Mitigating satellite motion in GPS monitoring of traveling ionospheric disturbances

Abstract

We discuss the impact of satellite motion on the use of compact arrays of GPS receivers for estimating the velocity of traveling ionospheric disturbances (TIDs). It is shown that satellite motion has subtle effects upon standard techniques of waveform cross correlation, or time difference of arrival, which can easily lead to spurious TID velocity estimates. We present some improved techniques for cross-correlating TID waveforms while taking account of the Doppler shifts created by satellite motion. In addition, we discuss some improved techniques for separating TID waveforms from background ionospheric trends, such as diurnal variation, based on high-order polynomial fitting with well-defined frequency selectivity. The application of these techniques to a sensor array in the UK is discussed. Key Points GPS satellite motion causes modulation of observed traveling ionospheric disturbances (TIDs) Modulation of TID waveforms complicates estimation of TID velocities Motion-aware cross-correlation techniques produce more robust TID velocity estimates.