Saturday, May 16, 2009

Live In Orbit: Hubble Spacewalk 3 Under Way

A pair of NASA astronauts are making their way outside shuttle Atlantis this morning on a mission to outfit the Hubble Space Telescope with a state-of-the-art spectrograph and repair a broken planetary camera.

Atlantis lead spacewalker John Grunsfeld and mission specialist Drew Feustel switched their protective spacesuits to battery power at 9:35 a.m., marking the official start of the third of five planned spacewalks to service the Hubble telescope.

The start came as Atlantis, with Hubble on a work platform at the aft end of its cargo bay, flew 350 miles above the Indian Ocean, tracking toward the west coast of Australia.

Grunsfeld is wearing a spacesuit with red stripes on its legs and is answering to the radio call sign "EV-1." Feustel is "EV-2" and is wearing an all-white spacesuit.

The astronauts will be making their way out of the shuttle airlock and then will spend their first half-hour or so checking their braided steel safety tethers, gathering up tools and attaching a foot restraint to the end of the shuttle's 50-foot robot arm. Feustel will anchor himself to the restraint for the servicing work. Atlantis mission specialist Megan McArthur is operating the arm

The next order of business will be to remove the COSTAR instrument -- a refrigerator-sized module that is equipped with mirrors that correct for the flaw in the telescope's primary mirror.

The instrument was installed in December 1993 and has served since then the same purposes as contact lenses. It has enabled Hubble spectrographs to operate despite the flaw in the primary mirror, which was ground to the wrong prescription, rendering the telescope near-sighted.

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