Shuttle Astronauts Wrap up Third Spacewalk at Station

by Tariq Malik, Senior Editor

Date: 08 June 2008 Time: 05:05 PM ET

Shuttle Astronauts Wrap up Third Spacewalk at Station

STS-124 spacewalker Mike Fossum retrieves insulation covers and restraints from the robotic arm of Japan's Kibo lab outside the ISS on June 8, 2008.
CREDIT: NASA TV.

HOUSTON — Two astronauts floated outside the International Space Station (ISS) Sunday on their mission?s last spacewalk to make a cooling system service call and wrap up work on its new Japanese lab.

Spacewalkers Michael Fossum and Ronald Garan replaced a refrigerator-sized tank filled with nitrogen to pressurize the station's ammonia cooling lines.

But the seemingly mundane maintenance task gave Garan two grand views of Earth and space from the tip of the station?s 57-foot (17-meter) robotic arm as he toted first the empty 550-pound (249-kg) tank, and then its replacement, from one end of the station to the other. NASA likened the maneuver to that of a giant windshield wiper.

?A lot different with the planet down there,? Garan said from his perch 80 feet (24 meters) above the space station and 215 miles (346 km) above Earth.

?Isn?t it a great view,? Fossum asked as the station flew high over Peru.

?Unbelievable,? Garan replied.

NASA astronaut Karen Nyberg and Japanese spaceflyer Akihiko Hoshide flew the station?s robotic arm for Garan from inside the orbiting lab. Discovery shuttle pilot Ken Ham choreographed the work from inside the docked orbiter?s flight deck.

The two astronauts began their spacewalk at 9:55 a.m. EDT (1355 GMT) just a few minutes before dawn over the southern Pacific Ocean just off the coast of Peru. It was the third of NASA?s STS-124 mission to deliver Japan?s massive, $1 billion Kibo laboratory and a new crewmember to the space station.

In addition to swapping out the nitrogen tank, Fossum and Garan removed insulation covers and restraints from a window and the robotic arm of Japan?s new tour bus-sized Kibo laboratory. They also deployed a set of metal shields between the 37-foot (11 meter) lab and its smaller storage attic to protect against damage from orbital debris or tiny space rocks.

The spacewalkers worked swiftly, starting out more than a half hour early and completing all their main tasks plus a few extra chores.

One extra task sent Fossum to the station?s port side solar array rotary joint, a 10-foot (3-meter) wide gear designed to spin the station?s left solar wings like a paddlewheel to track the sun. He collected a sample of some gray dust-like material that he first spotted last week in a Thursday spacewalk.

The port solar array joint is working fine, but engineers on Earth hope that the samples collect by Fossum will help ongoing efforts to repair a similar gear on the starboard side that been damaged by metal shavings.

Sunday?s spacewalk marked the 112th excursion dedicated to space station construction and the last of three spacewalks planned for Discovery?s STS-124 mission. Fossum and Garan spent a total of 20 hours and 32 minutes working outside the station during their three spacewalks.

The spacewalk was the sixth career excursion for Fossum, who ended with a total of 42 hours and one minute of spacesuit-clad work. He now ranks 12th on the list of all time spacewalkers. The three STS-124 spacewalks were the first for Garan, who is also making his first spaceflight on the mission.

?Well, there are the stars,? Garan said during one of his robotic arm rides as he peered out into the depths of space.

Fossum said a young student once asked him if it actually was possible to see the stars while working on a spacewalk.

?I told him I never had the chance to turn my lights off and look,? he said. ?Indeed, you can.?

NASA is broadcasting Discovery's STS-124 mission live on NASA TV on Saturday. Click here for SPACE.com's shuttle mission updates and NASA TV feed.