In the summer of 1992, astronaut Jeff Hoffman was in quarantine, preparing to launch aboard Space Shuttle Atlantis with the Tethered Satellite and the EURECA free-flying payload, when he fell into conversation with Don Puddy, head of Flight Crew Operations. Puddy was interested in Hoffman’s plans after the mission. Several astronauts had already been approached about their willingness to be considered for flights to the Mir space station, but Hoffman’s height ruled that out. Only one other mission captured his attention. The first servicing mission to the Hubble Space Telescope stood out like a jewel on the Shuttle manifest in December 1993 and as a professional astronomer, Hoffman – like many of his peers in the Astronaut Office – found that it exerted an irresistible pull.
“What I’d really love,” he told Puddy, “being an astronomer, I’d love to go on this Hubble mission.”
Puddy laughed. “Oh, yeah. You and the rest of the office!”
Hoffman assumed that his chances of selection were minimal, but in addition to his flight experience he had one other credential which made him an attractive choice for the mission: he was one of few astronauts in the office, at that time, with EVA experience. Seven years earlier, in April 1985, Hoffman had participated in the Shuttle programme’s first contingency spacewalk in a fruitless attempt to activate a deployment switch on the malfunctioning Leasat-3 satellite. With several intricate and complex EVAs scheduled for the Hubble mission, NASA mandated that all members of the four-person spacewalking team must have prior EVA expertise. This was not simply a case of NASA being overly cautious. With the loss of Challenger still fresh and the embarrassing failure of Hubble’s ability to resolve distant objects, due to a flaw in its primary optics, the mission to fix the $1.5 billion showpiece telescope was crucial. Congressional support for Space Station Freedom hung on the edge of a knife and any failure on NASA’s part could spell its cancellation.
“Whoever was going to be doing something on the Hubble mission had to have done it before,” recalled Hoffman in his NASA oral history. “You had to have somebody who had already been a commander, somebody who had already been a pilot, four people who had already done EVAs and somebody who had already done a significant arm operation.” In March 1992, Story Musgrave had been assigned as payload commander for the flight, designated STS-61, and in August Hoffman and fellow astronauts Kathy Thornton and Tom Akers joined him to support as many as five ambitious EVAs. Four months later, in December, Dick Covey, Ken Bowersox and Swiss astronaut Claude Nicollier were named, respectively, as commander, pilot and operator of the Shuttle’s 50-foot-long Remote Manipulator System (RMS) mechanical arm, which would pluck Hubble out of orbit, anchor it into the Shuttle’s payload bay for repairs and subsequently deploy it back into space to begin its reinvigorated studies of the Universe.
Having received such a plum assignment, the STS-61 team bore the brunt of much good-natured ribbing from their fellow astronauts. On one occasion, Thornton quipped to her crewmates: “Well, guys, everybody is gonna hate us now!”
Covey’s arrival on the crew was particularly interesting. He had flown the Leasat-3 repair mission in August 1985 and thus was well-versed in the rendezvous, proximity operations and servicing associated with a large payload, but his previous stints as Acting Chief of the Astronaut Office and Acting Director of Flight Crew Operations certainly also played a part in his selection. In the summer of 1992, he was called to a meeting by Aaron Cohen and Paul Weitz, head and deputy head of the Johnson Space Center, and offered two choices: he could either be the ‘real’ Chief of the Astronaut Office or he could command the Hubble flight. By his own admission, it took Covey “about two seconds” to make his choice…
The mission was enormously complex in its scope. Hubble was nothing less than a national treasure; so much so that in the early 1980s NASA Administrator Jim Beggs insisted that the space agency place it on the same level of importance as the Shuttle itself. Its mandate was to open our eyes to the mysteries of the Universe as never before, peering deeper into the cosmos than any other telescope, looking right back to the very dawn of time. Technical difficulties delayed its launch until October 1986 and the loss of Challenger meant that Hubble did not eventually reach orbit until April 1990. Several weeks later, the triumph of finally getting the telescope aloft was shattered when it failed a focusing test. Its images produced peculiar fuzzy blurring, caused by a condition known as ‘spherical aberration’ in the primary mirror.
In essence, the mirror’s manufacturer, Perkin-Elmer, had ground it to the wrong specification, removing too much glass and polishing it too flat…by just 2.2 microns, a mere fiftieth of the width of a human hair! The result was that Hubble was unable to acquire sharp images. Over the following months, NASA was hauled over the coals in both Congress and the media; Newsweek described Hubble as a $1.5 billion “blunder”. Plans accelerated into high gear to develop a mechanism whereby the telescope’s capabilities could be restored to their advertised level of accuracy.
NASA promptly established an investigating committee, chaired by Lew Allen, head of the Jet Propulsion Laboratory. His report, published in November 1990, harshly criticised the assembly of the ‘reflective null corrector’, an optical device used to determine the figure of Hubble’s primary mirror. The location of a lens in this device had been improperly measured and the null corrector guided the polisher to shape a perfectly smooth mirror…albeit with the wrong curvature. During the fabrication of the mirror, engineers simply assumed the perfection of the mirror and the reflective null corrector, rejected other independent tests and convinced themselves that no problems existed.
In orbit, the problem was manifested most visibly in images from Hubble’s Wide Field Planetary Camera (WFPC, nicknamed ‘the whiffpick’) and Faint Object Camera, both of which suffered in terms of spatial resolution and ability to acquire sharp images of distant celestial sources. At the same time, the aberration was well-characterised and stable and over time astronomers were able to optimise Hubble’s images with sophisticated techniques such as ‘deconvolution’, whereby software algorithms and processing methods removed much of the blurring. Spectroscopy was less severely affected, because the instruments needed less focused light, and by increasing exposure times it was possible to gather valuable data. By the end of 1991, the telescope had made almost 2,000 quality observations of hundreds of astronomical targets, including storms on Saturn and images of Pluto’s tiny moon, Charon, and a quarter of all papers presented before the American Astronomical Society drew directly on Hubble data.
It was not enough, however, and the telescope still fell far short of what it should have been able to achieve. The primary mirror could not be changed out in orbit, but what could be done was fit a device known as Corrective Optics Space Telescope Axial Replacement (COSTAR) to restore focusing to Hubble’s Faint Object Camera, Faint Object Spectrograph and Goddard High Resolution Spectrograph. Built by Ball Aerospace, COSTAR’s installation would require the removal of the High Speed Photometer and subsequent instruments for Hubble would be specifically designed with their own corrective optics.
Dr John Wood of NASA’s Goddard Space Flight Center was placed in charge of the COSTAR development process. Its installation and that of a new whiffpick (WFPC-2) would come atop a hefty pile of work for the First Servicing Mission (SM-1), which already involved the replacement of Hubble’s twin solar arrays, Rate Sensing Units, Electronic Control Units and fuse plugs. The mission – already complex – morphed into something which would represent nothing less than an opportunity for NASA to prove itself triumphantly…or fail spectacularly. In its January 1990 manifest, the agency listed SM-1 as a five-day flight in June 1993, with a crew of five, suggesting a maximum of only two or three EVAs, but as 1991 wore into 1992 it became increasingly clear that the mission would run to as long as 11 days and feature a record-breaking five EVAs over five days. (The flight plan actually offered the scope for a sixth and seventh EVA, although these were unneeded.) That demanded a crew of seven, with two alternating teams of spacewalkers, to reduce fatigue and enhance the likelihood of mission success.
“Doing five [EVAs] really pushed the bounds of what people thought we could do,” Covey recalled in his oral history. “Even with four EVA crew members, even with an 11-day mission, it just started pushing the bounds. There was a lot of scrutiny on it and a lot of focus on it.” The size of Endeavour’s quarry posed additional problems. Hubble was far larger than anything with which the Shuttle had previously rendezvoused in orbit and Claude Nicollier was faced with the unenviable challenge of manoeuvring his EVA crewmates, along with phone-booth-sized pieces of hardware, into position with extreme delicacy and precision. “The integrated operations,” said Covey, “of Shuttle manoeuvring, RMS activities and EVAs, although now commonplace, wasn’t back then. So integrating all of those activities and the crew activities together was a big part of my role as the commander.”
To be fair, the audacity of the mission filled NASA’s top brass with dread. The memory of Challenger still loomed large in many minds and the August 1993 loss of Mars Observer, only days before it was due to enter orbit around the Red Planet, added to the popular sense of NASA as a failure-prone organisation. An article in Aviation Week hinted that WFPC-2 might be flawed and it so unnerved the Clinton Administration that NASA Administrator Dan Goldin was invited to attend an audience with the President himself to discuss the space agency’s level of readiness for SM-1. It has been suggested that Clinton offered Goldin two stark choices: to either make the Hubble repair mission work or to face the prospect of an entirely new NASA, with drastically altered form and capabilities. Mistakes simply could not be tolerated.
The heat was on the agency, on the STS-61 crew and on the thousands of engineers and technicians responsible for ensuring that COSTAR and WFPC-2 were ready for launch in early December 1993. Nerves frequently became frayed in the final months. “Are we missing something?” was the introspective question often asked of themselves and each other. Some engineers jokingly decided to spend the New Year in Acapulco, figuring that if SM-1 succeeded they might return home to the United States and if it failed they would be forced to wait tables in Mexico for the rest of their lives!
Training for the STS-61 astronauts was also difficult at times. “We were invited to come down to NASA Headquarters to meet with Dan Goldin,” remembered Jeff Hoffman. “He told us quite frankly that NASA’s future was in our hands. That was the time when we were waiting for Congress to approve the construction of the space station. Everybody recognised that assembling the space station was going to take a lot of sophisticated EVAs, of the sort that we were getting ready to do for Hubble, so if we went up thinking that we could fix Hubble and then it turned out that we couldn’t, how could people trust NASA to build a space station? That was the attitude.”
Story Musgrave had been assigned to lead the planning of the EVAs, as payload commander, and he had pushed very hard to commit to Endeavour as the orbiter which would carry out the mission. He particularly highlighted the vehicle’s improved capabilities over her sister vehicles (including the capacity for a long mission) and succeeded in getting his way: in NASA’s January 1992 manifest, the SM-1 mission was scheduled for Atlantis, but by December had shifted to Endeavour. All of the spacewalkers recognised the need to develop physical strength to handle the demands of their space suits and build the necessary stamina for six or seven hours outside. Thornton worked out in the gym, as did the others, although by Hoffman’s admission most of the servicing tasks did not demand immense physical strength, but placed greater emphasis on “technical co-ordination”, involving them “being very careful in how you moved things around and not messing anything up”.
The delicacy involved in each of the spacewalking tasks was further complicated by the need for sunlight never to enter Hubble’s interior, because it carried the potential to evaporate organic contaminants and potentially ruin the sensitive ultraviolet optics. Consequently, the mission was planned with the Shuttle’s belly positioned to face the Sun – but this, in turn, meant that temperatures in the payload bay and in the astronauts’ suits would fall precipitously. Already, the criticality of the EVAs had obliged NASA, in March 1993, to assign veteran spacewalker Greg Harbaugh as a backup crewman, ready to step in if circumstances dictated.
And they almost did.
On 28 May, Musgrave was performing an eight-hour suited equipment test in one of the thermal vacuum chambers at the Johnson Space Center, when he complained of intense cold in his right hand. He persevered and after finally removing his suit at the end of the test, he noticed discolouration and numbness (they were “black and purple”, according to Hoffman) in his fingers. Flight surgeons quickly identified severe frostbite and Musgrave was referred to a specialist in Alaska for treatment. At this stage, Hoffman was unsure what would happen. “I don’t know exactly what they did to him,” he told the oral historian, “but they managed to save his fingers, and he flew, but that definitely got management’s attention.”
That ‘attention’ was both positive and negative for Musgrave. On the positive side, it led to the elimination of the belly-to-Sun attitude, in favour of an attitude in which Covey and Bowersox would execute short attitude manoeuvres per orbit to ensure that sunlight did not enter the telescope. In Dick Covey’s recollections, the single-mindedness of Musgrave towards training for the mission caused some anger and even demands for his removal from the crew. “Story had been around for a long time,” said Covey. “There was this concerted effort to use Story’s injury as a reason to get him thrown off the crew by some people with the agency and the centre and I had to go fight that…The reasons were political and personality-based, rather than technically based on his capabilities and whether he was going to recover from his injuries. That was hard to deal with.” Harbaugh was also recovering from recent knee surgery and, for a while, struggled to even don a space suit, but both he and Musgrave were declared ready for the mission.
A windstorm on 30 October 1993 prompted the movement of Endeavour from Pad 39A to Pad 39B, following contamination of the payload changeout room, with much anticipation of a successful launch on 1 December. The attempt was scrubbed due to high winds and the presence of a ship in the restricted waters, but, after a 24-hour delay, STS-61 blazed into the darkened Florida skies at 4:27 am EST on the 2nd. Several burns of Endeavour’s manoeuvring thrusters over the following two days closed their separation distance from Hubble by around 60 nautical miles per orbit, until, early on the 4th, Jeff Hoffman spotted the telescope through his binoculars…and noted that one of its solar arrays – due to be replaced by Thornton and Akers during the second EVA – appeared bent in a 90-degree angle. At 3:48 am, Covey brought the orbiter to a position just 30 feet from Hubble and Nicollier was able to gingerly extend the RMS and grapple the target.
“Houston,” radioed Covey, triumphantly, “Endeavour has a firm handshake with Mr Hubble’s telescope.”
“There’s smiles galore down here,” replied Capcom Susan Helms.
The first major objective of the mission had been accomplished. Yet the real challenge of the five back-to-back EVAs and the very real uncertainty over whether the efforts of the astronauts would succeed remained to be seen.
The second part of this article will appear on MondayMissions » ISS »