Sounding of the deforming solid earth surface: new opportunities for spaceborne Differential SAR Interferometry techniques to detect and monitor displacements affecting the ground and the built-up environment

We discuss in this work, through the analysis of four selected case studies, some new opportunities for the detection and monitoring of displacements affecting the ground surface and the built-up environment, through Differential SAR Interferometry (DInSAR) techniques. This is done by exploiting the data acquired by currently operating SAR constellations, such as SAOCOM-1 (providing L-band data), Sentinel-1 (providing C-band data), and COSMO-SkyMed (providing X-band data), and by also envisaging those that will be soon available through the forthcoming missions, as for the case of the NIMBUS SAR constellation (that will also provide X-band data). The first case study shows how the L-band SAR data, in particular those systematically acquired by the SAOCOM-1 twin systems, allow to retrieve surface displacements in areas characterized by vegetation, where shorter-wavelength sensors have typically limited performance. The second experiment is based on the Sentinel-1 C-band DInSAR measurements and permits us to envisage new scenarios for improving surface deformation analysis of very wide areas by exploiting external data, such as the ECMWF ERA5 and the ETAD ones, with the aim of mitigating possible atmospheric artifacts, thus enhancing the retrieved surface displacements accuracy. The third experiment highlights how the high resolution SAR data acquired by the X-band sensors of the COSMO-SkyMed constellation permit the investigation of small-scale displacements relevant to single buildings or infrastructures of the built-up environments, even when they are located in areas where extended deformation phenomena occur. The last case study explores the potentials of the forthcoming NIMBUS SAR X-band constellation in future DInSAR scenarios, assessing its prospective impact on the displacement monitoring capabilities for the entire Italian territory. The final discussion is devoted to summarizing the main findings learned through the presented case studies and to highlighting further possible impacts on the future developments of the DInSAR techniques.