An analysis of ship azimuth smearing in spacebome SAR imagery

Strong azimuth smearing that is quite common in many SAR ship images, especially at higher incidence angles as the case for spaceborne SAR, is always observed on the “power side” (closer to radar) of ship images. Several possible explanations were considered including sidelobes, angular scintillation or glint, and moving equipment such as marine radar, but none could be proven by a detailed signal analysis. The most plausible mechanism is that this effect is created by reflections from circularly moving surface water particles and capillary waves around the ship. This is consistent with the ship image smearing always appearing on the side of the ship that is closest to the radar and is supported by comparing the time-frequency signatures of the measured smeared ship images with those of the simulated radar double-bounce signals from the waves near the ship.