On the way up, several pieces of foam broke loose from the external fuel tank. Some struck the orbiter's underside.
The foam loss and any damage to the shuttle's heat-shedding tiles will be the focus of attention for the next several days as engineers review photos, video clips, and radar data taken during the launch and ascent.
In addition, the shuttle and station crews will conduct a pair of scheduled on-orbit inspections, which occur before the orbiter docks with the space station.
Some of the debris came off fairly late in the ascent, according to Mike Moses , the shuttle's payload integration manger, and so would be relatively harmless. At a post-launch briefing he explained during that phase of the flight the shuttle and any loose foam would be traveling at the same speed. So foam coming in contact with the orbiter at that stage would do little or no damage.
The biggest concern centers around foam that breaks free while the atmosphere is still thick enough to dramatically slow the foam down, increasing the relative speed at which the rapidly rising shuttle collides with it.
"We saw some stuff. Some of it doesn't concern us. Some of it you really just can't speculate on right now," Mr. Moses said.
Mission managers said that their initial impression was that a few tiles had been struck and some of the tiles' surface finish removed. If that proves to be the case, the crew has a repair kit on board that would allow them to repair the tiles during a space walk. If the tiles are gouged, the repair kit contains a putty-like substance astronauts can use to fill the voids.
"We have the tools in front of us and the processes in front of us to go clear this vehicle for entry" at the end of the mission. Mr. Moses said.
Endeavour is carrying the last two pieces of hardware needed to complete Japan 's $1-billion Kibo laboratory. It's also carrying six fresh batteries -- each the size of a coffee table -- that will store electricity from some of the station's solar panels.
And one of the shuttle's outbound crew members, Tom Kopra , will remain on the station as part of a regular station-crew rotation. Japanese astronaut Koichi Wakata , who has been aboard the station since the end of March, will return with the shuttle.
With all the delays, mission planners had to juggle the schedule a bit to accommodate the previously scheduled arrival of a Russian Progress resupply capsule.
The shuttle mission will last it's originally scheduled 16 days But its 12-day stay at the station will be cut short a day to make way for the Progress's arrival. Shuttle tasks that would have been undertaken during the orbiter's final day at the station will instead be performed the day after the shuttle leaves.