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Minimum Hardware Navigation Concept for LEO Satellites using Information Fusion

Improved operational autonomy is required for the operation of any single satellite within a LEO satellite network. One onboard function, which is an interesting candidate to be implemented with an increased level of onboard autonomy is apparently the navigation function, which is in charge of the determination of the instantaneous satellite orbital position and attitude. This paper aims to demonstrate the capabilities of a minimum hardware configuration which could be an interesting candidate for the cost optimized implementation of the onboard navigation function. The hardware baseline consists of one integrated GPS/GLONASS receiver as primary equipment for nominal operation. Backup navigation is based on magnetometer measurements of the geomagnetic field and real-time processing of landmark images which are provided by a payload earth observation camera. The fusion of the different information sources is performed by advanced filtering and estimation methods. First results are presented which have been derived from the TUD-Satellite demonstration mission "Satellite based Monitoring of Mobile Objects" as application reference. This mission uses an earth observation camera for road traffic monitoring purposes and allows perfectly the maximum use of payload resources in the sense, that both the camera as sensor device and a large part of the follow-on image processing software can be used "free of charge" for the generation of navigational landmark data. The paper discusses the overall system architecture, different filtering options and gives performance results verified by simulation for both nominal (GPS/GLONASS) and backup (magnetometer/landmark) operation.