A close-up view of the heat shield on space shuttle Discovery's nose was provided by Expedition 18 crewmembers on the International Space Station before docking on March 17, 2009 during STS-119.
This story as updated at 5:47 p.m. EDT.
Astronauts aboard the space shuttle Discovery gave their spacecraft?s heat shield a final health check on Thursday to search for any dings from space junk.
Shuttle commander Lee Archambault and his crew scanned the spacecraft for any new damage caused by micrometeorites or orbital debris as they prepare for a planned Saturday landing to end a landmark mission that boosted the International Space Station to full power.
?To the untrained eye, it looked very, very clean,? shuttle flight director Paul Dye said as the inspection ended.
Space debris has been a growing concern of late, with Archambault using Discovery?s thrusters to help move the space station clear of a piece of orbital junk earlier this week. It was the third debris event in two weeks for the station, one of which sent its three-astronaut crew to take shelter in its docked Soyuz lifeboat when a piece of space trash zoomed close by without enough warning to move the outpost.
?It?s part of the business,? NASA deputy shuttle program manager LeRoy Cain said of space debris last week. ?It comes with the territory and we?ll continue to do whatever is necessary to avoid debris where and when we know about it.?
Cain said the recent spate of space debris events, which were brought to the forefront by a Feb. 10 crash between two satellites, are random occurrences. Archambault, too, has said the recent events were likely just by chance.
?We have had a couple of these in the last couple of weeks, but as a far as I know it?s coincidental that we?ve had just a couple in this close timeframe,? Archambault told reporters earlier this week.
Discovery undocked from the space station Wednesday after eight days of construction work install the outpost?s last set of solar wings. The shuttle beamed back the first views of the space station with all four of its solar arrays, two per side, as it backed away from the station and began the trip home.
?It really was spectacular,? a shuttle astronaut radioed Mission Control last night.
Heat shield check
In their inspection today, the shuttle?s seven-astronaut crew used cameras and laser sensors at the tip of Discovery?s 50-foot (15-meter) inspection boom to scan the heat-resistant panels lining its wing edges and nose cap. The survey, a now-standard late heat shield inspection, is identical to one performed by the astronauts just after launch.
Discovery?s heat shield has already received a clean bill of health with respect to launch debris from its March 15 liftoff. A small ding near the aft on a left wing elevon is the most notable damage, but not a threat to the shuttle or its astronaut crew, mission managers have said.
Thursday?s survey is designed to search for new damage cause by tiny space rocks or other debris while Discovery was docked the space station.
NASA has kept a close watch on the integrity of its shuttle heat shields since the tragic 2003 loss of the shuttle Columbia and its astronaut crew during re-entry. A piece of fuel tank debris damaged that shuttle?s left wing during launch, leading to its destruction during re-entry.
Discovery?s heat shield, by comparison, appears to be in extremely fine shape. Engineers will study the data and images from today?s survey before clearing the shuttle for its planned Saturday landing at the Kennedy Space Center in Cape Canaveral, Fla.
Discovery is completing a 13-day mission to the International Space Station, where shuttle astronauts performed three spacewalks to install the new solar wings. They also helped repair the station?s urine recycler and replaced one member of the outpost?s crew - NASA astronaut Sandra Magnus - with Japanese astronaut Koichi Wakata.
Wakata is Japan?s first long-term resident of the space station and due to return to Earth in three months. Magnus will complete a 4 1/2-month mission to station when she returns with Discovery?s crew on Saturday.
Discovery left the space station one day before the launch of a Russian Soyuz spacecraft carrying the outpost?s new crew and the world?s first repeat space tourist - American billionaire Charles Simonyi. Simonyi is paying about $35 million for his second trip to the station in two years in a deal brokered with Russia?s Federal Space Agency by the Virginia-based firm Space Adventures.
The Soyuz lifted off on time at 7:49 a.m. EDT (1149 GMT) from the Central Asian spaceport of Baikonur Cosmodrome in Kazakhstan. It is due to arrive at the station on Saturday at 9:14 a.m. EDT (1314 GMT), a few hours before Discovery is slated to land in Florida.
SPACE.com is providing continuous coverage of STS-119 and Charles Simonyi?s with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for shuttle mission updates and SPACE.com's live NASA TV video feed.
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