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35 Years Ago: STS-41G – A Flight of Many Firsts

The 13th flight of the Space Shuttle program, STS-41G was notable for many firsts and records. It was the first mission focused almost entirely on studying the Earth through the use of a satellite, multiple instruments and cameras, as well as crew observations to accomplish these goals. The crew of STS-41G also set several firsts. The Commander, Robert L. Crippen, became the first astronaut to make a fourth flight aboard the Space Shuttle. He did so only 5½ months after returning from his previous mission, STS-41C, becoming the first American to make two trips into space in one calendar year and the first to fly back-to-back missions on the same orbiter. The Pilot, Jon A. McBride, was making his first flight into space. The three Mission Specialists were Kathryn D. Sullivan, Sally K. Ride, and David C. Leestma. This marked the first time that two women flew in space at the same time, with Ride becoming the first American woman to fly a second mission and Sullivan the first American woman to conduct an Extravehicular Activity (EVA), or spacewalk. Leestma was the first of the astronaut class of 1980 to make a space flight. The two Payload Specialists, Marc Garneau, the first Canadian in space, and Paul D. Scully-Power, a civilian employee of the US Naval Research Laboratory and the first oceanographer and the first Australian-born American citizen to fly in space, rounded out the seven-member crew, the largest crew flown to that time.

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Left: STS-41G crew patch. Right: STS-41G crew photo (front, left to right): McBride,
Ride, Sullivan, and Leestma; (back, left to right) Scully-Power, Crippen, and Garneau.

The Earth Radiation Budget Satellite (ERBS), managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, contained three instruments to measure solar and thermal radiation of the Earth in an effort to better understand global changes in climate. NASA’s Office of Space and Terrestrial Applications sponsored a cargo bay-mounted payload (OSTA-3) consisting of four instruments. Managed by the Jet Propulsion Laboratory in Pasadena, California, the Shuttle Imaging Radar-B (SIR-B), an updated version of SIR-A flown on STS-2, used synthetic aperture radar to support investigations in diverse disciplines such as archaeology, geology, cartography, oceanography, and vegetation studies. Making its first flight into space, the 900-pound Large Format Camera (LFC) took images of selected Earth targets on 9-by-18-inch film with 70-foot resolution. The Measurement of Air Pollution from Satellites (MAPS) experiment provided information about industrial pollutants in the atmosphere. The Feature Identification and Location Experiment (FILE) contained two television cameras to improve the efficiency of future remote sensing equipment. In an orbit inclined 57 degrees to the Equator, the instruments aboard the Space Shuttle Challenger could observe more than 75% of the Earth’s surface. 

The Orbital Refueling System (ORS), managed by the Johnson Space Center in Houston, was not directly an Earth observation payload, but it was designed to assess the feasibility of conducting an on-orbit refueling of the Landsat-4 remote sensing satellite, then planned to take place in 1987, as well as Department of Defense satellites that were not designed for on-orbit refueling. In the demonstration, the astronauts remotely controlled the transfer of hydrazine, a highly toxic fuel, between two tanks mounted in the payload bay. During a spacewalk, two crewmembers simulated connecting the refueling system to a satellite and later tested the connection with another remotely controlled fuel transfer. Rounding out the payload activities, the large format IMAX camera made its third trip into space, with footage used to produce the film The Dream is Alive.

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Left and middle: Two views of the launch of Challenger on the STS-41G mission.
Right: ERBS just before the RMS released it.

Space Shuttle Challenger roared off Launch Pad 39A 15 minutes before sunrise on Oct. 5, 1984, to begin the STS-41G mission. The launch took place just 30 days after the landing of the previous mission, STS-41D. That record-breaking turnaround time between Shuttle flights didn’t last long, as it was broken just 26 days after Challenger’s landing with the launch of Discovery on STS-51A. Eight and a half minutes after liftoff, Challenger and its seven-member crew were in space and shortly thereafter settled into a 218-mile high orbit, ideal for the deployment of the 5,087-pound ERBS. The crew noted that a 40-inch strip of Flexible Reusable Surface Insulation (FRSI) was missing from the right hand Orbiter Maneuvering System (OMS) pod, presumably lost during launch. Mission Control determined that this would not have any impact during reentry.

Ride grappled the ERBS with the Shuttle’s Canadian-built Remote Manipulator System (RMS) or robot arm but when she commanded the satellite to deploy its solar arrays, nothing happened. Mission Control surmised that the hinges on the arrays had frozen, and after Ride oriented the satellite into direct sunlight and shook it slightly on the end of the arm, the panels deployed. She released ERBS about two and a half hours late and McBride fired Challenger’s steering jets to pull away from the satellite. Its onboard thrusters boosted ERBS into its operational 380-mile high orbit. With an expected two-year lifetime, it actually operated until October 14, 2005, returning data about how the Earth’s atmosphere absorbs and re-radiates the Sun’s energy, contributing significant information about global climate change.

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Left: The SIR-B panel being opened in Challenger’s payload bay.
Right: McBride with the IMAX camera in the middeck. 

Near the end of their first day in space, the astronauts opened the panels of the SIR-B antenna and activated it, also deploying the Ku-band antenna that Challenger used to communicate with the Tracking and Data Relay System (TDRS) satellite. The SIR-B required a working Ku-band antenna to downlink the large volume of data it collected, although it could store a limited amount on onboard tape recorders. But after about two minutes, the data stream to the ground stopped. One of the two motors that steered the Ku antenna failed and it could no longer point to the TDRS satellite. Mission Control devised a workaround to fix the Ku antenna in one position and steer the orbiter to point it to the TDRS satellite and downlink the stored data to the ground. Challenger carried sufficient fuel for all the maneuvering, but the extra time for the attitude changes resulted in achieving only about 40% of the planned data takes. Among the SIR-B discoveries was the 3,000-year old lost city of Udar in the desert of Oman.

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Left: Patch for Garneau’s mission. Right: Spiral eddies in the eastern Mediterranean Sea.

During the second mission day, the astronauts lowered Challenger’s orbit to an intermediate altitude of 151 miles. Flight rules required that the SIR-B antenna be stowed for such maneuvers but the latches to clamp the antenna closed failed to activate. Ride used the RMS to nudge the antenna panel closed. From the orbiter’s flight deck, Leestma successfully completed the first ORS remote-controlled hydrazine fuel transfer. Garneau began working on his ten CANEX investigations related to medical, atmospheric, climatic, materials and robotic sciences while Scully-Power initiated his oceanographic observations. Despite greater than expected global cloud cover, he successfully photographed spiral eddies in the world’s oceans, particularly notable in the eastern Mediterranean Sea.

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Left: Sullivan (left) and Ride on Challenger’s flight deck. Right: Garneau and Scully-Power
working on a Canadian experiment in
Challenger’s middeck.

The third day saw the crew lower Challenger’s orbit to 140 miles, the optimal altitude for SIR-B and the other Earth observing instruments. For the next few days, all the experiments continued recording their data, including Garneau’s CANEX and Scully-Power’s oceanography studies. Leestma completed several scheduled ORS fuel transfers prior to the spacewalk.  Preparations for that activity began on flight day 6 with the crew lowering the cabin pressure inside Challenger from the normal sea level 14.7 pounds per square inch (psi) to 10.2 psi. This was done to prevent the buildup of nitrogen bubbles in the bloodstreams of the two EVA crewmembers, Leestma and Sullivan, that could result in the development of the bends. The two verified the readiness of their spacesuits.

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Left: Leestma (at left, with red stripes on his suit) and Sullivan during their EVA.
Right: Traditional inflight photo of the STS-41G crew (front, left to right) McBride, Ride, Sullivan, and
Leestma, (back, left to right) Scully-Power, Crippen, and Garneau.

On flight day 7, Leestma and Sullivan, assisted by McBride, donned their spacesuits and began their EVA. After gathering their tools, the two translated down to the rear of the cargo bay where the ORS was positioned. With Sullivan documenting and assisting with the activity, Leestma installed the valve assembly into the simulated Landsat propulsion plumbing. Having completed the ORS objectives, Leestma and Sullivan proceeded back toward the airlock, stopping first at the Ku antenna where Sullivan secured it in place. They returned inside after an EVA that lasted 3 hours and 29 minutes. After the conclusion of the EVA, the crew brought Challenger’s cabin pressure back up to 14.7 psi.

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Left: Space Shuttle Challenger landing at KSC at the end of the STS-41G mission.
Right: The crew of STS-41G descends from
Challenger after completing a highly successful mission.

During their final full day in space, Challenger’s crew tidied the cabin for reentry and completed the final SIR-B and other Earth observations. On Oct. 13, the astronauts closed the payload bay doors and fired the OMS engines over Australia to begin the descent back to Earth. Because of the mission’s 57-degree inclination, the reentry path took Challenger and its crew over the eastern United States, another Shuttle first. Crippen guided the orbiter to a smooth landing at KSC, completing a flight of 8 days, 5 hours, and 24 minutes. The crew had traveled nearly 3.3 million miles and completed 133 orbits around the Earth.

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Left: Missing insulation from Challenger’s right hand OMS pod as seen after landing. Middle: Missing tile from Challenger’s left wing.
Right: Damage to tiles on
Challenger’s left wing.

As noted above, on the mission’s first day in space the crew described a missing strip of FRSI from the right hand OMS pod. Additional damage to Challenger’s Thermal Protection System (TPS) was discovered after the landing. Several tiles on the underside the vehicle’s left wing were damaged and one tile was missing entirely, presumably lost during the reentry phase. Engineers found the culprit for the missing tile to be the water proofing that was used throughout the TPS that allowed debonding of the tiles. To correct the problem, workers removed and replaced over 4,000 tiles, adding a new water proofing agent to preclude the recurrence of the problem on future missions.

Read recollections of the STS-41G mission by Crippen, McBride, Sullivan, Ride, and Leestma in their oral histories with the JSC History Office. Enjoy the crew’s narration of a video about the STS-41G mission.