Buzz Aldrin on July 20, Aldrin and Armstrong entered "Eagle", and began the final preparations for lunar descent. At 17:44:00 "Eagle" separated from the "Columbia". Collins, alone aboard "Columbia", inspected "Eagle" as it pirouetted before him to ensure the craft was not damaged, and that the landing gear was correctly deployed. Throughout the descent, Aldrin called out navigation data to Armstrong, who was busy piloting the "Eagle". Five minutes into the descent burn, and above the surface of the Moon, the LM guidance computer (LGC) distracted the crew with the first of several unexpected alarms that indicated that it could not complete
Buzz Aldrin Collins recovered he joined Armstrong's crew as CMP. In the meantime, Fred Haise filled in as backup LMP, and Aldrin as backup CMP for Apollo 8. An effect of this was that while the CMP usually occupied the center couch on takeoff, Aldrin occupied it rather than Collins, as he had already been trained in it before Collins arrived. Apollo 11 was the second all-veteran multi-person crew on an American mission, the first being that of Apollo 10. An all-veteran crew would not be flown again until STS-26 in 1988. Early versions of the EVA checklist had the Lunar Module