Computation of Precision Ephemeris coefficients in the GNSS message: Practical results from a proficient algorithm

In the frame of a simulation facility developed for the Italian Space Agency (ASI) and the Air Navigation Services company (ENAV), Telespazio handled the problem of generating the Precision Ephemeris (PE) parameter sets for a simulated Galileo constellation. The approach was recently extended to real GPS constellation vehicles, using as input the accurate orbit data rendered available by the International GNSS Service (IGS). The goal of PE coefficients is to describe with high accuracy the orbit path of each navigation satellite, using a semi-analytical propagation model that is common to both GPS and Galileo. Deriving PE is non an easy task, also due to the high accuracy requested in the reconstruction of satellite orbit position and velocity in ECEF coordinates. Proposed article describes the technique which was developed and characterizes the promising PE quality in terms of accuracy results, compared with best available GPS orbit profiles. Significance of the work is also motivated by the fact that public papers concerning computation of Precision Ephemeris are quite rare in the panorama of GNSS technical articles.