Theories And Methods Of Geosynchronous Synthetic Aperture Radar(SAR) Differential SAR Interferometry(D-InSAR) Three-Dimensional Deformation Measurement

With the advantages of the short revisit and the long observation time for the target area,geosynchronous differential synthetic aperture radar interferometry(GEO D-InSAR)can realize the rapid deformation monitors for the eruptions of the sudden nature disasters,such as earthquakes and landslides.Especially,the long observation time of GEO D-InSAR makes it have the capability of obtaining abundant multi-angle data,which can achieve a high accurate three-dimensional(3D)deformation of the target area.Therefore,it is an effective method to address the drawbacks that the low Earth orbit synthetic aperture radar(LEO SAR)has a long revisit time and the 3D deformation retrieval accuracy is very poor.However,because of the high orbit,GEO D-InSAR 3D deformation retrieval faces many problems.First,to obtain the GEO D-InSAR one-dimensional(1D)deformation of a high accuracy is the foundation of the high-accuracy 3D deformation retrieval.However,under the heavy impacts of the un-parallel repeat-track,the squint mode and the multi-disturbance,the coherence and the phase accuracy of the interferogram degrade obviously.In the meantime,the traditional deformation retrieval model will have obvious errors.Especially,under the condition of the long integration time and the large observation area,the low working frequency of the system not only gives rise to the obvious deterioration by ionospheric disturbance,but the corresponding mechanism is very complex.Moreover,when expanding from 1D to two-dimensional(2D)or more than 2D in the deformation retrieval,because the multi-aperture is used,it is necessary to study the optimal selection of the sub-apertures under the multi-angle geometry to optimize the deformation retrieval accuracy.At the same time,the proper models for deformation retrieval and the error analysis should be established,and the impacts of the various orbits and the system parameters on the retrieval accuracy need to be considered as all.At last,the effective validation experiment for GEO D-InSAR 3D deformation retrieval should be designed and conducted.Focusing on the aforementioned problems,the detailed contents and main contributions of the thesis are as follows:1.Considering GEO D-InSAR system faces serious perturbation and multi-disturbance impacts,the thesis deals with the method and performance of GEO D-InSAR 1D deformation retrieval.1)As for the impacts of the various decorrelation sources,we accurately model the decorrelation sources and analyse the related influences quantitatively.The required system parameters and the accuracies of the processing algorithms are given.With respect to the serious rotational-induced decorrelation brought by the un-parallel repeat-tracks,we proposed an optimal InSAR data acquisition method based on a criterion of minimal rotational-induced decorrelation,which can mitigate the severe rotational-induced decorrelation;2)We quantatively analysed the impacts of the phase noise,orbit and the digital elevation model errors and the tropospheric disturbance on the GEO D-InSAR interferometric phase,which suggests that all the three error sources contribute to millimeter-level deformation errors under the ideal designed system parameters and the processing operations.3)Based on the optimal sensitivity to the height variation and the squint range-Doppler localization equation,the proper height and deformation retrieval models fitting for geosynchronous synthetic aperture radar(GEO SAR)squint mode were deduced,which can realize the high-accuracy height and deformation retrieval.2.Considering the severest impact of temporal-spatial ionospheric disturbance in themulti-disturbance impacts,we studied its influences on GEO D-InSAR and themitigation methods.1)Facing the invalidation of the background ionosphere ‘frozen model' under the long integration time,we construct a background ionosphere signal model of temporal-spatial variation.The corresponding impacts of the relative image shifts and the mismatch decorrelation,and the interferometric phase screen errors are deduced.The analysis of the real background ionosphere dataset suggests that azimuth mismatch decorrelation and the interferometric phase screen error are the main problems brought by the background ionospheric disturbance;the mitigation method for the interferometric phase screen error based on the coherent points is proposed,which can obtain a centimeter-level deformation accuracy for a large scene with a swath of more than one hundred kilometers;2)Considering the drawbacks of the lack of the quantitative analysis and the ignoring of the amplitude scintillation impact in the conventional analysis of the ionospheric scintillation impacts on SAR,we have deduced the analytic expression between the azimuth imaging parameters and the scintillation parameters in the presence of the amplitude-phase scintillation based on the scintillation sampling model and power spectra analysis.Our study shows that the deterioration of the azimuth integrated sidelobe ratio dominates the impacts;by virtue of the analytic expression and the bivariate normal transformation model,the relationship between the coherence and the scintillation intensity indexes is obtained,which suggests a moderate scintillation can cause the obvious decorrelation;we propose an avoiding method for the ionospheric scintillation by the orbit-optimization strategy and a joint amplitude-phase compensation autofocusing algorithm based on entropy minimum to mitigate the impacts of ionospheric scintillation on interferometry processing.3.Considering the disadvantage that the along-track deformation cannot be measured by 1D D-InSAR deformation retrieval,GEO SAR 2D deformation retrieval based on the multiple-aperture interferometry(MAI)is studied in the paper.Aimed at the long full-aperture of GEO SAR,expressions of the 2D deformation and its error by MAI processing under the GEO SAR squint mode are deduced;the optimal MAI sub-aperture selection method by mainly evaluating the along-track baseline length is proposed;we verify that GEO D-InSAR system has a longer optimal along-track baseline length due to the nearly ‘spotlight' imaging for the target,and can obtain a higher along-track deformation retrieval accuracy compared with the LEO D-InSAR system;the performances of the along-track deformation retrieval under different designed orbits and system parameters are discussed in detail;the three-step correction approach is proposed to address the problems of the geometric distortion and the multicycles flat-earth and topographic phases brought by the large geometrical difference between the forward-and backward-looking interferograms,which helps realize the high accuracy 2D deformation retrieval.4.Considering the capability of obtaining abundant multi-angle data by GEO D-InSAR and the problem that it is impossible to fully evaluate the deformation of the disaster if the 3D deformation is lacked,GEO D-InSAR multi-angle 3D deformation retrieval is studied.As GEO D-InSAR system has the advantage of abundant multi-angle data acquisition by beam control,according to the energy consumption(required times of the beam control)and accuracy,the models and the errors of 3D deformation retrieval based on MAI and the multi-angle observation method are deduced,which can realize3 D deformation retrieval under the multi-angle geometry;considering the lacks of the proper criterion for the evaluation of holistic 3D deformation accuracy and the optimal sub-aperture selection methods,a criterion for the evaluation of holistic 3D deformation accuracy based on position dilution of precision is proposed,and the optimal sub-aperture selection methods are also obtained according to the criterion;the analysis method for the optimal 3D deformation retrieval accuracy and the optimal sub-aperture selection under different orbit configurations and geo-locations based on the artificial neural network is proposed,which provides the theoretical support for the orbit design with the optimal 3D deformation retrieval accuracy;based on the Bei Dou-2 inclined geosynchronous orbit navigation satellite and the two-channel direct-signal antennae,we design and realize the GEO D-InSAR 3D deformation validation experiment for the first time,which not only verifies the feasibility of GEO D-InSAR system for 3D deformation retrieval and the effectiveness of the theoretical analysis and the proposed methods,but a 3D deformation retrieval accuracy of a centimeter-level and even a millimeter-level can be obtained by GEO D-InSAR under the condition of a good coherence.