Which NASA program immediately preceded Apollo and practiced rendezvous and docking?

Which NASA program immediately preceded Apollo and practiced rendezvous and docking? Project Gemini did.

Project Gemini was NASA’s second human-spaceflight program, conducted after Project Mercury and while Apollo was still being developed. Its central purpose was to master the techniques needed for lunar missions, including long-duration flight, orbital maneuvering, spacewalking, rendezvous, and docking.

Gemini spacecraft carried two astronauts and flew ten crewed missions in 1965 and 1966. The program used the Agena Target Vehicle as a separate spacecraft for practicing orbital approaches and docking. Gemini 6A achieved the first rendezvous with Gemini 7 in December 1965, and Gemini 8 completed the first docking with an uncrewed Agena in March 1966.

The program also demonstrated endurance beyond the planned duration of a lunar mission. Gemini 5 lasted nearly eight days, while Gemini 7 remained in orbit for almost 14 days. These achievements let Apollo focus on lunar operations rather than developing basic orbital techniques from scratch. Project Mercury came before Gemini; Skylab came later as an Apollo-derived space-station program.