GMES Sentinel-1 Interferometric Wide Swath Mode Implementation Study: TOPS Doppler Spectrum Analysis and Antenna Mis-Pointing

Abstract

This technical note evaluate Doppler-related focussing effects in the TOPS mode, which analyses the influence of the Doppler centroid during the focussing of SAR data. As it will be shown, certain degradation in terms of phase errors and impulse response shifts can appear in scenes with strong topography variations. Besides the numerical evaluation, also a compensation approach is presented, and the results are validated using experimental interferometric TOPS data acquired by TerraSAR-X. A further topic addressed in the TN is the mis-pointing estimation with TOPS data and the estimation of the 2-way antenna pattern. The former needs to consider the special characteristics of the TOPS signal by using a deramping function, whose sensitivity analysis is also shown. The 2-way antenna pattern estimation is a viable option to avoid using ground-receivers, but some aspects need to be considered in order to achieve the required measurement performance. Both approaches are analysed and validated using TerraSAR-X TOPS data takes over the Amazon rainforest.