Except for actually landing on the moon's surface, the Apollo 10 mission included all aspects of an actual lunar landing. It was the first complete manned Apollo spacecraft to operate around the moon.
Objectives included a scheduled 8-hour lunar orbit of the separated lunar module, plus descending toward the lunar surface to a height of about 9 miles before ascending for rendezvous and docking with the Command / Service modules.
Data gathered in this trial landing dealt with the influence of the moon's gravitational effect. It also helped refine the Earth-based spaceflight tracking techniques, and to check out Lunar Module's programmed trajectories, radar, and lunar flight control systems. During the flight 12 color television transmissions to Earth were planned making it the first time a color television picture was transmitted from an Apollo mission.
Soon after leaving its low Earth orbit, the Command / Service module separated from the S-IVB stage. It then turned around and docked to the top of the Lunar Module. This stacked combination gave the 3-man crew extra space to maneuver during its mission to the moon. Once in lunar orbit, Young remained alone in the Command Module, known as Charlie Brown, while Stafford and Cernan flew the Lunar Module. The Lunar Module crew checked out the radar and ascent engine, and surveyed the Apollo 11 landing site. The lunar module on this flight was not equipped to land.
Unlike most of the other manned missions to the moon that used the Lunar Module, Apollo 10 did not leave the Lunar Module on the moon's surface. After carrying out a successful lunar orbit and docking procedure, the Lunar Module (called "Snoopy") was jettisoned and sent into an orbit around the Sun where it is most likely to be still orbiting the sun even today. In fact, there are groups of amateur astronomers trying to identify the exact location of the Lunar Module.
May 18, 1969 / Launch Complex 39-B
Eugene A. Cernan
John W. Young
Thomas P. Stafford
CSM-106 (Charlie Brown) and LM-4 (Snoopy)