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 (similar to 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 (similar to 500 km); (2) the maximal electron density N-m from absolute TEC inversion is closer to NmF2 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.