CAPE CANAVERAL, Fla. -- Spacewalking NASA astronauts took a giant step toward reviving the Hubble Space Telescope's sightless infrared eyes Friday, outfitting the observatory with an experimental refrigerator designed to resuscitate a comatose camera.

What's Next: Tomorrow in Space

Shuttle Columbia's astronauts will cast the renovated Hubble Space Telescope back into orbit Saturday before heading off on a three-day trip back to Earth. Now mounted on a shuttle cargo bay work stand, the 13-ton observatory will be deployed around 5 a.m. EST (1000 GMT) as Columbia flies high over the Atlantic Ocean. A pair of shuttle engine firings will follow, propelling the spaceship and its six-man, one-woman crew toward a 4:30 a.m. EST (0930 GMT) landing Tuesday at Kennedy Space Center. Click here for mission updates and live NASA TV coverage beginning at 4 a.m. EST (0600 GMT) Saturday.

Amid the most exacting plumbing job ever attempted in orbit, John Grunsfeld and Rick Linnehan bolted the new cryogenic cooler inside Hubble and hung a huge radiator outside the observatory.

To hook them up, stiff power and coolant lines were threaded through a small Hubble vent hole, but another six weeks of testing will be required before NASA knows whether the camera can be brought back from the dead.

Said Hubble project scientist Ed Cheng: "The team certainly hasn't let down its guard yet, because we have a very exciting couple of months to follow."

The seven astronauts aboard Columbia, nevertheless, were ecstatic.

After all, the crew already had pulled off chancy transplant surgery on the electrical heart of Hubble, and the astronauts also equipped it with two new solar wings and the most powerful planetary camera ever launched into orbit.

"We've given Hubble a new power system that will take it off into the next decade of discovery. We've given it new eyes to see deeper into the universe than it's ever been able to see before," Grunsfeld said.

"The best word that I can think of to describe this servicing mission is awesome," added NASA Hubble Project Manager Preston Burch. "That's like in, totally awesome, dude."

Coming at the tail end of a $172 million Hubble overhaul, the fifth and final spacewalk for Columbia's crew got underway at 3:46 a.m. EST (0846 GMT) as the ship cruised 362 miles (579 kilometers) above South Africa.

With the four-story telescope mounted to a cargo bay work stand, Grunsfeld and Linnehan made their way up to an instrument bay that houses Hubble's Near-Infrared Camera and Multi-Object Spectrometer, also known by the acronym NICMOS.

Armed with a portable power socket wrench, the astronauts unbolted and swung open the door to the bay before taking a quick gander inside.

"It's nice to see an old friend, NICMOS," said Grunsfeld, who took part in a 1999 Hubble servicing mission. "Been a couple of years."

Installed in February 1997, the $110 million instrument was designed to operate at temperatures near absolute zero, conditions that would enable its infrared sensors to detect the faint heat of stars and galaxies in the most remote regions of the universe.

The heart of its supercold cooling system: a thermos-like flask of nitrogen ice needed to keep detectors chilled at minus 352 degrees Fahrenheit (minus 213 degrees Celsius).

A miniscule heat leak, however, exhausted the nitrogen ice supply by January 1999, and the instrument has been in a scientific coma ever since.

In a bid to bring NICMOS back to life, Grunsfeld and Linnehan fitted the instrument with a $21 million "cryocooler" that will use neon gas to chill detectors to minus 334 degrees Fahrenheit (minus 203 degrees Celsius).

The refrigerator will employ three tiny turbines spinning at 400,000 rpm -- or 100 times the maximum speed of a typical car engine -- to circulate neon gas within the instrument.

Heat built up within the new cooling system then will be dumped overboard through a radiator that the astronauts mounted on the outer hull of the telescope. And despite astonishing turbine speeds, the novel refrigeration system is virtually vibration-free -- which is crucial to the telescope's ability to snap crisp, clear pictures of the cosmos.

"It's very much a pioneering-type technology," said Burch.

A prototype of the new cooler was successfully tested on the same 1998 shuttle flight that returned famed NASA astronaut and former U.S. senator John Glenn to space.

And Grunsfeld helped set the stage for the revival of NICMOS during the 1999 Hubble servicing mission, opening up a vent valve that allowed any residual nitrogen from the instrument's old cooling system to escape the observatory.

Rigging up the new cooler, however, was no easy task.

Next page: Playing it cool