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STS-61

Endeavour launched from Kennedy Space Center on December 2, 1993 at 4:27 AM EST and landed at Kennedy on December 13 at 12:25 AM EST. The shuttle orbited 163 times at an altitude of 321 nautical miles at an inclination of 28.45 degrees and travelled 4.4 million miles. The mission lasted 10 days, 19 hours, 58 minutes, and 37 seconds.

This was the first mission to repair and maintain the Hubble Space Telescope. It involved the second longest spacewalk to date at nearly 8 hours.

The final shuttle flight of 1993 was one of most challenging and complex manned missions ever attempted. During a record five back-to-back space walks totaling 35 hours and 28 minutes, two teams of astronauts completed the first servicing of the Hubble Space Telescope (HST). In many instances, tasks were completed sooner than expected and the few contingencies that did arise were handled smoothly.

Hubble rendezvous, grapple and berthing occurred on flight day three, with Nicollier using the remote manipulator system arm to position the 43-foot (13-meter) long Hubble upright in payload bay. Throughout mission, commands to Hubble issued from Space Telescope Operations Control Center (STOCC) at Goddard Space Flight Center. After each servicing task was completed, STOCC controllers verified electrical interfaces between replacement hardware and telescope.

On flight day four, first EVA team of Musgrave and Hoffman performed EVA #1, replacing two Rate Sensing Units (RSUs), each housing pair of gyroscopes; two Electronic Control Units which direct the RSUs; and eight electrical fuse plugs. The only unexpected problem occurred when Hoffman and Musgrave had difficulty closing compartment doors after replacing the RSUs. This was a 7 hour, 54-minute space walk second longest in U.S. history to date, topped only by STS-49 EVA lasting eight hours, 29 minutes. During EVAs, Nicollier operated a robot arm carrying one of two EVA crew members.

Installation of new solar arrayswas accomplished during EVA #2, performed on flight day five by Thornton and Akers and lasting six hours, 35 minutes. Timeline was re-worked to accommodate jettison of one of two original solar arrays, which could not be fully retracted due to kink in framework. Other solar array stowed in payload bay and the replacement pair were installed without difficulty.

The expected four-hour replacement of one of Hubble’s five scientific instruments, Wide Field/Planetary Camera (WF/PC), completed in about 40 minutes by Hoffman and Musgrave during EVA #3 on flight day six. Also, two new magnetometers were installed at top of telescope during the six-hour, 48-minute EVA.

EVA #4 was performed on flight day seven by Thornton and Akers. The High-Speed Photometer, one of Hubble scientific instruments, was removed and replaced with Corrective Optics Space Telescope Axial Replacement (COSTAR) unit. The task took less time to complete than expected. COSTAR was designed to redirect light to three of four remaining Hubble instruments to compensate for a flaw in the primary mirror of telescope. Thornton and Akers also installed a co-processor to enhance memory and speed of Hubble computer.

During a six-hour, 50- minute EVA, Akers set new U.S. cumulative space-walking record of 29 hours, 39 minutes, topping Eugene Cernan’s 20-year-old record of 24 hours, 14 minutes.

The final EVA was performed by Hoffman and Musgrave on flight day eight. During the seven-hour, 21-minute-long EVA #5, Hoffman and Musgrave replaced Solar Array Drive Electronics (SADE) unit and installed Goddard High Resolution Spectrograph Redundancy (GHRS) kit and installed two protective covers over original magnetometers. After space walk completed, the new solar arrays and two high-gain antennas were deployed by STOCC. HST was re-boosted to a slightly higher orbit of 321 nautical miles (595 kilometers) on flight day eight prior to the last EVA.

Hubble was redeployed on flight day nine. Release was delayed several hours to allow troubleshooting of erratic data telemetry from Hubble subsystems monitor; problem had occurred before and was not related to servicing. President Clinton and Vice President Gore congratulated crew, and the Swiss Minister of Internal Affairs called the following day to congratulate Nicollier.

Endeavour was crewed by Commander Richard O. Covey, Pilot Kenneth D. Bowersox, and Mission Specialists Kathryn C. Thornton, Claude Nicollier (Switzerland), Jeffrey A. Hoffman, and Tom Akers.

STS-61


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