Simulation model and on-ground performances validation of the PAT system for the SILEX program

摘要

Abstract: This paper presents a description of the simulation model and the on-ground performances validation 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 terminals mounted on low earth orbit (SPOT 4) and geostationary orbit (ARTEMIS) spacecrafts. Due to the limited laser beam divergence angle (typical intersatellite distance of 45000 km) a very accurate pointing performance is required. The PAT subsystem is in charge of the initialization of link (acquisition), of the tracking of incoming beam and of the pointing of emitted laser beam. Taking into account all disturbance sources (host spacecraft vibrations, electromechanical or optical noises) the pointing performance is less than 2 $mu@rad over a frequency bandwidth of 1 kHz. In a first part, a short presentation of the retained strategies (phases of the PAT mission, operating modes) and functional architecture (control laws, sampling frequencies) is given. In order to validate the PAT performance assessment, which is based on measurements at equipment level and analysis at subsystem level, a complete time simulation software has been developed. The second part of the paper presents in detail the simulation model (equipment modeling, dynamical simulation of the terminal structure, operating modes management) and the associated outputs. A System Test Bed (STB) using functional breadboards of each terminal equipment and simulating two terminals in real time, has been built in order to demonstrate the feasibility and assess the performances of an intersatellite optical communication link. The third part of the paper describes the chosen design and architecture for the PAT validation on STB. The last part of the paper will show the validation of a pointing system for optical intersatellite communication, thanks to the combination of simulations and STB measurements.!