Sentinel-1 InSAR processing: challenges and opportunities

Abstract:

Radar interferometry has been successfully applied to measure ground deformation for over two decades. However, until now the data have been acquired on an ad-hoc basis. The recently-launched Sentinel-1 mission is the first to acquire global data systematically. Moreover, the default mode of radar acquisition for Sentinel-1 is the Terrain Observation by Progressive Scans (TOPS). In this new acquisition mode the steering of the radar antenna in the along-track direction induces that certain areas of the image are illuminated more than once and any surface deformation projects with a different line-of-sight unit vector across the scene. The consequence is that the scanning feature of Sentinel-1 TOPS mode make interpretation and analysis of differential interferograms more complex to process and interpret than the traditionally use of radar interferometry. However, at the same time, it also presents a number of opportunities such as redundant data, and increased sensitivity to along track displacement. Here, we present in detail the basic processing steps which differ from the traditional stripmap mode interferometry, and we illustrate some of the special features with actual results of significant deformation events: the 2014-2015 eruption of Pico do Fogo volcano and The 2015 Gorkha (Nepal) earthquake. Here, we show that the new Sentinel-1 TOPS-mode interferometry can be used to estimate relevant geophysical parameters, and most applications should not be affected by the new mode. The planned 20 year Sentinel-1 mission, provides access to a wealth of open and free high-quality radar data that should greatly improve our understanding of deformation phenomena in the future.