Apollo 10 was the fourth crewed 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 Apollo Lunar Module (LM) was flown to a descent orbit within 8. 4 nautical miles (15. 6 km) of the lunar surface, at the point where powered descent for landing would normally begin. Its success enabled the first landing to be attempted on the Apollo 11 mission two months later.