As GPS/CDGPS is the state of the art in absolute and relative navigation, it is anticipated that many missions involving cooperative rendezvous or docking will implement it. The proposed FDIR system has the potential to significantly improve the robustness and survivability of these spacecraft in the face of GPS failure or interruption. Thus the proposed FDIR method would benefit missions as basic as commercial manned spacecraft docking with ISS or commercial space stations or as advanced as missions where small spacecraft work collaboratively to create sparse arrays, synthetic apertures, or other distributed sensors networks. Other applications include spacecraft that are used to assemble large space structures, such as a manned mission where the Orion MPCV docks with another Orion MPCV or other spacecraft like the Multi-Mission Space Exploration Vehicle or Deep Space Habitat. Finally, the technology stands to benefit cooperative satellite servicing missions. The technologies developed in this project will be integrated into our work for DARPA's System F6 project. This work is focused on the guidance, navigation and control software necessary to support cluster flight. Many of the wireless communication systems being proposed for F6 produce range and range-rate measurements, and the navigation system will likely be GPS based, making it an ideal platform the proposed FDIR system. It can also be used to support other DoD or commercial multi-satellite missions that involve cluster flight, orbital rendezvous or even docking. It is anticipated that in a few years commercial manned spacecraft will dock with the ISS or other commercial space stations. Commercial systems are especially sensitive to size, weight, power, and cost and will benefit from the proposed FDIR enhancements when building rendezvous capable vehicles at any scale.