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.