Discovery will return home after a 13-day mission to the International Space Station, seen as a critical step for the US space program's recovery from the 2003 Columbia disaster.
"You are cleared for entry," a mission official said from ground control in Houston, Texas after engineers analysed high definition footage of the shuttle’s wings and nose-cap.
The pictures were taken by the Discovery crew took after the orbiter undocked from the International Space Station (ISS) on Saturday and there seemed to be no damage from space debris hitting the exterior.
While the space shuttle crew readied for the return trip, Mission Control was keeping a close watch on the weather around the Kennedy Space Center in Florida, where Discovery was scheduled to land approximately 9:14 am local time on Monday (10.14 pm AEST).
Clean mission: commander
National Aeronautic and Space Administration (NASA) officials said the late check for space debris hits was a first, and more inspections were carried out during this mission than ever before.
"It's been a very, very clean mission. We've had very few glitches," Discovery commander Steven Lindsey said in an interview with US television networks. "We got a clean bill of health," he said.
NASA hopes the mission will help ease concerns over the shuttle program that have persisted since Columbia burst into flames upon re-entry into the Earth's atmosphere in February 2003, killing the crew of seven.
Like last year's first post-Columbia flight, the latest 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 orbiting space station is a key component in US plans to send astronauts back to the moon, and eventually to Mars.
Astronauts 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 crew aboard the shuttle delivered critical supplies and removed vast quantities of garbage, 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's doomed flight, piercing the shuttle's heat shield and causing the orbiter to break apart as it returned to Earth.
The tank shed some debris this time around, but NASA found no damage on Discovery's heat shield.
Weather permitting, Discovery should land Monday morning at the Kennedy Space Centre but if the weather is unfavorable, the orbiter would have another opportunity to touchdown at KSC about 90 minutes later.
It 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 that rainstorms were common at this time of year along southern Florida's Atlantic coast.