This
story was updated at 6:25 p.m. EST.
HOUSTON —
Two shuttle astronauts swapped out a cooling system tank outside the
International Space Station (ISS) in a Wednesday spacewalk, the first for German
spaceflyer Hans Schlegel since an illness kept him from an earlier excursion.
Schlegel
and U.S.
astronaut Rex Walheim replaced a refrigerator-sized pressure tank during
the nearly seven-hour maintenance job, which came two days after the German
spaceflyer skipped an earlier spacewalk due to an undisclosed medical issue.
"Hello to
all the people of Germany," Walheim said as the station passed over Schlegel's
home country. "What a pleasure it is to be up here spacewalking with one of
your native sons, Hans Schlegel."
The 56-year-old
Schlegel said Tuesday that he was feeling much better and looking forward
to today's spacewalk, which swapped out an empty nitrogen tank serving the
space station's port side cooling system with a brand new one.
"It's great
to be part of an international team," said Schlegel, a veteran European Space
Agency (ESA) astronaut, before he floated across the station's new
Columbus lab. "I'm holding onto Columbus. That's a good feeling."
While the
spacewalkers worked outside, mission managers cleared Atlantis' heat shield of
any concerns for reentry and extended the shuttle's
STS-122 flight by one more day. Landing for the now 13-day mission is set
for 9:06 a.m. EST (1406 GMT) on Feb. 20.
Station and
shuttle astronauts also continued to start up the 23-foot (7-meter) long
Columbus laboratory for orbital flight. The joint station and shuttle crew
attached the ESA-built laboratory to the ISS on Monday and opened it for
business a day later.
The lab's
activation was delayed due to a software glitch that prevented commands from
the ESA's control center near Munich, Germany to reach computers aboard
Columbus by way of the station's U.S. command system.
"The
computer problem is straightened out," said Sally Davis, NASA's lead ISS flight
director for Atlantis' mission. "We know what caused the software glitch and we
know what to do to get around it."
Flight
controllers cleared old commands in the computer system and restored
communications between the Munich operations center and Columbus. Engineers
worked through the night to fix the glitch, which delayed Columbus' activation
by less than 24 hours, Davis said.
"A few
people didn't get very much sleep last night," she added.
Tank
swap success
Schlegel
and Walheim appeared to move swiftly through today's six-hour, 45-minute
spacewalk, which began at 9:27 a.m. EST (1427 GMT) as Atlantis and the ISS flew
high above the west coast of South America.
Astronauts
installed the 550-pound (249-kg) tank, known as a Nitrogen
Tank Assembly, on the station's Port 1 truss segment in 2002, though it has
since used up its 80-pound (36-kg) supply of gaseous nitrogen. Stored under
extreme pressure — nearly 80 times that of an average car tire — the nitrogen
is used to pressurize ammonia coolant lines that run through the station's
radiators.
Walheim
toted the replacement tank into place from the tip of the station's Canadarm2
robotic arm, which was controlled by crewmates Leland Melvin and Stanley Love
inside the ISS. Shuttle pilot Alan Poindexter choreographed the spacewalk from
inside Atlantis.
The
spacewalkers completed their tank swap with time to spare, which they filled by
inspecting a set of misaligned metal debris shields tied down to the station's
hull. They also wrapped thermal covers around a set of metal pins attached to
the 1.4 billion euro ($2 billion) Columbus lab to prevent them from getting to
cold, but were unable to take extra photos of a dinged handrail near the
station's Quest airlock.
Love
discovered a 2 millimeter divot in the handrail — which Mission Control dubbed
the "Love Crater" — during a Monday spacewalk.
Today's
spacewalk marked the 103rd dedicated to space station construction and the
second of the Atlantis crew's STS-122 mission. Walheim and Love are scheduled
to step outside the ISS one more time on Friday to attach a pair of experiments
to the Columbus lab's exterior and retrieve a failed gyroscope.
By its
conclusion, Walheim racked up a total of 28 hours and 58 during his four career
spacewalks while Schlegel closed with six hours and 45 minutes in one
spacewalk. To date, Atlantis astronauts have spent 14 hours and 43 minutes
working outside the ISS during the STS-122 mission.
"It's an
incredible view," Schlegel said as the spacewalk ended.
NASA is
broadcasting Atlantis' STS-122 mission live on NASA TV. Click here for SPACE.com's
shuttle mission coverage and NASA TV feed.
advertisement
