NASA: Space shuttle Discovery undocking, heading for home

Shuttle will circle space station for heat shield inspection before flying home

With three spacewalks behind them, the International Space Station restocked with supplies and a new tank of coolant in place, the space shuttle today Discovery is undocking and heading for home.

The shuttle, set to undock from the space station at 3:26 p.m. EDT, is scheduled to land at Cape Canaveral in Florida on Saturday. But first, after today's undocking, the shuttle craft will move about 450 feet away from the orbiter so the station crew can examine the outside of the shuttle to see if there's any damage. At the same time, the shuttle crew will inspect the space station for any as-yet undiscovered damage.

The fly-around maneuver is standard procedure for every shuttle that undocks from the space station.

After the space station crew checks out the exterior of the shuttle, Discovery's own crew will use its onboard robotic arm, with an attached boom and camera, for one last inspection of the shuttle's heat shields before heading for re-entry with the Earth's atmosphere. Engineers on the ground will examine the images and data to check Discovery's thermal protection system.

NASA has been especially diligent about studying the heat shields since the space shuttle Columbia broke apart on reentry on Feb. 1, 2003. According to NASA, an investigation found that the disaster was caused by a hole in the heat-resistant panels that protected the wing from the high temperatures of reentry.

On Saturday, the shuttle's crew wrapped up the third and last spacewalk of the 13-day mission, installing two GPS antennas, routing avionics cables and installing a payload attachment system.

In the two previous spacewalks, astronauts uninstalled an empty ammonia tank and then installed a new, full tank. The ammonia is used to cool the interior of the space station.

The astronauts also used a spacewalk to move the new Colbert treadmill into the space station.

NASA in April had named the treadmill after comedian Stephen Colbert, who had waged a massive online effort to have the new wing of the space station named after him.

NASA had launched an online poll to choose a name for the new wing, which will house life support equipment, controls for the space station's robotic arm and the new treadmill. Colbert rallied his fans, known as Colbert Nation, to go to NASA's Web site to cast write-in votes for "Colbert" as the new name. The name "Colbert" got more than 230,000 votes -- 40,000 more than "Serenity," the top-ranked NASA-suggested name.

Naming the wing Colbert didn't sit right with the folks at NASA so they named the wing Tranquility and named the treadmill after the enterprising comedian.

Copyright © 2009 IDG Communications, Inc.

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