Apollo 10 (May 18–26, 1969) was a human spaceflight, the fourth crewed mission in the United States Apollo program, and the second (after Apollo8) to orbit the Moon. NASA described it as a "dress rehearsal" for the first Moon landing, and designated it an "F"mission, intended to test all spacecraft components and procedures short of actual descent and landing. While astronaut John Young remained in the Command and Service Module (CSM) orbiting the Moon, astronauts Thomas Stafford and Gene Cernan flew the Apollo Lunar Module (LM) to within of the lunar surface, the point at which powered descent for landing would begin on a landing mission, before rejoining Young in the CSM. After orbiting the Moon 31 times, Apollo 10 returned safely to Earth; its success enabled the first crewed landing during Apollo 11 two months later. While NASA had considered attempting the first crewed lunar landing on Apollo 10, mission planners ultimately decided that it would be prudent to have a practice flight to hone the procedures and techniques. The crew encountered some issues during the course of the flight, namely pogo oscillations during the launch phase and a brief, uncontrolled tumble of the LM ascent stage in lunar orbit during its solo flight; however, the major mission objectives were accomplished. Stafford and Cernan observed and photographed Apollo 11's planned landing site in the Sea of Tranquility. Apollo 10 spent approximately 61 hours orbiting the Moon, for about eight of which Stafford and Cernan flew the LM apart from Young in the CSM, and about 8 days total in space. Additionally, Apollo 10 set the record for the highest speed attained by a crewed vehicle: 39,897 km/h (11.08 km/s or 24,791 mph) on May 26, 1969, during the return from the Moon. The mission's call signs were the names of the Peanuts characters Charlie Brown for the CSM and Snoopy for the LM, who became Apollo 10's semi-official mascots. Peanuts creator Charles Schulz also drew mission-related artwork for NASA. Framework Background By 1967, NASA had planned the steps that needed to be taken prior to an attempt to land on the Moon. It approved a list of mission types, designated by letters, that needed to be flown prior to a landing attempt, which would be the "G" mission. The early uncrewed flights were considered "A" or "B" missions, while Apollo 7, the crewed-flight test of the Command and Service