Nominal and observation-based attitude realization for precise orbit determination of the Jason satellites

Geodetic satellites are a main contributor of today’s monitoring of our planet. Highly accurate satellite measurements require precise satellite orbits. In this thesis, the influence of using attitude observations in contrast to a nominal yaw steering model for the Precise Orbit Determination (POD) of the three Jason satellites is investigated. The daily available attitude observation data, composed of satellite attitude quaternions and solar panel rotation angles, is analyzed and combined to weekly attitude files. The extensive and necessary preprocessing includes the detection and elimination of outliers, data resampling and the optimal interpolation of missing data. Orbits based on Satellite Laser Ranging (SLR) observations to the satellites Jason-1, Jason-2 and Jason-3 are computed for an overall timespan of approximately 25 years. Within the orbit analysis, observation outliers and maneuvers are removed. The revised orbits are recalculated using either the nominal yaw steering model for the realization of the attitude or the observation-based approach. The comparison of the resulting orbits shows an improvement in the overall mission Root Mean Square (RMS) of SLR residuals of 5.93 % (Jason-1), 8.27 % (Jason-2) and 4.51 % (Jason-3) from nominal to observed attitude realization. About 75 % of all orbital arcs calculated with the observation data result in a smaller RMS. POD-related parameters show a better coincidence with the target values in case of observation-based orbits. Orbit solutions of the GeoForschungsZentrum Potsdam (GFZ) and Centre National D’Etudes Spatiales (CNES) – both use a combination of geodetic tracking techniques which increases the orbit accuracy – are used for external orbit determination. This comparison shows an approximately 10 % better coincidence with observation-based orbits than in the nominal case. Additionally, the influence of the preprocessed orbits on estimated SLR station coordinates is investigated. The orbit characteristic draconitic period is clearly reduced in the station coordinates when using observation-based attitude data.