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. It was replaced by the Atlas I, which had an improved guidance system.The first stage was derived from the SM-65 Atlas missile, and a Centaur was used as the second stage. The first stage was also flown without the Centaur, as the Atlas H.