On the use of Numerical Weather Models for improving SAR geolocation accuracy

In order to ensure sub-pixel accuracy of geocoded SAR products, precise estimation and correction of the Atmospheric Path Delay (APD) is needed, in particular for the new generation of high resolution satellite SAR sensors (TerraSAR-X, COSMO-SkyMed). The goal of the present study is to assess the performances of operational Numerical Weather Models (NWM) as tools for APD mitigation. The Regional Atmospheric Modeling System (RAMS) has been selected for this purpose. In order to guarantee an accurate knowledge of both the satellite orbit and the target position, TerraSAR-X data and corner reflectors have been used for the experiment. Differential GPS measurements confirm that NWM are able to estimate APD with an accuracy of few decimeters. Therefore, NWM can be also exploited as tools for providing preliminary indications on the amount of orbital or timing errors. The analysis has been hence extended to COSMO-SkyMed data.