of operation, information and images returned by Hubble continue to revolutionize astronomy, literally causing scientists to rewrite textbooks, and have dramatically altered how the public views the wonders of the universe. On the technical side, the launch of Hubble and the servicing missions to maintain and upgrade its capabilities have proven conclusively the value of maintainability of space-based scientific platforms. 

Watch the STS-61 crew narrate a video of their Hubble servicing mission.

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Dec 04, 2023

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      Slayton called Borman, who was with Lovell and Anders conducting tests with their spacecraft in Downey, California. He ordered Borman to immediately fly to Houston, where he offered him command of the new circumlunar Apollo 8 mission, which Borman accepted. His crew would swap missions with McDivitt’s, who agreed to fly an Earth orbital test of the LM in February 1969, putting that crew’s greater experience with the LM to good use. The training challenge fell on Borman’s crew, who now had just four months to train for a flight around the Moon.
      Left: Apollo Program Director Samuel C. Phillips. Middle left: Associate Administrator for Manned Space Flight George E. Mueller. Middle right: Deputy Administrator Thomas O. Paine. Right: Administrator James E. Webb.
      On Aug. 14, representatives from MSC, MSFC, and KSC attended a meeting in Washington with NASA Deputy Administrator Thomas O. Paine and Apollo Program Director Phillips, the senior Headquarters officials present as NASA Administrator James E. Webb and Associate Administrator for Manned Space Flight George E. Mueller attended a conference in Vienna. The group discussed Low’s proposal and agreed on the technical feasibility of accomplishing a circumlunar flight with Apollo 8 in December. During the discussion, Mueller happened to call from Vienna and when they presented him with the proposal, he was at first reticent, especially since NASA had yet to fly Apollo 7. He requested more information and more time to consider the proposal so he could properly brief Webb. Paine then polled each center director for his overall assessment. Von Braun, who designed the Saturn V rocket, stated that whether it went to the Moon or stayed in Earth orbit didn’t matter too much. Debus stated that KSC could support a Saturn V launch in December – as noted above, his team was already processing both the rocket and the spacecraft. Gilruth agreed that the proposal represented a key step in achieving President Kennedy’s goal, and emphasized that the mission should not just loop around the Moon but actually enter orbit. Following additional discussions after Webb’s return from Vienna, he agreed to the plan, but would not make a formal decision until after a successful Apollo 7 flight in October. NASA kept the lunar orbit plan quiet even as the crews began training for their respective new missions. An announcement on Aug. 19 merely stated that Apollo 8 would not carry a LM, as the agency continued to assess various mission objectives. Ultimately, the plan required President Lyndon B. Johnson’s approval.
      Left: Astronaut Neil A. Armstrong ejects just moments before his Lunar Landing Research Vehicle crashed. Middle left: Pilot Gerald P. Gibbons, left, and astronaut James B. Irwin prepare to enter an altitude chamber for one of the Lunar Module Test Article-8 (LTA-8) vacuum tests. Middle right: Astronauts Joe H. Engle, left, Vance D. Brand, and Joseph P. Kerwin preparing for the 2TV-1 altitude test. Right: One of the final Apollo parachute tests.
      As those discussions took place, work around the country continued to prepare for the first lunar landing, not without some setbacks. On May 8, astronaut Neil A. Armstrongejected just in the nick of time as the Lunar Landing Research Vehicle (LLRV) he was piloting went out of control and crashed. Managers suspended flights of the LLRV and its successor, the Lunar Landing Training Vehicle (LLTV), until Oct. 3. Astronauts used the LLRV and LLTV to train for the final few hundred feet of the descent to the Moon’s surface. On May 27, astronaut James B. Irwin and pilot Gerald P. Gibbons began a series of altitude tests in Chamber B of the Space Environment Simulation Laboratory (SESL) at MSC. The tests, using the LM Test Article-8 (LTA-8), evaluated the pressure integrity of the LM as well as the new spacesuits designed for the Apollo program. The first series of LTA-8 tests supported the Earth-orbital flight of LM-3 on Apollo 9 while a second series in October and November supported the LM-5 flight of Apollo 11, the first lunar landing mission. In June, using SESL’s Chamber A, astronauts Joseph P. Kerwin, Vance D. Brand, and Joe H. Engle completed an eight-day thermal vacuum test using the Apollo 2TV-1 spacecraft to certify the vehicle for Apollo 7. A second test in September certified the vehicle for lunar missions. July 3 marked the final qualification drop test of the Apollo parachute system, a series begun five years earlier. The tests qualified the parachutes for Apollo 7.
      History records that Apollo 11 accomplished the first human landing on the Moon in July 1969. It is remarkable to think that just one year earlier, with the agency still recovering from the Apollo 1 fire, NASA had not yet flown any astronauts aboard an Apollo spacecraft. And further, the agency took the bold step to plan for a lunar orbital mission on just the second crewed mission. With a cadence of a crewed Apollo flight every two months between October 1968 and July 1969, NASA accomplished President Kennedy’s goal of landing a man on the Moon and returning him safely to the Earth.
      John Uri
      NASA Johnson Space Center
      View the full article
    • 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 European Space Agency
      An international team of astronomers using the NASA/ESA/CSA James Webb Space Telescope have directly imaged an exoplanet roughly 12 light-years from Earth. While there were hints that the planet existed, it had not been confirmed until Webb imaged it. The planet is one of the coldest exoplanets observed to date.
      View the full article
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