The Apollo 10 spacecraft stands, illuminated by launch pad spotlights, at Kennedy Space Center in Florida in this photo from May 4, 1969. It launched on May 18, 1969, with astronauts Thomas P. Stafford, Eugene A. Cernan, and John W. Young aboard.

The Apollo 10 mission encompassed all aspects of an actual crewed lunar landing, except the landing. It was the first flight of a complete, crewed Apollo spacecraft to operate around the Moon. Pertinent data to be gathered in this landing rehearsal dealt with the lunar potential, or gravitational effect, to refine the Earth-based crewed spaceflight network tracking techniques, and to check out lunar module programmed trajectories and radar, and lunar flight control systems. Twelve television transmissions to Earth were planned. All mission objectives were achieved.

See more photos from the Apollo 10 mission.

https://www.nasa.gov/image-article/readying-apollo-10-for-launch/