Time-domain backprojection for precise geodetic coding of spaceborne SAR imagery

A new era of precise-orbit determination for space-borne SAR permits time-domain backprojection of the data for accurate geocoded image production. In this work, time-domain backprojection is applied to Level 1.0 data from the ALOS/PALSAR instrument to form imagery at two sites in southern California. The accuracy of the backprojection is verified by comparing the measured position of a corner reflector at a calibration site to its position in the formed SAR imagery. The observed offset of the corner reflector is <2 m in the range direction and 12 m in the cross-range or along track direction. Images backprojected in an absolute WGS-84 Cartesian system onto 1/3 arc second or 10 m posting digital elevation data exhibit no gross registration errors. This indicates that the backprojection image formation method may be useful for processing differential radar interferometry (D-InSAR) products, where topography terms must first be removed.