The objective of this study is to identify redundancy concepts avoiding passive, non-operating redundancies which allow for a graceful performance degradation in case of failures across all typical spacecraft platform functions, while addressing system mass and cost savings.

The current redundancy approach is often intended to maintain or re-establish full functionality and performance capability in case of failure of a primary system or equipment. This naturally leads to build and carry system resources that may never be used in case the primary system works reliably throughout its operational life. On the other hand, alternative concepts exist which implement simply the capability of maintaining certain acceptable level of performance (i.e. graceful or acceptable degradation) in case the primary system fails. Instead of primary and secondary units each providing full functionality and performance capability, a set of units is used which all have to function actively to achieve full performance but provide a degraded performance or even functionality in case one or more of these units fails (i.e. performance-centred redundancy approaches). Such graceful degradation could also potentially satisfy the required functional and performance needs to achieve mission success while avoiding to carry passive, non-operating secondary units just for a potential failure case. This is of particular interest e.g. for spacecraft facing stringent mass and budget constraints. The main tasks are to first assess the possibility to implement the spacecraft's platform functionalities in terms of performance, and second to identify for each platform function the most suitable redundancy approach avoiding unused equipment in fault free condition while providing acceptable performance degradation in case of failure.