The Atlas G, also known as Atlas G Centaur-D1AR was an American expendable launch system derived from the Atlas-Centaur. It was a member of the Atlas family of rockets, and was used to launch seven communication satellites during the mid to late 1980s. Atlas G consisted of an improved Atlas core with modernized avionics and stretched propellant tanks. The Centaur stage also had several updated components and other technical improvements. It was replaced by the Atlas I, which had an improved guidance system.