Pointing Acquisition And Tracking System For Silex Inter Satellite Optical Link

Abstract

This paper is concerned with the architecture and functional analysis of the Pointing Acquisition and Tracking (PAT) subsystem of the European Silex program (Semiconductor laser Intersatellite Link Experiment). The Silex scenario is composed of two optical terminals mounted on low earth orbit, and geosynchronous orbit spacecrafts. High rate communication between the two terminals requires very accurate tracking performances over a high bandwidth taking into account satellite vibrations as well as PAT electromechanical or optical noise. In a first part, a detailed presentation of the retained functional architecture in terms of control laws and strategies, steering algorithms and related signal processing is given, while a second part presents the design choices retained for the PAT equipments. Emphasis will be given on the different operating modes strategy and switching required by the different phases of the PAT mission : acquisition, tracking and pointing. Finally, aperformance analysis is carried out that concerns the rejection capacity with respect to vibrations generated by the host spacecraft, as well as optical sensors noise and mechanism error effects. Spacecraft vibrations profile is derived from in flight measurements on SPOT1 satellite and on ground measurements on SPOT2. Performance analysis will be illustrated by time and frequency simulations based on equipment modelling, and actual performances measurements derived from current associated technological programs.

Optical Communication in Space: Challenges and Mitigation Techniques

“…First, the coarse tracking is performed by means of a control loop driving the coarse pointing mirror. Later, the controller logic on the satellite commands the fine beam steering element to keep the received signal bore sighted on the detector [203], [204]. This angular control of beam steering mirror is achieved by the error signal that is the difference between the current position of the on-board mounted laser satellite and the beacon signal from the ground station.…”

Far-field spot compression without energy loss in main lob in wireless laser communication

“…In such cases, by increasing the intensity of the incident beam, the lost energy in main lob caused by spot compression can be compensated for. As is known, the energy in wireless laser communication, especially in space laser communication, is very precious and limited [10,11], then there is no sufficient energy to compensate for the main lob energy loss in spot compression. Therefore energy loss in the main lob caused by spot compression must be considered seriously in wireless laser communication.…”

Active disturbance rejection controller of fine tracking system for free space optical communication

“…Active disturbance rejection technology develops and enriches the essence of PID, the new practical technology eliminates error based on error, open up and use especial nonlinear-effects. Especially on those occasions that requires high-speed and high-precision control in the space environment, the ADRC technique shows its superiority even more [1][2][3][4][5][6][7][8] .…”