Two astronauts
aboard the International
Space Station (ISS) will don NASA spacesuits Friday to rehearse an upcoming
spacewalk that will prepare their orbital laboratory for future
construction.
ISS
Expedition 13 astronauts Jeffrey
Williams and Thomas
Reiter will step into their U.S.-built Extravehicular Mobility Units (EMUs)
as practice for an Aug. 3 spacewalk to ready the station's primary cooling system
for activation during an upcoming NASA shuttle mission.
Russian
cosmonaut Pavel
Vinogradov, mission commander for Expedition 13, will assist the
spacewalkers as they don their orbital work clothes, NASA said, adding that
next week's six-hour spacewalk will begin at 9:55 a.m. EDT (1355 GMT).
"This EVA
consists of many maintenance tasks...most of those are in support of the upcoming
STS-116 mission, which is the flight after next," said Dana Weigel, NASA's extravehicular
activity (EVA) flight director, during a Thursday mission briefing.
NASA's
STS-116 shuttle flight is set to launch toward the ISS aboard the Discovery
orbiter on Dec. 14, just over three months after the planned Aug. 28 liftoff of
its predecessor STS-115
aboard Atlantis, the space agency has said.
Kirk
Shireman, NASA's deputy space station program manager, said the Aug. 3
spacewalk is the first of no less than eight EVAs dedicated to support ISS construction
between visiting shuttle missions.
"This EVA
next week is very important to put us into a position to conduct all those
flights," Shireman said of the 15 or so remaining shuttle missions to complete
the ISS by 2010, when NASA's three-orbiter fleet is retired.
Williams, a
NASA astronaut who arrived
on the ISS with Vinogradov on April 1, will serve as EV-1 during the upcoming
spacewalk and don a red-striped spacesuit.
Reiter, the
first long-duration ISS astronaut for the European Space Agency and Germany,
will wear an all-white spacesuit as EV-2. He arrived
at the station aboard NASA's shuttle
Discovery on July 6.
Critical
cooling
Of the numerous
tasks planned for Williams and Reiter during their upcoming spacewalk, the most
critical are the installation of a new motor and replacement of a broken
control box for three radiators mounted to a swivel platform on the station's
starboard side.
A duplicate
radiator platform sits on the station's port side, though only one radiator on
either system is currently unfurled, NASA said.
The new
motor to be installed is one of two that allow the radiators' platform to rotate
independently of the ISS as the station orbits Earth. The control box- a
replacement for a unit that failed in 2004 - will regulate radiator deployment and
the valves for the vital liquid ammonia that transports waste heat to the
radiators themselves.
Weigel said
the spacewalkers will also install a temporary cooling fluid line - known as a
shunt jumper - to the starboard radiator system during the EVA.
"We want to
make sure the system is functioning properly," Weigel said of the station's
independent starboard and port cooling systems, adding that only then can the
radiators be filled with liquid ammonia.
A busy
spacewalk, a larger crew
In addition
to working on orbital cooling systems, Williams and Reiter will mount a new
device - known as a Floating Potential Measurement Unit - to the Earth-facing end
of the station's Starboard One (S1).
"This is
going to provide a great view for the crew," said Paul Boehm, NASA's lead
spacewalk officer for Expedition 13.
The new
device will monitor the voltage potential that builds up as the outpost's solar
arrays generate power. A previous probe was tossed into
space last year after astronauts noticed that bolts securing it to the ISS
were loosening, prompting debris concerns.
Williams
and Reiter will also install a pair of materials exposure experiments to the
space station's hull and test an infrared video camera's ability to detect shuttle
heat shield damage during their spacewalk, Boehm said.
If time
permits, they could retrieve a balky global positioning system antenna, set up
a new light outside the ISS or install a vent for use during future experiments
inside NASA's Destiny laboratory, he added.
Next week's
EVA will mark the third career spacewalk for both Williams and Reiter, but will
be the first in more than three years to leave an ISS astronaut inside the
orbital laboratory.
ISS crew
size reductions following NASA's 2003
Columbia accident forced two-astronaut
teams to leave the space station empty, its internal hatches shut and
systems monitored by flight engineers on Earth.
Reiter's
arrival earlier this month returned the ISS to its three-person
crew size.
"Now we
have an extra body to help the crew get into and out of the suits, as well as
someone inside in case we have work that we need them to do during the
spacewalk," Weiger said.
NASA
will provide a live broadcast of the ISS Expedition 13 crew's Aug. 3 spacewalk
on NASA
TV beginning at 9:00 a.m. EDT (1300 GMT). You are invited to follow
the spacewalk using SPACE.com's
NASA TV feed, which is available by clicking here.
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