For the vast majority of geostationary satellites currently in orbit, station keeping activities including orbit determination and maneuver planning and execution are ground-directed and dependent on the availability of ground-based satellite control personnel and facilities. However, a requirement linked to satellite autonomy and survivability in cases of interrupted ground support is often one of the stipulated provisions on the satellite platform design. It is especially important for a geostationary military-purposed satellite to remain within its designated orbital window, in order to provide reliable uninterrupted telecommunications services, in the absence of ground-based resources due to warfare or other disasters. In this paper we investigate factors affecting the robustness of a geostationary satellite’s orbit in terms of the maximum duration the satellite’s station keeping window can be maintained without ground intervention. By comparing simulations of orbit evolution, given different initial conditions and operations strategies, a variation of parameters study has been performed and we have analyzed which factors the duration is most sensitive to. This also provides valuable insights into which factors may be worth controlling by a military or civilian geostationary satellite operator. Our simulations show that the most beneficial factor for maximizing the time a satellite will remain in the station keeping window is the operational practice of pre-emptively loading East-West station keeping maneuvers for automatic execution on board the satellite should ground control capability be lost. The second most beneficial factor is using short station keeping maneuver cycle durations.

1. INTRODUCTION
2. METHODS
    2.1 Orbit Propagation
    2.2 Station Keeping Maneuver Modeling
    2.3 Latitude Free Drift Duration
    2.4 Worst Case Timing of Loss of Ground Control
    2.5 Initial Orbital Parameters
3. RESULTS AND DISCUSSIONS
    3.1 Baseline Case
    3.2 Station Keeping Window Size
    3.3 Station Keeping Longitude
    3.4 Orbit Determination Uncertainty
    3.5 Cross-Coupling Prediction Error
    3.6 Station Keeping Cycle Duration
    3.7 Station Keeping Maneuver Pre-Loading
    3.8 Station Keeping Year
    3.9 Quantitative Summary of Results
4. CONCLUSIONS
REFERENCES

• Hyung Je Woo(Agency for Defense Development) Corresponding Author
• Bjorn Buckwalter(Satconsult)