COSMIC 电离层掩星反演模拟及星座优化

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_mF₂ and N_mF₂ were 4.2 km and 0.26×10⁴ cm^–3, respectively, with relative errors of 1.66% and 4.95%, respectively. The linear regression coefficient of determination R² for the ionospheric h_mF₂ and N_mF₂ 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.