External sensor arrays for assisting pointing, tracking and acquisition in FSO communication

A key component of establishing free-space optical communication between ground stations, satellites, and lunar nodes consists of accurate pointing, tracking, and beam acquisition. This investigation explores the use of sensor arrays external to the receiver aperture for sampling the incoming transmitted beam for the purpose of estimating the pointing error. Different arrays of sensors and different combinations of sensors processed with the traditional quadrant detector algorithm were evaluated based on the ability to accurately predict the direction of pointing error under a variety of beam widths and turbulence conditions. MATLAB simulations demonstrate that different configurations perform best under different conditions, and thus a combination of configurations with flexible processing capabilities provides the most promising approach. Beam width proved to be the most important factor in prediction accuracy.