On the Exploitation of the ETAD Product for Filtering Out the Atmospheric Phase Screen From Medium Resolution DInSAR Measurements: An Extensive Performance Analysis

One of the biggest challenges for the proper retrieval of the Earth surface deformation through the differential synthetic aperture radar interferometry (DInSAR) technique is the capability of effectively filtering out the atmospheric phase screen (APS), which often affects DInSAR measurements. In this work we investigate the effectiveness of the new auxiliary product developed by the European Space Agency, the extended timing annotation dataset (ETAD), to remove APS from both DInSAR interferograms and deformation time series generated at medium spatial resolution from Copernicus Sentinel-1 (S1) SAR images. First, we show that the straightforward application of the ETAD correction layers to medium-resolution DInSAR interferograms entails the generation of artifacts, introduced by the ETAD tropospheric layers. Accordingly, we present a methodology aimed at properly recalculating such tropospheric corrections by exploiting the standard deviation and the mean of the ETAD digital elevation model layers of the considered SAR images sequence and by taking into account the locally quasi-linear dependence of the tropospheric signal with respect to the elevation. Second, we carry out a thorough experimental analysis to evaluate the performance of the ETAD APS corrections for both interferograms and deformation time series. Finally, the performance evaluation analysis is extended to the results obtained by applying the APS corrections generated through the ECMWF ERA-5 data. An extensive comparison of the results achieved through the ETAD and ERA-5-based approaches is also discussed. The overall analysis is focused on an S1 dataset of 104 SLC images acquired over Central/Southern Italy from ascending orbits, between 2018 and 2020.