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This study seeks to estimate the expected orbit determination accuracy for high altitude, highly inclined satellites using the Global Positioning System. Sun-synchronous and critically inclined orbits were studied for this paper. Gipsy-Oasis II was used for observation simulation and satellite state estimation. Data simulation and error estimation was accomplished through the processing of multiple satellite orbits through a prescribed range of initial conditions, most notably perigee altitude and orbit eccentricity A filter auto-tuner was developed to automate filter tuning and thus minimize satellite state estimation error. Errors introduced into the orbit determination process were JGM-3 1-sigma gravity clones, reduced fidelity atmospheric density models, and errors in the a priori satellite state. Results illustrate the expected state estimation accuracy given a desired orbit type, eccentricity, and altitude. As expected, the primary factor influencing state accuracy is the orbit altitude.