Orbital Error Modeling And Analysis Of Spaceborne InSAR

Spaceborne repeat-pass synthetic aperture radar interferometry is a key technique for large-area deformationmonitoring.Measurements can be biased by errors originating from amultitude of different sources.Each error source having itsown characteristics,signals with different spatial or temporalproperties are superposed to the signal of interest.Whenground deformation is the signal of interest,it is the aim ofInSAR processing to estimate and consecutively eliminate ormitigate all other signal contributions.Inaccuracies in the satellite orbits affect interferogramsin the form of an almost linear signal and scale the heightambiguity The commonly used method to mitigate the orbital error is to calculate the residual baseline error by the Fast Fourier Transform on the residual phase.Alternatively,the residual phase is fitted with the quadratic surface.These two methods are applicable in most cases,but does not apply in the presence of a large-scale deformationsignal like tectonicmovement or tides that has similar spatialcharacteristics.After the occurrence of the InSAR technique,the least squares method is used to calculate the residual phase of the baseline error in the interferogram.Based on the combination of different temporal and spatial baselines,according to the adjustment principle,the quasi-absolute orbital errors are calculated.Besides,cross validation is applied to estimate the reliability of orbit accuracy.There is also a model for joint estimation deformation rates and orbital errors.Some studies regard the track error as not relevant in time or the impact of orbital errors can be ignored in time series InSAR.However,for high-precision deformation monitoring,orbital errors have an measurable effect on the results,so it is necessary to model and analyze the orbital errors.Based on the current research on modeling and analysis of baseline errors and orbital errors,some work has been done on the orbital errors of spaceborne InSAR.Firstly,this paper elaboratesthree methods of baseline estimation which is based on orbit,inteferogram and ground control points respectively.The principle,the applicable conditions and the implementation process of the three main methods are introduced.Three methods of baseline estimation arecompared and validated by GF-3 with whose effect and applicability are analyzed.Secondly,a baseline estimation method based on ground control points phase residual weighting is proposed.The algorithm is validated,compared and analyzed by simulated data.The experiment shows that this method can reduce the effect of the atmospheric propagation delay phase and deformation phaseand improve the accuracy of baseline estimation.Finally,according to the principle of orbital error network adjustment,the orbit error network adjustment of Envisat ASAR data in Los Angeles area is realized.Forquality control on the network level,iterative data snoopinghas proven its capability to detect and reject outliers.