Multi-Spot Tracking System for Free-Space Optical Communication

Abstract

This article describes a multi-spot tracking system for free space optic communications systems suitable for tracking optical terminals observed within the field-of-view of a wide angle telescope. The article explains the conversion of the terminal position to the position in the plane of the tracking sensor and the subsequent recognition and tracking of terminals. In the first part of the article camera image processing is described. Then, basic projection of optical terminal into the tracking sensor plane (into the active surface of a camera) is expressed by using geometry and matrix optics. Afterwards, the angle resolution of optical terminal in plane of the receiver is obtained by using the Airy disk approximation. The basic projection is then extended to the calculation of the Earth-satellite system followed by spot tracking, where method for determining the optical terminal and the state machine is explained.