Laser communication between spacecraft allows high data rates for low power duc to the immense antenna gains involved, but at the expense of great difficulties in Pointing, Acquisition & Tracking (PAT). Classically this is achieved using a steering mirror in a wide bandwidth tracking loop. This paper describes the experimental investigation of an alternative approach in which the whole telescope is isolated from disturbances so that much lower tracking bandwidth becomes sufficient. The system was tested on a motion table covering the whole ESTeC microvibration environment specification and showed a worst error of 500nrad rms, this at100Hz. This is compatible with "burst error" criterial. The problem of making fast acquisition movements was addressed & solved. Many valuable lessons were learned.
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