This proposal is for the development a fault detection and isolation (FDI) algorithm for a formation of satellites but processed at a ground station. The algorithm will be capable of operating when measurement data is available on an intermittent basis. An FDI algorithm for faults in the three translational and rotational modes of 4 satellites flying in formation in a highly elliptical orbit will be designed during the Phase 1 effort. The satellites will carry a limited suite of instruments, just sufficient to determine faults in the three translational and rotational modes and include a GPS receiver. Communication with a ground station will only be available near perigee. The measurement data is not stored and transmitted in bursts, so these communication blackouts represent a break in the time history of measurements. The proposed development will mitigate these breaks so that fault detection and isolation can be performed faster than in a simple, cyclical restart implementation. Furthermore, their elliptical orbit will carry the satellites beyond the GPS constellation. The proposed development will account for the loss of GPS coverage as well investigate ways of extending the useful of GPS (when signals are weak) for fault detection and isolation.