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NASA considers, rejects record sixth shuttle spacewalk
Discovery's return still set for Friday
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February 18, 1997
Web posted at: 5:00 a.m. EST (1000 GMT)(CNN) -- NASA briefly considered -- but decided against -- a record sixth spacewalk Tuesday for the shuttle Discovery astronauts after a possible glitch appeared in the Hubble Space Telescope's steering system.
Astronauts Mark Lee and Steve Smith had just finished repairing the Hubble's torn outer insulation in a three-hour operation when NASA officials notified them of the new problem.
Astronauts on spacewalk put blankets on Hubble 
403K/7 sec. small QuickTime movie 1.3MB/7 sec. large QuickTime movie One of four devices called a reaction wheel, used to maneuver the orbiting telescope, was performing sluggishly and NASA debated whether to replace it.
The shuttle is carrying a spare reaction wheel as a backup for a previously planned reaction wheel replacement that took place over the weekend. The wheel that acted up Tuesday was not the newly installed wheel.
But engineers decided the suspect reaction wheel was healthy.
"We just completed a test on reaction wheel No. 2. It's good," Mission Control told the astronauts after three hours of testing the unit.
Coming home
The release of the spacecraft from shuttle repair platform to free flight is scheduled for 1:41 a.m. EST Wednesday. Discovery is scheduled to return to Florida on Friday.
The replacement would have required another venture into the cargo bay by two spacewalkers. Instead, Mission Control gave the OK for the final step in the Hubble upgrade procedure, raising its orbit by about 10 miles.
Mission Control had decided an added day in orbit for the seven Discovery astronauts was out of the question. There is fuel for an extra two days that would be reserved for a shuttle emergency, such as bad landing weather.
The big job Monday night and early Tuesday was repairing the tattered Hubble foil-shielding. Lee and Smith used ropes, clips and wire to fasten reflective insulation over rips in the Hubble's protective cover.
Scientists at NASA believe the unforeseen wear and tear on the orbiting platform's insulation is the result of solar radiation.
As they orbited over 350 miles above the earth in the mission's fifth spacewalk, Lee and Smith used six 9-inch-by-16-inch sections of material to cover breaks in the insulation that NASA feared might endanger sensitive Hubble electronics.
A frustrating job
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Working much of the time in darkness with only suit-mounted lights for illumination, Lee found the chore so frustrating that he twice cursed audibly.
NASA plans a more permanent fix during the next service call in three years. The astronauts snipped off a piece of the damaged insulation to bring back home for analysis.
A surprise met Lee and Smith at the conclusion of their Hubble patch job. Before entering the shuttle they inspected the section of Hubble that astronauts are scheduled to work on in three years during the next shuttle service mission.
Aluminum handrails originally painted yellow had turned different shades, while some had even begun to crack and peel. Although not an immediate threat to the Hubble, the flaking is one more indication of the inhospitable nature of space.
CNN's John Holliman asked Ed Weiler, a NASA scientist, Tuesday morning what factors were most likely to determine the telescope's life span.
Weiler focused on earth-bound factors rather than mechanical problems in orbit. The scientist said that although Hubble's original planned life was 15 years, the telescope would operate as long as the science being produced was valuable and the shuttle was flying to service the platform.
CNN's John Holliman, The Associated Press and Reuters contributed to this report.
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- Astronauts complete fourth spacewalk - February 17, 1997
- Three down, two to go - February 16, 1997
- Astronauts dodge space junk for third spacewalk - February 16, 1997
- Astronaut savors first walk in space - February 15, 1997
- Spacewalkers get to work on Hubble tuneup - February 14, 1997
- 'It's a beautiful sight' - February 13, 1997
- Shuttle Discovery blasts off on Hubble service mission - February 11, 1997
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- Johnson Space Center Shuttle Countdown STS-82
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