COSMIC电离层掩星反演模拟及星座优化

COSMIC Ionospheric Occultation Inversion Simulation and Constellation Optimization Research

基于卫星导航系统精密星历和NeQuick模型模拟COSMIC星座电离层掩星事件的几何过程和物理数据,并采用改正TEC法和“洋葱分层”算法反演电离层三维电子密度.模拟反演得到的电子密度廓线与模型变化趋势一致,偏差较小.电离层h_(m)F_(2),N_(m)F_(2)的绝对误差分别为4.2 km和0.26×10^(4)cm^(–3),相对误差分别为1.66%和4.95%,反演值与模型值的线性回归决定系数R2分别为0.956和0.950,表明掩星反演模拟完整可靠、正确有效.在几何模拟正确的基础上,分析了COSMIC-2完全组网时的掩星观测性能及多系统GNSS对掩星数量及空间分布特征的影响.为提高未来掩星事件的时效性及时空分布的均匀性,提出了一种掩星分布均匀性指数,并且通过非支配排序遗传算法实现掩星星座卫星总数、轨道面数、轨道倾角的最优确定.

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 h_(m)F_(2) and N_(m)F_(2) were 4.2 km and 0.26×10^(4)cm^(–3),respectively,with rela tive errors of 1.66%and 4.95%,respectively.The linear regression coefficient of determination R2 for the ionospheric h_(m)F_(2)and N_(m)F_(2) inversion results and model values were 0.956 and 0.950,respectively,indicating 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 proportional 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 determine 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.