Integrated modular avionics for spacecraft — User requirements, architecture and role definition

This paper describes, from the perspective of the European Space Agency (ESA), the benefits of incorporating software partitioning technology, based upon the Integrated Modular Avionics (IMA) concept, into the spacecraft flight software architecture in terms of improving the reliability and security of space systems as well as the efficiency of the software development and validation processes. The result of the spin-in shall be known as Integrated Modular Avionics for Space (IMA-SP). One problem faced in space projects is how to manage software complexity. Larger industrial teams are needed to ensure responsibility for the software lifecycle, due to the increased functions and capability required for future missions. The problem is further complicated by the fact that uncorrelated spacecraft applications with different levels of criticality are integrated together into a single core software image, meaning a modification in one application results in regression testing all other applications at the maximum level of criticality. IMA is a solution that allows the aviation industry to manage their avionics complexity. IMA defines an integrated system architecture that preserves the fault containment and 'separation of concerns' properties of the federated architectures, where independent functional chains share a common computing resource. Each functional chain, or application, is protected against interference from other chains by a memory protection strategy and a guaranteed sole access to the computing resources. Applications are isolated from each other in time and memory using software partitions and communicate through controlled channels. An on-going study has derived a baseline IMA- SP definition covering: system requirements, software architecture; application services, lifecycle and process; and failure handling concepts. The findings from this study are presented in this paper.