'What You Saw Was What You Got': 25 Years Since the STS-32 Mission to Snatch LDEF (Part 1)

Twenty-five years ago, next week, the crew of shuttle Columbia retrieved the giant Long Duration Exposure Facility (LDEF). The satellite's orbit had degraded to such an extent that it was only weeks away from an uncontrolled re-entry. Photo Credit: NASA

Twenty-five years ago, next week, the crew of Shuttle Columbia retrieved the giant Long Duration Exposure Facility (LDEF). The satellite’s orbit had degraded to such an extent that it was only weeks away from an uncontrolled re-entry. Photo Credit: NASA

Twenty-five years ago, next week, on 9 January 1990, the crew of Columbia rocketed into orbit on a mission which would begin to turn away from the trauma of the Challenger disaster and set the sights of the shuttle program on the future. Astronauts Dan Brandenstein, Jim Wetherbee, Bonnie Dunbar, Marsha Ivins, and David Low embarked on a flight which would both deploy and retrieve Earth-circling satellites and which would set a new record for the longest mission in the shuttle’s history at that time and even offered the crew a humorous opportunity to don Santa suits and sneak an inflatable birthday cake aboard Columbia for their commander.

The first player in the story of STS-32 had actually risen to orbit almost six years earlier, aboard Challenger on Mission 41C in April 1984. The Long Duration Exposure Facility (LDEF) was a 12-sided, bus-sized satellite, intended to accommodate experiments for long-term exposure to the harsh radiation and microgravity environment of low-Earth orbit. However, no one could have foreseen at the time of its launch how long-term its tenure away from the Home Planet would be. Original plans called for Brewster Shaw’s crew to retrieve it from space on Mission 51D in February 1985, but then a team of astronauts under the command of Dan Brandenstein spent several months preparing for the intricate task, with an anticipated launch date of 19 March. Unfortunately, the cancellation of Mission 51E in early March had a knock-on effect upon Brandenstein’s flight and the LDEF retrieval was again delayed. Brandenstein and his crew eventually flew Mission 51G in June 1985, and by the time of the Challenger disaster the following January the recovery of LDEF was anticipated no earlier than Don Williams’ Mission 61I in September 1986.

The satellite was a peculiar object, measuring 29.8 feet (9.1 meters) long and 14 feet (4.2 meters) in diameter and weighing 21,000 pounds (9,520 kg). At its most basic, it was a frame of aluminum rings and longerons, loaded with trays for 57 experiments. Shortly after the formation of NASA in October 1958, researchers began to seriously consider building a satellite that could carry materials science samples in order to assess how the harsh environment caused them to degrade over time. By the early 1970s, these ideas had acquired a name, the Meteoroid and Exposure Module (MEM), to be carried aloft by the shuttle and retrieved a few months later. As the name implied, its focus was upon the impact of micrometeoroid damage on satellites and how best to protect them. Subsequently renamed LDEF, the contracts for its design and development were granted to NASA’s Langley Research Center in Hampton, Va.

Emblazoned with the surnames of the crew, STS-32 patch includes Syncom 4-5, Columbia and LDEF in pride of place. Image Credit: NASA

Emblazoned with the surnames of the crew, STS-32 patch includes Syncom 4-5, Columbia and LDEF in pride of place. Image Credit: NASA

The structure was complete by 1978 and, after tests, was kept at Langley until a shuttle flight became available. By this point, its objectives had expanded from micrometeoroid research to studies of changes in material properties over time, performance tests of new spacecraft systems, evaluations of power sources, and conducting crystal growth and space physics. The satellite was designed to be reusable and adaptable for differing lengths, though ultimately it would fly only once. Its length was divided equally between six bays for the experiment trays, with a central “ring” at the midpoint connected by longerons to the end frames. Aluminum “intercostals” linked each longeron to adjacent rows of longerons on each side and removable bolts joined the longerons to the end frames and intercostals. This meant LDEF could be made “shorter” or “longer” if a mission required it. Experiment trays were then clipped into the rectangular openings between the longerons and intercostals.

Two grapple fixtures for the shuttle’s Canadian-built Remote Manipulator System (RMS) mechanical arm were provided: one to allow it to be held for deployment and retrieval and a second to send signals to initiate the experiments. It had no attitude control system and, said one engineer, “what you saw was what you got”: a passive container with no maneuvering capabilities. It was designed to remain in orbit by being placed into a “gravity gradient” attitude, with one end facing Earth, making an on-board propulsion system unnecessary. This also freed it from acceleration forces or contamination caused by thruster firings.

The orientation of LDEF also meant that the two “ends” would be subjected to a unique thermal environment, although all parts of the satellite were subjected to daily temperature changes as the Sun “rose” and “set” every 90 minutes and solar angles changed annually. Heat management was accomplished by coating the interior surfaces with high emissivity black paint, which kept thermal gradients across the structure to a minimum and maximized heat transfer across LDEF’s body. The experiments were also spread evenly to equalize thermal properties across the satellite. Eighty-six trays—72 around the circumference, six on the Earth-facing end, and eight on the space-facing end—accommodated the 57 experiments. These covered four disciplines: materials and structures, power and propulsion, science and electronics, and optics. They captured interstellar gas atoms to better understand the Milky Way Galaxy’s formation, observed cosmic rays and micrometeoroids, studied shrimp eggs and tomato seeds, and investigated the impact of atomic oxygen on different materials, including solar cells.

The STS-32 stack rolls into the mist on its way to Pad 39A. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

The STS-32 stack rolls into the mist on its way to Pad 39A. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

With the entire shuttle fleet grounded in the wake of the Challenger tragedy, the fate of the satellite was rendered precarious. Trajectory specialists estimated that by early March 1990, at the very latest, LDEF—which lacked its own propulsion capability—would be unable to maintain itself in orbit and would tumble back into Earth’s atmosphere and a fiery destruction. Since many of its experiments promised to yield valuable data, particularly as NASA devised new materials for Space Station Freedom, it was imperative that a shuttle mission be staged as soon as possible after Return to Flight (RTF) to bring LDEF home.

That was the task of Dan Brandenstein’s STS-32 crew, named by NASA in November 1988 for launch in November of the following year. The assignment of Brandenstein seemed unsurprising, given that he had already trained to lead the LDEF retrieval and was only days away from commanding the mission in March 1985. Having said this, many of the pilots in the astronaut office regarded STS-32, with its rendezvous commitment, as one of the “plum” shuttle mission assignments and felt that Brandenstein, who had replaced John Young as chief of the corps in April 1987, was picking the best flight for himself. Whatever the reality, one other crew member had also trained extensively for the LDEF retrieval. Mission Specialist Bonnie Dunbar would be at the controls of Columbia’s RMS arm to grapple the giant satellite and maneuver it into a berth in the payload bay.

The other members of the STS-32 crew were all rookies, but all would contribute hugely to the space program in the following years. Pilot Jim Wetherbee would go on to become the only U.S. astronaut to command five missions, and flight engineer Marsha Ivins would enjoy a 36-year career with the space agency and install the Destiny laboratory module onto the International Space Station (ISS), whilst David Low—son of former NASA Deputy Administrator George Low—would prove instrumental in drawing the Russians to the negotiating table as partners in the ISS.

Expected to be the first shuttle crew to spend Christmas in orbit, this gag photograph of the STS-32 crew fell flat when the mission was postponed until January 1990. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

Expected to be the first shuttle crew to spend Christmas in orbit, this gag photograph of the STS-32 crew fell flat when the mission was postponed until January 1990. Photo Credit: NASA, via Joachim Becker/SpaceFacts.de

One of Low’s key roles on STS-32 was the deployment of the U.S. Navy’s Syncom 4-5, the fifth and final military communications satellite in a series which traced its genesis back to 1978. Four of these drum-shaped, Hughes-built spacecraft had been placed into orbit on a series of pre-Challenger shuttle flights and, although one suffered a catastrophic failure of its Ultra-High Frequency (UHF) electronics, another was triumphantly retrieved, “hot-wired” and returned to full operations. The Syncom to be released under Low’s auspices, therefore, would be essential in completing the “minimum-size” constellation of four satellites needed by the Navy.

Columbia required several tries before finally making it into space for STS-32. Launch was originally planned for 18 December 1989, which—judging from the ten-day duration—would have made Brandenstein’s crew the first team of shuttle astronauts to remain in orbit over Christmas. This fact evidently played so much on their minds that they privately organized an impromptu crew portrait to be taken, in which they posed in Santa suits, hats, and dark glasses. Fortunately, their NASA name tags at least made them identifiable. Unfortunately, problems with getting Pad 39A ready for its first launch in almost four years resulted in a delay until no sooner than 8 January 1990, so the Santa joke fell flat.

Since the return to flight of STS-26, most missions had lasted around five days, but STS-32 was to break this cycle by approaching the shuttle program duration record of 10 days and seven hours, set by the Spacelab-1 crew in December 1983. (The press kit reported that STS-32 was to last nine days and 21 hours.) Although the deployment of Syncom 4-5 and the retrieval of LDEF would consume only the first three days and did not specifically require a lengthy mission, NASA wanted to exercise the opportunity to demonstrate the shuttle’s capabilities, because it planned to modify Columbia for a series of Extended Duration Orbiter (EDO) flights lasting up to a month.

Processing of the orbiter involved modifications to support the longer mission. A fifth set of cryogenic oxygen and hydrogen tanks were installed underneath Columbia’s payload bay floor, and by the end of November 1989 the shuttle had been rolled out to Pad 39A, marking the first use of this launch complex since Mission 61C. After a delay until 8 January to finish work on the pad, the weather became the next issue. “Our main concern,” said Air Force meteorologist Ed Priselac on the 6th, “is that low-level cloudiness will not clear out of here very quickly.” The threat also included rain showers and high-altitude clouds, which reduced the prospects of acceptable weather on the 8th to just 40 percent. The odds of successfully launching that day were reduced yet further by the relatively short, 54-minute “window,” which had been precisely timed to allow Columbia to rendezvous with LDEF on the third day of the mission.

STS-32 launches on 9 January 1990, in pursuit of LDEF. Photo Credit: NASA

STS-32 launches on 9 January 1990, in pursuit of LDEF. Photo Credit: NASA

NASA engineers also expressed concerns that pad hardware used to load cryogenic propellants into the External Tank (ET) might leak, but these concerns proved unfounded. Otherwise, the attempt on 8 January proceeded smoothly: The crew were strapped into their seats by mid-morning, although the clock was held at T-9 minutes by unsatisfactory conditions at the Shuttle Landing Facility (SLF) runway. In an effort to keep the option of launching open, the clock was restarted and counted down to T-5 minutes—the point at which Jim Wetherbee would start the Auxiliary Power Units (APUs)—but was held again. Just when it seemed that the weather might just co-operate, a faulty electronics component signaled a possible glitch with Pad 39A’s sound suppression water system. A team of engineers were hurriedly sent to check the system and were satisfied that everything was normal, but then the weather closed in once again and prompted a scrub.

Brandenstein’s crew had more luck the next day and STS-32 thundered into space precisely on the opening of the hour-long launch window at 7:35 a.m. EST on 9 January 1990. A picture-perfect ascent established them on an orbital “racetrack” to reach LDEF and retrieve it on 12 January. In the meantime, the astronauts spent their first day in space by concentrating on two major objectives: checking out the RMS arm, which Bonnie Dunbar called “a beautiful piece of hardware,” and preparing to deploy Syncom. At 8:18:39 a.m. EST on the 10th, a little under 25 hours after launch, the satellite was released as Columbia flew above Africa. Low radioed to Mission Control that the deployment looked good. A few minutes later, Brandenstein and Wetherbee performed a separation maneuver to create a safe distance before the first engine burn. Syncom’s manufacturer, Hughes, was exceptionally pleased with the performance of their product. “It was as good as you can get,” said spokesman Tom Bracken. “Everything looks great.”

A series of maneuvers by the satellite’s own propulsion system were required to achieve its “slot” in geostationary orbit at an altitude of 22,300 miles (35,900 km). The first, at 8:53 a.m., involved Syncom 4-5 firing its solid-fueled motor to boost itself into an elliptical transfer orbit. This was later circularized and the perigee raised to geostationary altitude. During this time, Dunbar uncradled the RMS and used one of its cameras to photograph the first Syncom burn. Several additional maneuvers were made by the satellite to achieve its final orbit, which it accomplished by 13 January. Following a month-long period of checks, it was declared operational and joined its siblings. Later in 1990 and 1991, it was used to support military communications during the U.S.-led Operations Desert Storm and Desert Shield in Iraq.

The success of Syncom 4-5 was the last time that one of these frisbee-like deployments was performed from the shuttle, marking the end of an era in many respects. Yet only a fraction of the STS-32 mission had passed. Ahead lay an intricate rendezvous profile which would put the capabilities of Columbia, her crew, and the collective brain of NASA to the ultimate test.

 

The second part of this article will appear tomorrow.

 

 

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