The Nasa Apollo 10 Mission

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The Apollo 10 spacecraft was the second Apollo mission to orbit the Moon, and the first to travel to the Moon with the full Apollo spacecraft, consisting of the Command and Service Module (CSM-106, "Charlie Brown") and the Lunar Module (LM-4, "Snoopy"). The primary objectives of the mission were to demonstrate crew, space vehicle, and mission support facilities during a manned lunar mission and to evaluate LM performance in cislunar and lunar environment. The mission was a full "dry run" for the Apollo 11 mission, in which all operations except the actual lunar landing were performed. The flight carried a three man crew: Commander Thomas P. Stafford, Command Module (CM) Pilot John W. Young, and Lunar Module (LM) Pilot Eugene A. Cernan.

On 22 May Stafford and Cernan entered the LM and fired the SM reaction control thrusters to separate the LM from the CSM at 19:36:17 UT. The LM was put into an orbit to allow low altitude passes over the lunar surface, the closest approach bringing it to within 14 km of the Moon. All systems on the LM were tested during the separation including communications, propulsion, attitude control, and radar. Numerous close-up photographs of the Moon's surface, in particular the planned Apollo landing sites, were taken. The LM descent stage was jettisoned into lunar orbit. The LM and CSM rendezvous and redocking occurred 8 hours after separation at 03:22 UT on 23 May.

Mission Activities of Apollo 10 included:

1. A variety of engineering tests were performed, considerable photography was obtained, and landmark tracking data were gathered to reduce the size of the landing ellipse for the next space mission. The major activity for this mission was, of course, the simulated lunar landing with the lunar module.
2. Lunar Module Activation - The checkout proceeded smoothly and was completed in about two hours. The lunar module appeared to be in the same condition as observed during closeout activity before launch. Transfer of stowage items and required housekeeping chores were performed. The transfer from command module to lunar module power was performed without incident. A landmark tracking training exercise was also performed during the checkout period.
3. Lunar Module Operations - The lunar module testing phase of the mission lasted for more than six hours and involved a number of operations: the undocking and separation of the lunar module; a series of communications and radar checks; the firing of the descent engine and moving to within 8 miles of the lunar surface; checking the landing radar over one of the selected landings sites; and modifying the orbit in preparation for the return to the command module, staging the lunar module to simulate an ascent from the lunar surface, and performing the rendezvous with the command service module.
4. Landmark Tracking - This was one of the activities planned for the final day in lunar orbit. Landmark tracking was performed on four landmarks each revolution for four consecutive revolutions. This activity required close coordination between the commander, command module pilot, and the network.

All detailed test objectives were satisfied with the exception of the lunar module steerable antenna and relay modes for voice and telemetry communications. Problems with the steerable antenna test objective were due to the track mode not being switched properly. The communication relay modes test objectives were not demonstrated due to a lack of time rather than any problems.

Highlights of the mission include:

• Demonstration of color TV camera operating from space.
• The second Apollo mission to orbit the Moon.
• This was the first time the complete Apollo spacecraft had operated around the Moon and the second manned flight for the lunar module.
• Two Apollo 10 astronauts descended to within eight nautical miles (14 kilometers) of the Moon's surface, the closest approach ever to another celestial body to date.
• All aspects of Apollo 10 duplicated conditions of the lunar landing mission as closely as possible in anticipation of a future mission's landing on the moon.
• Apollo 10 was the only Apollo mission to launch from Launch Complex 39B.
• The maximum separation between the LM and the CSM during the rendezvous sequence was about 350 miles (563 km) and provided an extensive checkout of the LM rendezvous radar as well as the backup VHS ranging device aboard the CSM, flown for the first time on Apollo 10.