This story
was updated at 8:17 p.m. EDT.
CAPE
CANAVERAL, Fla. -- NASA mission managers cleared the space shuttle Atlantis and
its seven-astronaut crew for a planned Thursday landing after resolving two
final issues.
Late
Wednesday, engineers completed studies into a small bit of fluff poking out
from heat shield panels near the tip Atlantis' left wing and new data related
to the shuttle's torn engine pod blanket repaired during the shuttle's STS-117
flight. Neither item was thought to be of major concern, but NASA officials
opted to clear them just the same, the space agency said.
"We're just
going to review those two. I think we're going to stomp them flat," said John
Shannon, NASA's deputy shuttle program manager, late Wednesday. "And then we're
going to be done with it and we'll be ready to come home."
Atlantis
and its STS-117 astronaut crew are due to land on a runway here at NASA's
Kennedy Space Center (KSC) Thursday at 1:55 p.m. EDT (1755 GMT), though
anticipated thunderstorms and thick clouds near the landing strip may preempt
the orbiter's Earth return, mission managers said.
"I know the
forecast right now is no go, but clearly weather changes," said Norm Knight,
NASA's ascent and entry flight director for the shuttle flight, during the
afternoon briefing. "As we get closer, we'll get a better handle on the
forecast models."
Commanded
by veteran shuttle flyer Rick Sturckow, Atlantis' seven STS-117 astronauts are
wrapping up a 13-day mission that delivered a pair of new starboard
solar arrays, trusses and one new crewmember to the International Space
Station. The mission included four spacewalks to install the new massive
girders and solar wings, as well as to furl an older solar array atop the
station and staple
down a loose thermal blanket on Atlantis' left aft engine pod.
During that
blanket repair, engineers found that its underlying layer did not match those
used in launch heating simulations, leading some to believe the area might have
been subjected to ascent temperatures just slightly higher than those
predicted. The mistake, while late-breaking, posed no risk to Atlantis or its
crew, mission managers said.
"The
engineering and safety teams believe it's absolutely no risk at all to
reentry," Shannon said.
The bit of
left wing fluff, actually a piece of frayed filler material, was seen during a second
heat shield inspection of Atlantis by its astronaut crew using a
sensor-laden extension of the orbiter's robotic arm.
The survey,
known as a late inspection, found no signs of damage from micrometeorites or
orbital debris. Late inspections are now standard to all shuttle missions
following the loss of seven astronauts and the shuttle Columbia in 2003.
After a
late Wednesday meeting, mission managers cleared both issues to set the stage
for Thursday's planned landing.
"The
polling was unanimous on both issues," NASA spokesperson Allard Beutel told SPACE.com
of the positive decision. "We're clear to land at the Kennedy Space Center,
weather permitting."
Florida
landing preferred
Atlantis
has enough supplies to stay in orbit until Sunday, though mission managers plan
to land the shuttle by Saturday and keep the final day in reserve in case of an
unexpected malfunction.
The weekend
landing opportunities are largely due to the power conservation efforts by the Atlantis
crew during their flight, when NASA managers were considering extending the
mission a day or so to
aid computer issues - since resolved - aboard the ISS.
"It's definitely
a luxury," Knight said of the extra landing opportunities. "Clearly we use
those judiciously and we don't treat them lightly."
Knight said
Atlantis will attempt to land at KSC during two Thursday opportunities - the first
at 1:55 p.m. EDT and the second at 2:30 p.m. EDT (1830 GMT). If weather
intervenes, the shuttle will wave off until Friday.
The space
agency's backup landing strip at Edwards Air Force Base in California will be
called up in addition to KSC for any Friday or Saturday landing attempts, he
added.
NASA
prefers to land space shuttles at KSC because it is home to the orbiter's
hangars and launch sites. It allows for a faster turnaround to prime each
orbiter for its next launch. Atlantis' next flight, aimed at hauling the
European Space Agency's Columbus laboratory to the ISS, is slated to liftoff in
December.
Landings at
Edwards Air Force Base, where orbiters are met by engineers at NASA's Dryden
Flight Research Center and ferried back to KSC atop a modified 747 jet,
typically add about one extra week and a cost of $1 million to a shuttle's
turnaround time.
NASA is
broadcasting the space shuttle Atlantis' STS-117 mission live on NASA TV. Click here for mission updates and
SPACE.com's
video feed.
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