NASA moved the space shuttle Endeavour to the launch pad early Friday, a precautionary step in case it is needed as a rescue spacecraft for the upcoming Hubble Space Telescope mission.
Endeavour arrived at its destination before sunrise. It marks the first time NASA has had a space shuttle on the launch pad as a rescue ship.
Atlantis and its seven astronauts are set to blast off on the last Hubble repair mission next month. NASA needs Endeavour on standby to bring the astronauts home in case Atlantis suffers irreparable damage during its flight.
While working on Hubble, they will be far away from the international space station, which could normally be used as a safe haven for several weeks if their shuttle were seriously damaged.
Atlantis' launch is set for Oct. 10, but it could be delayed because of payload problems. Essential insulation was blown off the telescope's replacement batteries earlier this week and that must be repaired.