Estimation of Ionosphere-Compensated Azimuth Ground Motion with Sentinel-1

This paper deals with the mitigation of ionospheric effects in the estimation of azimuth ground motion using Sentinel-1 images. Thanks to the high accuracy of Sentinel-1 azimuth orbit timings, precise absolute measurements of azimuth ground displacements are possible, nevertheless, variations in the ionosphere electron content can introduce significant errors. Azimuth shifts are usually estimated with the Enhanced Spectral Diversity technique in the burst overlap areas. The ionospheric phase contribution can be estimated with the split-spectrum method. In this paper, the correction of ionospheric errors in azimuth shifts is realized by compensating the ionospheric phase in the burst overlap areas; this is only possible when considering the correct ionospheric height and the squint angles. The technique is thoroughly described in the paper. Experiments shows how this procedure can sensibly mitigate the ionospheric influence on azimuth shifts, improving the measurements of geophysical phenomena as, for example, earthquakes.