Orion 4 (USA-139) (NROL-6)

The Orion 3 and 4 (RIO 3, 4) satellites, which are generally known as 'Advanced Orion' or 'Mentor', are geostationary signals intelligence satellites, which replaced the Magnum / Orion series. Their purpose is to intercept missile telemetry from Russia and China and the COMINT capability of the Mercury satellites was merged into this series. These satellites are launched under the designation Mission 7600.

The Orion 3 and 4 (RIO 3, 4) satellites, which are generally known as 'Advanced Orion' or 'Mentor', are geostationary signals intelligence satellites, which replaced the Magnum / Orion series. Their purpose is to intercept missile telemetry from Russia and China and the COMINT capability of the Mercury satellites was merged into this series. These satellites are launched under the designation Mission 7600.