Method to Measure Light Spot Position in Beacon-Less Inter-Satellite Communication System

This article focuses on a beacon-less Inter-satellite optical wireless communication (Is-OWC) system. This system uses the same wavelength for the transmitted and received laser beams and uses part of communication light beam as beacon light instead of an additional high divergent beacon laser. Thus, a part of transmitted light will be reflected in optical path and leaked into acquisition, tracking and targeting (ATP) subsystem. This reflected light will seriously interfere with the spot position measurement of received light. To solve this problem, we propose a new method based on intensity modulation and cyclic cross-correlation (CCR). Experiment results show that even when the reflected and received beams differ in intensity by 91.7 times, we can still accurately detect the received light spot position by using the proposed method, where the maximum error is 0.026 mrad and the root mean square error is as low as 0.012 mrad.