Communication Concepts for Self-Organizing Distributed Small Satellite Systems

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Space flight is facing a paradigm shift: groups of small, cooperating satellites are more and more considered as a promising alternative to classical monolithical satellite systems. This allows for more flexible missions and new application scenarios, in combination with reduced cost and improved resilience, but at the same time demands new and - compared to the state of the art in the field - significantly more complex communication and coordination mechanisms. The proposed project will establish a basis for communication mechanisms in future systems of cooperating small satellites. The aim is a robust overall system which makes efficient use of communication bandwidth and energy and which can deal with and compensate (partial) faults. It is, for instance, necessary to exchange status and position information between satellites, to transfer sensor data to the ground in an energy-efficient way and to communicate commands reliably to the satellite network.The project uses two specific scenarios from the area of earth observation as a starting point and focuses on questions of communication protocol design in such systems. The first scenario considers a formation of earth observation satellites, that is, a group of satellites which stay relatively close together and cooperatively adjust their orientation. Together they perform optical or magnetical measurements and make use of their position offsets for simultaneous measurements at multiple locations or from different angles. The second scenario is based on a satellite constellation, i.e., satellites on spatially widely separated orbits, which track the current positions of transponders (e.g., on trains, ships or airplanes) in a vast area. This scenario therefore comes with significantly different, but nevertheless likewise practically relevant requirements.In both cases the specific characteristics of small satellite networks will be leveraged to increase the communication efficiency. These characteristics include predictable contact times between network stations and knowledge about the amount, origin and structure of aquired data. In comparison to other fields, the availability and consumption of (solar) energy and other resources can also be predicted well in advance. This can be used for transmission planning or for cooperative data aggregation between satellites. The designed protocols and mechanisms will be evaluated analytically, through simulations and in experiments.