A strategy for identification and development of safety critical software embedded in complex space systems

Abstract

Software used in safety critical applications demands new concepts covering techniques concerning thorough analyses and design for high-integrity systems with embedded software. Categorization and implementation requirements with the overall intent to prevent reliance of safety on complex design components, to reduce the amount of safety critical software, and to separate the remaining critical part from non-critical software applications are presented. The purpose of the software criticality analysis (SCA), which has been developed for the Columbus Programme, is to analyse the system for implementation of those requirements. All software components will be categorized according to their involvement in critical functions. The SCA is demonstrated taking the rendezvous and berthing function of the Columbus Free Flyer with the Space Station Freedom as an example. For software, which remains being categorized as critical, exceptional techniques to achieve exceptional quality apply. A characterization of those managerial, development, analysis, and assurance techniques is given. They are related to the Columbus Software Development Standards forming the baseline of any Columbus Space Segment Software development process.