The United States Air Force\u27s Navstar Global Positioning System (GPS) provides high-accuracy space-based navigation and time distribution to suitably- equipped military and civilian users. The system consists of earth-orbiting satellites and a world-wide network of ground stations. A single operational control center, the GPS Master Control Station (MCS) monitors, maintains, and commands the GPS satellite constellation. The on-going deployment of the complete satellite constellation and recent changes in the operational crew structure may invalidate previously used planning and management paradigms. There is currently no analytical method for predicting the impact of these and other environmental changes on system parameters and performance. Extensive testing cannot be performed at the MCS itself due to the criticality of the GPS mission and lack of operational redundancy. This research provides and validates a discrete event simulation model of the MCS operations center task flow, focusing on the creation and testing of a sliding-window MCS activity scheduler. The simulation was validated using MCS historical data. Experiments were conducted by varying the number of ground stations and satellite constellation size available to the simulation. The results, while not quantitatively trustworthy, were used to draw general conclusions about the GPS operational environment
