In May 1988 the Air Force issued Martin Marietta a contract to launch 10 DSCS-III satellites, starting in 1992. However, as the Atlas-Centaur could put only 2.3 tonnes into geosynchronous transfer orbit this required the development of an upgraded vehicle. This Atlas II had the uprated MA-5A power plant on which the auxiliary chambers were replaced by RS-27 engines, a stretched tankage, and a longer Centaur to increase the capacity to 2.8 tonnes, sufficient for a DSCS-III with an Integrated Apogee Boost Subsystem. The inaugural launch of the Atlas II on 7 December 1991 deployed Eutelsat 2F3, and the first DSCS-III went up on 11 February 1992.
The Atlas IIA had a Centaur with an uprated engine that increased the capacity to geosynchronous transfer orbit to 3 tonnes. Martin Marietta had expected that this would be able to launch the Intelsat 7 series, but these satellites put on so much mass in development that the first stage had to be reinforced to support four Castor IVA strap-ons in order to increase the capacity of 3.7 tonnes. The first Atlas IIA was launched on 10 June 1992 with Intelsat K. After its introduction on 16 December 1993 with Telstar 401,9^95 the more powerful Atlas IIAS began launching the Intelsat 7 series.
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