Strategies for Mitigating the Impact of Ionospheric and Tropospheric Delay on Sentinel‐1 Interferograms in Northwestern Argentina

Abstract

This study investigates the impact and mitigation of ionospheric and tropospheric delays on Sentinel‐1 interferograms in northwestern Argentina. The research focuses on the Santa María Basin in the south‐central Andes, a region characterized by moderate seismic deformation, monsoonal moisture supply, a steep east‐west rainfall gradient, and its location on the southern crest of the Equatorial Ionization Anomaly. We used ERA5 reanalysis data, validated with local Global Navigational Satellite Systems (GNSS) data, to estimate tropospheric delays. Ionospheric delays were estimated through split‐spectrum processing and interpolated GNSS data. Tropospheric delays are usually one order of magnitude larger than ionospheric delays in the descending track. In contrast, the ionospheric delay for the ascending (evening) track data is larger at the equinoxes than that of the tropospheric delay and requires correction. Furthermore, the ascending track showed a fivefold larger ionospheric delay variability than for the descending (morning) track data. This variability exhibits a strong positive correlation with the 11‐year solar cycle and displays a semi‐annual pattern. Ionospheric activity significantly affects burst alignment, leading to higher median absolute deviation of azimuth offsets for ascending pairs, especially during equinoxes, which can cause phase jumps between bursts of up to 2 mm. Accurate mitigation of both atmospheric delays is crucial for reliable deformation monitoring in the region. Failing to correct for these long‐wavelength atmospheric biases, especially from the ionosphere, could mask real, slow tectonic deformation signals in InSAR measurements. We provide a framework for correcting InSAR time series impacted by strong atmospheric delays.