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.
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 2irad 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.