(AP) -- Astronauts aboard space shuttle Discovery conducted a final inspection of the vehicle Thursday and at first glance found no significant damage which would prevent it from returning to Earth.
Mission managers will decide whether it's safe for Discovery to land Saturday at the Kennedy Space Center in Florida once engineers finish studying the results of the five-hour, routine survey. They said Thursday afternoon they hadn't detected any areas of concern so far.
Astronauts combed the outside of the shuttle with a 50-foot inspection boom mounted on Discovery's robotic arm. The boom was equipped with laser and camera tools that beamed images and data back to Mission Control.
"To the untrained eye, it looked very, very clean," said Paul Dye, lead flight director.
Astronauts were looking for damage from micrometeorites or space debris that may have hit the shuttle as it was docked to the international space station for eight days. The results were being compared with those taken during an inspection on the mission's second day.
The procedure was put in place after the 2003 Columbia disaster killed seven astronauts. A piece of foam from Columbia's external tank damaged the shuttle's wing during launch, allowing fiery gases to penetrate the orbiter during its descent back to Earth.
Discovery undocked from the space station on Wednesday after its seven-person crew delivered and installed power-generating solar wings at the orbiting outpost. Discovery was orbiting Earth for two days before it was to re-enter Earth's atmosphere on Saturday.
Astronaut Sandra Magnus joined the crew for the return trip after living four months at the space station. She spent two sessions on the shuttle's exercise machine Thursday in order to prepare her body for the effects of gravity.
"Sandy is on her way home," space station commander Mike Fincke radioed Mission Control. "We certainly enjoyed working with her."
As Discovery left the space station's neighborhood 220 miles above earth, another space vehicle was headed its way.
A Soyuz capsule carrying Russian cosmonaut Gennady Padalka, U.S. astronaut Michael Barratt and U.S billionaire space tourist Charles Simonyi blasted off for the space station Thursday from the Baikonur cosmodrome facility in Kazakhstan. Padalka and Barratt are replacing Fincke and Russian flight engineer Yury Lonchakov as long-term residents at the orbiting outpost. Simonyi's second trip to the station as a space tourist will last until April 7, when he'll return to Earth with Fincke and Lonchakov aboard the Soyuz.
Fincke watched the launch live on television from the space station and called it "picture-perfect."
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: NASA's Webb Telescope mirror tripod in action (Video)