电离层GPS掩星反演技术研究

GPS无线电掩星技术是崭新的、高效的地球大气层和电离层探测技术，但仍在发展和完善之中.本文详细推导了Abel积分和绝对TEC电离层反演方法，研究了如何解决Abel积分产生的上下限异常问题；用COSMIC发布的GPS原始数据进行了反演计算，将结果与地面电离层测高仪数据进行了比较，最后讨论了周跳对反演结果的影响问题.结果表明：（1）在较高轨道高度（约800 km），Abel积分与绝对TEC方法的反演结果基本一致，都与电离层测高仪反演结果符合良好；在较低轨道高度（约500 km），绝对TEC反演精度优于Abel积分反演精度；（2）绝对TEC反演的最大电子密度N_m较Abel积分法获得的结果更接近于电离层测高获得的峰值电子密度N_mF₂，绝对TEC反演法更加严密和有效；（3）周跳对绝对TEC反演结果的影响较Abel积分反演结果的影响更为敏感，但无论哪种方法，周跳对反演精度都造成严重损失.综合而言，绝对TEC反演法是更优的方法.

Research on ionospheric inversion of GPS occultation

GPS radio occultation measurements are brand-new and highly effective, which can detect atmosphere and ionosphere, but still in the development and perfection. This paper deduces in detail the inversion method of Abel integral and absolute TEC for occultation data, studies how to solve the problem of singularity at the upper and lower part derived from the Abel integral, carries out the inversion calculation with the GPS original data from COSMIC, compares the results with the ionosondes measurements, and finally discusses the effect of cycle slip on the inversion results. These results show that: (1) the results retrieved from the Abel integral and absolute TEC inversion are consistent on the whole at higher orbits altitude (~800 km), and in good agreement with those measured by ionosondes; the results retrieved from absolute TEC inversion are in better agreement with those obtained from ionosondes than that by the Abel integral inversion at lower orbits attitude (~500 km); (2) the maximal electron density N_m from absolute TEC inversion is closer to N_mF₂ from ionosondes than that from Abel integral inversion, and the method of the former is more rigorous and effective than that of the latter; (3) absolute TEC is more sensitive to cycle slip than Abel integral, but for the two ways significant loss of inversion precision due to cycle slip always exists. In a word, the absolute TEC inversion method is better.