The Fiber Optic Gyro (FOG) is a fully static inertial measurement technology that is free of any moving part and have a much better reliability than classical mechanical gyroscope technologies.
Astrix 120 is made of 4 independent closed loop FOG 120 gyroscope channels, assembled on a common baseplate.
This configuration offers a redundancy and a failure detection capability. It improves also the nominal performances, by using 4 channels ON at the beginning of the mission (then 3 channels ON after one failure).
Astrix 120 FOG can satisfy the needs of most Earth Observation & Telecom satellites.