Astronauts finish repairs on Hubble

December 09, 1993|By Ann LoLordo | Ann LoLordo,Staff Writer

The Hubble Space Telescope repair team concluded its fifth and final space walk today, a servicing stop dominated by the nuts and bolts of space mechanics and a little screw that almost got away.

In slightly more than 7 hours and 21 minutes, astronauts F. Story Musgrave and Jeffrey A. Hoffman finished the last repairs on NASA's $1.6 billion telescope, packed up their tools and closed out the servicing end of the mission with yet another flawless, though taxing, performance.

With Hubble's new tangerine-colored solar panels unfurled, Hubble was set to be returned to orbit tomorrow. Before the shuttle Endeavour lets go of the telescope, a command will be sent to reopen the Hubble's aperture door.

"I bet there are some smiles up there right now," mission control specialist Greg Harbaugh said to the crew. "We all have big grins down here."

But after a night he likened to riding "a roller coaster," Milt Heflin, the lead flight director, wanted to reserve his enthusiasm for a successful deployment of the telescope and safe journey home for the crew.

"It's not over 'til it's over," said Mr. Heflin, who had been anxious about today's spacewalk and a perceived problem with the telescope's computer. "It's not over and I refuse to get too excited too early."

During a spacewalk that began at 10:30 last night, Mr. Musgrave and Mr. Hoffman installed a new electronics unit that drives the position of the telescope's solar panels, put in a backup power supply for the telescope's spectrograph and used a special tool to manually lower the arms of the solar panels.

They fit new covers -- fashioned from pieces of insulation and handmade yesterday inside the shuttle -- onto two sensor boxes atop the telescope to prevent exposed foam from possibly contaminating Hubble's mirrors. The covering of one of the boxes fell apart in Mr. Hoffman's hands during an earlier &L spacewalk.

By last night, the mission's most complex repairs had been executed with precision and speed. The astronauts installed two optics packages to correct the flaw in Hubble's misshapen mirror; replaced two pairs of gyroscopes that point the telescope and the solar panels; expanded the memory and speed of the telescope's on-board computer; and replaced two magnetometers, which help guide the telescope by measuring Earth's magnetic field.

The completion of five spacewalks -- a record in the 12-year history of the shuttle program -- and the successful work undertaken should go a long way toward proving man's ability to repair satellites in space and boost NASA's plan to build a manned space station.

"You guys have pretty much done it all up there," Mr. Harbaugh, of mission control, told the crew.

It's been a remarkable week for the seven-member crew of Endeavour, especially its four spacewalkers, whose high-flying acrobatics often were played out against a backdrop of the spinning blue Earth. Before the Dec. 2 launch, the mission to repair Hubble's blurred vision had been billed as the most complex manned space project since the Apollo moon landings. But the ease with which the astronauts installed sensitive equipment and repaired key operational components of the telescope made it seem as routine as changing the oil in a car.

Tethered to the shuttle's mechanical arm, or perched from it, the astronauts performed their tasks with unqualified precision. The details of the mission were choreographed to the number of turns it took to twist off a particular bolt.

Working in pairs, they moved across Hubble's mirrored surface and up and down its 43-foot length in the slow motion of space. Three hundred and sixty miles above the Earth, the astronauts repaired NASA's observatory while the shuttle cruised at 17,000 miles a minute.

They worked in the heat of the sun and the glare of a night spotlight shining through the window in Endeavour's cabin. They also added to the estimated 6,700 pieces of space junk when Astronaut Kathryn "KT" Thornton tossed a damaged solar panel from the top of Hubble, rather than cart it home.

While the complicated tasks of the mission were completed earlier in the mission, the final fix to Hubble today posed its own unique problems.

The installation of a new solar electronics drive unit was a tedious task that took twice as long as expected to finish. It involved securing a connector with screws that are less than a half inch long while wearing a thick, clumsy space suit glove.

"Sorry it took so long," Mr. Musgrave said to mission control in Houston as the duo finished up. "I gave it my best shot. These little tiny screws . . . "

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