Nasa passed up the shuttle Discovery's first landing opportunity today, bedeviled for a second day by fickle weather at the Kennedy Space Center in Florida.
Flight directors were assessing a second and final opportunity to land the shuttle in Florida at 7.23 pm EDT (2323 GMT).
If the wet and windy weather continues as expected, Nasa will divert Discovery and its seven astronauts to the shuttle's backup landing site at Edwards Air Force Base in California. Touchdown at the Mojave Desert base would occur at 8.53 pm EDT today (0053 GMT on Saturday).
"Basically we have a very unstable day at the Kennedy Space Center," said mission commentator Rob Navias.
Discovery is returning from a 14-day mission to restock the International Space Station with food and supplies for the six-member live-aboard crew, and to deliver equipment for fluid physics and materials science experiments.
The station, a $100 billion project of 16 nations, is scheduled to be finished next year after six more shuttle missions. Nasa then plans to retire its three-ship fleet of shuttles and move on with development of a capsule and rocket that could ferry crews to the moon as well as to the space station.
Those plans may change as President Barack Obama considers the findings of a study team that determined Nasa's budget is about $3 billion a year too small to reach the moon.
The shuttle returns with space station flight engineer Tim Kopra, who has been in orbit for two months. He was replaced by rookie astronaut Nicole Stott, who was the last station crew member to catch a ride on the shuttle. Nasa will begin paying Russia to fly astronauts to the space station, at a cost of about $50 million a seat.
Reuters