Analysis And Correction Of Ionospheric Impact On Spaceborne SAR Measurment Accuracy

Spaceborne SAR has become one of the important means of Earth observation,with the advantage of all-time and all-weather.During the propagation process,the SAR signal will inevitably be affected by the ionosphere,resulting in the decrease of measurement accuracy,particularly in the low frequency bands.How to effectively improve the measurement accuracy of spaceborne SAR,has become an emerging hot issue in the field of SAR data processing.For these needs,funded by the National 863 Program,this paper conducted research work focusing on ionospheric effects on SAR measurement accuracy and correction.The main work and innovations of this paper are as follows:1.From the perspective of spatial and temporal variation of the ionosphere,the applicability of IRI2012 and GIM model in China was analyzed,and the relationship between the ionospheric TEC disturbances and solar storms,geomagnetic storms was verified with TEC perturbation index.Two refinement algorithms for ionospheric empirical models were described,and the experiment about IGS-based space-time associated interpolation was conducted.2.SAR imaging model affected by ionosphere and SAR stereotactic model were theoretically analyzed,and the effects of different ionospheric TEC model on different band SAR stereo positioning accuracy was quantitatively analyzed through experiments.The correction methods were proposed through the analysis of SAR stereotactic process,including OPRC method and slope distance direct calibration,achieving the correction of the ionosphere effect on the SARstereoscopic positioning accuracy.3.The basic principle of ionospheric phase delay effect on DEM generated by spaceborne InSAR was analyzed,and CATBE method was proposed.Introducing the correction method into the InSAR height measurement process,the experiment was conducted for the effect of different ionospheric TEC distribution pattern on spaceborne InSAR height measurement and calibration,and the effectiveness,applicability and practicality of CATBE was verified.4.Summarizing the foregoing key technologies and correction algorithms,the simulation system was constructed.It has been used in the National 863 Project,implementing the comparison and interpolation refinement of ionosphere models,ionospheric effect on SAR stereotactic precision and correction,and ionospheric effect on InSAR height measurement accuracy and compensation.