Propagation effects at radio frequencies on satellite navigation systems

Abstract : The report discusses the effects of the neutral and ionized atmosphere on radio frequency signals used in satellite navigation systems. Knowledge of the signal velocity along the transmission path is necessary to properly interpret the navigation measurements. A technique for taking into account the influence of the neutral atmosphere on radio frequency signals is discussed. The algorithm is based on modeling of the refractive index as a function of surface temperature, pressure, and humidity. Several techniques for accounting for the effects of the ionized atmosphere at VHF and UHF are considered. Recent results are presented on the development of corrective algorithms that could be used operationally by navigators. The techniques developed are based on real-time prediction of the atmospheric electron density distribution. (Author)