COSMIC Ionospheric Occultation Inversion Simulation and Constellation Optimization Research
Using precise GNSS ephemeris and the NeQuick model,we simulated the geometric process and physical data of COSMIC ionospheric Radio Occultation(RO),and inverted the three-dimensional electron density of the ionosphere using the calibrated TEC method and"onion layering"algorithm.The obtained electron density profile was found to be consistent with the model trend with small deviations.The absolute errors of ionospheric hmF2 and NmF2 were 4.2 km and 0.26×104 cm-3,respectively,with rela tive errors of 1.66%and 4.95%,respectively.The linear regression coefficient of determination R2 for the ionospheric hmF2 and NmF2 inversion results and model values were 0.956 and 0.950,respectively,indi-cating the completeness,correctness,and effectiveness of the occultation inversion simulation.Building on the correct geometric simulation,we analyzed the occultation observation performance of COSMIC-2 and the influence of multi-GNSS on the number and spatial distribution characteristics of occultation.It is found that the number of navigation satellites participating in the occultation observation is propor-tional to the occultation event,and the uniformity of the occultation distribution significantly improves with the increase in navigation satellites.To enhance the timeliness of future occultation events and the uniformity of their spatial and temporal distribution,the uniformity index of occultation distribution is proposed and improved the COSMIC-2B using a fast non-dominated sorting genetic algorithm to deter-mine the optimal total number of occultation satellites,number of orbital planes,and orbital inclination.The optimal configuration of 38/19/1∶800 km,75.21° was found,achieving the design goals of N≤40,F=1,h=800 km,72°≤i<90°.With 106 satellites including GPS,Galileo,GLONASS,and BDS-3 in one hour,this configuration can observe 2675 occultation events with uniform spatial and temporal distribution.
COSMICIonosphereOccultation inversionSimulationElectron density
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