The Atlas-Agena was an American expendable launch system derived from the SM-65 Atlas missile. It was a member of the Atlas family of rockets, and was launched 109 times between 1960 and 1978. It was used to launch the first five Mariner unmanned probes to the planets Venus and Mars, and the Ranger and Lunar Orbiter unmanned probes to the Moon. The upper stage was also used as an unmanned orbital target vehicle for the Gemini manned spacecraft to practice rendezvous and docking.