Application of SVD-based R-T-S optimal smoothing algorithm to POS for airborne SAR motion compensation

Position and orientation system (POS) has been used widely to compensate for the motional error of an airborne synthetic aperture radar (SAR), and its navigation precision has a direct effect on SAR imaging. In order to obtain higher navigating precision and numerical stability, an algorithm of Rauch-Tung-Striebel (R-T-S) optimal fixed interval smoothing based on singular value decomposition (SVD) was used in POS. The smoothed best estimate of position, velocity and attitude can be obtained by forward-pass Kalman filter (KF) based SVD and backward-pass R-T-S optimal fixed interval smoothing based SVD. This method not only has excellent numerical stability but also eliminates the necessity of system transition matrix inversion. The semi-physical simulation results show that this method has better precision and data smoothness than the KF currently in engineering application, and it may be an effective method for POS post-processing.