Final inspections of the orbiter's wings and nosecap dispelled concerns about possible damage from the impact of space debris, the space agency said on Sunday.

"Is the vehicle cleared for entry?" Discovery commander Steven Lindsey asked.

"You are cleared for entry," a mission officer said from ground control in Houston, Texas after engineers analysed high definition footage of the shuttle. The footage was taken by the Discovery crew took after the orbiter undocked from the International Space Station (ISS) on Saturday.

The landing will bring to an end the 13-day mission the National Aeronautic and Space Administration hopes will help ease concerns over the shuttle program in the wake the 2003 Columbia shuttle disaster.

"It's been a very, very clean mission. We've had very few glitches," Lindsey said in an interview with US television networks. "We got a clean bill of health," he said.

The late check for space debris hits was a first, and Discovery has been inspected more than any previous shuttle mission.

Like last year's first post-Columbia flight, Discovery's mission was largely aimed at improving safety before NASA resumes regular launches to finish the ISS by 2010, when the three-shuttle fleet is retired.

NASA says the ISS is key to US ambitions to send astronauts back to the moon, and eventually to Mars.

Mike Fossum and Piers Sellers successfully performed three spacewalks, spending more than 21 hours outside Discovery, to test shuttle repair techniques and fix equipment needed to continue building the ISS.

The four men and two women aboard the shuttle delivered critical supplies to the ISS and removed vast quantities of trash, discarded material and experiment results from the orbiting laboratory.

The crew also dropped off European Space Agency astronaut Thomas Reiter of Germany, who became the space station's third resident.

The mission is the second since the Columbia disaster and the first since the shuttle fleet was grounded a year ago after the shuttle's external tank shed a large chunk of foam on take-off.

A similar piece of foam insulation had peeled off on Columbia doomed flight, piercing the shuttle' heat shield and causing the orbiter to burst out in flames as it returned to Earth.

The tank shed some debris this time around, but NASA found no damage on Discovery's heat shield.

If weather permits, Discovery is expected to land at 9:14 am (1314 GMT) Monday on the 4,572-meter (15,000-foot) runway at the Kennedy Space Center (KSC) on Florida's Atlantic coast.

Should weather be unfavorable, the orbiter would have another opportunity to touchdown at KSC about 90 minutes later, and has until Wednesday to land, either at the Florida space center or at alternative landing facilities in California and New Mexico.

"I think we have a pretty good shot at getting to Kennedy on Monday," said Steven Stich, the mission's landing director. "The weather looks fairly reasonable," he said, pointing out however that rainsstorms were common at this time of year in southern Florida.

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