The launch of space shuttle Atlantis has been delayed until tomorrow (Saturday) at the earliest after the failure of two of four sensors which monitor liquid hydrogen levels in the vessel's fuel tank, Reuters reports.

The glitch was spotted during routine checks as the tank was being filled with fuel. The offending sensors form part of a back-up safety system which shut down the shuttle's main engines once the ship reaches space, or "if a problem occurs after liftoff".

NASA explained: "On Thursday morning, two of the four engine cutoff, or ECO, sensors inside the liquid hydrogen section of the tank failed a routine prelaunch check. Following the launch postponement, the tank's liquid oxygen and liquid hydrogen were drained.

"While the tank was being emptied, engineers monitored and collected data on the liquid hydrogen sensors that failed. During that process, another sensor gave a false reading, indicating that the tank was 'wet', when it was dry. All ECO sensors are now indicating dry as they should be."

Atlantis has a launch window extending to 13 December, and when it eventually gets off the ground will carry the European Space Agency's Columbus laboratory to the ISS.

US astronauts commander Stephen Frick, pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin and Stanley Love will be joined by Germany's Hans Schlegel and Leopold Eyharts of France on the 11-day mission. ®

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