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Spacewalkers pull off toughest Hubble repairs yet

SPACEWALKING astronauts gave the Hubble Space Telescope a more commanding view of the cosmos by installing a new high-tech instrument yesterday, then pulled off their toughest job yet: fixing a broken camera.

It was the third spacewalk in as many days for the shuttle Atlantis crew and the most intricate ever performed because of the camera repairs. Astronauts had never before tried to take apart a science instrument at the 19-year-old observatory.

Hubble's chief mechanic, John Grunsfeld, deftly opened up the burned-out camera and removed all four electronic cards that needed replacement.

"Somehow I don't think brain surgeons go 'woo-hoo' when they pull something out," one of the astronauts observed from inside Atlantis.

To everyone's surprise, the new cards and power supply pack went in just as smoothly. And the astronauts found themselves running ahead of schedule for a change, their spacewalk lasting the allotted 6.5 hours. The first two spacewalks ended up running long because of unexpected difficulties encountered with Hubble, last visited seven years ago.

The astronauts cheered when Mission Control radioed up the news that the repaired camera had passed the first round of testing.

"That's unbelievable," Grunsfeld said.

A second round of testing was expected to last well into the night.

Initial second-round testing didn't go quite as perfectly as NASA had hoped. Two channels - wide-field and high-resolution - were dead on the camera. Amid time constraints, NASA could only choose to fix one: the wide-field. But they had held out a slight hope that fixing wide-field would somehow also work on the high-resolution. Test results last night showed that as expected the high resolution channel wasn't working, but it was too early to call it a failure. Results were still not in on wide-field late yesterday.

Early yesterday evening, Mission Control told astronauts that a new spectrograph that spacewalkers also installed passed both its tests. Atlantis crew responded with what has become customary whooping it up.

Even with two spacewalks remaining, including the repair of a major instrument today, NASA managers were handing out accolades and declaring the telescope already improved.

"We're enjoying the moment and savoring it," Hubble program manager Preston Burch said at a news conference yesterday afternoon.

Atlantis' crew broke out in grins.

In a video sent to Earth taken before the spacewalk, Mike Massimino, who spacewalked Friday and will do so again Sunday, compared dealing with Hubble to a heavyweight fight. But he also was looking like the winner in such a bout.

"We don't warranty any of the work," Massimino joked for the camera in a heavy New York accent. "Labor's not guaranteed."

The high-stakes job unfolded 350 miles (563 kilometers) above Earth. Orbiting so high put Atlantis and its astronauts at an increased risk of being hit by space junk.

Earlier, Grunsfeld and his spacewalking partner, Andrew Feustel, accomplished their first task, hooking up the US$88 million Cosmic Origins Spectrograph.

They made room for the new supersensitive spectrograph - designed to detect faint light from faraway quasars - by removing the corrective lenses that restored Hubble's vision in 1993.

"This is really pretty historic," Grunsfeld said as he and Feustel hoisted out the phone booth-size box containing Hubble's old contacts.

Hubble was launched in 1990 with a flawed mirror that left it nearsighted. But the newer science instruments have corrective lenses built in, making the 1993 contacts unnecessary. The latest addition, the cosmic spectrograph, is expected to provide greater insight into how planets, stars and galaxies formed.

The switch to the spectrograph proved straightforward.

Fixing the 7-year-old camera was far more complicated. The instrument - called the Advanced Camera for Surveys - suffered an electrical short and stopped working two years ago. But ground controllers had been able to eke out a minimal amount of science since.

Before it broke, the surveys camera provided astronomers with the deepest view of the universe in visible light, going back in time 13 billion years.

NASA considered this repair job - and one planned today on another failed science instrument - to be the most delicate and difficult ever attempted in orbit. Neither instrument was designed to be handled by astronauts wearing thick, stiff gloves.

NASA hopes to keep Hubble working for another five to 10 years.

If all goes well, the final spacewalk is set for tomorrow and the telescope will be released Tuesday from Atlantis. This last mission to Hubble cost more than US$1 billion.


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