It has already been mentioned that a SpaceWire router can act as a data concentrator. Another example of this is shown in Figure 11.
Figure 11 Router as Data Concentrator
Instrument 1 is a high data rate instrument and is connected by direct links to the routers in the prime and redundant data-handling systems. Instruments 2-5 are lower data rate instruments which are, for example, all situated in one area of the spacecraft. To reduce the size of the cable harness the data from Instruments 2-5 are concentrated by a SpaceWire router and sent to the prime or redundant data-handling units over single SpaceWire links.
The advantages of this architecture are:
- Reduced cable mass
- High rate instrument(s) have direct connection to data-handling unit
- Low to moderate rate instruments are connected via concentrating router
The disadvantages of the particular architecture shown in Figure 11 are:
- Have to be aware of potential blocking in router – need to consider traffic on network
- Concentrating Router is not redundant
The concentrating router can be made redundant if required by adding redundant SpaceWire links and interfaces.
This type of architecture is suitable for payload data-handling systems with distributed clusters of instruments which are being served by centralised data-handling unit.