The last two launches officially scheduled for the year, which could be followed by one more shuttle mission if budgets allow, will mark the end of the US space shuttle program.
Discovery, which was to launch in November but was postponed due to leaks on its external fuel tank, is to attempt take off at 4:50 pm (2150 GMT) on Thursday, February 24.
Endeavour is set for liftoff from NASA`s Kennedy Space Center in Florida on April 19 at 7:48 pm (0048 GMT).
Astronaut Mark Kelly is scheduled to lead Endeavour`s mission, and NASA declined to comment this week on whether that plan still stands.
Kelly`s wife, Arizona Congresswoman Gabrielle Giffords, is recovering from a bullet to the head after a gunman went on a lethal shooting spree at a grocery store where she was meeting with voters. (*)