Introduction
While most scientists using remote sensing are familiar with passive, optical images from the U.S. Geological Survey’s Landsat, NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS), and the European Space Agency’s Sentinel-2, another type of remote sensing data is making waves: Synthetic Aperture Radar, or SAR. SAR is a type of active data collection where a sensor produces its own energy and then records the amount of that energy reflected back after interacting with the Earth. While optical imagery is similar to interpreting a photograph, SAR data require a different way of thinking in that the signal is instead responsive to surface characteristics like structure and moisture.
More: https://earthdata.nasa.gov/learn/what-is-sar