Shuttle forecast: Desert landing? The only time a space shuttle touched down at NASA's landing strip in the New Mexico desert, in 1982, the air held so much grit that workers spent days cleaning it out of the ship. They even had to chip out a hardened mixture of dust and fuel from the thrusters. Now NASA is preparing for the possibility that, for the first time in 24 years, it will once again have to land a shuttle at that same strip, the White Sands Space Harbor. After 13 days in orbit, shuttle Discovery is due to touch down Friday as early as 3:56 p.m. ET. It will not be a standard shuttle landing because NASA has less time to play with, and it will force NASA to make some difficult choices. A combination of tight schedules and bad luck conspires to make a White Sands landing more likely than in other years. Bad weather is forecast Friday for both the shuttle's primary landing site at Florida's Kennedy Space Center and the backup site at California's Edwards Air Force Base. Good weather is forecast for White Sands. "I wouldn't go so far as to say any of the sites is a leading candidate," mission operations chief Phil Engelauf said Wednesday, while conceding that "today's forecast looks more encouraging for White Sands than for the other sites." Before this mission, NASA always managed shuttle flights so the ship could spend an extra day in space in case of equipment problems and another extra day for bad weather. This time, the bad-weather day was eaten up by an unplanned spacewalk to fix a balky solar panel on the International Space Station. That leaves only one day's cushion. On Sunday, the shuttle would run out of fuel to make power. So for the first time in the shuttle's 25-year history, NASA officials are racing to prepare all three landing strips for the first landing opportunity Friday. Usually only the strip at Kennedy Space Center is readied for the first landing opportunity. Shuttles are stored and groomed for flight at Kennedy and also launch from there, so landing in Florida saves NASA time and money. When weather has been bad at Kennedy, NASA also has prepared the backup site at Edwards Air Force Base. Fifty of the shuttle's 114 safe returns have been at Edwards. NASA prefers not to land at Edwards because the shuttle must be shipped from California to Florida atop a special Boeing 747 jet. That costs $1 million and adds a week or more to the time needed to turn the shuttle around for the next flight. White Sands has never been prepared for a first landing attempt because it has less infrastructure than the other sites. The cold temperatures expected this weekend make it more likely that thrusters would leak and pipes would freeze. That adds "risk to the ground personnel," said a memo sent to Discovery's crew Wednesday and posted on NASA's website. Then there's the dust, which gives White Sands its name. It's "white and very fine, almost like talcum powder," says Gordon Fullerton, the pilot of shuttle Challenger for the 1982 New Mexico landing. He said the dust got into "every fissure of the orbiter." At least landing at White Sands would not be more difficult for Discovery commander Mark Polansky, says Jack Lousma, Columbia's commander for the '82 landing. As part of their shuttle training, astronauts fly a jet that mimics the shuttle's handling over White Sands, so "the crew is very familiar with the area," he says. On Friday, entry flight director Norm Knight will have to juggle all three sites and decide whether it would be best to bend rules about acceptable landing weather. "The one thing we always like to have is more options and more margin," Engelauf said. "We've taken a little bit of the latitude off of the table. … It makes Norm's job a little more difficult."