SpaceWire is a

spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, ...

communication network A telecommunications network is a group of nodes interconnected by telecommunications links that are used to exchange messages between the nodes. The links may use a variety of technologies based on the methodologies of circuit switching, mess ...

based in part on the

IEEE 1355 IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC). IEC 14575 is a low-cost, low latency, scalable serial interconnection system, originally intended for communication between la ...

standard of communications. It is coordinated by the

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (120 ...

(ESA) in collaboration with international space agencies including

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeedin ...

JAXA The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into o ...

, and RKA. Within a SpaceWire network the nodes are connected through low-cost, low- latency,

full-duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...

, point-to-point serial links, and

packet switching In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the p ...

wormhole routing Wormhole flow control, also called wormhole switching or wormhole routing, is a system of simple flow control in computer networking based on known fixed links. It is a subset of flow control methods called Flit-Buffer Flow Control. Switching i ...

routers. SpaceWire covers two (physical and data-link) of the seven layers of the

OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that 'provides a common basis for the coordination of SOstandards development for the purpose of systems interconnection'. In the OSI reference model, the communications ...

for communications.

Architecture

Physical layer

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 In telecommunications, asynchronous communication is transmission of data, generally without the use of an external clock signal, where data can be transmitted intermittently rather than in a steady stream. Any timing required to recover data f ...

and allows speeds between 2 Mbit/s and 200 Mbit/s, with initial signalling rate of 10Mbit/s. DS-DE is well-favored because it describes modulation, bit formats, routing, flow control, and

error detection In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communi ...

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 Low-voltage differential signaling (LVDS), also known as TIA/EIA-644, is a technical standard that specifies electrical characteristics of a differential, serial signaling standard. LVDS operates at low power and can run at very high speeds ...

(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 Failover is switching to a redundant or standby computer server, system, hardware component or network upon the failure or abnormal termination of the previously active application, server, system, hardware component, or network in a computer net ...

. The fail-over features let data find alternate routes, so a spacecraft can have multiple data buses, and be made fault-tolerant. SpaceWire also allows the propagation of time interrupts over SpaceWire links, eliminating the need for separate time discretes.

Link layer

Each transferred character starts with a parity bit and a data-control flag bit. If data-control flag is a 0-bit, an 8-bit LSB character follows. Otherwise one of the control codes, including end of packet (EOP).

Network layer

The network data frames look as follows: One or more address bytes are used for the routing. Addresses are either physical ones (0-31), or logical ones. The difference is that the physical addresses are deleted from the frame header during routing - which is used for hop-based routing (based on path specified in the frame itself). Logical addresses may be deleted as well, depending on the router configuration.

Interconnection

The hardware devices may be connected either directly, or via a SpaceWire router. In the former case, usually pairs of devices are used to guarantee a fail-safe operation - which is however handled by the software. A SpaceWire router is usually a

crossbar switch In electronics and telecommunications, a crossbar switch (cross-point switch, matrix switch) is a collection of switches arranged in a matrix configuration. A crossbar switch has multiple input and output lines that form a crossed pattern of int ...

-type device, operating in

wormhole switching Wormhole flow control, also called wormhole switching or wormhole routing, is a system of simple flow control in computer networking based on known fixed links. It is a subset of flow control methods called Flit-Buffer Flow Control. Switching is ...

mode. This also may limit the speed of the communication to the lowest common speed. The routing decisions are based on the programmed routing table and the initial incoming frame contents.

Uses

SpaceWire is used all around the globe. Its use began primarily in ESA projects, but it is currently used by

, RKA, and many other organizations and companies. Some NASA projects using it include the

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Sp ...

, Swift's

Burst Alert Telescope Neil Gehrels Swift Observatory, previously called the Swift Gamma-Ray Burst Explorer, is a NASA three-telescope space observatory for studying gamma-ray bursts (GRBs) and monitoring the afterglow in X-ray, and UV/Visible light at the location ...

, the

Lunar Reconnaissance Orbiter The Lunar Reconnaissance Orbiter (LRO) is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. Data collected by LRO have been described as essential for planning NASA's future human and robotic missions t ...

LCROSS The Lunar Crater Observation and Sensing Satellite (LCROSS) was a robotic spacecraft operated by NASA. The mission was conceived as a low-cost means of determining the nature of hydrogen detected at the polar regions of the Moon. Launched immed ...

, the

Geostationary Operational Environmental Satellite The Geostationary Operational Environmental Satellite (GOES), operated by the United States' National Oceanic and Atmospheric Administration (NOAA)'s National Environmental Satellite, Data, and Information Service division, supports weather fo ...

(GOES-R), and the SCaN Testbed, previously known as the Communications, Navigation, and Networking Reconfigurable Testbed (CoNNeCT). It has also been selected by the

United States Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national sec ...

for Operationally Responsive Space. SpaceWire initiatives are being coordinated between several Space Agencies in the frame of

CCSDS The Consultative Committee for Space Data Systems (CCSDS) was founded in 1982 for governmental and quasi-governmental space agencies to discuss and develop standards for space data and information systems. Currently composed of "eleven member agenc ...

in order to extend its communication model to the Network and Transport Layers of the

. SpaceWire supports highly fault-tolerant networks and systems, which is one reason for its popularity.Dr Barry M Cook; Paul Walker
"Ethernet over SpaceWire - software issues"
4links.co.uk, p. 2

Protocols

The ESA has a draft specification in place for the Protocol ID. The following Protocol ID's have been assigned in ECSS-E-ST-50-11:

References

Other sources

ESA-

ESTEC The European Space Research and Technology Centre (ESTEC) is the European Space Agency's main technology development and test centre for spacecraft and space technology. It is situated in Noordwijk, South Holland, in the western Netherlands, al ...

. *[http://www.ecss.nl/forums/ecss/_templates/default.htm?target=http://www.ecss.nl/forums/ecss/dispatch.cgi/standards/showFolder/100630 ECSS-E-50-12A (SUPERSEDED only document number has been changed to ECSS-E-ST-50-12C) SpaceWire - Nodes, links, and networks], ESA-

.
ECSS-E-ST-50-11C Draft 1.3 "Space engineering - SpaceWire protocols"

External links

SpaceWire Homepage (ESA)European Cooperation for Space Standardisation - ECSS4Links PublicationsInternational SpaceWire Conference 2007International SpaceWire Conference 2008International SpaceWire Conference 2010International SpaceWire Conference 2011

International SpaceWire Conference 2013STAR-Dundee Knowledge Database
*http://www.interfacebus.com/SpaceWire_Avionics_Bus.html Commercial providers of SpaceWire equipment:
STAR-DundeeSpacewire.frAeroflexAeroflex Gaisler
*

Astrium Astrium was an aerospace manufacturer subsidiary of the European Aeronautic Defence and Space Company (EADS) that provided civil and military space systems and services from 2006 to 2013. In 2012, Astrium had a turnover of €5.8 billion and 1 ...

MicrochipAurelia MicroelettronicaIngespace4LinksRUAG SpacePnP InnovationsTELETEL SATTTech
- Gateway for SpaceWire to 1GbE Ethernet, with Leon-2FT CPU SpaceWire IP Cores:
4LinksSTAR-DundeeAeroflex Gaisler

CEA IRFUCESR CNRS
CeCILL-C license)
NASA Goddard - tech transfer
*OpenCores.org
SpaceWire
an
SpaceWire Light

SpaceWire UKPnP Innovations
Articles:

{{James Webb Space Telescope Computer buses ECSS standards Fault-tolerant computer systems James Webb Space Telescope