With Hurricane Josephine posing less of a threat to the Florida coast, space shuttle flight directors today confirmed Challenger's landing for Saturday and then turned their attention to Thursday's double spacewalk -- including the first by an American woman.

But although flight directors were returning to their original schedule, they insisted that they were not committed to a Saturday landing or even a touchdown at Florida's Kennedy Space Center. Everything depends on what Josephine does in the next few days.

"If the weather is unacceptable, if we've got a hurricane sitting over the Cape on Saturday, then we'll go right on into Edwards Air Force Base in California either Saturday or Sunday," Flight Director Cleon Lacefield said at Houston's Johnson Space Center. "We'll make our wave-off decision at the last minute if we have to."

Early this morning, flight directors scheduled the once-postponed spacewalk of astronauts David C. Leestma and Kathryn D. Sullivan for Thursday morning instead of moving it back to Friday, as they were thinking of doing if Josephine made a move toward the coast.

In any case, Sullivan will be the first American woman to walk in space. Soviet cosmonaut Svetlana Sovitskaya walked in space last July.

Sullivan and Leestma are due to don space suits early Thursday morning, then step through the shuttle's airlock and into its cargo bay at 11:33 a.m. EDT. The two astronauts are to spend between three and four hours in the cargo bay, where they will lock up the two "leaves" of a 15-foot-wide imaging radar experiment, transfer 550 pounds of cold, toxic hydrazine fuel from one tank to another and fasten down an erratic radio dish antenna that has troubled the mission from the beginning.

The most important part of Thursday's space walk is the fuel transfer, an experiment never done in space. It is a rehearsal for a later shuttle crew that will transfer fuel to an orbiting Landsat satellite that has run out of maneuvering fuel.

Sullivan is to stow the imaging radar antenna, while Leestma is to perform most of the fuel transfer, using wrenches and tools to open valves that will move fuel from one tank to a second and then back to the first.

The crew has been able to pump hydrazine fuel from one tank to another by radio commands from the cabin, but the spacewalk will be the true test of what a later crew can accomplish. The weightlessness of space makes it difficult to move liquid from one place to another.

After the fuel transfer, Sullivan and Leestma are to move to the edge of the cargo bay to lock down the flopping antenna. It must be stowed and locked to clear the cargo bay doors when they're closed just before reentry on Saturday. The astronauts may even take a sleeping bag with them to cover the antenna and tie it down to make sure it doesn't flop around inside the cargo bay during Challenger's return to Earth.

Sullivan, who has been described as the "plumber's apprentice" to Leestma during the fuel transfer, may well get to take over during the antenna stowing.

Said Lacefield: "It's a crew call. They'll both decide at the last minute who gets to do what."