Deliberate act

Like the new planetary camera, the now obsolete instrument weighs about 850 pounds (382.5 kilograms) and is the size and shape of a large kitchen refrigerator.

STS-109

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Anchored to the end of the shuttle's 50-foot (15-meter) robot arm, Newman opened the observatory bay and grabbed two handles on the front of the big box. Slowly, the spacewalker slid the camera off its guide rails and out of the observatory while Massimino tracked tight clearances.

"Looks good. Very nice. You've got about one foot and the instrument is out," said Massimino, who was perched on a nearby portable work platform.

"About halfway there. Got about nine inches to go. Six inches. Just about another inch," he added as the instrument was edged over the lip of the bay. "Okay, I see you clear of the telescope by a couple inches. I see you clear by about one foot. You're clear."

Holding the huge camera at arm's length, Newman got a ride back down to the shuttle's cargo bay, courtesy of robot arm operator Nancy Currie. The last of Hubble's original instruments ultimately was stowed in a carrier for a return trip to Earth.

The installation of Hubble's new camera came off in a similar manner and was just as deliberate.

With millions of dollars worth of hardware in hand, Newman gently eased the new camera into the empty telescope bay while Massimino made sure the fragile instrument didn't bang into the observatory.

"Okay, you're right over the lip of the telescope by about four inches. Keep it coming. Come just a little left, a half an inch to the left. That's good," Massimino said.

"I think we're going in," Newman replied.

"Looks real good. Nice and smooth. You've got about one inch to go, maybe two inches," Massimino added. "There you go. You got it."

Armed with a pistol-grip power socket wrench, the spacewalkers quickly bolted the new camera into place and hooked up electrical cabling.

A subsequent "aliveness test" confirmed that the new camera had been installed properly and was working as advertised.

"These guys just did a fantastic job out there," Linnehan told flight engineers at NASA's Mission Control Center in Houston. "I mean it was picture-perfect. They lined it up, got it in there, and on the first try, engaged the latches."

The seven-hour, 30-minute spacewalk was capped with a little get-ahead work and a few clean-up chores.

Newman and Massimino removed thermal covers that had been put in place Wednesday to protect sensitive science instruments and spacecraft control systems while Hubble was powered down for an electrical heart transplant.

What's more, the astronauts installed and wired up an electronics package that will route power to an experimental instrument cooling system to be set up during a fifth spacewalk Friday.

Grunsfeld and Linnehan will take on that job around 3:30 a.m. EST (0830 GMT), aiming to revive an infrared camera-spectrometer that has been dormant since 1999.

The renovated Hubble is scheduled to be set free Saturday before the shuttle crew heads off on a three-day trip back to Earth. Landing here at NASA's Kennedy Space Center now is scheduled for 4:30 a.m. EST (0930 GMT) next Tuesday.