NASA said Space Shuttle Endeavour has a gouge in its belly that may have been caused by ice that broke off the fuel tank a minute after liftoff.

The gouge, about 3 inches square, was discovered as Endeavour docked with the international space station on Friday. It was detected with zoom-in photography taken shortly before the linkup.

NASA said it's not clear how significant the gouge is at this point. A mission official said it may have to be repaired during a spacewalk.

On Sunday, the astronauts will inspect the area, using the 100-foot robot arm and extension beam. Lasers on the end of the beam will gauge the exact size and depth of the gouge. That will help determine if a repair job is necessary.

The examination of the shuttle for damage is now a routine part of shuttle missions. A chunk of the foam insulation broke off the fuel tank and damaged the wing of Columbia in 2003, leading to its destruction on re-entry.

Shuttle, Space Station Link Up

As the international space station and space shuttle Endeavour flew over the Pacific Ocean on Friday, the two craft came together precisely and linked up.

Endeavour will stay seven to 10 days as it adds pieces to the space station, delivers supplies and helps with repairs.

Friday afternoon, astronauts were supposed to use the robot arms on the shuttle and space station to transfer a truss from one craft to the other.

On Friday, Endeavour came within 600 feet of the international space station and performed a giant backflip so station crew members could zoom in for pictures of the craft. The photos will be sent to Houston for analysis.

The most worrisome foam fragment struck the shuttle nearly a minute after liftoff. It resulted in a spray or discoloration on the right wing.

Teacher Works Robot Arm

On Thursday, teacher-astronaut Barbara Morgan got a chance to show off her space skills. Morgan took the controls of the robot arm during damage inspections.

Morgan's crewmates will be put to work over the next two weeks installing a huge, square-shaped beam to the exterior of the station and replacing a broken gyroscope. Three spacewalks are planned; a fourth is possible.

Morgan was initially an alternate in the teacher-in-space program with McAuliffe. After the Challenger disaster in 1986, she returned to her teaching career while still performing some duties for NASA. She has been at the agency training for missions since 1998.