On its expected last full day in orbit, the crew of space shuttle Discovery on Friday was set to check out its flight control systems and steering jets in preparation for landing the next day.

The shuttle's heat shield has already been given the thumbs up for the return trip to Earth.

"Discovery is coming home," Garrett Reisman, who is returning on the shuttle after living on the international space station for three months, said Friday.

Friday is "a get ready for entry day" as the shuttle's entry systems are tested to ensure they are working properly, said LeRoy Cain, chairman of the mission management team.

Late Thursday afternoon, engineers finished scrutinizing all the images of the shuttle's heat shield on the wing and nose collected Wednesday with a laser-tipped inspection boom.

"Looks like you have a clean orbiter," Mission Control radioed the shuttle astronauts.

Discovery's heat shield was set to be given formal clearance for landing during the mission management team's meeting Friday afternoon. Discovery is scheduled to land Saturday morning in Florida.

The thermal survey _ an exhaustive search for damage _ was conducted later than usual because the astronauts had to wait until they got to the space station to retrieve their inspection pole. There wasn't enough room aboard Discovery for the pole at liftoff because the Japanese lab they had took up nearly all the room in its payload bay.

The inspection is one of the safety measures put in place by NASA after the 2003 Columbia accident. Columbia was destroyed during re-entry as a result of a gashed wing.

Discovery's crew of seven delivered and installed the new lab named Kibo, Japanese for hope, to the space station.

Besides delivering the new lab, the shuttle also dropped off Gregory Chamitoff, the station's newest crew member. He traded places with Reisman. Chamitoff will stay on the station for six months.

"We had a very successful shuttle mission, with the Japanese module attached. It's a very big facility now," Chamitoff told German President Horst Kohler during a call to the space station Friday morning in which the outpost's three-man crew spoke with German officials.

The 37-foot lab, about the size of a bus, is the biggest room at the space station. Kibo also has a storage closet and a 33-foot robotic arm. A final section _ a "porch" for exterior experiments _ and a second, smaller robotic arm will be delivered next year.

Discovery also brought a pump that fixed the space station's malfunctioning toilet. The problem had forced the station's three-man crew to flush manually with extra water several times a day.

NASA, meanwhile, continues investigating what caused extensive damage at the launch pad used to shoot Discovery into orbit two weeks ago.

About 5,300 bricks flew off the pad during Discovery's launch on May 31, exposing a thick concrete wall underneath. The pad was built for the Apollo moon shots, and the bricks might not have adhered properly to the wall of the flame trench when they were installed in the 1960s, Cain said.

The flyaway bricks posed no danger to Discovery, but NASA wants to fix the flame trench _ designed to deflect the exhaust of the booster rockets _ so it does not get worse. Cain said he's confident it will be repaired in time for the next shuttle flight in October.

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