SpaceWire

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SpaceWire is a spacecraft communication network based in part on the IEEE 1355 standard of communications. It is coordinated by the European Space Agency (ESA) in collaboration with several European space companies. Within a SpaceWire network the nodes are connected through low-cost, low-latency, full-duplex, point-to-point serial links and packet switching wormhole routing routers. SpaceWire covers two (physical and data-link) of the seven layers of the OSI model for communications.

1 Architecture
2 Uses
3 References
4 External links

[edit] Architecture

SpaceWire's modulation and data formats generally follow the data strobe encoding - differential ended signaling (DS-DE) part of the IEEE Std 1355-1995. SpaceWire utilizes asynchronous communication and allows speeds between 2 Mb/s and 400 Mb/s. DS-DE is well-favored because it describes modulation, 8B/10B_encoding bit formats, routing, flow control and error detection in hardware, with little need for software. SpaceWire also has very low error rates, deterministic system behavior, and relatively simple digital electronics. SpaceWire replaced old PECL differential drivers in the physical layer of IEEE 1355 DS-DE by low voltage differential signaling (LVDS). SpaceWire also proposes the use of space-qualified 9-pin connectors. SpaceWire and IEEE 1355 DS-DE allows for a wider set of speeds for data transmission, and some new features for automatic failover. The fail-over features let data find alternate routes, so a spacecraft can have multiple data buses, and be made fault tolerant.

[edit] Uses

SpaceWire is not only used in ESA projects, but also in some NASA spacecraft [1]. For example, it is being used in the James Webb Space Telescope, Swift's Burst Alert Telescope, or the Geostationary Operational Environmental Satellite. SpaceWire initiatives are being co-ordinated between several Space Agencies like ESA and NASA in the frame of CCSDS in order to extend its communication model to the Network and Transport Layers of the OSI model.