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Spacewalkers pull off toughest Hubble repairs yet
(Agencies)
Updated: 2009-05-17 14:39

Spacewalkers pull off toughest Hubble repairs yet
Astronaut Andrew Feustel, on the shuttle's robotic arm, and John Grunsfeld in Atlantis' payload bay with the Hubble Space Telescope in the background near the end of their spacewalk in this image from NASA TV May 16, 2009. [Agencies]
The high-stakes job unfolded 350 miles above Earth. Orbiting so high put Atlantis and its astronauts at an increased risk of being hit by space junk. NASA had another shuttle on launch standby in case a rescue was needed.

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Earlier, Grunsfeld and his spacewalking partner, Andrew Feustel, accomplished their first task, hooking up the US88 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 — taking out the 7-foot-long box containing the corrective lenses and putting in the spectrograph — proved straightforward. It's exactly the kind of replacement work astronauts performed on four previous repair missions.

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. Ground controllers had been able to eke out a minimal amount of science but wanted it back in full operation.

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 Sunday 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.

Grunsfeld unscrewed 32 fasteners to reach the camera's electronic guts, all the while working around a corner that prevented him from seeing everything he was doing. He used long tools designed just for the job — and got it done faster than planned.

NASA hopes to keep Hubble working for another five to 10 years. Already, the astronauts have given Hubble two top-of-the-line science instruments, fresh batteries and gyroscopes, and a new science data unit.

If all goes well, the final spacewalk is set for Monday and the telescope will be released Tuesday from Atlantis.

This last mission to Hubble cost more than US$1 billion.