Doppler Frequency Estimation and Tracking of Iridium NEXT Satellites

Low Earth Orbit (LEO) satellites, with their wide coverage area and high signal strength, constitute an important source of signals of opportunity (SoOP). In this study, Doppler frequency estimation and tracking based on the orbit prediction of Iridium NEXT, one of the LEO satellites, are addressed. Two models are used to predict the Doppler frequency. Estimation algorithms, QSE and HAQSE, based on DFT interpolation, are applied to these models, and their performances are evaluated in detail through simulations for three different sampling frequencies. Simulation results demonstrate that both models can estimate the Doppler frequency with high accuracy even at low SNR values, and that the proposed methods are both reliable and effective for LEO satellite systems.