Atlas II

Atlas II was a member of the Atlas family of launch vehicles, which evolved from the successful Atlas missile program of the 1950s. It was designed to launch payloads into low earth orbit, geosynchronous transfer orbit, or geosynchronous orbit. The Vernier engines on the first stage of the Atlas I were replaced by a hydrazine fueled roll control system. This series used an improved Centaur II upper stage, the world's first cryogenic propellant stage, to increase its payload capability. Atlas II also had lower-cost electronics, an improved flight computer, and longer propellant tanks than its predecessor, Atlas I.