Enhanced Radiative Force Modeling of the Tracking and Data Relay Satellites

Orbit determination (OD) approaches operationally model the Tracking and Data Relay Satellites (TDRS) as homogenous spheres for nonconservative force modeling. To improve definitive orbit determination and prediction accuracies, and to employ TDRSS tracking of user satellites within various geophysical investigations, a detailed TDRS spacecraft model has been developed. The enhanced TDRS model represents the spacecraft as a combination of twenty-four flat plates. The radiative forces acting on each plate are computed and vector summed to produce the overall acceleration on the spacecraft center of mass. An initial model, based on pre-launch engineering information, has been refined to better fit observed spacecraft accelerations. The Goddard TDRS-5 Model 3 (GT5M3) improves orbit accuracy, yields better fits to the tracking data, significantly reduces residual accelerations, and improves orbit prediction capability.