Saturday, May 16, 2009

Live In Orbit: Spacewalkers Ace Tough Repair Job

Spacewalking astronauts breezed through an unprecedented repair job on the Hubble Space Telescope today, reviving a broken planetary camera during what was expected to be the toughest task on a mission unmatched in terms of degree of difficulty.

Atlantis lead spacewalker John Grunsfeld delicately unscrewed 32 tiny bolts, opened up the Advanced Camera for Surveys and then deftly replaced four failed circuit boards.

"The fourth card is out," Grunsfeld said. "Woo-hoo!"

"Somehow I don't think brain surgeons go 'woo-hoo' when they pull something out," one of his crewmates noted from inside shuttle Atlantis.

The planetary camera that was installed in 2002 but it suffered several power failures in 2006 and 2007, knocking out two of its three channels.

Grunsfeld outfitted the camera with a new power supply and new circuit boards. To do so, he cut shielding away from the camera and then removed a cover plate held in place with 32 tiny, non-captive screws that could have floated off into the telescope and caused serious damage.

In a bid to keep the screws from getting loose, Grunsfeld put a specially designed "capture fixture" over the cover plate. Then used a new mini-power tool to back the screws out into the capture fixture.

The cover plate and the capture fixture both were pulled off the camera, enabling Grunsfeld to swap out the four failed circuit boards. Then he equipped the camera with a new set of circuit boards and a new low-voltage power supply to complete the repair.

The complicated job originally was supposed to be done over two spacewalks. The timeline, however, had to be squeezed so that the astronauts could add an extra job -- the installation of a new science instrument controller -- to their to-do list. The new Science Instrument Control & Data Handling unit was put in place on Thursday.

The astronauts are closing up the telescope and then will be heading back into the shuttle.

You can watch all the action unfold here in The Flame Trench. Simply click the NASA TV box on the righthand side of this page to launch our NASA TV viewer, and be sure to refresh this page for periodic updates.

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