Apollo 10 was the fourth manned mission in the United States
Apollo space program, and the second (after
Apollo 8) to orbit the
Moon. Launched on May 18, 1969, it was the
F mission: a "dress rehearsal" for the first
Moon landing, testing all of the components and procedures, just short of actually landing. The
Lunar Module (LM) came to within of the
lunar surface, the point where the powered descent to the lunar surface would begin. Its success enabled the first landing to be attempted on
Apollo 11 in July, 1969.