The ESA (European Space Agency's) Sentinel-1A/B satellites are equipped with synthetic aperture radar (SAR) instruments that record continuous all-weather, day-and-night imagery. SAR energy beams can penetrate cloud and tree canopy cover to detect very small changes to the height, shape, and position of Earth surfaces. The ability of Sentinel-1 to capture detailed SAR images anywhere at any time makes them excellent tools for producing interferograms and digital elevation models to track the movement of Earth's plates.