电离层延迟对星载InSAR精度的影响

Study on andsimulation the impact of ionospheric delay on the accuracy of spaceborne InSAR

针对电离层对L、P等较长波段的星载合成孔径雷达干涉测量(InSAR)成像产生的相位延迟效应会造成InSAR精度下降的问题,建立电离层相位延迟模型,分析背景电离层TEC对不同波段SAR信号的距离和相位延迟,给出了TEC和SAR相位延迟之间的关系曲线;提出用沿电磁波传播斜距上的电子积分总量STEC来代替垂测TEC,采用简化射线描迹方法进行STEC估计,提高了TEC计算精度;通过仿真实验分析不同TEC分布模型对InSAR精度的影响。实验结果表明,因干涉测量中基线估计的补偿效应,使得成像范围内等量分布的TEC对测量精度无明显影响;成像范围内TEC值随空间位置不同而发生变化时,对InSAR的精度将产生较大影响,需要考虑电离层的校正。

With a dispersive medium and various scales of Ionospheric irregularities, phase delay of may decrease the interferometry measurement accuracy for L, P and other long band interferometric syn- thetic aperture radar （InSAR）. Therefore, this paper conducts a research on the influence of Ionospheric phase delay on the L-band spaceborne InSAR accuracy, with an Ionospheric phase delay model estab- lished. And then the distance delay and phase delay of different band SAR signal caused by background ion- osphere mean TEC can be calculated. Thus the relationship between the Ionospheric TEC and phase delay of SAR signal can be curved. In this paper, the vertical distance measured TEC is replaced with STEC a- long the electromagnetic wave propagation, and a simplified method of ray tracing on the satellite signal path is proposed to estimate Ionospheric delay （STEC）, which can improve the TEC calculation accuracy; The effect of different TEC distribution models on the precision of InSAR is analyzed through a simulation experiment. The experimental result shows that uniformly distributed TEC in the imaging field has no ap- parent effect on the measurement accuracy since it can be compensated by utilizing baseline estimation pa- rameters, whereas when TEC varies in position, it has great impact and the correction technical methods must be considered.