Orion 1, 2 (Magnum 1, 2)

The Magnum / Orion 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.

The Magnum / Orion satellites were, like their predecessors, built by TRW. They were considerably larger with an launch mass of 2200 to 2700 kg. The main intercept antenna reflector dish has reportedly a size of about 100 m to allow to monitor lower power transmissions and provide a better accuracy for transmitter position determination. They were mainly used to intercept a wide range of signals, including telemetry from Soviet missile tests and were reportedly also capable intercepting military and diplomatic communications of the Soviet Union. According to other reports, they also received data from emplaced sensors in the Soviet Union and elsewhere.

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

The satellites of this series were built for direct insertion into geosynchronous orbit by the IUS upper stage so no internal apogee propulsion system was needed. Small hydrazine liquid propellant thrusters were used to refine the final positioning.

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. Orion-1 remained functioning for more than another two decades, at least to November 2009 and probably until sometime in 2013.

Orion 2 (USA 48) was launched on 23 November 1989 on Shuttle flight Discovery STS-33R with IUS upper stage. Reportedly it replaced Orion 1 at the 70° position. Orion-2 remained functioning at least to November 2009 and probably until sometime in 2013.

These satellites were operated from the Pine Gap, Australia, ground station.

They were succeeded by the 'Advanced Orion' series.