Before SpaceWire became a standard, many spacecraft primes and equipment manufacturers had their own proprietary communication interface for inter-unit communications, e.g. connecting high data-rate instruments to mass-memory units. This resulted in several different communication links being used on a spacecraft, increasing the cost and extending the time required for spacecraft integration and test. There was a clear need for a standard on-board communication link that would simplify spacecraft development.
Back in 1992, when work on what became SpaceWire started, there was also substantial interest in high performance digital signal processing systems which were beyond the capability of the single-chip devices available at that time. The use of parallel processing was investigated and this required some form of network to interconnect the individual processing elements. The Inmos Transputer, a microprocessor designed for parallel processing was studied, and the serial communication links being developed for the T9000 Transputer were identified as being an attractive solution for spacecraft on-board networking. This serial link technology was subsequently published as IEEE 1355-1995.
Several radiation tolerant devices were developed using the IEEE 1355-1995 standard and it was used on some space missions. However, there were many problems with this standard, which had to be resolved if this technology was to continue to be used for ESA spacecraft. University of Dundee received a contract from ESA to examine and solve these problems which eventually resulted in the SpaceWire standard.
SpaceWire aims to:
- facilitate the construction of high-performance on-board data-handling systems,
- help reduce system integration costs,
- promote compatibility between data-handling equipment and subsystems, and
- encourage re-use of data-handling equipment across several different missions.
Use of the SpaceWire standard ensures that equipment is compatible at both the component and sub-system levels. Instruments, processing units, mass-memory devices and down-link telemetry systems using SpaceWire interfaces developed for one mission can be readily used on another mission. This:
- reduces the cost of development (Cheaper),
- reduces development timescales (Faster),
- improves reliability (Better),
- increases the amount of scientific work that can be achieved within a limited budget (More).