"A Fault Tolerant High Speed Network for Inter Satellite Links"
Kawsu Sidibeh and Tanya Vladimirova
Surrey Space Centre, University of Surrey
Incorporating IP-compliant technologies could potentially allow seamless interoperability and connectivity between all subsystems in a single spacecraft as well as between spacecraft in a constellation or formation. An inter-satellite link network distribution system based on IP-compliant wired and wireless protocols implemented using commercial-off-the-shelf (COTS) components will contribute significantly to the implementation of Internet in the sky. These COTS protocols will achieve a fault tolerant connectivity using intra and inter satellite links with less redundancy, more flexibility and will be of particular benefit to smaller spacecraft that are constrained by mass and volume .
The main goal of this research is to emulate scenarios for building a communication platform for transfer of telecommand, telemetry and data information between satellites. This system is aimed at distributed satellite missions using a cluster or a constellation of small satellites. The communication scheme is based on a combination of the wireless standard IEEE 802.11 and the high-speed interface protocol SpaceWire. SpaceWire  offers appropriate features for nodes, links and routers from two commercial standards, IEEE 1355 and LVDS, with improvements necessary to ensure that it is suitable for many space missions.
We propose that the bus and air interface structures of IEEE 802.11 and SpaceWire are combined to support a fault tolerant and yet high performance network for the communication needs of autonomous distributed multi-spacecraft formations or constellations.
In this paper an approach to implementation of a communication platform for transfer of telecommand, telemetry and data information between satellites will be outlined. The results of performance analysis with respect to two protocols, IEEE 802.11 and SpaceWire, will be discussed. A SpaceWire soft core, written in VHDL, will be implemented in FPGA with improvements necessary to ensure that it is suitable for various types of space missions.
1.K.Sidibeh; T.vladimirova; “Inter-Satellite Links in LEO Constellation of Small Satellites”, submitted to the International Journal on Space Communications.
2. S.M.Parkes et al, “ SpaceWire- Links, Nodes, Routers and Networks”, European Cooperation for Space Standardization, Standard No. ECSS-E50-12A, Issue, January 2003.
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