The mission was the second shuttle flight totally dedicated to deploying a Department of Defense payload, after STS-51-C. Its cargo was classified, but it was reported that two (USA-11 and USA-12) DSCS-III (Defense Satellite Communications System) satellites were launched into stationary orbits by an Inertial Upper Stage. The DSCS satellites used X-band frequencies (8/7 GHz). Each DSCS-III satellite had a design life of ten years, although several of the DSCS satellites have far exceeded their design life expectancy.

DSCS-3 (Defense Satellite Communications System 3) are geostationary communications satellites, which provide a robust anti-jam, nuclear hardened capability that supports Department of Defense (DoD) worldwide requirements, White House and Diplomatic communications. They are the follow-on generation of the DSCS-2 satellites.

The system is used for high priority communications such as the exchange of wartime information between defense officials and battlefield commanders. The system provides uninterrupted secure voice and high-data rate communications to globally fixed and mobile DoD users, NATO, the United Kingdom, the Diplomatic Telecommunications Service, and the White House Communications Agency.

Orion 1 (USA 8) was launched on Shuttle flight Atlantis STS-51-J with IUS upper stage.