Development and validation of a predictive model for the estimation of station keeping operations for electric propulsion geostationary satellites via passive observables

Electric propulsion (EP) systems provide very high thrust efficiency and low fuel consumption compared to chemical propulsion systems. Therefore, geostationary (GEO) spacecraft designers often prefer them to optimize the mass budget of satellites. Given the same delta-v burn with respect to chemical propulsion, these systems are characterized by more efficient lower thrust levels and longer, more frequent maneuvers. These peculiarities have a significant impact on space traffic management because an independent observer cannot accurately estimate the propulsion parameters and perform a correct orbit determination while observing an EP satellite during a station-keeping maneuver. Moreover, the observer cannot rely on an accurate long-term orbit propagation. This paper proposes the implementation of a model for orbit determination (OD) of electric propulsion GEO satellites and the propagation of computed state vectors. The developed model is able to estimate the epoch and magnitude of the spacecraft’s station keeping thrusts, modelling them as a series of quasi-impulsive thrusts. Leveraging a historical record of spacecraft observations, the model can also predict its future maneuvers, allowing the user to obtain useful information regarding the station-keeping strategy of the observed satellite. The model has undergone a validation process based on the comparison of the state vectors and maneuvers computed with an optical ground-based telescope with those predicted by the model itself. This validation has enhanced confidence in the model’s ability to support satellite operations and facilitate the decision-making process regarding possible collision avoidance maneuvers, a central theme for the long-term sustainability of the GEO orbit.