The Calibration of ERS SAR Imagery for Land Applications

DLR, Oberpfaffenhofen, D-82234 Wessling, Germany.ABSTRACTThe estimation of radar cross-sections from SARimagery requires the data to be calibrated. For the ERS-1 and ERS-2 SAR instruments, details of the calibrationsteps required for ERS SAR PRI and SLCI productsgenerated at the ESA Product and Archive Facilities(PAFs) have been issued by ESA [1]. The purpose ofthis paper is to give an overview of these calibrationsteps with an emphasis on the calibration of ERS SARimagery for land applications.INTRODUCTIONThe ERS-1 and ERS-2 SAR missions have been inoperation since July 1991 and April 1995 respectively.They have fully lived up to their expectations bysuccessfully demonstrating the ability of imaging radarsto provide valuable long-term earth observation data toseveral categories of users. These range from the near-real time operators to research project groups workingoff-line on environmental issues.Many users, including those working on landapplications, require the SAR products from ERS-1 andERS-2 be calibrated (absolutely and relatively).Absolute calibration supports the geophysicalinterpretation of SAR data by relating the digital valuesin data products to the physical and meaningfulestimation of the normalised radar cross-section σ