Ray-tracing solar radiation pressure modeling for QZS-1

Precise orbit determination requires accurate models for the orbital perturbations. Next to the well-known gravitational forces, the solar radiation pressure (SRP) is the main perturbation for navigation satellites. SRP results from the interaction between the photons of the Sun and the surfaces of the satellite. Hence, its modeling depends on proper knowledge of the geometry and optical properties of the satellite. Previous work showed that the use of an a priori box-wing model for the SRP significantly improves the estimated orbit products as well as orbit predictions compared to purely empirical models. However, the presently available box-wing models for the first satellite of the Japanese Quasi-Zenith Satellite System, QZS-1, do not consider an accurate geometry. Based on a computer-aided design model of the QZS-1 satellite, a ray-tracing simulation is performed to compute SRP accelerations in a more realistic manner. The resulting SRP model is validated through QZS-1 precise orbit determination over a two year data arc covering yaw-steering and orbit-normal attitude regimes. In yaw-steering mode, the ray-tracing model shows a better overall performance than a box-wing model and improves the standard deviation of QZS-1 satellite laser ranging residuals by a factor of three compared to orbits without a priori model. On the other hand, the ray-tracing SRP model does not account for thermal accelerations and thus performs worse than an adjusted box-wing model in orbit-normal mode.