NASA gave Discovery and its crew of seven astronauts a "'go' for the deorbit burn" after scrapping its first attempt to land the huge craft because of low lying clouds and strong winds at Florida's Kennedy Space Center landing site.

The three to four minute burn will slow Discovery's orbit so it can slip back into the Earth's atmosphere at 25 times the speed of sound, ready for a 3:14 pm (1914 GMT) landing.

Discovery's arrival, shooting above Central America and the Gulf of Mexico, will be announced with a triumphant double sonic boom to shake the Kennedy Space Center.

In anticipation of a smooth landing NASA said the crew, who spent nine days of their mission docked at the International Space Station (ISS), spent part of Friday checking over the shuttle's flight control surfaces.

These components "need to guide the orbiter's unpowered flight through Earth's atmosphere," the space agency said in statement.

The hundred-tonne glider will descend for just over an hour from an altitude of 217 miles (350 kilometers), with all the maneuvers operated automatically by onboard computers until flight controls are passed over for a manual descent just in the last three minutes.

Crew members also checked for damage to the craft that may have been sustained during their flight -- a standard operating procedure after February 2003 when the Columbia shuttle disintegrated as it re-entered Earth's atmosphere, killing all seven crewmembers.

The accident was blamed on a piece of debris that broke off the external tank at launch and struck one of Columbia's wings, gouging a hole in it.

When Columbia was just minutes away from touchdown, super-heated air penetrated the aircraft's insulation and burned through the structure of the wing, eventually causing the shuttle to break up.

The shuttle program resumed with the first lift-off of Discovery in July 2005.

After packing and organizing the shuttle cabin, Discovery crew members Friday gathered on the flight deck to discuss their flight with students of Punahou School in Honolulu, Hawaii, NASA said.

Discovery docked at the ISS on March 17, two days after its launch. One of the mission's biggest tasks was to deliver the orbiting laboratory's last set of solar arrays, which were successfully unfurled Friday.

The ISS now has four solar panels, two per wing, containing 32,800 cells that convert sunlight into electricity.

They will boost the outpost's full power generation from 90 to 120 kilowatts, providing the power the space station needs to carry out scientific experiments in the European Columbus laboratory and Japan's Kibo lab.

After being delivered by Discovery, astronaut Koichi Wakata has become the first long-stay Japanese crewmember to remain on the ISS. He replaced US flight engineer Sandra Magnus, who had been on the outpost since November and is returning to Earth aboard the Discovery.

During the mission the shuttle crew and ISS residents enjoyed a 30-minute video conference call from the White House with US President Barack Obama and some Washington schoolchildren.

Space-fan Obama, also flanked by lawmakers, peppered the crew with questions, wanting to know everything about life in space from the latest mission of the Discovery space shuttle to fitness, food and hairstyles.

"I'm told that you're cruising at about 17,000 miles per hour. So we're glad that you are using the hands-free phone," Obama told the astronauts floating several hundred miles above Earth.

"Mr President, we go around the planet once every 90 minutes. It's quite a thrill, and it is very fast, and we see 16 sunrises and 16 sunsets every day," said ISS commander Michael Fincke.

The next manned space launch, for the shuttle Atlantis, is scheduled for May 12 in a final mission to repair and maintain the Hubble space telescope.

Eight more shuttle launches are scheduled up to September 30, 2010 -- the retirement date for the orbiter crafts.

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