HOUSTON -- A
pair of spacewalking astronauts will venture outside the International Space
Station (ISS) Wednesday to prime the orbital laboratory for future construction
as NASA works to determine whether a heat shield repair is required for the
shuttle Endeavour.
Endeavour
shuttle astronaut Rick Mastracchio and ISS flight engineer Clayton Anderson are
set to begin their planned
6.5-hour spacewalk at 11:01 a.m. EDT (1501 GMT) to prepare the space
station's Port 6 (P6) truss for a major move later this year.
"The
tasks on this spacewalk are all geared towards the STS-120 mission
preparations," said Matt Abbott, NASA's lead STS-118 shuttle flight
director, in a Tuesday briefing. NASA's STS-120- mission is slated to launch in
late October with a new room for the ISS.
While the
two spacewalkers toil outside the ISS, NASA mission managers expect to complete
tests to determine whether repair tasks will be added to another STS-118
spacewalk to fix a small cut in two of the belly-mounted heat tiles along
Endeavour's underbelly. The damage was caused by an errant piece
of fuel tank debris about one minute after the shuttle's Aug. 8 launch.
John
Shannon, chairman of Endeavour's mission management team, said late Tuesday
that a preliminary analysis has shown that the orbiter is safe
to fly without a repair. But engineers wanted extra time to make sure that landing
without a heat shield fix would not cause further damage that could require more
extensive repairs once the spacecraft returns to Earth.
A decision
on whether a spacewalk repair will be necessary is anticipated for sometime
late Wednesday, NASA has said.
Priming
P6
Slated to
launch in late October aboard the Discovery orbiter, NASA's STS-120 mission
will deliver the new Harmony connecting node and feature the relocation of the
space station's mast-like P6 truss from its vertical perch to a permanent
position on the orbital laboratory's port-most side.
"P6 is
going to eventually be moved from the zenith part of station to the
portside," Mastracchio said before flight. "So we have to kind of
clean up P6."
To do that,
Mastracchio and Anderson will pry an S-band antenna from P6 and reattach it to
the station's horizontal Port 1 truss segment. The spacewalkers will also move
a pair of large equipment pushcarts from their position on the portside of the
station's railcar-like Mobile Transporter to the starboard side, which will
clear a path for the robotic arm base for future ISS construction.
Mastracchio
and Anderson are also due to retrieve a pair of materials exposure experiments
and a P6 truss transponder, as well as install new communications gear during
their excursion. The spacewalk will mark the third for Mastracchio and the STS-118
mission, as well as the second career excursion for Anderson.
Commanded
by veteran shuttle flyer Scott Kelly, Endeavour's 14-day mission is delivering about
5,000 pounds (2,267 kilograms) of cargo, a new spare parts platform and a small
spacer segment for the starboard side of the space station's main truss. The
shuttle's STS-118 crew includes teacher-turned-astronaut
Barbara Morgan, who first joined NASA in 1985 as the backup for Teacher in
Space Christa McAuliffe before the Challenger tragedy a year later.
Rejoining
STS-118
Today's
spacewalk marks a return of sorts for Anderson to Endeavour's astronaut crew.
The
Expedition 15 crewmember originally trained to launch to the space station on
the STS-118 mission, but he was
reassigned to NASA's earlier STS-117 flight - which launched in June - to
relieve fellow American spaceflyer Sunita Williams as an ISS flight engineer.
But despite arriving ahead of his former crewmates, Anderson said he looked forward
to a familiar set of tasks.
"My
mission with 118 is essentially unchanged from what it was before," Anderson
said in a preflight NASA interview. "The only thing that's really
different is, I don't spend the first three days, from launch to docking, with
the 118 crew -- I do it with 117."
Anderson is
slated to perform up to two spacewalks with the STS-118 crew. In addition to
today's excursion, he is also set to perform a series of ISS maintenance tasks
with STS-118 spacewalker Dave Williams, of the Canadian Space Agency, on Friday.
Prior to
Endeavour's arrival, Anderson spent a good portion of his time packing up experiments
and cargo to ride back to Earth with the STS-118 crew.
"Clay
Anderson is still part of this crew in my mind," Mastracchio told SPACE.com
before launch. "Clay just went ahead of us, to get things set up for us."
NASA is
broadcasting Endeavour's STS-118 mission live on NASA TV. Click here for mission updates and
SPACE.com's NASA TV feed.
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