SAR backscatter imaging

SAR backscatter imaging is the base active-radar method for all-weather surface imaging. It uses a synthetic-aperture radar payload to form calibrated amplitude images of surface backscatter at metre-to-tens-of-metres scale, independent of daylight and most cloud conditions.^[1] It serves flooding, sea ice, oil spill screening, maritime surveillance, and the downstream SAR wind and wave methods that start from SAR image products.

The method needs radiometric calibration, incidence-angle metadata, polarisation metadata, and enough antenna, power, downlink, and processing margin for imaging modes. Interpretation fails when geometry dominates the target signal: layover, shadow, foreshortening, speckle, wind roughening, wet-surface effects, and incidence-angle variation can all look like real surface change unless the product is terrain-corrected and normalised.

Demonstrated implementations include Sentinel-1 C-SAR, ALOS-2 PALSAR-2, and ICEYE X-band SAR. C-SAR provides C-band SAR modes including Interferometric Wide swath imaging at 250 km swath and 5 x 20 m ground resolution.^[1] PALSAR-2 adds L-band SAR with spotlight, stripmap, and ScanSAR modes plus single, dual, compact, and full-polarisation options.^[2] ICEYE provides X-band SAR imaging modes for repeat commercial monitoring, with sub-metre tasking modes and day-night, all-weather operation.^[3]