Research on the equivalent nadir point of bistatic SAR with geostationary illuminator and LEO or UAV receivers

The problem of how to determine the position of equivalent nadir point of bistatic SAR with geostationary illuminator and low earth orbit (LEO) or unmanned air vehicle (UAV) receivers is very important. Considering high-orbit (or huge-range) characteristic of geostationary bistatic SAR the paper treats the earth surface as an ellipsoid surface and gives several models related to range. After studying the internal relation between the range-surface and the iso-range contours on the earth surface the paper presents a simplex-based approach to determine the position of equivalent nadir point of geostationary bistatic SAR. In simulation experiments the theoretical analyses and the simplex-based approach are tested and verified and the influence of earth curvature has been observed and analyzed.