GPS无线电掩星反演大气参数中的算法研究

针对目前无线电掩星技术反演地球大气参数算法中的不足,给出一种参数代换法,以解决无线电掩星中Abel积分的广义形式不适合高精度地进行数值积分的问题,在大气折射角随待测点的地心距呈指数函数衰减的假定下,对应两种算法分别生成相应的大气折射率,折射率绝对差最大值出现在低层大气,可达到约为7个折射率单位,两者的差异随高度递增逐渐“缩小”;而从折射率的相对差方面考虑,折射率相对差的变化趋势是随高度递增而逐渐增大。

Study of Algorithms Employed in Inverting Terrestrial Atmospheric Parameters by GPS Radio Occultation

Taking into account shortcomings in algorithms employed in inverting terrestrial atmospheric parameters by GPS radio occultation, a variable transform is raised in this text. By this transform, we have managed to solve the problem that original form of Abel integral was digitally integrated to comparatively poor accuracy. To make comparisons, we assess the refractivity under two different algorithms, assuming that the bending angle due to refractive atmosphere decreases exponentially with the increase of distance of the considered point from the geocenter. It shows that the maximum of absolute difference between two algorithms reaches roughly as large as 7 refractivity units, and absolute difference decreases with increasing altitude; whereas, on the other hand, the relative difference of refractivities increases with the increasing altitude, which is diametrically different from the trend of absolute difference.