The six astronauts aboard the space shuttle were set to make final preparations to re-enter the Earth's atmosphere for a 9:14 am (1314 GMT) touchdown at the Kennedy Space Center in Cape Canaveral, Florida, weather permitting.

"We're looking forward to a good day and all hoping for good weather," said Commander Steven Lindsey, after mission control in Houston, Texas, woke up the four men and two women to the tune of "The Astronaut" by pop band Something Corporate.

The final moments of a shuttle mission are among the most dangerous, and it was upon re-entering Earth's atmosphere that Columbia had burst into flames in February 2003, killing all seven astronauts.

NASA hopes Discovery's mission will help ease concerns over the shuttle program that have persisted since the disaster.

Like last year's first post-Columbia flight, the latest shuttle voyage was largely aimed at improving safety before NASA resumes regular launches to finish constructing the International Space Station (ISS) by 2010, when the three-shuttle fleet will be 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.

"I hope our legacy was that we closed out the return to flight test portion of the program following the Columbia accident," Lindsey told the ABC television network. "I personally believe we are back on track."

Before giving the green light to prepare for a return to Earth, NASA experts viewed footage of the orbiter's wings and nosecap to ensure they had not suffered damage from the impact of sand-sized micrometeorites.

Once the crew get the final go-ahead, Lindsey and co-pilot Mark Kelly will rotate the orbiter into its descent position and fire up the two orbital jets for three minutes to lose enough altitude to begin re-entry into the Earth's atmosphere.

Slowing down the orbiter by about 300 kilometers (190 miles) per hour, at a time when Discovery is still flying at about 29,000 kilometers (18,000 miles) per hour, gets the shuttle off its orbit and into a plunge toward Earth that lasts over an hour.

About 30 minutes before landing, the craft encounters the first layers of Earth's atmosphere.

At that stage, the shuttle is no longer powered by engines, but glides toward the shuttle landing facility. Two sonic booms are expected to be heard as it slices through the atmosphere.

It touches down at about 350 kilometers (220 miles) per hour, and coasts to a stop with the help of a drag chute.

Should bad weather prevent a landing at the Kennedy Space Center on Monday, Discovery has another opportunity 90 minutes later, or could land by Wednesday, at the latest, at an alternate facility in California or another in New Mexico.

But NASA officials hoped a flawless, on-time touchdown at the Kennedy Space Center's 4,572-meter (15,000-foot) runway would cap what they have called a very successful mission.

During their 13 days in space, astronauts Mike Fossum and Piers Sellers 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 delivered critical supplies and removed vast quantities of trash, discarded material and experiment results from the orbiting laboratory.

They 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 because the shuttle's external tank had 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.

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