Satellite constellation resiliency is an important consideration gaining momentum at the top levels of the Air Force and at Air Force Space Command (AFSPC). The increased availability of threats to satellite systems is challenging the capabilities provided by space assets. We use the System Effectiveness Analysis Simulation (SEAS) to model the Global Positioning System (GPS) constellation in an urban canyon environment. The GPS provides information to a special operation force (SOF) in their effort to recover a weapon of mass destruction (WMD). By varying the type of operations and the number of satellites lost in the simulation, insight is gained into the impact of degradation through the selected top level mission metrics. Statistical difference tests and a designed experiment reveal a resiliency threshold on the number of satellites removed from the constellation. As a result, we conclude that the GPS constellation is resilient even after the loss of several satellites.