Final shuttle mission to deliver Alpha Magnetic Spectrometer to the International Space Station. Image Credit: AMS-02 Roma Group

NASA announced Tuesday a re-scheduling of the launch dates for its final two shuttle missions to accommodate payload preparations.

Shuttle Discovery’s eight-day re-supply mission to the International Space Station, which had been scheduled for a Sept. 16 lift off, is moving to Oct. 29. Discovery will deliver Leonardo, an equipment storage compartment.

Shuttle Endeavour’s 10-day mission to deliver the Alpha Magnetic Spectrometer to the station, which had been tentatively scheduled for a late November lift off, moves to Feb. 28, 2011. The AMS is an external observatory, prepared by a large team of international scientists, for studies of cosmic rays and anti-matter.

The space agency has not yet made a decision on whether Atlantis, which will be prepared as the rescue mission shuttle for the Endeavour flight, will be launched instead as an operational mission. That decision will likely not be made until August.

If Atlantis were to fly again, as some in Congress are urging, NASA would prefer a June or July 2011 lift off. Discovery’s six member crew is led by veteran astronaut Steve Lindsey. Endeavour’s six-member crew is led by veteran astronaut Mark Kelly.