Abstract
The retrieved electron density profile of ionospheric radio occultation (RO) simulation data can be compared with the background model value during the simulation and the inversion error can be obtained exactly. This paper studies the inversion error of ionospheric RO through simulation. The sources of the inversion errors are analyzed. The impacts of measurement errors, such as the errors in phase measurements and satellite orbits, are very small and can be neglected. The approximation of straight-line propagation introduces errors at the height of the F1 layer under solar maximum condition. The spherical symmetry approximation of the electron density distribution is found to be the main source of the inversion error. The statistical results reveal some characteristics of the inversion errors. (1) The relative error increases with enhanced solar activity. (2) It is larger in winter than in equinox season, and it is smallest in summer. (3) For all seasons, it is smaller at middle latitude than at other latitudes. (4) For all seasons and geomagnetic latitudes, it is smaller at daytime than at other times. The NmF2 of the ROs from COSMIC are compared with the measurements of ionosondes, and the relative differences show the same dependencies on season, geomagnetic latitude and local time, as the relative errors of the simulated ionospheric ROs.
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Acknowledgments
The IGS provided the GPS orbit data. This research was supported by grants 40204011 from Chinese Natural Science Foundation and KGCX3-SW-408 from the Chinese Sciences of Academy. The authors thank the two anonymous referees for their advices to improve this paper, and thank Dr. Alfred Leick for his help to improve the English in the paper.
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Wu, X., Hu, X., Gong, X. et al. Analysis of inversion errors of ionospheric radio occultation. GPS Solut 13, 231–239 (2009). https://doi.org/10.1007/s10291-008-0116-x
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DOI: https://doi.org/10.1007/s10291-008-0116-x