编队卫星InSAR空间基线修正的建模与精度分析

Modeling and precision analysis of spatial baseline modification of formative satellites InSAR

星载GPS接收机相对定位获得的编队星间基线,与用于星载InSAR测高的基线并不相同。给出了从GPS测量基线到InSAR测高基线的关联建模,包括天线相位中心与几何中心的偏差修正、GPS接收机到SAR天线的安装部位修正以及基线矢量的坐标系转换等环节。推导了基线的修正和转换公式,并进行了相应的精度分析。对于极限基线之内的宽编队,相位中心变化造成的基线差别在亚毫米量级,一些时刻达到与测高基线精度指标相当的厘米量级,必须加以修正;在编队中由于三轴稳定卫星之间的相对姿态数值通常较小,坐标系转换误差引起的基线修正误差在亚毫米量级。

The baseline between the formative flying satellites can be obtained by the relative positioning based on spaceborne GPS receivers. However, it is not identical with the one applied in the spaceborne InSAR height measurement. The associated modeling from the GPS measurement baseline to the InSAR height acquisi- tion baseline is presented. Several steps are included in the overall conversion, such as the offset modification between the phase center and the geometric center of antennas, the fixing position modification from the GPS re- ceiver to the SAR antenna and the reference frames conversion of the baseline vectors. The modification and conversion formulas are deduced, and the corresponding precision analyses are also carried out. Simulations show that the baseline vector offset caused by the antenna phase center variation in a loose formation within the critical baseline range must be modified, for it is at the sub-millimeter level and sometimes even higher and rea- ches the precision level of the InSAR baseline requirement at the centimeter level. The baseline modification er- ror introduced by the reference frames conversion error is at the sub-millimeter level as the relative attitudes are usually small between three-axis stabilized satellites in a formation.