The six astronauts aboard the space shuttle were aiming for a 9:14 am (1314 GMT) touchdown at the Kennedy Space Center (KSC) in Cape Canaveral, Florida.

"For the time being, the weather is looking good," said Allard Beutel, a spokesman at the Atlantic seashore facility, adding however that officials were keeping a close watch on a nearby rainshower front.

Early Monday, the crew shut the huge doors on the outside of the payload area in readiness for the return journey.

"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.

The National Aeronautics and Space Administration (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.

NASA says the orbiting space station is a key component in US plans to send astronauts back to the moon, and eventually to Mars.

Once the crew get the final go-ahead, Lindsey and co-pilot Mark Kelly 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.

As it slices through the atmosphere, the shuttle is no longer powered by engines, but glides toward the shuttle landing facility. 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 the scheduled KSC landing, Discovery has another opportunity about 90 minutes later, and has until Wednesday to be back on the ground. If a Florida touchdown is not possible, it could head to an alternate facility in California or another in New Mexico.

But NASA officials hoped a flawless, on-time touchdown at KSC'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 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.

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