"We've got a great ship and it's ready to come home. It's going to be a safe landing," pilot Mark Kelly said in interviews. "Based on what we've seen so far and what the risk is, I think all of us feel really comfortable."
NASA space station flight director Rick LaBrode praised the crew Friday, saying: "We got our money's worth out of them."
"The mission has gone just outstanding," he said.
The extra shuttle inspection Friday is the first to occur this late in a mission. It was devised by NASA to make sure there's never again a disaster on par with the Columbia accident that killed seven astronauts in 2003.
The crew planned to inspect Discovery's left wing using sensors at the end of a 50-foot-boom attached to Discovery's 50-foot robotic arm. The sensors will scan for any near-invisible holes and cracks in the wing 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, on Day 11, 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 of the 13-day mission.
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 any signs of damage.
After leaving the space station on Saturday, the crew also planned to examine the shuttle's right wing and nose using the robotic arm again.
NASA managers gave Discovery a clean bill of health and cleared it for landing as early as Monday morning. They were monitoring glitches with two auxiliary units that power the shuttle's hydraulics system used for steering and braking during landing, but they didn't 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.
"Fortunately ... they're pretty minor problems," Kelly said.
Discovery's six crew members also planned to finish packing up 4,000 pounds of space station trash and equipment that they will haul back to Earth.
The crew woke up to a recording of the Aggie fight song, played for astronaut Mike Fossum, the first Texas A&M graduate in space.
"You know Mike, there are quite a few Aggies right here in Mission Control, and all throughout Texas, who have been watching you intently during this mission," said astronaut Steve Swanson from Mission Control in Houston. "I think we can say the eyes of Texas are upon you."