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April History Milestone: STS-1, STS-37 and Apollo 13
April is a historic month for noteworthy missions controlled by JSC’s flight controllers—STS-1, the first flight of the Space Shuttle Program and the safe return of the Apollo 13 astronauts. Few are probably aware of other significant human spaceflight missions that flew this month. STS-37, which launched and landed in April 1991, is just one example that illustrates the importance of flight crew training and contingency planning.

S37-96-010: GRO

The GRO hovers above the cargo bay of space shuttle Atlantis. Credit: NASA

JSC’s Mission Operations Directorate’s (MOD) mantra is plan, train, fly. Astronauts fly as they train, and crews simulate on-orbit activities through realistic ground simulations. In April 1991, the five-member crew of STS-37 encountered a problem deploying the Gamma Ray Observatory (GRO), one of four of NASA’s Great Observatories that also included the Hubble Space Telescope (HST), the Chandra X-ray Observatory and Spitzer Space Telescope.

GRO followed the launch of the Hubble Space Telescope (HST) by one year. Weighing just over 35,000 pounds, the GRO was—at the time—the heaviest astrophysical payload to be deployed by a shuttle flight crew. STS-37 Mission Specialist Jerry Ross likened the observatory to a “diesel locomotive.” The satellite was big; GRO weighed more than Hubble and was denser. Astronomers hoped that the GRO would provide answers to gnawing questions about the origins and history of the universe, as well as the birth, evolution and death of stars, and supply vital information about quasars, pulsars and black holes.

On the third day of the flight, Mission Specialist Linda Godwin used the shuttle’s arm to move the GRO out of the payload bay. The solar array panels unfolded as expected, and Crew Commander Steve Nagel remembered telling Ross, “Well, we’re out of the woods now.” But, the GRO’s high-gain antenna would not open, even after the crew fired the Orbiter’s reaction control jets and shook the observatory with the Canadarm. After several efforts to free the antenna failed, Mission Specialists Ross and Jay Apt donned their spacesuits to complete the first unscheduled spacewalk in six years. Coincidentally, Ross had participated in the last shuttle spacewalk before the Challenger accident occurred.

Ross remembered being nervous about going outside, not because it had been six years since his last EVA but because, “I didn’t know what was wrong with it. I didn’t know if we could fix it or not.” Because the solar arrays had been deployed, it was possible that the crew would not be able to bring the observatory home. The agency needed the satellite to work. Just a year earlier astronomers found that the HST’s primary mirror had been ground improperly, and NASA became a lightning rod. Astronaut Jeff Hoffman explained, “Hubble was the butt of jokes on late-night talk shows. It was denounced in the U.S. Congress. There were cartoons of the great disasters of history. Right next to the Hindenburg was Hubble.”

S37-18-032: Astronaut Jerry Ross

Astronaut Jerry Ross peers into the orbiter crew cabin and smiles after manually extending the observatory’s antenna. Credit: NASA

Ross might have thought about the HST but fixing the GRO antenna was his greatest concern as he entered the payload bay. He pushed the observatory a few times, and after only a few minutes, the antenna came loose and Ross locked the antenna into position.

“And that was a really good feeling,” Ross explained. “Demonstrating where the man in the loop can help a robotic system and let it go off and do some really great science.”

MOD and the crew had planned for a contingency spacewalk and Ross and Apt had spent hours training in JSC’s Weightless Environment Training Facility. Ross later recalled thinking, “‘Yeah, they’ll never need any of these,’” when training in the water tank, “but we ended up needing it.” After the crew landed at Ellington Field Nagel explained how training had paid off for the STS-37 crew. “No matter what nook and cranny we got into, we had been there before or in a similar place in training." When the antenna failed to open, Nagel said, “It was just like running a sim over again. Except with much higher stress levels.”

The GRO went on to provide valuable scientific data to scientists. On June 4, 2000, the observatory stopped gathering data when it re-entered the Earth's atmosphere.

For more information on this exciting mission, be sure to read the interviews conducted with Ross and Nagel, available on the JSC History Portal.
Jennifer Ross-Nazzal