Ready For Its Friday Night Date

(CBS)  After almost two weeks of delay, space shuttle Endeavour was patched and poised to blast off Friday night, with clear skies and gentle breezes in central Florida.

However, CBS News Correspondent Peter King reports bad weather 4,000 miles away at two emergency landing strips in Spain threatened to interfere. The weather there was dismal, with rain, thick clouds, wind and turbulence.

NASA began fueling the ship's rockets just after noon.

NASA spokesman Bruce Buckingham said the space agency was pressing ahead with the countdown and holding out hope that one of the two Spanish airstrips would be acceptable by the 8:15 p.m. EST launch time. Only one locale is needed; it would be used only if the shuttle developed engine trouble or some other emergency in the minutes following liftoff.

"We're taking our best shot today," Buckingham said. "The weather, we'll deal with it when we get down to launch."

NASA has had to delay shuttle launches only a few times before because of bad weather overseas. The last time was in 2000.

The shuttle's fueling — and its launch — were nearly delayed by a troublesome gaseous nitrogen valve in the ship's mobile launch platform, reports CBS News Space Consultant Bill Harwood. The valve is part of a system that purges critical areas with inert nitrogen gas as required. In the event of an on-pad engine shutdown, known as a redundant set launch sequencer abort, the nitrogen purge system could prove crucial.

Endeavour's flight to the international space station had been postponed by a leaking oxygen line and a damaged robot arm. The damage was caused by workers who accidentally rammed a platform into the 50-foot robot arm.

The robot arm is needed to lift a 14-ton girder from the payload bay for installation on the space station.

Besides performing construction work, the shuttle astronauts will deliver a fresh three-man crew to the space station and bring back the one American and two Russians who have been on board since early June. Friday was their 170th day in orbit.

NASA's last countdown was halted Nov. 10 at the two-hour mark because of a leak in the astronauts' oxygen supply. A cracked hose was replaced. The robot-arm damage occurred while workers were hunting for the leak.

The space agency currently staffs only two landing sites overseas, on opposite ends of Spain.

A Moroccan air base that used to serve as an emergency landing site has not been considered for months because of security concerns. It would take more than a week for NASA to get it ready, Buckingham said.

CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.