The far ultraviolet spectroscopic explorer (FUSE) instrument data system

This paper describes the architecture for the IDS flight hardware and its real-time embedded flight software. The design uses commercial off-the-shelf (COTS) software components as much as possible, to reduce cost and software development time. The features of the IDS design that provide radiation hardness and fault tolerance are described. Implementation of software to meet the functional requirements is accomplished using a relatively small number of prioritized real-time tasks. A commercial real-time operating system kernel manages and supports these tasks. Inter-task communication is described, as are the software test and validation methods. The paper shows how custom ground support equipment was developed to facilitate software development and testing. Reliable communications between the IDS and the FUSE spacecraft bus are accomplished using a MIL-STD-1553B bus that has an imposed, deterministic real-time protocol. Similarly, communication between the IDS and the other instrument subsystems uses a second MIL-STD-1553B bus that has its own time division multiplex real-time protocol. The design of these real-time protocols is described, with particular attention to reliability and testability.