The proposed model-based Fault Management system addresses the need for cost-effective solutions that enable higher levels of onboard spacecraft autonomy to reliably maintain operational capabilities. The system will provide onboard off-nominal state detection and isolation capabilities that are key components to assessing spacecraft state awareness. The ability to autonomously isolate spacecraft failures to component levels will enable faster recovery thereby reducing down time. Model-based systems can provide better fault coverage than traditional limit-checking systems. The proposed system in particular will result in a relatively compact software package because it relies only on modeling nominal behavior; fault models are not needed. Thus this approach has the capability to detect any off-nominal behavior including un-modeled faults. Health information produced by the FM system can be used to make resource allocation and planning and scheduling decisions by ground operations or by other on-board autonomy agents. The system can be built and tested standalone potentially reducing FM developmental and testing costs. The FM system provides an evolutionary approach to full onboard autonomy as it can first be implemented and tested in ground-based systems and then migrated onboard spacecraft. Onboard fault management will be crucial to NASA mission success particularly during critical times where the situation changes rapidly and unpredictably with no opportunity for operator support.