Grating lobe returns in RADARSAT EH4 images

The RADARSAT SAR sensor uses an electronically steered planar antenna. In addition to a “standard” beam set, there are a number of experimental “extended beams”. For the “extended high beams”, the (right pointing) mainlobe is far enough from the physical boresight (normal to the antenna) that a significant grating lobe on the opposite side of the physical boresight is expected. A good configuration for detecting grating lobe return is to have the mainlobe directed at ocean and the grating lobe pointing at land. Since there is little or no return from the ocean at high incidence angles, the data will be dominated by the grating lobe return. The authors examine an Extended High 4 scene of an area of ocean off the Newfoundland coast, taken during an ascending pass. Partially processed images are used to identify grating lobe return. When the processing parameters are set for the grating lobe targets, a relatively clear image of Lake Champlain on the Vermont/New York border is formed