 Edwin " Buzz " Aldrin was originally the backup LMP . When Lovell was rotated to the prime crew , no one with experience on CSM @-@ 103 ( the specific spacecraft used for the mission ) was available , so Aldrin was moved to CMP and Fred Haise brought in as backup LMP . Neil Armstrong went on to command Apollo 11 , where Aldrin was returned to the LMP position and Collins was assigned as CMP . Haise was rotated out of the crew and onto the backup crew of Apollo 11 as LMP . 
