The mission was the first shuttle flight dedicated to the Department of Defense (DoD), and most information about it remains classified. For the first time, NASA did not provide pre-launch commentary to the public until nine minutes before liftoff. The Air Force only stated that the shuttle successfully launched its payload with an Inertial Upper Stage on the mission's seventh orbit. It is believed that the payload was a Magnum/ORION ELINT satellite.

The Orion (Magnum) satellites are geostationary signals intelligence satellites, which replaced the Rhyolite/Aquacade series. Their purpose was to intercept missile telemetry from the Soviet Union and China. Originally developed under the codename Magnum, their name was replaced by Orion (RIO) before the first launch.

Additionally to the SIGINT task, these two satellites also included a communications cross-link system in space and had some limited data relay capability.

Orion 1 (USA 8) was launched on 24 January 1985 on Shuttle flight Discovery STS-51-C with IUS upper stage. For monitoring the western portion of the Soviet Union it was likely positioned around 70° East for five years.