By Jeff Franks HOUSTON, June 22 (Reuters) - NASA looked to Mother Nature for guidance on Friday as it sought for a second day to bring space shuttle Atlantis and seven astronauts home from a two-week-long mission. The U.S. space agency said weather would decide if Atlantis lands at Kennedy Space Center in Florida or at back-up site Edwards Air Force Base in California. Atlantis, returning from a trip to the International Space Station, was scheduled to land on Thursday at Kennedy but got waved off due to bad weather. NASA officials said the shuttle has enough supplies to stay in space until Sunday, but they want it back before then. "We are going to try to land tomorrow," shuttle communicator Tony Antonelli told the astronauts on Thursday from Johnson Space Center. Weather forecasts predicted more rain and clouds at Kennedy on Friday, but NASA said it would try to land Atlantis there at about 2:18 p.m. EDT (1818 GMT). If the clouds persist, the shuttle would instead go to Edwards in the Mojave Desert north of Los Angeles. Forecasts called for possible high winds that also could scuttle a landing. If neither site is suitable, Atlantis would have to wait until Saturday and White Sands Space Harbor in New Mexico, where a space shuttle has landed only once, would become a third landing option. "On Saturday, if we still have not landed, we'll bring up all three sites. This is what we call 'pick 'em day,'" flight director Norm Knight said. The postponed landing is part of a pattern of delays in this shuttle mission. It was supposed to fly in March but the launch had to be put off for three months while NASA repaired the external fuel tank, damaged by a hail storm in late February. It finally launched on June 8. Atlantis was scheduled to fly for just 11 days, but NASA postponed its return to Earth for two days to fix a torn thermal blanket that is part of the shuttle's heat shield. Despite the setbacks, the shuttle crew accomplished its main task: installing a 17-ton metal truss on the station to prepare the half-finished, $100 billion complex for upcoming additions from Europe and Japan. The truss included a new pair of solar energy panels to generate more electricity for the expanding outpost. The Atlantis mission was the first of four shuttle flights scheduled this year as NASA works to finish the space station, a project of 16 nations, before the shuttle fleet is retired in 2010.
