The launch of the Endeavour spacecraft for the STS-127 mission, originally scheduled for 13 June 2009, has been delayed to fix a leak on the rocket.

The leak related to the gaseous hydrogen venting system outside Endeavour’s external fuel tank is being repaired by changing out internal seals in the ground umbilical carrier plate (GUCP) that is attached to the external tank.

The vent line runs from the GUCP to a ‘flare stack’ where excess hydrogen is safely burned off.

The shuttle will be ready for lift-off by 17 June, although that date coincides with the scheduled launch date of Nasa’s lunar reconnaissance orbiter / lunar crater observation and sensing satellite (LRO/LCROSS).

It has been decided that if repairs are successful, Endeavour will be launched on 17 June and the LRO/LCROSS launch will take place on 19-20 June 2009.

However, if the spacecraft doesn’t launch for the International Space Station that day, LRO/LCROSS will launch instead and the STS-127 mission will make an attempt on 20 June.

The STS-127 mission will involve spacewalks to install the new Japanese Laboratory outside the ISS for experiments.