The orbiter landed on schedule under overcast skies at the Kennedy Space Center at 9:14 am (1314 GMT) after what the National Aeronautics and Space Administration (NASA) called a highly successful mission.

Officials heaved a sigh of relief as a parachute deployed from the shuttle's rear, and Discovery came to a full stop on the 4,572-meter (15,000-foot) Atlantic seashore runway, safely returning the six astronauts to Earth.

"Welcome back Discovery and congratulations on a great mission," ground control told the crew of six, as they shut down the systems and prepared to leave the space vehicle.

"The crew of Discovery is safely home," mission control said.

Two high-altitude aircraft equipped with high-tech cameras accompanied Discovery as it glided to the landing strip after soaring over southern Mexico and across the Gulf of Mexico. Its arrival was heralded by two resounding sonic booms.

The final moments of the mission are among the most critical, and it was upon re-entering into the Earth's atmosphere that Columbia had burst into flames on February 1, 2003.

As it slices through the atmosphere, a shuttle is no longer powered by engines, but glides toward the landing facility. It touches down at about 350 kilometers (220 miles) per hour.

NASA hoped Discovery's successful mission would help ease concerns over the shuttle program that have persisted since the Columbia disaster, and pave the way for a resumption of regular flights in August.

Like last year's first post-Columbia flight, the latest shuttle voyage was largely aimed at improving safety of the shuttle missions that are critical to plans to complete construction of the International Space Station (ISS) by 2010.

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

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 three-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, when Discovery blasted off from KSC on July 4, but NASA found no damage on Discovery's heat shield.

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