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  • Software Dependability \& Safety

    Paper number



    Mr. Bart Roeloffs, LogicaCMG, United Kingdom


    Ms. Suzana da Mota Silva, The Netherlands


    Ms. Jo Choi, United Kingdom


    Mr. Ronald Bugter, The Netherlands




    Within the space industry the demand of software solutions has rapidly increased within the last decade. In such environment, Software Dependability & Safety disciplines are being challenged with the request for safer and more reliable equipment. Without proper software dependability process or the lack of safety confidence, the software safety case can not be justified and the system can never be achieved. The objective of this paper is to demonstrate several approaches which have proven to be effective in terms of building confidence in the software Dependability & Safety process.

    Software Dependability & Safety analysis are increasingly complex as the safety boundary is not limited to only the system itself, but also correlates with Human dependability and Hardware/Software interactions. The key of the modern safety case is to address system integration and safety issues during the overall space system’s life cycle and to involve correlated aspects beyond system boundary. Following our experience in Dependability & Safety analysis in the European Galileo Satellite Navigation program, several techniques have provided a considerable contribution to the justification of our safety cases:

    • Probabilistic Risk Assessment for software systems with high (human) interactions, where operators and procedures play a crucial role.
    • Probabilistic Software Fault Tree modeling with a quantified barrier effectiveness principle.
    • Combining Galileo Software Standard (GSWS) and the standard for functional safety of electrical and electronic programmable equipment (IEC-61508) to give a better understanding of the residual risk and the associated tolerance.
    • Iterative based Failure Mode Effect and Criticality Analysis (FMECA), which aims to measure the effectiveness of the software barrier by specific test scenarios.

    The presented techniques have proven to be effective and have been tailored in the European Galileo Satellite Navigation program. The proposed paper aims to discuss the contentious software dependability techniques which have been conducted beyond the scope of the Galileo Software Standard (GSWS). The discussion will mainly be focused on the effectiveness of the techniques and whether quantified software analysis should be stimulated further in the space industry.

    Abstract document


    Manuscript document

    IAC-08.D5.2.11.pdf (🔒 authorized access only).

    To get the manuscript, please contact IAF Secretariat.