Replacement for the SDS-2 satellites, which from Molniya-type orbits, provided data relay services for optical reconnaissance and other military spacecraft. The Atlas-IIAS payload capability indicates they had a mass under 3600 kg, compared to 6000 kg for the SDS-2 series. Therefore they surely had a different payload, and may have had a substantially different mission.

Typical orbit: Believed 400 x 38000 km, 63.2 deg inclination. Mass: 3,600 kg (7,900 lb). Associated Launch Vehicle: Atlas IIAS.

• 2000 December 6 - USA 155 - Launch Site: Cape Canaveral. Launch Vehicle: Atlas IIAS. Mass: 3,600 kg (7,900 lb). Perigee: 35,780 km (22,230 mi). Apogee: 35,790 km (22,230 mi). Inclination: 0.00 deg.

  Classified satellite. Launch delayed 24 hours by RL10 engine problem in upper stage. USA 155 was a classified National Reconnaissance Office satellite. The Centaur placed the payload in a 176 x 831 km parking orbit and then in a 270 x 37490 km x 26.5 deg geostationary transfer orbit. The spacecraft was probably either a data relay satellite (to relay spy satellite imagery and data to the ground) and/or a signals intelligence satellite.

• 2001 October 11 - USA 162 - Launch Site: Cape Canaveral. Launch Vehicle: Atlas IIAS. Mass: 3,600 kg (7,900 lb).

  The Atlas AC-162 Centaur entered a 176 x 907 km x 28.2 deg parking orbit at 0242 GMT and then made a second burn to deploy its payload in a 274 x 37538 km x 26.5 deg geostationary transfer orbit at 0301 GMT. USA 162 was rumoured to be a data relay satellite used to return data from imaging satellites similar to the one launched on October 5 2001. It was also possible that the satellite is a signals intelligence payload. The satellite is owned and operated by the National Reconnaissance Office (NRO).

• 2004 August 31 - USA 179 - Launch Site: Cape Canaveral. Launch Vehicle: Atlas IIAS. Mass: 3,600 kg (7,900 lb).

  63rd and last flight of Atlas IIAS. 576th and final launch of Rocketdyne-powered Atlas rockets. Final launch from LC36A after 42 years of use. Launch delayed from June 24 and 25, July 1 and 27, August 27, 28, 29 and 30. The payload was probably a communications satellite used to relay data from imaging spy satellites.