HOUSTON —
Two astronauts will step outside the International Space Station (ISS) Sunday
to pay a service call on the orbiting lab's cooling system.
Discovery
shuttle astronauts Mike Fossum and Ron Garan are slated to begin their
spacewalk at about 10:32 a.m. EDT (1432 GMT), marking the third excursion of their mission
to the space station, to replace an empty nitrogen tank.
"This is
basically a scheduled maintenance," said Annette Hasbrook, lead space station
flight director for Discovery's
STS-124 mission. "It's like the 50,000-mile checkup on your car."
The
refrigerator-sized tank is used to pressurize ammonia lines that provide
cooling for space station systems.
If time
allows, Fossum will revisit the station's port-side solar array gear, a massive
10-foot (3-meter) wide joint that rotates the station's left solar arrays like a
paddlewheel to track the sun. He spotted what appeared to be grease and gray
dust on part of the joint during
a Thursday spacewalk and engineers hoped he could collect samples of the material
for return to Earth.
"That
bearing looks to be in pretty good shape," Fossum said of the joint.
The port
solar array joint has been working fine, but the station's starboard-side gear
has been damaged by metal shavings and used only intermittently since last fall.
Fossum's inspection of port joint, engineers hope, will aid recovery efforts of
its starboard counterpart.
Discovery's
seven-astronaut crew is in the middle of a planned 14-day mission to deliver Japan's
$1 billion Kibo
research laboratory and swap out one member of the station's three-man
crew. The shuttle launched May 31 and is scheduled to land on Saturday.
Orbital
service call
Garan will
spend the bulk of his spacewalking time today perched at the tip of the space
station's 57-foot (17-meter) robotic arm, riding it between work sites as it
sweeps from one side of the main truss to the other like a giant windshield
wiper blade six stories tall.
"This is
going to be an absolutely spectacular [spacewalk]," Garan said in an NASA
interview. "So this maneuver right here takes about 20 minutes, and on the top
here I'll be almost 100 feet above the station, looking straight down at the
aft of the station and the Earth 250 miles below. So it'll be a pretty
spectacular view."
NASA
astronaut Karen Nyberg and Japanese spaceflyer Akihiko Hoshide will control the
station's robotic arm during the spacewalk, with Discovery pilot Ken Ham
choreographing the work from inside the shuttle. Working together, the
astronauts will replace the empty 550-pound (249-kg) nitrogen tank on the
station's starboard truss with a full one currently perched on a port-side
spare parts platform.
Fossum and
Garan also plan to remove a set of launch restraints and insulation covers from
the robotic arm and a window of the station's new tour bus-sized Japanese Kibo
laboratory. They're also expected to deploy debris shields in the space between
the 37-foot (11-meter) module and its rooftop
storage module.
The two astronauts
are also expected to return a repaired video camera to the station's exterior
during the spacewalk. The excursion will mark the third career spacewalk for
Garan and the sixth for Fossum.
"Walking in
space is an awesome experience," Fossum said Saturday. "It's unlike anything
else you'll experience anywhere."
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.
advertisement
