Whether used to view Earth’s surface through clouds or at night, to measure the thickness of polar ice sheets, to map long-abandoned mines, or to monitor subsidence, synthetic aperture radar (SAR) imaging has become a standard remote sensing tool. While optical satellites have higher resolution, radar imagery is better for change detection. Governments and private companies can use SAR satellites to monitor wide swaths of land or water from relatively low orbits, then follow up with higher resolution systems to zoom in on, say, an unidentified ship approaching a shore. Capacity continues to grow, as new satellites are launched. The two biggest challenges now for this segment of the geospatial industry are to develop software tuned to the requirements of specific users and to train them in using the data.