Spaceborne Scansar Radiometric Correction Key Technologies

ScanSAR mode plays an important role in Synthetic Aperture Radar (SAR)technology development by means of its ability to offer wide swath coverage.Because of its particular operation mechanism special radiometric variations appearin the ScanSAR images, which need to be corrected properly. Considering thatScanSAR has been included in many modern satellite SAR systems and will also beincluded in the satellite our country plans to advance, it is quite necessary to doresearch on the critical radiometric correction technologies for ScanSAR.Through analyzing those special radiometric variations in ScanSAR images, thispaper has explored the approaches for scalloping compensation and beam bandcorrection. As for azimuth scalloping compensation, accurate Doppler Centroidestimation is needed. Besides, superior scalloping correction function also plays animportant role which needs to be derived from specific ScanSAR azimuthparameters. As for beam band correction, accurate roll angle estimation is needed inorder to guarantee elevation antenna pattern correction precision. Moreover, theinter-beam radiometric discrepancy should also be estimated and compensatedproperly. Through study on the factors inhibiting current ScanSAR roll angleestimation algorithms, this paper proposes two improved algorithms. One is basedon lease square estimation and the other works by searching for the minimization ofa parabola function. Both improved algorithms can estimate roll angel andinter-beam radiometric discrepancy simultaneously. In this way better roll angleestimation canbe reached and beam band correction can be benefited. Byintegrating those critical radiometric correction technologies for ScanSAR, thewhole correction scheme for ScanSAR is proposed based on ScanSAR imagingprocedure. By means of simulation, the feasibility of the radiometric correctiontechnologies and scheme is verified.