HOUSTON - Astronauts aboard NASA's space shuttle Discovery will begin a
final inspection of their spacecraft's wings today in a first-ever hunt for any signs of
impact from miniscule space rocks.
Discovery's
STS-121 mission specialists Lisa
Nowak and Stephanie
Wilson will scan the shuttle's port wing with its sensor-laden inspection
boom to determine whether micrometeorites or other orbital debris have struck
the spacecraft during its stay at International Space Station
(ISS).
"Any
spacecraft in orbit has a fundamental risk of being hit by something,"
Discovery's pilot Mark Kelly told CNN Friday during a series of space-to-ground
interviews on NASA TV. "By doing a late inspection, it will slightly reduce the
risk of damage to our thermal protection system, or at least, if there is
damage we'll know about it."
Friday's
late inspection is slated to begin at 1:18 p.m. EDT (1718 GMT) after Discovery's
astronauts unberth the Italian-built
Leonardo cargo module from the ISS and stow it in the shuttle's payload
bay. Once Discovery and its six-astronaut crew undock from the ISS on Saturday,
Nowak and Wilson - which flight controllers dubbed the "ROBO chicks" in today's
execute package - will also inspect the shuttle's nose cap and starboard wing.
"It is more
remote than ascent debris," Wilson told CBS News today of the micrometeorite
threat.
Nowak added
that the initial Flight
Day 2 inspections of Discovery's heat shield coupled with focused
looks after the shuttle docked at the ISS should help make this weekend's
final checks of the orbiter's nose and wing leading edges go smoother. Discovery's
heat shield has already been cleared
of any launch debris concerns.
Steve Poulos,
NASA's orbiter project manager, told the Associated Press Thursday that the
late inspections could reduce the odds of losing a spacecraft due to
micrometeorite damage from the average 1 in 210 to about 1 in 282.
Discovery's
STS-121 mission is NASA's the second shuttle to visit the
ISS since the 2003 Columbia
accident and the last of two test flights before major construction
resumes on the orbital laboratory. Launched
on July 4, the 13-day
mission has returned the station to its three-person capacity,
delivered vital supplies to the outpost and tested shuttle heat shield repair
tools and methods.
Engineers
on the ground continue to study a pair of
issues with two of three Auxiliary Power Units (APUs) that power Discovery's
hydraulics during reentry and landing.
A
workaround has been developed for an errant heater in one of the units, and
calls for the STS-121 crew to switch to a backup or orient the Discovery
towards the Sun to keep the APU warm. The second problem, a potential fuel
leak, is still under study, according to today's flight execute package.
Back to
work
Discovery's
STS-121
crew and the three-astronaut Expedition
13 team aboard the ISS are getting back to work today after a light
day of rest and nominal duties on Thursday.
In addition
to having a joint meal aboard the ISS and speaking with their families from
orbit, the STS-121 astronauts fielded several questions from reporters on Earth
and - in the case of one spacewalker - Texas governor Rick Perry.
A graduate
of Texas A & M University, Perry called STS-121 mission specialist and
fellow Aggie Michael Fossum to congratulate him on completing the third
and last of the spacewalks planned for his mission.
"I just
wanted to call to tell you how proud we are of you Mike, the entire state of Texas," Perry told Fossum. "Of course, the Aggies are up in great arms and in celebration
today to have the first Aggie in space, you're making history Mike."
Fossum thanked
Perry for his support for NASA's Johnson Space Center (JSC) here in Houston and graciously accepted an offer for 50-yard-line tickets for the big football game
between the Texas A & M Aggies and the University of Texas Longhorns later
this year.
Fossum's
crewmate Wilson, a Longhorn, was also offered the tickets, Perry said.
Fossum,
Wilson and Nowak are making their first spaceflight for Discovery's STS-121
mission. While all three of them have waited long - at least 10 years for
Wilson and Nowak and 25 for Fossum, the patience has paid off.
"It was
definitely a long wait and it was definitely worth it," Nowak said Thursday. "This
is a trip of a lifetime...it's thrilling to be up here."
The
Associated Press contributed to this report.
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