Retrieval On GPS Neutral Atmospheric Radio Occultation

GPS radio occultation observation technology,as an emerging technology for the application of navigation satellites in the 21st century,it is an important means of space exploration technology.GPS radio occultation neutral atmospheric inversion technology can obtain high-precision,all-weather neutral atmospheric parameters through global observation data provided by occultation observation satellites.The technology is used in weather forecasting,space environment exploration,astronomical observation,and national defense security fields have a wide range of application prospects.Based on the basic principles and development status of GPS neutral occultation neutral atmospheric inversion technology,this dissertation focuses on the existing problems of domestic radio occultation inversion algorithms,and conducts in-depth research on geometrical optical inversion algorithms and full-spectrum inversion algorithms.Considering that many error factors in the process of radio occultation inversion may cause inversion results to be affected,the method of simulation analysis is used for in-depth analysis.The following three points are the main research contents of this article and the corresponding conclusions:(1)The GPS neutral ambiguity neutral atmospheric geometry inversion algorithm was implemented.Based on the additional phase delay data published by COSMIC,this paper presents a detailed description of the specific flow of a geometrical optical inversion algorithm based on a single signal,and finally achieves a neutral atmospheric geometry optical inversion algorithm,and gives a geometric optical inversion example.From the inversion example,it can be seen that the geometrical and optical inversion algorithm has good inversion effects on the refractive index profile above 10 km,dry temperature and dry pressure profiles,and the inversion results are comparable to the ECMWF results.Thus the higher troposphere has a certain degree of credibility.(2)Taking into account the error problem in the neutral inversion of GPS radio occultation,an in-depth simulation analysis of the factors that may cause inversion errors in the inversion process is performed.In this paper,based on EGOPS simulation software,three-dimensional ray tracing method is used to simulate 426occultation events in a day,and the error characteristics of various error sources such as clock error,orbit error,noise error and amplitude are statistically analyzed.Some useful conclusions have been drawn:The higher the stability of the bell,the higher the inversion accuracy.To ensure the accuracy of the inversion,the stability of the bell needs to be controlled at2*10~-1313 or more;The precision of the existing orbit determination Can fully meet the occultation inversion needs;The noise error has a greater impact on the accuracy of occultation inversion.When the Gaussian phase noise error at 4mm,the relative deviation is close to-6%;In addition,local multipath error period influence is much smaller than the impact of the amplitude,the amplitude and temperature RMS errors are positively correlated over 20 km.The amplitude has a great influence on the inversion accuracy of higher atmosphere.(3)The process of neutral atmospheric processing for GPS radio occultation was established,the full spectrum inversion algorithm was used in the low troposphere region,and the traditional geometrical optics inversion algorithm was used in the higher troposphere.In order to effectively solve the problem of atmospheric multipath in the neutral atmospheric inversion,the full spectrum inversion method(FSI)is used in the low troposphere,and the traditional tropospheric inversion method is used in the higher troposphere.The curved horn profile is finally obtained through the Abel integral.This method was used to process the occultation data published by COSMIC,and the results were compared with the corresponding ECMWF analysis field data.The relative deviation of the FSI algorithm's inversion results was within 0.5%and the standard deviation was within 2%.The overall inversion result is indistinguishable from the COSMIC inversion,indicating that the full-spectrum inversion algorithm has high inversion accuracy and applicability.