Precise SAR satellite orbit parameters determination based on Ground Control Points

Aim to solve the georeferencing problem of spaceborne SAR imagery, accounting for the orbit physics model and the impact of the earth perturbations, some description models such as four parameters model and polynomial model could be applied to determine the satellite orbit parameters. However the orbit state vectors solved by 5 satellite state vectors supplied by header file in SAR data files could hardly acquire precise orbit parameters, which would greatly effect on the accuracy of co-registration, phase unwrapping, baseline estimation and the generation of Interferogram and DEM (Digital Elevation Model). In this paper, combined with R-D (Range-Doppler) conformation equation and earth ellipsoid equation, which explicitly describe the relationship of corresponding pixel between the 2D image coordinate and the 3D cartographic coordinate of ground targets, an advanced orbit model algorithm by adding few GCPs (Ground Control Points) to improve satellite state vectors is presented. All the correlative formulas are deduced and the orbit parameters can then be iteratively determined through solving a linear equation set consisting of the error equations from all GCPs under Recursive Least Square (RLS) algorithm. The algorithm is tested on an ERS SCL (Single Complex Looked) scene with a series of simulation experiments and the improved orbit parameters and contrasted with accurate SAR orbit data supplied by DEOS institution of Delft University in Holland, which could be demonstrated of validity and stability.