CAPE CANAVERAL: The space shuttle Endeavour's heat shield appears to have been damaged by a piece of ice that hit the orbiter shortly after lift-off.
A gouge, about 19sq cm, was spotted in zoom-in photography taken by the space station crew shortly before Endeavour delivered teacher-astronaut Barbara Morgan and her six crewmates to the orbiting outpost on Friday.
John Shannon, chairman of the mission management team, said if the gouge was deep enough, the shuttle astronauts might have to patch it during a spacewalk.
The astronauts will inspect the area, using a 30m robot arm and extension beam. Lasers on the end of the beam will gauge the exact size and depth of the gouge and engineers will determine whether the damage is severe enough to warrant repairs.
The gouge -- white against the black tiles on the underside of Endeavour -- is several metres from the starboard main landing gear door.
It appears to be the result of ice, though engineers are not positive; the damage could have been caused by a piece of foam insulation that came off the external fuel tank.
The US space agency has carefully inspected the orbiter's protective tiles in the missions that followed the shuttle Columbia disaster of February 2003.
Columbia's heat shield was pierced by a piece of insulating foam that peeled off its external fuel tank during lift-off, causing the shuttle to disintegrate as it
re-entered Earth's atmosphere. Seven astronauts died.
Earlier on Friday, Endeavour docked with the space station after performing an orbital backflip that allowed a close-up look for damage from the launch.
With Cdr Scott Kelly at the controls, Endeavour pulled up to the space station and parked as the two spacecraft soared above the South Pacific.
While still 190m out, Cdr Kelly steered Endeavour through a complete somersault so the three space station residents could photograph the shuttle's belly.
The backflip has been standard procedure ever since the Columbia disaster, providing a rare camera view of the shuttle's underside.
Besides the gouge, NASA is concerned that three pieces of foam insulation from the external fuel tank might have struck
Endeavour during Wednesday's launch.
Two are believed to have hit the shuttle's right wing.
Mission managers do not suspect any critical damage. They said the foam fragments were probably too small and one came off too late in the launch to pose a threat.