The space shuttle Discovery lifts off from launch pad 39A at the Kennedy Space Center in Cape Canaveral, Florida May 31, 2008. (Xinhua/Reuters Photo)

The space shuttle Discovery lifts off from launch pad 39A at the Kennedy Space Center in Cape Canaveral, Florida May 31, 2008.(Xinhua/Reuters Photo)

The space shuttle Discovery lifts off from launch pad 39A at the Kennedy Space Center in Cape Canaveral, Florida May 31, 2008.(Xinhua/Reuters Photo)

The underside of the Space Shuttle Discovery is seen in a camera view from the orbiter's external fuel tank as it separates from the tank in this image from NASA TV May 31, 2008.(Xinhua/Reuters Photo)

The crew of the space shuttle Discovery departs crew quarters for the launch pad at the Kennedy Space Center in Cape Canaveral, Florida May 31, 2008.(Xinhua/Reuters Photo)