HOUSTON - The space shuttle Discovery's
heat shield, so vital to returning its STS-121 astronaut crew home to Earth,
appears to be in fine shape based on early image analysis, mission managers
said Thursday.
"Overall, a
really clean vehicle," said NASA's John Shannon, deputy shuttle program
manager, of Discovery during a mission briefing here at Johnson Space Center
(JSC). "We were looking for things to talk about at one point, it is so clean."
Discovery's
heat shield could be given a clean bill of health by the end of the weekend, Shannon said.
Shannon's comments came after an initial analysis
of some of the 352 high-resolution images of Discovery's heat shield taken earlier
today by astronauts aboard the International Space Station (ISS) during the shuttle's
morning docking. A further review is pending, but analysts have identified
only a few targets for possible follow-up inspections on Friday by the STS-121
crew.
Among them
are:
- An area
along Discovery's nose cap that appears to have been missed during an
earlier laser
instrument scan on Wednesday. Analysts are studying the high-fidelity
images taken of the orbiter by Expedition
13 astronauts Pavel
Vinogradov and Jeffrey
Williams to determine whether they fill in the needed gaps.
- A
newly-found gap filler jutting from between two tiles well aft on
Discovery's belly, just ahead of an umbilical door where a strut connected
the orbiter to its external tank. "It's really cockeyed," Shannon said. "It almost came out, but not quite."
- A piece
of fabric-like material poking out just behind the shuttle's nose cap that
does not appear to be a gap filler, but merits extra interest.
- And the previously
known gap filler discovered Wednesday by the STS-121 crew during
orbital boom inspections of Discovery's port wing leading edge.
Heat shield
imagery analysts were expected to convene at 7:00 p.m. EDT (2300 GMT) to decide
exactly which items merit time during a four-hour block on Friday reserved for
additional boom inspections by primary shuttle robotics operators Lisa Nowak
and Stephanie Wilson.
"I would
say we'd probably use all of that four hours," Shannon said of the follow-up
inspections, adding that the estimate allows for the time needed to slowly move
the orbital boom from Discovery's nose cap region to the aft gap fillers.
Shannon added that additional study has
pinned down the area of the sheet of foam that peeled free in pieces from
Discovery's fuel tank during launch. Early estimates set the area at about the
size of an 8.5 by 11-inch (21 by 27-centimeter) sheet of paper, but the actual
size was a bit larger at 12.3 inches by 14.2 inches (31 by 36 centimeters),
with a thickness of up to one inch (2.5 centimeters), Shannon said.
"The
initial report from the external tank project was that we did not violate any
conditions that we set pre-flight," Shannon said.
The seven
Discovery astronauts are NASA's second shuttle crew to fly to the ISS since the
2003 Columbia accident.
They have ferried European Space Agency (ESA) astronaut Thomas Reiter
to join the Expedition 13 crew, and will deliver some of their 3.6 tons of
cargo to the station on Friday.
Inspection
boom of the future
Shannon said discussions are underway on
the future of Discovery's orbital inspection boom, which adds 50 feet (15
meters) to the shuttle's already 50-foot robotic arm. The boom carries
sensitive visual and laser cameras, as well as a laser radar, to scan an
orbiter's heat shield.
During NASA's
STS-118 mission - currently slated to launch in mid-2007 - shuttle officials plan
to launch a set of brackets for the ISS to accommodate the boom so a newer,
smaller version could be developed.
"The
thought is that we would like to have a smaller, better boom that's a little
bit easier to use with better sensors to fly up on the space shuttle," Shannon said. "You want that nice long boom from a reach standpoint but from an inspection
standpoint you'd like a little smaller boom."
The current
boom gives access to much of an orbiter's surface, and will be tested for its
potential as a work platform by STS-121 spacewalkers Piers Sellers and Michael
Fossum on Saturday. But the boom does weigh about 800 pounds (362 kilograms),
which takes a hefty bite out of a shuttle's cargo lift capability, NASA said.
"We'd like
something a little less so we can carry up more cargo," Shannon said.
The current
shuttle inspection boom could be installed at the ISS about five shuttle
flights in the future, he added.
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