Hubble Space Telescope Gets New "Brain" And Guidance Sensor

Flight controllers said all major activities of the space walk, the second of three on consecutive days of Discovery’s space telescope repair and improvement mission, had been accomplished. Controllers reported that power was reaching both of the new pieces of equipment.

“The brains of Hubble have been replaced,” said Mission Specialist John Grunsfeld, who worked Thursday in Discovery’s cabin with the space-walking crew members outside. About 30 minutes later Hubble began thinking with those new brains. At an evening mission status briefing, John Campbell, Hubble Space Telescope program manager, said the functional checkout of the new computer showed it was functioning well. Checkout of the Fine Guidance Sensor, is continuing.

The length of Thursday’s space walk made it the third longest in history, behind only the 8-hour, 15-minute effort on Wednesday by Payload Commander Steve Smith and Grunsfeld and an 8-hour, 29-minute space walk by three Endeavor astronauts on STS-49 on its Intelsat rescue mission in May 1992.

Replacement of one of Hubble’s two S-band transmitters is a highlight of Friday’s space walk by Smith and Grunsfeld. The transmitter to be replaced had failed. The second transmitter was able to carry the load alone, so no science was lost. The transmitters are considered very reliable, and unlike most of the equipment aboard Hubble, they were not designed to be changed out in orbit. Special tools were developed to enable astronauts to do the job more easily. Installation of a Solid State Recorder to replace a less reliable and less capable 10-year-old recorder is the second major item on the schedule.

Also on the timeline of the space walk, scheduled to begin at 1:50 p.m. CST, is installation of new insulation on equipment bay doors. The spacewalk could, like its two predecessors on STS-103, begin earlier if the crew completes preparations early. Flight controllers are anxious to end this third space walk at 8 p.m. as scheduled.

Discovery remains is in excellent condition, in an orbit with a high point of 380 statute miles and a low point of 364 miles. The next status report will be issued at 11 a.m. Friday, or as events warrant.