Simulating GPS Radio Occultations using 3-D numerical ray tracing

Abstract

Ray tracing is an important tool for the operation of GPS L-band frequency signal propagation; in particular GPS RO techniques where accurate and near real-time results are often required. Ray tracing techniques are commonly used for calculating the path of an electromagnetic signal in a medium specified by a position dependent refractive index, such as the Earth's atmosphere. In this study three dimensional numerical ray tracing techniques are used to simulate GPS L-band signals received by the LEO satellites and primarily focusing on regions of increased electron density gradients such as the equatorial anomaly. The down range refractive gradients on the GPS to LEO signal paths will be investigated. The ionosphere is a birefringent medium due to the presence of the Earth's magnetic field. The effects of the Earth's magnetic field on the transmitted signals and the paths of the ordinary and extraordinary signals are investigated.