Discovery is running on emergency fuel after NASA extend its stay at the International Space Station to repair a stubborn solar panel, using one of the craft's two spare days set aside to allow for landing delays.
With only 24 hours of reserve fuel and unfavourable weather at Kennedy Space Center in Florida, NASA is preparing backup landing sites at Edwards Air Force Base in California and White Sands, New Mexico. High cross winds are making a landing attempt at Edwards unlikely, but White Sands is currently clear. Landing at Edwards will delay the next shuttle launch by a one week, but landing at White Sands will push back Discovery's relaunch date at least a month. Only one shuttle has ever landed at White Sands, in 1982.
The next and final landing opportunity at Kennedy today is at 5.32pm. Three landing windows exist at Edwards - 5.27pm, 7pm and 8.36pm - along with two at White Sands at 5.27pm and 7.02pm. Landing opportunities also are available Saturday at all three sites, but NASA has stated it plans to bring the shuttle back to Earth today.