CAPE CANAVERAL, Fla. (AP) _ NASA called off Thursday's launch of space shuttle Atlantis after detecting problems with a pair of fuel gauges in its big external tank, a recurring problem ever since the Columbia disaster.
Shuttle managers said they would try again Friday, provided the problem can be solved quickly.
Preliminary indications are that the problem might be with an open circuit rather than the gauges themselves _ perhaps a spliced line or bad connector _ which would be easier to fix.
``We're keeping all our options open,'' said launch director Doug Lyons.
Shuttle managers planned to meet in the afternoon to decide on a course of action.
Lyons said he was hopeful the launch team would get another crack at getting Atlantis off the pad before the end of next week. Because of poor sun angles and computer concerns, NASA would have to wait until the beginning of January to launch Atlantis and the European Space Agency's space station lab, Columbus, if they aren't flying by next Thursday or Friday.
Thursday's postponement was a keen disappointment for the European agency. The $2 billion lab has been in the works for nearly a quarter-century, and was held up for years by NASA's repeated space station design problems and, more recently, the 2003 Columbia tragedy.
The three astronauts aboard the international space station also were dismayed by the news.
Shuttle commander Stephen Frick passed on some consoling remarks through Mission Control.
``He says that he's sorry they're going to be a little bit late and they'll get there as soon as they can,'' Mission Control radioed the space station crew. ``Aw, that was sweet,'' commander Peggy Whitson replied from orbit.
NASA had begun filling Atlantis' fuel tank and was testing the four engine-cutoff sensors in the liquid hydrogen section when two of them failed. Even though they were commanded to indicate the tank was empty, the two kept showing the tank was full, Lyons said. At least three of these sensors must work properly to proceed with a launch.
``Right then, we knew we had an issue and we stopped,'' Lyons said.
The launch was still more than eight hours away, and Frick and his six crewmates had yet to climb aboard.
The sensors are part of a critical backup system to ensure that the shuttle's three main engines don't shut down too soon or too late during liftoff. Problems with the sensors have delayed shuttle launches before, most recently in September 2006. The trouble began cropping up following the Columbia disaster.
The postponement broke NASA's streak of on-time shuttle launches for the year. Each of the year's previous three countdowns ended in on-the-dot departures.