Real-time approach for development of scientific space instrument software

The paper summarises experience from development of on-board software for three scientific space instruments. Two alternative development philosophies were considered. The obvious approach is to focus on the scientific functions of the instrument, and then interface the program to the "hardware" by ad hoc means. An alternative approach was suggested by our experience on industrial applications: considering the software from the real-time point of view. This approach was selected. The paper describes central issues of space instrument software development in the framework of real-time programming. We generalise the real-time approach to cover all issues related with the environment: timing of software functions' execution, support for the project life cycle, and the instrument autonomy concept. We highlight the importance of real time kernel and its extensions as the vehicle for environmental adoption.