Payload snag likely to delay shuttle program's end

NASA is re-evaluating the launch dates for the final two shuttle missions because a science instrument scheduled to fly in July won't be ready in time.

The change could push the final shuttle mission, which had been targeted for mid-September, closer to the end of the year.

NASA is considering a range of scenarios that could include swapping the last two missions or swapping their payloads.

Endeavour was targeted to launch the Alpha Magnetic Spectrometer to the International Space Station on July 29.

But scientists have decided to change a magnet inside the particle physics instrument, which is designed to detect dark matter, delaying its readiness by an as yet undetermined period of time.

The changes will not impact the next scheduled mission by Atlantis, which could roll out to launch pad 39A today or tomorrow and is targeted to launch May 14.

NASA had planned to fly out the remaining three shuttle missions by the end of the 2010 fiscal year, ending Sept. 30. Discovery, which landed today, was to launch Sept. 16.

But Congress gave the shuttle program $600 million for the first quarter of the 2011 fiscal year to provide schedule flexibility in case weather or technical problems caused delays.

IMAGE: The Alpha Magnetic Spectrometer. Credit: NASA.