This story was updated at 1:46 p.m. EDT (1736 GMT).
HOUSTON -- Astronauts aboard NASA's space
shuttle Endeavour took a close look at a gouge on the underbelly of their
orbiter Sunday while mission managers discussed whether to add a few extra days
to their flight to the International Space Station (ISS).
"The primary thing that we're
going to look for is how deep it is," John Shannon, chairman of
Endeavour's STS-118 mission management team, said of the damage during a
Saturday briefing here at NASA's Johnson Space Center.
A piece
of foam insulation about the size of a grapefruit fell from a bracket on
Endeavour's external tank and bounced off a metal strut to damage the
belly-mounted tiles during the orbiter's Aug. 8 launch. Radar images caught a
spray of debris and possible ice reminiscent of that seen during the debris hit
that led to NASA's 2003
Columbia accident, but Shannon said the event was much less severe than
that which afflicted Columbia.
The
gouge, which is about 3 1/2 inches (about nine centimeters) and just over
two inches (five centimeters) long, sits about four feet (1.2 meters) behind
Endeavour's starboard landing gear door. The tiles in that area are just over
an inch (2.5 centimeters) thick, but the precise depth of the damage site will
be determined during today's inspection using a laser scanning tool at the end
of a 50-foot (15-meter) extension to Endeavour's own robotic arm.
A closer look
During today's heat shield survey,
STS-118 mission specialists Tracy Caldwell and Barbara Morgan - a former Idaho
schoolteacher-turned-astronaut - used Endeavour's 50-foot (15-meter) robotic
arm to grapple its inspection boom and scan five spots along the shuttle's
hard-to-reach underside. Shuttle commander Scott Kelly aided in the
activity, NASA said.
In addition to the damaged tile, Caldwell
and Morgan were to inspect three other dings caused by the foam debris, as well as
a piece of frayed fabric near Endeavour's main landing gear door during their
three-hour survey.
The inspection began just before 12:00
p.m. EDT (1600 GMT) after Endeavour's robotic arm took its extension boom from
the clutches of the space station's own robotic appendage. The shuttle's arm cannot
grab the boom directly while Endeavour is docked at the ISS due to clearance
issues with station hardware.
NASA called for the focused
inspection on Friday after a photographic survey of Endeavour's heat shield
performed by the space station's Expedition 15 crew before docking. The new
images and data will help determine whether the damage tile will require a
spacewalk repair, mission managers said.
Shannon added late Saturday,
however, that the chance of sending an astronaut to repair the tile by coating
it with either a protective paint, heat-resistant cover or filling it with a goo-like
filler material is unlikely based on the current data.
NASA has kept a close watch on the
integrity of shuttle heat shields since the tragic loss of the Columbia orbiter
and its seven-astronaut crew in 2003. A 1.67-pound (0.75-kilogram) piece of
foam damaged that orbiter's left wing-mounted heat shield at launch, leading to its
destruction during reentry.
While shuttle astronauts inspect
Endeavour's heat shield, the ISS crew continued a 28-hour repair job to replace
corroded cables and an electronics box that led to a Russian computer crash in
June. Expedition 15 commander Fyodor Yurchikhin and Oleg Kotov worked
to mop up condensation behind panels containing the cables they were replacing.
Meanwhile, NASA engineers recovered
a primary U.S. command computer aboard the ISS that shut down unexpectedly
during a Saturday spacewalk, apparently due to a software glitch. The glitch
had no impact on ISS or spacewalk operations, and the computer's two backups
kicked in as planned, mission managers said.
"Last night we did power cycle
it and reconfigured all of those computers so they were in a good state for
today's operations," ISS flight director Heather Rarick said
in a Sunday morning update.
Possible mission extension
While Endeavour's crew inspects the
shuttle's heat shield, mission managers on Earth will discuss whether to extend
the STS-118 spaceflight by three extra days based on the performance of a new Station-to-Shuttle
Power Transfer System.
Endeavour astronauts successfully
activated the new system after docking at the ISS on Friday,
which allows the orbiter to draw on the station's solar power grid rather than
its own fuel cell resources.
"It's a long extension cord
with some power converts to convert the space station voltages to the voltage
that the shuttle can use," Kelly said before flight.
The drop in fuel cell use led one of
the three aboard Endeavour to grow colder than usual overnight, sounding an
alarm that awoke the STS-118 crew. Fight controllers adjusted settings on
acceptable fuel cell temperatures to avoid repeat alarms, NASA said.
Endeavour's construction mission to
the ISS was initially slated to run 11 days and include three spacewalks to
deliver a new starboard segment of the station, a spare parts platform and
about 5,000 pounds (2,267 kilograms) of cargo for the orbital laboratory's
crew. The three-day extension would mark a record 10-day stay at the ISS for a
shuttle and allow the STS-118 crew to perform an extra, fourth spacewalk to
support station construction, NASA has said.
Joel Montalbano,
lead ISS flight director for Endeavour's flight, said the new system has been
performing continuously since its Friday activation.
"That power transfer is doing
fantastic," he added.
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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