Forecasters expect clear skies for the shuttle's planned 1:02 pm (1802 GMT) landing at the National Aeronautic and Space Administration's Kennedy Space Center at Cape Canaveral, Florida.

If the weather holds, at 1659 GMT NASA's flight director will order shuttle commander Pamela Melroy to engage Discovery's small orbit motors for just less than two minutes to brake the craft so it can begin its hour-long descent to Earth.

If the weather is not ideal, shuttle astronauts will have a second chance 90 minutes later. If that still does not work, NASA will have until Saturday to find a good time to bring home the shuttle and its seven astronauts.

NASA could also order Discovery to land at Edwards Air Force Base in southern California or, as a last resort, the White Sands base in New Mexico.

If Discovery lands in either alternate place NASA would have to fly it back to Cape Canaveral on the back of a specially modified 747 jet.

In its descent Discovery will cross the United States from the northwest down to the southeast in Florida, landing at Cape Canaveral.

NASA officials earlier reported no damage to Discovery's crucial insulation that could endanger the ship during its descent.

The five men and two women aboard Discovery, including Italian astronaut Paulo Nespoli, inspected the craft's thermal skin for damage from micro-meteorites or other objects using a high-definition camera and a scanner attached on the end of a robotic arm operated from inside the cabin.

Discovery separated from the ISS early Monday after an 11-day stay in which astronauts worked on expanding the space station.

The mission required a risky, unplanned spacewalk to repair damage to two solar arrays caused when they were unfurled on wings far out from the station.

US astronaut Scott Parazynsky, a medical doctor by training, spent more than four hours on Saturday attached to the end of a robotic boom knitting together the damaged solar panels.

Braving possible electrocution, Parazynsky used makeshift wire "cufflinks" to fix the tears caused by a snagged wire when the panels opened.

Before heading back to Earth, the shuttle flew around the ISS so crew members could snap images of the repaired solar antenna to document the latest construction work to the orbiting outpost.

On the mission Discovery astronauts also delivered the Italian-built Harmony module, which will connect US, European and Japanese science labs on the ISS.

Their work paves the way for the European Columbus science lab to be installed in the next shuttle mission in early December, and the Japanese Kibo lab, due to be delivered in early 2008.

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