Agena target vehicle

The Agena Target Vehicle (@'dZiːn@; ATV), also known as Gemini-Agena Target Vehicle (GATV), was an uncrewed spacecraft used by NASA during its Gemini program to develop and practice orbital space rendezvous and docking techniques, and to perform large orbital changes, in preparation for the Apollo program lunar missions. The spacecraft was based on Lockheed Aircraft's Agena-D upper stage rocket, fitted with a docking target manufactured by McDonnell Aircraft. The name 'Agena' derived from the star Beta Centauri, also known as Agena. The combined spacecraft was a -long cylinder with a diameter of , placed into low Earth orbit with the Atlas-Agena launch vehicle. It carried about of propellant and gas at launch, and had a gross mass at orbital insertion of . The ATV for Gemini 6 failed on launch on October 25, 1965, which led NASA to develop a backup: the Augmented Target Docking Adapter (ATDA), a smaller spacecraft consisting of the docking target with an attitude control propulsion system but without the Agena orbital change rocket. The ATDA was used once on Gemini 9A after a second ATV launch failure on May 17, 1966, but failed as a docking target because its launch shroud failed to separate. Each ATV consisted of an Agena-D-derivative upper rocket stage built by Lockheed Aircraft and a docking adapter built by McDonnell Aircraft. The Agena was launched from Cape Kennedy's Launch Complex 14 on top of an Atlas booster built by the Convair division of General Dynamics. The Agena first burn would occur shortly after shroud jettison and separation from the Atlas over the Atlantic Ocean. Over Ascension Island, a second burn would place the Agena into a low circular orbit. The McDonnell Gemini spacecraft would then be launched from Launch Complex 19, as soon as 90 minutes later. Both countdowns would proceed in parallel and required close synchronization. The Gemini would rendezvous and dock with the Agena as soon as Gemini's first orbit toward the end of the program. Gemini 11's Richard F. Gordon, Jr.