GPS Satellite Range and Relative Velocity Computation

In this work the estimation of a Global Positioning System satellite orbit is considered. The range and relative velocity of the satellite is computed in the observer’s local reference frame (topocentric system of coordinates) by including the Earth gravitational perturbations (up to J3 term) and the solar radiation pressure. Gauss perturbation equations are used to obtain the orbital elements as a function of time, from which the position vector is derived.