HOUSTON - The
astronauts aboard the space shuttle Discovery are again scanning their
orbiter's heat shield to get a second look at slightly damaged areas seen in a
previous sweep.
The crew is
using Discovery's camera and laser-tipped orbital boom sensor system (OBSS) to
study at least nine parts of the shuttle's thermal protection system before the
end of the day. The operation is part of a six-day heat shield verification
plan, though shuttle managers and Discovery's crew have both expressed confidence
that the orbiter is fit for reentry and landing.
"Right now,
the indications are very good," Wayne Hale, NASA's deputy shuttle program
manager, said Thursday. "We don't see anything major."
After
studying images from Thursday's docking
and Wednesday's OBSS survey
of the nose cap and reinforced carbon carbon (RCC) panels along Discovery's
wing leading edges, shuttle engineers picked out 11 specific sites where they
found interesting nicks, scuffs or blemishes in the orbiter's heat shield.
Two of
those sites will be inspected in tandem with Saturday's spacewalk
activities, during which STS-114 mission specialists Soichi Noguchi and Stephen
Robinson will test out tile and RCC repair methods on intentionally damaged
samples in the payload bay, NASA officials said.
The
spacewalk is the first of three for Noguchi and Robinson to install a spare
parts platform outside the ISS, replace one broken gyroscope and repair the
power system of among other tasks.
STS-114
pilot James Kelly and mission specialist Charles Camarda are steering the
orbital boom system, with help from flight controllers. They began today's
inspection at about 8:44 a.m. EDT (1244 GMT).
Today's
OBSS look at Discovery's underside will yield much more information about the
tiles there than traditional, two-dimensional images. A boom-mounted laser can
generate three-dimensional views of tiles.
"What you
don't see is depth," said John Shannon, NASA's manager of flight operations and
integration for the shuttle program, of traditional imagery Thursday. "If you
had a gouged tile, we don't think we have but if you did, you'd only see the
white area."
Evaluating
damage to the shuttle's heat shield is a major goal for Discovery's STS-114
mission. NASA's last orbiter flight, Columbia's STS-107 mission, ended in
tragedy two weeks after a piece of external tank foam pierced a heat-resistant
panel on its left wing. The damage allowed hot gases into the wing during
reentry, which destroyed the orbiter on Feb. 1, 2003. Columbia's STS-107 crew
did not survive.
NASA
officials said Thursday that a small
piece of foam may have struck Discovery, but was not large enough to be a
concern and no damage has turned up from wing-mounted sensors and the initial
OBSS inspection. That foam shedding, and a larger piece which clearly missed
the orbiter, prompted NASA officials to hold
off on future shuttle flights until the problem is solved.
Meanwhile,
Discovery's crew is in the middle of their fourth day in space. Robinson and
Noguchi are spending the bulk of the day going through the tools they will need
for tomorrow's spacewalk.
Earlier
today, Kelly and mission specialist Wendy Lawrence installed
the Raffaello cargo pod at a port along the station's Unity module. That cargo
shipment is expected to be opened at about 10:49 a.m. EDT (1439 GMT).
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