Pointing, acquisition, and tracking system of the European SILEX program: a major technological step for intersatellite optical communication

Abstract

The overall architecture and the performances of the pointing, acquisition, and tracking (PAT) subsystem of the European SILEX program are examined. The mission constraints are described, and attention is given to the retained baseline built around a two-stage beam steering system, an open loop point-ahead control, and a full digital implementation. Performance prediction is based on signal processing, control algorithms, and detailed modeling of equipment and flexible structures. The way in which an accurate performance of the order of a microradian can be achieved with a correct allocation of the performance for each instrument of the system is shown. The rejection of the microvibrations coming from the platform when the terminal is operating is singled out as a key feature of the design. The PAT equipment and softwares - sensors, electromechanisms, and control units - are presented.