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 nautical mile (km) 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.