SPACECRAFT ARCHITECTURES FOR REAL-TIME COMPRESSION, HANDLING AND TRANSMISSION OF HIGH DATA RATES

摘要

Upcoming missions like on-orbit robotics, on-orbit servicing and real-time earth observation have demanding requirements concerning long link access periods and bi-directional, low latency communication between spacecraft and operator. To enable such missions, the Institute of Astronautics (LRT) at Technische Universitaet Muenchen (TUM) has developed concepts and technologies focusing on continuous, long duration real-time communication with satellites in low earth orbit (LEO). This is achieved by interactively teleoperating the spacecraft via geostationary data relay satellite (DRS). As signal roundtrip delay is critical in such operator-in-the-loop applications, particular challenges are low latency compression, routing, multiplexing and transmission of time critical data from several sources.Real-time Teleoperation (RTTO) requires high quality data feedback at high frequencies and hence induces high data rates on the return link. As typically communication is only feasible on one physical channel for DRS links, the arising data has to be compressed with lowest latency achievable. Two different real-time compression technologies are currently being developed and tested. One approach is the implementation of video compression algorithms in Field Programmable Gate Arrays (FPGAs) while the second uses a triple-redundant spacecraft computer system based on power-pc processors. A promising solution for routing and multiplexing of the still high rated compressed data is using the automatic router arbitration of spacewire networks.A Verification Environment for Real-Time Spacecraft Systems (VERTiS) is used to set-up and analyze the different technologies and concepts in an representative environment. By routing the multiplexed real-time signal via ESA's DRS ARTEMIS and including the imaging system, a compression system, spacewire network and modem, the end-to-end performance of the complete communication chain is measured. This paper compares different data handling architectures for real-time teleoperations and presents measurement results of tested and verified compression rates, signal latencies and error rates.