Propagation of satellite orbit modelling deficiencies into the global GNSS solutions – simulation-based study

The Non-Gravitational Perturbations (NGP), out of which the Solar Radiation Pressure (SRP) is the largest, have a significant impact on GNSS satellite orbits. In addition to the SRP, other relevant perturbations should also be taken into account, as this may result in substantial modelling errors if underestimated. Particularly, the force model should also consider Earth’s albedo in terms of the emitted and reflected radiation, as well as a physical satellite model (box-wing) with its optical and thermal properties.
GNSS satellite orbit modelling may suffer from deficiencies for various reasons (simplification of the complexity of the used model or uncertainty of the input information). The impact of such model errors on global GNSS data analyses is assessed in an error propagation study based on simulated observations. The influence of artificially introduced orbit errors on estimated parameters, e.g. Earth rotation parameters, orbit parameters (initial conditions and dynamical orbit parameters), station coordinates, station-wise troposphere parameters, as well as receiver and satellite clock corrections is investigated. In this study a dedicated simulation environment is used to analyse the relation between results and certain individual shortcomings in the NGP models. In addition, apart from a commonly used epoch-wise clock estimation, the analytical models for satellite clock corrections are introduced in order to exploit the high stability of the passive H-masers on-board the Galileo satellites. The simulation environment also allows to assess how the impact of float- versus fixed-ambiguities.
Finally, simulation-based analyses offer an excellent framework for more detailed validations and further refinements of the physical satellite models, which will consequently stabilize the global solution.