It was the first time such an inspection was occurring this late in a mission. The extra, late inspection was devised by NASA to make sure there was never again a disaster on par with the Columbia accident that killed seven astronauts in 2003.
The crew planned to inspect Discovery using sensors at the end of a 50-foot (15-meter) boom attached to Discovery's 50-foot (15-meter) robotic arm. The sensors will scan the shuttle's left wing for near-invisible holes and cracks caused by micrometeoroids, the dust-sized particles that make up the vast majority of debris circling Earth.
The space debris now also includes a spatula that astronaut Piers Sellers accidentally let go of during a spacewalk Wednesday. NASA said the spatula posed no risk to the space station or shuttle.
Sellers joked Friday that he would go to Home Depot to replace it upon his return. "I'm sure it will come out of my pay," he said.
Friday's inspection follows similar scans Discovery's crew conducted as it closed in on the space station on Day 2, and the close-up examinations of "areas of interest" on Day 4.
Discovery's commander, Steve Lindsey, also maneuvered Discovery into a backflip before docking on the third day so that the space station's two crew members could photograph the shuttle's belly for signs of damage.
NASA managers gave Discovery a clean bill of health and cleared it for landing on Monday. They were monitoring glitches with two auxiliary units that power the shuttle's hydraulics system used for steering in flight and braking during landing, but they did not expect them to have any impact on the mission. One power unit had problems with its heaters, and the other appeared to have a leak.
Discovery's six crew members also planned to finish packing up 4,000 pounds (1,814 kilograms) of space station trash and equipment they were hauling back to Earth.