The shuttle touched down at Kennedy Space Center at 6:21 am (1021 GMT), in the space shuttle program's 15th nighttime landing in Florida.

"Welcome back, Congratulations on return," NASA communicator Tony Antonelli told the Atlantis crew as they ground to a halt on the runway.

"It's nice to be back," answered Atlantis Commander Brent Jett, who piloted the third shuttle mission since the 2003 Columbia disaster that killed seven astronauts.

The shuttle's landing was delayed by 24 hours after several small, unidentified objects were discovered orbiting along with Atlantis. On closer inspection Wednesday, the objects were deemed to be objects lost by the shuttle during its maneuvers.

Shuttle program manager Wayne Hale said it was common to lose "little things", like a plastic bag or pieces of plastic, during shuttle missions.

The inspection also checked for damage to Atlantis' heat shield, which was found in good shape.

Atlantis blasted off from Kennedy Space Center on September 9 after five delays over a period of two weeks, due first to a lightning strike and a looming tropical storm, and then technical glitches.

It arrived at the space station two days later to install the first addition to the half-finished ISS since November 2002. The vehicle separated from the ISS on Sunday.

The astronauts used the station's Canadian-made robotic arm to attach a 16-tonne truss segment with two solar arrays to the ISS. Three spacewalks were then needed to set up the system.

Astronauts Heidemarie Stefanyshyn-Piper and Joe Tanner conducted the first and third space excursions, while Canadian astronaut Steve MacLean and US counterpart Dan Burbank performed the second spacewalk.

The solar arrays, unfurled last week, measure 240 feet (73 meters), and will ultimately provide a quarter of the outpost's power. They will be activated during a Space Shuttle Discovery mission planned for December, doubling the space station's current power capacity.

When it is finished in 2010, the station will be bigger than a five-room house and will weigh approximately 450 tonnes.

It will be equipped with four double solar panels capable of generating 110 kilowatts of electricity, enough to supply roughly 55 middle-class homes.

About 46 kilowatts of that will be used for scientific research, the scope of which will more than triple compared with what is currently available.

Space station manager Mike Suffredini noted on Tuesday that the Atlantis mission was complex but succeeded beyond expectations.

He warned, however, that future building missions will be even more difficult and will include tasks never performed in space.

NASA plans 15 more flights to complete construction of the ISS by 2010, when the three-shuttle fleet is to be retired.

The Atlantis mission was hailed as further confirmation that the shuttle program had returned to normalcy after being rocked when Columbia disintegrated on re-entry in February 2003.

The last two missions aboard the Discovery shuttle, in July-August 2005 and last July, were aimed at improving safety.

As part of the new safety measures, Atlantis's heat shield was photographed as it headed to the ISS to check for potential damage caused during liftoff.

The US space agency has strived to avoid damage to the orbiter's heat shield since a crack in Columbia's protective skin caused it to blow apart as it returned to Earth.

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