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Three down, two to go

NASA OKs fifth spacewalk for Discovery crew

Space walk

February 16, 1997
Web posted at: 10:45 a.m. EST

In this story:

JOHNSON SPACE CENTER (CNN) -- They dodged space debris flying at them at 17,500 miles per hour, weathered a glitch in an astronaut's spacesuit, and deftly installed equipment that was never designed to be handled by bulky space gloves.

They even took time out to enjoy some of the most spectacular pictures of their home planet taken from an orbiting shuttle, and send messages to loved ones several hundred miles below.

All in a day's work for the shuttle Discovery and its spacewalking telescope repair crew -- but the trickiest task is yet to come. In a galactic conference call early Sunday morning, the shuttle's crew told NASA mission managers they wanted an additional spacewalk to repair some unexpected damage to the Hubble Space Telescope's protective insulation.

NASA was surprised by the extent of damage -- not seen during the last repair trip to Hubble in 1993 -- to the Teflon foil that protects the $2 billion telescope from extreme temperatures in space. The material is ripped and cracked badly in places, and engineers fear pieces could tear loose and contaminate the telescope's delicate optics.

"Basically this thing is just falling apart, cracking all over the place," astronaut Mark Lee told mission control while inspecting the damage on spacewalk No. 3 Saturday night. Lee tried to tape a crack, but the adhesive didn't hold.

"It barely sticks," he said. "It doesn't do anything."

Lee and his spacewalking partner Steve Smith will make Discovery's fifth spacewalk early Tuesday morning, and will try a complicated series of repairs to prevent the cracked insulation from flaking off the telescope.

One procedure calls for the astronauts to install a wire mesh around two of the telescope's equipment bays, and another involves using long poles to rig an insulation blanket around a larger part of the telescope.

Discovery's crew will manufacture the repair materials from supplies aboard the shuttle.

Dodging space junk, then on to the 'mundane' repair work

Astronauts

Saturday began with an evasive action procedure of sorts -- a few hours after Commander Ken Bowersox had nudged the shuttle and its telescope cargo into an orbit two miles further from the incessant tug of Earth's atmosphere, NASA told him to boost it another half mile up.

The problem was an 8-inch square piece of an exploded rocket bearing down on the shuttle at 17,500 miles per hour. The debris, part of a Pegasus rocket launched in 1994 with a military research satellite aboard, was expected to pass within a half-mile of the orbiting shuttle and telescope, but mission managers wanted no chance of a collision.

Discovery will lift the Hubble another 2 miles before the end of this mission, settling the telescope into an orbit 375 miles away from the surface of the planet.

Lee

Saturday night's spacewalk, the third of a planned four, was delayed because of a glitch in the computer of Lee's $10.4 million spacesuit, but a reboot apparently solved the problem, and the astronauts -- anxious to get to work -- stepped into Discovery's open cargo bay.

Lee and Smith completed three upgrade tasks to the telescope, including the challenging replacement of a data interface unit that allows the various parts of Hubble to "talk" with one another.


Astronaut Story Musgrave, who orchestrated
the first Hubble repair three years ago, describes
wearing and moving around in a spacesuit
icon (23 sec./250K AIFF or WAV sound)
icon (45 sec./488K AIFF or WAV sound)

The job was made difficult by 18 separate cable connections needed to complete the installation, handled expertly by Lee despite the bulky spacesuit gloves.

Tape recorder

"Great hands, Mark," mission control's Jeff Hoffman told the astronaut when he finished.
icon (220K/20 sec. AIFF or WAV sound)

Lee and Smith also swapped a 1970s vintage analog data recorder with a new digital model, and replaced a wheel mechanism used to aim the telescope. The astronauts had to use a little extra power from an electric wrench when bolts holding the wheel assembly to the telescope refused to budge.



movie icon (653K/15 sec. Small frame QuickTime movie)

movie icon (1.6M/15 sec. Large frame QuickTime movie)


Lee also took a moment to send a long distance greeting to his wife, astronaut Jan Davis. icon (87K/8 sec. AIFF or WAV sound)

Two more spacewalks to go

Observatory

Joe Tanner, who took his first steps in space Friday night, and Greg Harbaugh are set to take the crew's fourth repair trip to Hubble Sunday night. The two, who easily replaced a guidance sensor the size of a baby grand piano during their first walk, will replace two more old telescope components, finishing Discovery's original repair mission.

Tanner and Harbaugh will also begin the insulation repair work.

Mission control added the fifth walk after Bowersox said he preferred that the scheduled spacewalks take place as planned. Managers considered delaying the fourth walk by a day, but settled on the additional time in space.

The crew was to redeploy Hubble on Monday, but that will be delayed until Tuesday. Discovery is still on schedule to return to Earth Friday.

Correspondent John Holliman and Reuters contributed to this report.

 
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