'A Question of Losing Science': 15 Years Since the Third Hubble Servicing Mission (Part 1)

Fifteen years ago, next week, Shuttle Discovery rocketed into orbit on a mission to dramatically service and repair the Hubble Space Telescope (HST). In doing so, the crew of STS-103—Commander Curt Brown, Pilot Scott Kelly, and Mission Specialists Steve Smith, John Grunsfeld, British-born Mike Foale, Frenchman Jean-Francois Clervoy, and Switzerland’s Claude Nicollier—became the first and only shuttle crew to spend Christmas in orbit and supported three critical spacewalks to bring the telescope back to operational status, after a series of mechanical malfunctions. Those three spacewalks each lasted in excess of eight hours, making them some of the longest EVAs ever performed in human history. Yet the mission itself came at a difficult time for NASA; flown on the cusp of the new millennium, it followed on the heels of a particularly hairy incident during the launch of Columbia on STS-93 and almost six months of inspections and repairs across the entire shuttle fleet.

At the time of STS-93—which deployed NASA’s Chandra X-ray Observatory in July 1999 and featured the first female spacecraft commander in history—NASA’s plans for the shuttle program were in flux, due to delays in the construction of the International Space Station (ISS). Provisionally, the agency targeted Endeavour to fly STS-99 and the Shuttle Radar Topography Mission (SRTM) in September, followed by Discovery on STS-103 to service Hubble in October and Atlantis on STS-101 to deliver equipment and supplies to the nascent space station in December. However, during the STS-93 ascent, Columbia suffered an electrical short, which knocked out two main engine controllers and left them running solely on their backups. The incident was worsened by a small leak of liquid hydrogen from the right-hand engine, which caused both it and its two siblings to shut down several seconds earlier than intended. Both events precipitated a lengthy series of inspections of all three orbiters’ wiring systems, which effectively grounded all three shuttle orbiters.

STS-103 was postponed from mid-October, and it remained unclear for some time whether it or STS-99 would fly first. Hubble teams only had half of their gyroscope control capability available—following failures earlier in 1999—which placed the iconic telescope one malfunction away from a total shutdown, whereas SRTM teams argued that valuable radar mapping data from their payload would be degraded if it was delayed until late in the winter. By mid-September, NASA opted to fly STS-103 no sooner than 28 October and STS-99 no earlier than 19 November, pushing STS-101 into January 2000, but it was stressed that even these revised dates were subject to change. The onslaught of Hurricane Floyd on Florida compounded the issue, and it was not long before STS-103 found itself delayed again, until 19 November and eventually the first week in December.

Technical troubles had not yet finished with STS-103. In early November, NASA managers ordered the replacement of one of Discovery’s three main engines, following concerns about a drill bit fragment lodged inside it. This pushed the launch until no earlier than 6 December. Attached to her External Tank (ET) and Solid Rocket Boosters (SRBs), the shuttle stack was transferred to Pad 39B on 13 November, following other work, but suspect wiring between the tank and boosters prompted more delay as corrective actions were implemented. Then, the newly replaced main engine failed a series of leak checks, pushing launch back to no earlier than 9 December and forcing NASA to the conclusion that if STS-103 was not off the ground by the 14th (a so-called “drop-dead date”), it would be postponed until mid-January 2000, owing to concerns about the much-hyped Year 2000 (Y2K) computer bug. Discovery needed to be on the ground, and fully powered-down, before the end of the year. A leak in a hydraulic system quick disconnect fitting on one of the shuttle’s Auxiliary Power Units (APUs) required replacement and inspections of potentially cracked wiring harnesses in the main engine compartment produced a further delay, first until 11 December and later settling on the 12th.

Frayed wiring and a crushed hydrogen conditioning line on one of Discovery’s main engines produced another headache, by which time NASA managers had extended the drop-dead timeframe available to launch STS-103 until no later than 18 December. However, it was stressed that waiting so close to the end of the year would require one of the four planned EVAs to service Hubble to be deleted and the mission duration shortened to no longer than 10 days. In the meantime, United Space Alliance (USA) determined that they could replace the crushed conditioning line at the pad and in time for a 16 December launch. With the successful replacement completed by the 13th, managers pressed ahead with a revised launch attempt on the 16th. Unfortunately, despite a 90 percent likelihood of acceptable weather conditions, this ultimately came to nothing, when a potential problem arose with the ET. Paperwork and X-rays indicated that oxygen line welds on the tank may have come from a “bad” batch which did not meet NASA’s stringent specifications. Although it was concluded that all was fine, the incident was followed by concern about the quality of propellant lines within Discovery’s main engines, which conspired to effect a 24-hour postponement until 17 December. Bad weather put paid to that launch attempt, with low clouds, rain, and gusty winds at the Kennedy Space Center (KSC) and any chance of acceptable weather on the 18th also proved hopeless.

By this stage, NASA Associate Administrator for Space Flight Joseph Rothenberg authorized another attempt on 19 December, but launching so late would require a shorter flight of eight days (rather than 10), the deletion of one of STS-103’s four spacewalks, and shortening the length of time required to drain toxic propellants and power down Discovery after her mission. Under its worst-case deservicing plans on the runway at Edwards Air Force Base, Calif., USA decided to reduce the post-landing safing time by simply powering the orbiter down. Instead of draining residual liquid oxygen and hydrogen, these cryogens would be allowed to vent overboard.

Launching on the 19th would produce a rendezvous and retrieval of Hubble on 21 December, followed by three EVAs on the 22nd, 23rd, and 24th, a deployment of the telescope on Christmas Day, and the return to Earth of STS-103 on the 27th. Former astronaut Don McMonagle, then serving as chair of the Mission Management Team, pointed out that a fourth EVA could not be attempted on such a short flight. “We do not intend to extend this mission beyond the 27th, unless there are mitigating circumstances that require us to do that,” he told journalists. “Mission success can be achieved in three EVAs. That is the plan for this mission.” Having said this, HST Project Scientist David Leckrone stressed that lists of get-ahead tasks had been formulated for the three EVAs, such that the crew could perform other work, such as replacing insulation blankets on the telescope.

By now, there remained no contingency time or opportunity to shorten the mission any further; if Discovery was not off the ground on the 19th STS-103 would be postponed until no sooner than 13 January 2000. As circumstances transpired, weather and technical conditions came together on 19 December and Discovery and her seven-man crew rocketed into orbit at 7:50 p.m. EST, right on the opening of that night’s 42-minute “launch window.” The successful launch came as a relief, after nine frustrating delays and nine agonizing weeks later than originally planned. It had been a peculiar launch campaign, with camps arguing on the one hand that a flight in December was not mandatory, whilst on the other that every possible attempt should be made to fly before the end of 1999.

Although Shuttle Program Manager Ron Dittemore had repeatedly stressed that there was “no pressure” to get STS-103 off the ground in December, he pointed out that it was equally not a casual decision to simply postpone the mission until January 2000. A great deal of processing work on the shuttle had already been completed, some of which would need to be repeated in the event that the mission was stood down for another three weeks. “We would actually have to back out of certain activities we have already performed on the vehicle,” he said, “and then we also believe our teams would suffer some because they would have a three-week layoff and we’d have to bring them back up to their peak training. There is some loss you suffer by going into January.” Dittemore also reflected on the words of a friend, who told him that “the road to success is always under construction.” The success that STS-103 was to become, during its eight days in space, had certainly lived through its own fair share of construction. Describing the successful launch as “a very nice Christmas present indeed,” David Leckrone was “thrilled to pieces” as the poor weather conditions finally cleared and Discovery speared into orbit.

STS-103 could not reach Hubble soon enough. When the four-man EVA team (or “payload crew”) of Smith, Grunsfeld, Foale, and Nicollier was announced in July 1998, it was tracking an ambitious mission in June 2000, which encompassed a record-breaking six spacewalks to install new hardware and imaging equipment aboard the telescope. All four men were veteran astronauts: payload commander Steve Smith had previously served aboard the second Hubble Servicing Mission (SM-2) in February 1997, whilst Mike Foale had performed EVAs from the shuttle and Russia’s Mir space station. It was their responsibility for their respective EVAs to ensure that all of the 300 tools were in the proper places and configurations for the required tasks. “We put those together,” said Foale, “we check them out, make sure the batteries for the power tools are charged up and gather those together in the airlock.” Although the other two astronauts, John Grunsfeld and Claude Nicollier, had no spacewalks to their credit at the time, both brought immense expertise to Servicing Mission (SM)-3. Nicollier had served as the operator of the shuttle’s Remote Manipulator System (RMS) mechanical arm on the SM-1 mission in December 1993, whilst Grunsfeld was a professional astronomer.

“The ambitious nature of this mission,” said Dave Leestma, then-director of the Flight Crew Operations Directorate, “made it important for the payload crew to begin its training as early as possible.” Original plans called for the six EVAs to replace Hubble’s Faint Object Camera (FOC) with the Advanced Camera for Surveys (ACS), replace Fine Guidance Sensor (FGS)-2, replace both solar arrays with rigid, high-efficiency ones, and replace an Engineering/Science Tape Recorder (ESTR) with a new Solid State Recorder (SSR). Ancillary tasks for SM-3 included fitting a cooling system to the telescope’s aft shroud in order to upgrade the thermal protection capacity of its systems, installing a new technology cryocooler for the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and attaching six voltage/temperature improvement kits to enhance Hubble’s battery-charging capability. Repairs to the telescope’s aging thermal insulation on its Sun-facing side was also planned, following a discovery by the SM-2 crew of areas of peeling. However, six back-to-back EVAs on a single flight was more than had ever been attempted in the shuttle’s history, and, according to David Leckrone, it was “shaping up to be quite a lengthy and complicated mission,” which pressed the envelope in terms of capability. With SM-3 assigned to Columbia, all eyes were on getting STS-93 off the ground in mid-1999, such that NASA’s oldest orbiter could complete several months modification and refurbishment in order to meet a mid-2000 launch date. However, the lengthy delays to STS-93 and the wiring inspections meant that Columbia would be out of service for far longer than intended.

“I’m not an astronomer,” admitted Steve Smith, “but from a layman’s perspective, the Hubble Space Telescope has been like a time machine. It’s given us views of things that have happened years ago in far away places, and in that respect it is kind of the thing of fiction. It is a time machine. It has given us an insight into things that have already happened before we were even alive and some of the views have been absolutely incredible. The Hubble Deep Field is my favourite image. Hubble was pointed towards what was considered a vacant piece of the sky for ten days, which is very unusual. When they got the image back, in this very small piece of the sky – about the size of the sky that you would see looking through a straw – they found 1,500 galaxies, just like the Milky Way. If you expand that finding over the entire sky around us, the implications are incredible.”

Equally incredible for Smith was the prospect of visiting Hubble for a second time, having previously served aboard the SM-2 mission in February 1997. “I’d always heard that once you see Hubble, you’ll never forget it,” he said, “that it really is this magical-looking space ship. And it really is a spectacular sight to see … and huge, much larger than I had ever imagined. Most of us who have gone to the Hubble Space Telescope have never seen it before and that was my challenge before STS-82. Even though we have mockups of it, it just doesn’t look the same in the water.”

The situation with the shuttle’s wiring problems in 1999 was compounded further by technical problems with Hubble itself. The telescope carried six gyroscopes to support its precise pointing requirements, but one had failed in 1997, another in 1998, and a third in early March 1999. Since Hubble needed a minimum of three gyroscopes to remain operational, this third failure placed it just one malfunction away from having to place itself into a protective “safe mode” and suspend astronomical research. Under flight rules, NASA was required to consider a “call-up” shuttle servicing mission before the failure of a fourth gyroscope. “Hubble is a priceless, irreplaceable resource and it’s got a finite life,” said David Leckrone, “so every month lost is a month lost forever to science.”

For Steve Smith, who was responsible for orchestrating the EVA timeline for SM-3, the news that their mission could no longer wait until June 2000 was met with a combination of dismay and euphoria. “In the second of 1998, we spent a lot of time in the water, working towards this six-EVA Hubble flight,” he said. “Most of the tasks we worked on were very difficult, very new tasks. When we finally got the news, we were in a meeting called the Cargo Integration Review and, just on the voice loops from NASA-Goddard, we heard that Hubble had suffered another gyroscope failure. It was at that moment that I thought to myself, ‘Gosh, I don’t think they can wait for us to go back up in the year 2000’. Although Hubble was still working perfectly well, it was a greater risk now, and we met the news with disappointment for the Hubble community, because we knew that their gem was now at a lower level of redundancy.” This was juxtaposed with another realization in Smith’s mind: “We’re gonna be part of this historic, launch-on-need effort to go restore Hubble’s redundancy.”

In spite of the gyroscope situation, others countered that Hubble was in a safe condition and could wait until after STS-99. “We can go get it and service it even if there are no gyros remaining,” said Shuttle Program Manager and former astronaut Bill Readdy. “It’s not a question of the safety of the spacecraft. It’s a question of losing science. The probability is that by the summer of 2000, one or more of the gyros would have failed. That’s what’s driving us.” Consequently, it was decided to split the SM-3 mission into two halves, with the first half scheduled for October 1999 and the second in September 2000. The so-called SM-3A mission would install—in order of priority—six new gyroscopes and six new voltage regulators to prevent battery over-charging, a new computer, a new FGS, a new S-band radio transmitter, and a new SSR. A year later, SM-3B would would install the new solar arrays and new cameras and cryocooler.

With SM-3A just seven months away, the three final members of the STS-103 crew were announced by NASA in mid-March 1999. Commanding STS-103 was Curt Brown, joined by pilot Scott Kelly and French RMS operator Jean-Francois Clervoy. With Brown making his sixth space flight, Foale his fifth, Nicollier his fourth, Smith, Grunsfeld, and Clervoy their third each, and only Kelly on his first mission, the STS-103 marked the most experienced shuttle crew ever launched into orbit, in terms of numbers of previous flights. On the eve of liftoff, they boasted 18 missions between them. The seven men would require every ounce of that experience during one of the most complex shuttle flights ever attempted.

The second part of this article will appear tomorrow.

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