Shuttle Crew to Scan Discovery's Wing for Space Rock Damage

The space shuttle Discovery as it appears docked at the International Space Station (ISS) during NASA's STS-121 mission in July 2006. CREDIT: NASA TV.

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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