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Astronauts step out for second spacewalk
February 15, 1997
Web posted at: 5:00 a.m. EST (1000 GMT)JOHNSON SPACE CENTER, Texas (CNN) -- The keen-eyed Hubble Space Telescope was upgraded Saturday with an instrument so sensitive it can spot an airplane flying a continent away by merely tracking the motion of its landing light.
The new guidance sensor, a collection of mirrors and lenses that locate a target star and point the huge telescope, replaced one that was nearing the end of its life.
Working in the dark much of the time, their work site illuminated mostly by floodlights built into their helmets, astronauts Joe Tanner and Gregory Harbaugh installed the 465-pound instrument -- the size of a baby grand piano -- with apparent ease. The job of removing the old and inserting the new took about three hours.
"We would end up doing this at night, wouldn't we Greg?" said Tanner.
"Oh sure," said Harbaugh. "Anybody can do it in the daytime."
They could have avoided doing the job during a nighttime pass, but, in their eagerness to start, they began the spacewalk an hour ahead of schedule. The space shuttle Discovery circles Earth once every 90 minutes -- nearly half the time in daylight, half in darkness -- with flashes of dawn and dusk in between.
Tanner and Harbaugh began their spacewalk by taking a different route out of the shuttle to avoid Friday night's unexpected twists and turns of the telescope's solar panels when the shuttle's airlock was depressurized. Once outside, the astronauts were treated to the glorious sight of the Earth circling at 5 miles a second below them.
"Welcome to space," mission control's Jeff Hoffman radioed to Tanner, who was making his first spacewalk. "It's nice seeing a big smile on your face. Have a good one."
New pictures
Once the new guidance sensor was in place, the world got to see what astronaut Story Musgrave called the best pictures ever of an astronaut doing work. His image mirrored on the Hubble's side, Tanner used NASA's version of an electric drill to seal the compartment on the telescope where the fine guidance sensor will operate.
The astronauts, making the second spacewalk of the Hubble renovation, noted that the telescope's insulation had long, spiderlike cracks. The damage wasn't there three years ago during the first repair mission.
Their next step was to install a new guidance sensor needed to lock onto astronomical targets. The device -- one of three -- provides incredible pointing stability, comparable to holding a laser beam focused on a dime 200 miles away, about the distance between Washington and New York.
Other Hubble parts to be installed by Harbaugh and Tanner in the open cargo bay: an electronic package for the sensor and a new data recorder.
Both men ended up with smudges of yellow paint on their pressurized gloves, as did Discovery's first spacewalking duo. The paint was from shuttle handrails, used by the astronauts to steady themselves outside.
Meanwhile, in the cockpit, the pilots planned to boost the shuttle into a slightly higher orbit in which Hubble will be released early next week.
Equipment upgrades
During the first spacewalk Thursday, astronauts Mark Lee and Steven Smith plugged two new science instruments into Hubble to expand its vision of the cosmos.
Lee and Smith turned in a by-the-book performance 370 miles above Earth during the first of four spacewalks to modernize the $2 billion Hubble, which was launched in 1990.
The new instruments -- a spectrograph with two-dimensional detectors and a near-infrared camera -- should be 30 to 40 times more efficient and powerful than the old ones, and allow astronomers to peer back into the universe practically to the beginning of time.
"One-hundred percent successful," Hoffman told the crew. "Great way to start."
Lee and Smith ventured outside the shuttle late Thursday night and spent 6 1/2 hours with the shimmering Hubble, using top-of-the-line power tools as well as old-fashioned muscle power to replace two 1970s-era spectrographs with modern gear.
"From an astronomical point of view, it is almost impossible to imagine the Hubble Space Telescope being any better than it's been for the last three years, but you guys have made it so," said Hoffman, an astronaut-astronomer who took part in the 1993 mission to fix Hubble's blurred vision.
The two new components passed initial electrical tests. But it will be several weeks before astronomers know for sure whether the instruments are working properly. NASA hopes to release the first improved images in early May.
Lee and Smith will go back out Saturday night to install more Hubble parts. Harbaugh and Tanner will wrap up the work Sunday night during spacewalk No. 4.
Correspondent John Holliman and the Associated Press contributed to this report.
Special sections:
CNN Interactive's extended coverageRelated stories:
- Spacewalkers get to work on Hubble tuneup - February 14, 1997
- Delayed Hubble spacewalk begins - February 14, 1997
- 'It's a beautiful sight' - February 13, 1997
- Shuttle Discovery blasts off on Hubble service mission - February 11, 1997
- Anxious NASA officials watch high readings on shuttle - February 10, 1997
- NASA looks for oxygen leak; shuttle liftoff still on schedul - February 9, 1997
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- Hubble Space Telescope Science
- Johnson Space Center Shuttle Countdown STS-82
- Space Station Mir Info Page
- Tracking the mission
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