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From: starrfie@hydro.la.asu.edu (Sumner Starrfield) Subject: HST Repair News: saturday and sunday morning Date: Sun, 5 Dec 93 9:45:37 MST Mission Control Center STS-61 Status Report #6 Saturday, December 4, 1993, 6 p.m. CST With the Hubble Space Telescope firmly anchored in Endeavour's payload bay, the seven-member crew was awakened at 5:57 p.m. CST to make ready for the first of five planned space walks. Flight controllers uplinked the song "Fanfare for the Common Man" by Aaron Copeland to start the day for Commander Dick Covey, Pilot Ken Bowersox and Mission Specialists Tom Akers, Jeff Hoffman, Story Musgrave, Claude Nicollier and Kathy Thornton. Musgrave and Hoffman are scheduled to step out of the orbiter's airlock at about 10:52 p.m. CST, but the six-hour space walk could begin as early as 10 p.m. if onboard preparations allow. The primary tasks for the first space walk are the replacement of the two gyroscope rate sensor unit packages, two electronic control units and eight fuse plugs that protect HST electrical circuits. At the start of the space walk, Musgrave and Hoffman will secure HST for the in-space work week by installing protective covers on the aft low gain antenna and exposed voltage bearing connector covers. At the end, they will set up the payload bay for Akers and Thornton, who will replace the two solar arrays the following day. At midnight, controllers at the Space Telescope Operations Control Center at the Goddard Space Flight Center will prepare the telescope for servicing by powering down rate sensor units 2 and 3 and disabling their heaters. At 3:50 a.m., they will turn off elements of the observatory that are powered through fuse plugs that will be replaced; those elements will be powered up again at 4:30 a.m. After the rate sensor units are replaced, controllers will check whether they are "alive" at 4:40 a.m. Functional testing of all the telescope's gyros will begin at 8:27 a.m., and functional testing of the fuse plugs will begin at 11:10 a.m. The STOCC will start the 73-minute-long retraction of the two solar arrays at 6:10 a.m. During a post-grapple survey of the telescope with the shuttle's robot arm cameras, the crew pointed out significant bowing and a kink in one of the bi-stem frame supports. The European Space Agency-built solar arrays are expected to retract in spite of the deformities, said Derek Eaton, ESA's project manager. All of Endeavour's systems continue to perform well as the shuttle circles the Earth every 95 minutes in a 320 by 313 nautical mile orbit. Mission Control Center STS-61 Status Report #7 Sunday, December 5, 1993, 7 a.m. CST Spacewalking STS-61 crew members Story Musgrave and Jeff Hoffman completed several servicing tasks and wrestled with balky gyro doors on the Hubble Space Telescope early Sunday morning during this mission's first of five ambitious spacewalks. Musgrave and Hoffman began their spacewalk about an hour earlier than scheduled by stepping out into the cargo bay about 9:44 p.m CST Saturday. The two astronauts, who both are veteran spacewalkers, meticulously stepped through their assigned servicing tasks on the HST, which is anchored in the Space Shuttle Endeavour's cargo bay. After leaving the airlock and moving into the cargo bay, the duo prepared the telescope, which towered above them, for a week full of work by installing protective covers on the aft low gain antenna and exposed voltage bearing connector covers. During the seven hour and 54 minute spacewalk, Musgrave and Hoffman successfully changed out the rate sensing units and the electronics control unit. The RSUs are pairs of gyroscopes on the telescope which are required to point and track HST. The astronauts also changed out eight fuse plugs that protect the telescope's electrical circuits. Hubble now has a full set of six healthy gyroscopes. The astronauts struggled with the latches on the gyro door when two of four gyro door bolts did not reset after the astronauts installed two new gyro packages. Engineers who evaluated the situation speculated that when the doors were unlatched and opened, a temperature change might have caused them to expand or contract enough to keep the bolts from being reset. With the efforts of determined astronauts in Endeavour's payload bay and persistent engineers on the ground, all four bolts finally latched and locked after the two spacewalkers worked simultaneously at the top and bottom of the doors. Musgrave anchored himself at the bottom of the doors with a payload retention device which enabled him to use some body force against the doors. Hoffman, who was attached to the robot arm, worked at the top of the doors. The duo successfully latched the doors when they simultaneously latched the top and bottom latches. The spacewalkers also set up the payload bay for mission specialists Tom Akers and Kathy Thornton who will replace the telescope's two solar arrays during the second spacewalk scheduled to begin at 10:52 p.m. CST today. The solar arrays provide power to the telescope. In anticipation of that spacewalk, Musgrave and Hoffman prepared the solar array carrier which is located in the forward portion of the cargo bay, and attached a foot restraint on the telescope to assist in the solar array replacement. Musgrave and Hoffman's spacewalk became the second longest spacewalk in NASA history. The longest spacewalk occurred on STS-49 in May 1992 during Endeavour's maiden flight. Spacewalking crew members during that flight were Tom Akers, Richard Hieb and Pierre Thuot. All of Endeavour's systems continue to perform well as the shuttle circles the Earth every 95 minutes in a 320 by 313 nautical mile orbit.
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