The U.S. space shuttle Discovery has landed in Florida, ending a resupply and maintenance mission to the International Space Station. Its successful flight means the space agency NASA can finally resume construction of the station.
Discovery's safe landing is an obvious relief to NASA, which was forced to halt assembly of the half-built space station more than three years ago when the shuttle Columbia disintegrated upon re-entry into the atmosphere.
Discovery, roaring like any other airplane, glided smoothly onto a runway at the Kennedy Space Center in Florida.
After landing, shuttle commander Steve Lindsey inspected the spacecraft and declared it free of damage, after its nearly nine million-kilometer journey.
"This is my fourth flight, and I've done four walk-arounds, and I've never seen a vehicle that looked as clean as this one did," said Steve Lindsey.
That is important to NASA, because it worked more than three years to ensure that shuttles suffer as little damage as possible from the kind of launch debris that doomed Columbia. That orbiter burned up when searing atmospheric gases entered a hole in its wing, caused by hard foam insulation that broke away from the external fuel tank during liftoff and hit it.
As a result, NASA removed or reshaped several areas of tank foam, installed an array of ground cameras to monitor launches, and put new cameras and sensors on shuttles to detect possible launch debris strikes or hits by micro-meteoroids while in orbit.
NASA chief Michael Griffin attributes Discovery's near-pristine condition to these new measures and a bit of luck.
"This is as good a mission as we've ever flown, but we're not going to get overconfident," said Michael Griffin. "We have to take it flight by flight."
During Discovery's two-week flight, two spacewalking astronauts tested new procedures to make repairs in orbit to the shuttle's fragile heat shield. The orbiter also transported a third crew member to the space station, which had only two since Columbia's accident. Station manager Mike Suffredini says it also hauled up new supplies and equipment, and its crewmembers made repairs to station systems critical to resuming the outpost's construction.
"So with this flight, in our minds, we are ready to get on with assembly, and we will do just that," noted Mike Suffredini.
Station assembly restarts late next month, when the shuttle Atlantis is to deliver a pair of solar energy panels, new batteries and a truss segment on which to mount other components.
NASA chief Griffin points out that shuttle flights are always risky and that station assembly missions are the most complicated that shuttles fly. He says only 16 shuttle flights remain before the fleet is retired in 2010, and more orbiter troubles could be ruinous for the space station's construction schedule.
"We don't have any slack [leeway]," he said. "We have just enough shuttle flights left to do the job. So, we can't afford to mess up."
Griffin thanked America's international partners in the space station program for their patience and support, while NASA took time to make shuttles safer to fly.