CAN Bus for Modern Spacecraft Control Systems

As the capability of spacecraft microprocessors increases, there is a growing trend for distributing the spacecraft control applications amongst remote terminals on the bus. This trend is seen both in payloads and in the spacecraft sub-systems.On the one hand, there is an increase in the proportion of data packet traffic on the onboard bus. On the other hand, as remote terminals become more "intelligent", they expect better services from the onboard bus. In particular, they expect to be able to access the bus to transfer data packets on demand, and many modern software architectures are based on messaging capabilities, where applications communicate with each other variable length messages that are generated asynchronously.The increasing "intelligence" in remote terminals, their demands for more comprehensive communication services, and the need to support multi-bus heterogeneous architectures, result in an increased use of higher level protocols and services across multiple and different onboard buses.This paper presents the ongoing effort realised within the ECSS CAN working group on defining the necessary services and associated data link protocols to standardise the usage of CAN bus in space applications.