A New Topography Profile Estimation Approach for Spaceborne SAR Based on Generalized Pencil-of-Function (GPOF)

In order to improve the signal-to-noise ratio (SNR) of spaceborne synthetic aperture radar for wide swath imaging, the technique SCan-On-REceive (SCORE) is always adopted to form a digital beam to track pulse echoes so as to improve the receiving gain. The prerequisite for the effective SCORE is that the information of topography profile is well known in advance, otherwise the beam center of the digital receiving beam will mismatch with the real Direction-Of-Arrival (DOA) of echoes, leading to the loss of receiving gain and that of consequent SNR. Furthermore, the Range Ambiguity-to-Signal Ratio (RASR) will also deteriorate due to this mismatch. To deal with this problem, this paper brings forward a novel approach based on Generalized Pencil-Of-Function (GPOF) that can efficiently and precisely estimate the topography profile from the raw data of received echoes. Compared with estimation approaches using spatial spectrum, our scheme does not have to implement the range compression at first, and thus the requirements on the onboard computation resources can be eased to a large extent. This paper, for the first time, presents the complete estimation procedures to evaluate the topography profile of scene, which consists of topography modelling, echo processing and the final topography reconstruction. By comparing with the real topography profile, the effectiveness of reconstruction result has been validated.