For a few hours in early April 1991, things could not get any worse for NASA. A year earlier, the first of its flagship “Great Observatories”—the $1.5 billion Hubble Space Telescope (HST)—had been launched into orbit, but initial tests revealed its optics to have been improperly ground. In essence, the telescope was unable to resolve celestial objects with the kind of precision that NASA had advertised. A shuttle repair mission had long been on the cards, but the dismal failure caused considerable embarrassment for a space agency still recovering from the loss of Challenger.
The four Great Observatories were meant to offer fundamental insights into the nature and evolution of the Universe, across virtually the entire electromagnetic spectrum. Hubble would observe at visible and ultraviolet wavelengths, whilst the Advanced X-ray Astrophysics Facility (AXAF) would study X-rays and the Space Infrared Telescope Facility (SIRTF) would cover the infrared region.
Yet in light of Hubble’s difficulties, in April 1991 NASA needed the second member of the fleet—the Gamma Ray Observatory (GRO), later named in honor of physicist Arthur Holly Compton—to work perfectly and begin to deliver the scientific bonanza that it had pledged. Had it not been for the remarkable efforts of the STS-37 crew of Atlantis, 30 years ago today, the second observatory’s future might have been seriously impaired.
At the time of launch, GRO was the heaviest astronomical observatory ever placed into orbit: it weighed 35,000 pounds (15,900 kg), of which more than a third was taken up by its scientific payload. It reminded astronaut Jerry Ross of a futuristic diesel locomotive.
“The thing was huge,” he told NASA’s Oral History Project. “Everything on it was real bulky, real thick, real heavy, and it was just very impressive of the stoutness of the satellite. Most times you go up to a satellite and you’re almost afraid to breathe on it, because it may fall apart on you!” Not so GRO. Its massive internal beams, which formed the central backbone of the spacecraft, were essential to supporting its large scientific instruments.
It could point itself at celestial targets for periods of days or weeks at a time, with an accuracy of just 0.5 degrees, and its hydrazine fuel supply was to be used not only for station-keeping, but also to execute a controlled re-entry at the end of the mission. This would prove critical when the time came for that re-entry in June 2000.
Built by TRW, it carried a pair of accordion-like solar arrays and a set of nickel-cadmium batteries to provide electrical power. Moreover, it was designed to operate from an orbit of 280 miles (450 km), high enough to avoid excessive atmospheric drag and low enough to avoid the effects of the Earth’s Van Allen radiation belts, which might compromise its observations.
Commanding STS-37 was veteran astronaut Steve Nagel, who saw his role as getting himself and his crew ready to fly, although a tremendous weight of responsibility also lay on his shoulders, for the $630 million GRO was a major scientific payload. “If it goes well, you take the pats on the back,” he told the NASA oral historian, “but if it goes poorly, you take the blame.” Nagel had no input in the selection of his crew, but he was intimately involved in dividing up their duties. When it came to the issue of contingency Extravehicular Activity (EVA), the one man who stood out was the only other veteran member, Jerry Ross, who already had two prior spacewalks under his belt.
STS-37 was not supposed to include an EVA—it was to spend five days in orbit, deploy GRO on the third day and return home—but this situation changed markedly. “Everybody wants to do an EVA,” said Nagel, “and I just used my own best judgement on that and try to give people what they want or have an aptitude for.” One crew member with limitless reserves of “aptitude” was Jay Apt, a physicist who had worked on GRO in his pre-astronaut days as a NASA payload controller. The final members of the crew were Ken Cameron as the pilot and another physicist, Linda Godwin, who would be responsible for deploying GRO.
During launch, it would be unpowered, save for provisions to keep its star tracker shutters closed, and it was to be electrically activated within 90 minutes of reaching orbit. Twenty-one hours into the mission, an in-bay checkout of GRO would begin, running through everything, from command and telemetry to control systems and communications, and this would serve as a partial rehearsal for the actual deployment.
On the third day of the mission, Godwin would lift GRO out of the bay with the shuttle’s Remote Manipulator System (RMS) mechanical arm and the observatory’s twin solar panels and high-gain antenna would unfold. She would then release the payload, which would power-up its systems over the following six hours and begin scientific operations within five days.
Whilst on the end of the RMS, the potential for anything to go wrong was vast: The solar arrays might not unfold correctly or the high-gain antenna might not open, and it was the responsibility of Ross and Apt to be in a position to perform a contingency EVA if necessary.
In fact, Apt had worked extensively on GRO and one of his achievements was helping to implement contingency capabilities—including EVA-friendly handholds—onto the spacecraft. For much of 1989, the two men trained extensively in the Weightless Environment Training Facility (WET-F) at the Johnson Space Center (JSC) in Houston, Texas, but did not anticipate that a real spacewalk would come their way.
That changed early in the spring of 1990. NASA had already begun work on an experimental Crew and Equipment Translation Aid (CETA), a hand-propelled “cart” to maneuver astronauts along the expansive trusses of Space Station Freedom. By the time CETA received formal approval for early tests, the final payload reviews for STS-37 had already taken place, but the enthusiasm of the crew led to it being added to their flight.
Due to a series of shuttle hydrogen leaks in the summer of 1990, STS-37 found itself delayed from April to November and, ultimately, into the spring of 1991. This gave the crew more time to prepare for a spacewalk, which would involve the movement of a CETA cart along a 45-foot (14-meter) extendible track in the shuttle’s payload bay. Manual, mechanical, and electrical methods of operating the hardware would be trialed.
In fact, Jerry Ross had performed the most recent EVA in the shuttle program on STS-61B in the fall of 1985, just weeks before the Challenger disaster. Yet the paucity of EVA experience in the Astronaut Office at the time was such that Ross expected Godwin and Apt to be handed the assignment. Commander Nagel, however, thought differently.
Nagel’s concern was not so much centered on CETA, but upon a possible secondary EVA objective: If anything went wrong with the GRO during deployment, a contingency spacewalk might be needed to save it. “I’d look really stupid,” he told Ross, as paraphrased in his NASA Oral History, “if we had to do some kind of contingency EVA on a primary payload and you weren’t one of the two guys that was outside!” Thus Ross and Apt pressed ahead with preparations for what was expected to be a single EVA for CETA trials.
Liftoff of STS-37 took place at 9:22 a.m. EDT on 5 April 1991. “Entirely nominal and entirely exciting,” was Cameron’s summary of his first launch into space. Two days later, the massive GRO hung above Atlantis’ payload bay at the end of the RMS, ready for deployment. To preserve the opportunity for Ross and Apt to go outside on a contingency EVA, the shuttle’s cabin had been depressurized and their space suits and the airlock had been checked out and were ready. As the crew watched, GRO’s two solar array “wings” were successfully unfurled.
At this point, Apt glanced over at Ross. “I guess everything’s downhill from here!” It was true: Deployment of the accordion-like arrays, which reached a wing span of 65 feet (20 meters), was one of their key worries. Next came the deployment of GRO’s high-gain antenna, which would provide high-rate communications with ground stations. Commands were issued for it to extend on its 10-foot (3-meter) boom.
But it did not move.
No fewer than six attempts were made to unfurl it, and Nagel and Cameron even tried shaking it open with a burst of the shuttle’s maneuvering thrusters. From the RMS controls, Godwin tried moving the arm relatively sharply, then halting relatively abruptly, but her efforts also had no effect. An EVA was the only option. Ross removed his wedding ring and handed it to Nagel. “Steve,” he said, “I’m going downstairs to get ready.”
Nagel nodded. A few minutes later, the call came from Mission Control for the spacewalkers to do just that. Entering the payload bay, Ross later reflected that his level of anxiety on this occasion was heightened by the urgency of fixing GRO.
“I didn’t know if we could fix it or not,” he told NASA’s oral historian, “and here we are, on the spot, to try to go out and fix this thing. And if we can’t, then we’ve got this great big lead weight. What are we going to do with it? We may not be able to bring it home, because the solar array’s already been deployed and the antenna’s partly released. Oh, man!”
Quickly, the two spacewalkers split up: Apt moved to the port side of the payload bay to set up tools, whilst Ross, on the starboard side, attended to the task at hand. Godwin moved the robot arm slightly to tilt the GRO toward him.
“The antenna,” Ross said, “was on the back side, facing the aft bulkhead of the orbiter, and the guys in the cockpit couldn’t see it from the aft windows.” By the time he reached the location of the antenna, Atlantis was passing out of direct communication with Mission Control and Ross used the quiet time to position himself in such a way that he could shake it open.
He knew that the antenna was relatively close to GRO’s hydrazine tanks, and he definitely did not want to ding them and risk having a highly-toxic leakage on his hands. By now Nagel, Cameron and Godwin were getting views from the aft payload bay cameras on their monitors and were able to offer Ross additional guidance.
He gave the antenna a couple of lateral shakes. It still felt solid; immovable. A few more tries, which Ross later described as “some relatively easy force-inputs,” achieved a measure of success, as it started to loosen up a little.
“I was probably putting in 45-50 pounds of force, is my recollection and I could tell it was starting to walk out,” Ross said later. “Finally, it came free and swung out about 30-40 degrees from the stowed position.” It turned out a thermal blanket had somehow gotten “hung up” on a bolt, and Ross’ repair had taken just 17 minutes.
He let out “a war whoop” and returned to the port side of the bay to join Apt. The two men gathered their tools, and Ross returned to GRO to begin the process of manually locking the antenna’s boom into its deployed position. “And that was a pretty good feeling,” he said. “I felt that I’d probably earned my keep for that day!”
At one stage, Ross took a breather, moving close to Atlantis’ aft flight deck windows to grin at his crewmates inside the cockpit. Inside, Nagel, Cameron and Godwin were eating lunch. “No, we were busy,” Godwin joked later. “We were very busy!”
At 5:36 p.m. EDT on 7 April, some three orbits and 4.5 hours later than planned, Godwin finally released a perfectly functioning GRO from the grasp of the arm. NASA’s second Great Observatory drifted serenely into the inky blackness to commence its mission. Ross and Apt had a ringside seat for much of this activity, for they were able to remain outside whilst the final checks on the observatory were performed. “During that period of time,” Ross told the oral historian, “Jay and I were allowed to stay outside on the spacewalk and to do a series of force measurements.”
The intention was to understand the kind of loads an astronaut might experience whilst in and out of a foot restraint and Ross performed “a whole series of maneuvers of turning wrenches, turning handles, maneuvering myself…a whole series of things that we were recording the data so that we could get more information.” Years later, Ross remembered working up a vigorous sweat, which streamed into his eyes at one stage, such was the level of exertion and exhaustion.
The spacewalkers were supposed to be back inside Atlantis’ airlock in time for the actual GRO release. It did not entirely work out that way. “I think the only thing that was still in the airlock when we released the satellite,” said Ross, “were our toenails! Jay and I were pretty well outside of the hatch … and then they fired the jets to move the orbiter away. That was really cool. We were over North Africa at the time that we released it and we were above the satellite, looking down. That was a pretty awesome sight.”
Ross and Apt prepared dinner for their crewmates that night to celebrate a remarkable day. Ross took charge of distributing “dessert”—malted milkballs—which Cameron noted were shared “fairly equitably”. Yet STS-37 had barely reached its halfway point. On 8 April, the spacewalkers returned outside for their originally planned six-hour EVA to perform a series of Space Station Freedom locomotion tests with the CETA.
A 24-hour delay to their landing, caused by bad weather at Edwards Air Force Base, meant that they finally returned home to California on the 11th. During his final approach, Nagel fell victim to an incorrect call on high-altitude winds and brought the orbiter down onto the runway, about 620 feet (190 meters) “short” of the threshold.
It was the first “low-energy” landing of the shuttle program and was not immediately noticeable to most spectators, since it was on the vast dry lakebed of Runway 17, but gained a lot of attention from Nagel’s fellow astronauts.
Years later, Nagel would blame himself for not being sufficiently aggressive when he rolled out onto final approach, but it made little difference to his career. His first shuttle command had triumphed in the face of adversity, placed a brand-new Great Observatory, fully functional, into orbit, and had gone a long way toward demonstrating not only that NASA needed a permanent space station, but that it needed the capabilities of men and women in space.