Sunday weather "very difficult" for Endeavour

Tonight is not looking like a great one for Endeavour to land as planned, either at its Florida home port or a backup site in California.

Showers and low clouds are forecasted in both places, meaning the six astronauts trying to end a two-week International Space Station assembly mission could be kept in space for an extra day.

In a 1:45 a.m. media briefing, Norm Knight, the entry flight director, noted that conditions could change over the next 24 hours and said the decision would "go down to the wire."

"(Today) is going to be a verry difficult weather day," he said. "We're going to play it by ear. Again, it's going to go down to the wire."

He said a "go/no-go" decision would likely be made about an hour before the deorbit burn that drops the orbiter from space and begins a fiery dive through the atmosphere.

The burn of Endeavour's Orbital Maneuvering System engines is scheduled at 9:14 p.m. EST for the first KSC landing opportunity at 10:20 p.m., on the mission's 217th orbit.

A second opportunity follows one orbit later, at 11:55 p.m.

Although the weather at Edwards Air Force Base in California's Mojave Desert doesn't look any better, Knight said Endeavour would try to land there early Monday if conditions allowed.

Two attempts at Edwards are possible at at 1:25 a.m. and 3 a.m. Monday.

"We're definitely going to try two KSC opportunities (today)," said Knight. "We're going to try our hardest to get on the ground safely. We'll look at Edwards...if an opportunity existed for Edwards (today), we'd probably take a shot at it."

If all those attempts are waved off, conditions late Monday are expected to be favorable at Edwards but worse at KSC, suggesting that Endeavour could be headed for a West Coast landing and ferry flight back to Florida.

White Sands Space Harbour in New Mexico would also be available as a third option Monday night, but the weather is forecasted "no go."

Endeavour could stay in orbit until Tuesday night if necessary, but managers are confident a landing will be possible Monday, if not sooner.

The shuttle crew plans to go to sleep at 6:14 a.m. today and awake at 2:14 p.m.

Deorbit preparations for the first KSC landing attempt are scheduled to begin three hours later.

The orbiter's payload bay doors would be closed around 6:30 p.m. About an hour later, the crew would dress in their orange launch-and-entry suits and start strapping into their seats on Endeavour's flight deck and mid-deck.

Endeavour is still awaiting formal clearance of its heat shields for re-entry, which is expected around 5 a.m.

IMAGES: Long-range ground tracks for Endeavour's two landing opportunities today at Kennedy Space Center, at 10:20 p.m. (top) and 11:50 p.m. (bottom) EST.