Performance analysis of satellite missions for multi-temporal SAR interferometry

Multi-temporal InSAR (MTI) applications pose challenges related to the availability of coherent scattering from the ground surface, the complexity of the ground deformations, atmospheric artifacts, and visibility problems related to ground elevation. Nowadays, several satellite missions are available providing interferometric SAR data at different wavelengths, spatial resolutions, and revisit time. A new and interesting opportunity is provided by Sentinel-1, which has a spatial resolution comparable to that of previous ESA C-band sensors, and revisit times improved by up to 6 days. According to these different SAR space-borne missions, the present work discusses current and future opportunities of MTI applications in terms of ground instability monitoring. Issues related to coherent target detection, mean velocity precision, and product geo-location are addressed through a simple theoretical model assuming backscattering mechanisms related to point scatterers. The paper also presents an example of a multi-sensor ground instability investigation over Lesina Marina, a village in Southern Italy lying over a gypsum diapir, where a hydration process, involving the underlying anhydride, causes a smooth uplift and the formation of scattered sinkholes. More than 20 years of MTI SAR data have been processed, coming from both legacy ERS and ENVISAT missions, and latest-generation RADARSAT-2, COSMO-SkyMed, and Sentinel-1A sensors. Results confirm the presence of a rather steady uplift process, with limited to null variations throughout the whole monitored time-period.

Copernicus Sentinel data are provided by ESA. ENVISAT and ERS data provided by European Space Agency Category-1 project N. 5367, “Subsidence monitoring in Daunia and Capitanata (Puglia Region, Italy) through multi-temporal point-target DInSAR techniques”. RADARSAT-2 Data and Products @ MacDonald, Dettwiler and Associates Ltd. 2014u2014All Rights Reserved. RADARSAT is an official trademark of the Canadian Space Agency. COSMO-SkyMed data are provided by ASI (Agenzia Spaziale Italiana) in the framework of the “Sperimantazione di dati COSMO-SkyMed per lo studio di deformazioni del suolo” research project. Finally, authors thank anonymous reviewers for their fruitful comments. This research was funded by the Italian Ministry of University and Research (MIUR) in the framework of “APULIA SPACE” project (PON03PE_00067_6), PON Ricerca e competitività 2007-2013.