HOUSTON - NASA's shuttle Atlantis
will spend two extra days in orbit to allow its astronaut crew to repair minor
heat shield damage and perform an extra spacewalk at the International Space
Station (ISS), mission managers said late Monday.
The extra time will allow engineers
on Earth to draw up plans to repair a damaged
heat-resistant blanket on the aft exterior of Atlantis, John Shannon, head
of NASA's STS-117 Mission Management Team, told reporters during mission
briefing here at NASA's Johnson Space Center.
"The right answer here, the better
part of valor, was to go ahead and put it down and secure it," Shannon said of
the damaged blanket.
Atlantis' STS-117 crew, commanded by
veteran shuttle flyer Rick Sturckow, launched towards the ISS on June 8 on a
planned 11-day mission to deliver new starboard
solar arrays and trusses to the orbital laboratory. The mission will now
run 13 days, with landing set for June 21, NASA officials said.
During launch, aerodynamic pressures
forced a 4-inch
by 6-inch (10-centimeter by 15-centimeter) triangular flap of the stiff, two-inch (five-centimeter) thick blanket on
Atlantis' left Orbital Maneuvering System (OMS) pod to fold back on itself.
"We think that the
astronauts will be able to go out there and just push this right back down,"
Shannon said. "When you push it, it stays."
The torn blanket, while not a flight risk to the Atlantis astronaut
crew during reentry, could lead to some damage to the OMS pod's internal
honeycomb-like graphite-epoxy structure and require additional time to repair
once the spacecraft returns to Earth, NASA has said.
"It was a 100-percent
consensus that the unknowns in the engineering analysis of the potential damage
to that graphite-epoxy layer under the blanket was not acceptable and we wanted
to go and fix it if we at all could," Shannon said. "So it was a very easy
decision today."
Shannon also added that,
on Monday, NASA engineers cleared other areas of Atlantis' heat shield --
specifically its heat-resistant belly-mounted tiles and carbon composite panels
along the wing edges and nose cap -- of concern. No focused inspection of those
areas will be required during the remainder of the STS-117 mission, he added.
"I don't think
we're going to have any problems at all on the underside of the vehicle,"
Shannon said.
NASA has kept a close
eye on the integrity of space shuttle heat shields since the 2003 Columbia
accident, in which that orbiter sustained wing damage at launch that led to the
loss of the spacecraft and its seven-astronaut crew. Shuttle crews now
routinely scan their spacecraft for signs of damage while in orbit
at the start and end of the spaceflights.
Repair plans evolve
Shuttle mission managers are not yet
certain when STS-117 crew will perform the thermal
blanket repair, nor which spacewalking team will step into space to make the
fix. The repair itself, however, is expected to take about an hour and a half
of spacewalking time.
The repair, which would be based off
the Atlantis shuttle's 50-foot (15-meter) robotic arm, could be placed during
the third planned spacewalk for the STS-117 mission or added to the newly
announced fourth excursion.
Spacewalkers Jim Reilly and Danny
Olivas would be on tap to perform the repair if it occurs during the mission's
third spacewalk on Friday. If the blanket fix moves to the fourth spacewalk,
set for Sunday, STS-117 mission specialists Steven Swanson and Patrick
Forrester would make the repair.
Shannon told SPACE.com that
the decision to add the fourth spacewalk to the STS-117 mission is not due to
the blanket repair alone.
The shuttle launched with enough
supplies for two extra days and additional spacewalks in case they should be
required during the tricky tasks of installing and activating the new Starboard
3/Starboard 4 truss segments, deploying their wing-like solar arrays, and
folding in an older solar wing, he said.
By adding the fourth spacewalk,
shuttle astronauts will be able to not only repair the torn thermal blanket,
but also accomplish several get-ahead spacewalk tasks to maintain or upgrade
the ISS, Shannon added.
With the mission extension, Atlantis
and its STS-117 crew are now slated to land on June 21 at 1:54 p.m. EDT (1754
GMT) after a 13-day construction mission to the ISS. The spaceflight, now in
its fourth day, is the first of up to four planned to continue space station
assembly this year.
"We appreciate the extra days in
space," Sturckow told Mission Control late Monday. "We'll make good use of
them."
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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