Shuttle launch moved to February

Atlantis will deliver the European Columbus laboratory to the ISS

As expected, the tentative 24 January launch of US shuttle Atlantis to the International Space Station (ISS) has been pushed back to 7 February.

The new date will give engineers more time to work on the orbiter's errant fuel sensor system.

The February opportunity is dependent on Russian agreement to reschedule a Progress supply ship mission to the ISS that is set for the same launch window.

Flight rules allow only one vessel at a time to dock at the station.

US space agency engineers are investigating why sensors in the shuttle's fuel tank relayed false readings during launch attempts on 6 December and 9 December, as well as during a fuelling test later in the month.

The sensors, which sit at the base of the shuttle's giant external tank, are part of a backup emergency system to cut off the orbiter's three main engines if they run out of hydrogen propellant before the ship reaches orbit.

Running the fuel pumps and engines without propellant going through them could trigger a catastrophic explosion.

Although they admit to not fully understanding the problem, engineers believe they have a fix; and are moving ahead with the installation of a new electrical connector plate in the wall of the shuttle's tank.

Atlantis' primary task is to deliver the Columbus laboratory, Europe's major contribution to the science endeavours on the International Space Station (ISS).

The 12.8-tonne, 1.3bn euro ($1.8bn; £0.9bn) module will carry out studies that would be impossible in the gravity experienced at the Earth's surface.

The laboratory will be installed by a joint US-European crew on Atlantis.