Space shuttle launch delayed until today

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CAPE CANAVERAL, Fla., Dec 7 (Reuters): NASA postponed Friday's launch of space shuttle Atlantis to resolve a fuel sensor problem and officials said it would be Saturday at the earliest before they tried again.
It was the second time Atlantis' launch was delayed, having originally been scheduled to go aloft Thursday until two sensors in its external tank failed a routine check.
Engineers believe the sensor problem, which cropped up while the shuttle was being filled with fuel for the space freighter's 8.5-minute sprint to orbit, was due to an open circuit.
Managers discussing whether to launch the orbiter Friday met all afternoon and into the evening.
NASA has until December 13 to launch the 11-day mission this year and take Europe's Columbus science laboratory to the space station. Atlantis must leave the station before the angle of the sun's rays change, which would overheat the orbiter.
There are four engine cut-off sensors in the ship's fuel tank that monitor levels of liquid hydrogen and two of them failed. The shuttle uses more than 500,000 gallons (2.2 million litres) of cryogenic hydrogen and oxygen to get into orbit.
The sensors are part of a backup safety system to shut down the shuttle's main engines once the ship reaches space or if a problem occurs after liftoff. If the engines continued to run once the fuel supply was gone, an explosion could destroy the orbiter.
Engineers need to drain the tank and verify all the sensors are working as they go dry, NASA said in a statement.
NASA wrestled with a series of fuel tank sensor problems as it attempted to resume shuttle flights following the 2003 Columbia accident.
The first post- Columbia mission in July 2005 was delayed 13 days due to sensor glitches.