A Study of the Impact of Heterogeneous Low Earth Orbit (LEO) Constellations on Global Ionospheric Tomography Inversions

The development of low earth orbit (LEO) satellites has provided the possibility to improve the accuracy of wide-area global navigation satellite system (GNSS) tomography; however, the existing LEO constellations were not designed to consider the effect on the improvement of the accuracy of GNSS computerized ionospheric tomography (CIT). In this paper, we use simulated observations to reconstruct a global higher-resolution three-dimensional (3D) ionospheric electron density (IED) model with a voxel-based model to explore the combined effects of heterogeneous LEO constellations on CIT. The results are as follows: (1) The number of grids crossed by rays increases after adding LEO satellites at different altitudes, while in the altitude interval of 100–300 km, the gain percentage increases with the number of LEO satellites at all four altitudes (300 km, 500 km, 800 km, and 1000 km). (2) The root mean square (RMS) gain percentages are positive after adding LEO satellite observations at 300 km and 500 km altitudes. Whereas, after adding LEO satellite observations at 800 km and 1000 km altitude, the RMS gain percentages from 100–300 km are negative. (3) From the overall percentage gain, the percentage RMS gain of all six plans exceeds 25%, with planB (96/96/60/30 LEO satellites at 300/500/800/1000 km, respectively) having the smallest percentage RMS gain of 27.31% and planA (192/96/60/30 LEO satellites at 300/500/800/1000 km, respectively) having the largest percentage RMS gain of 32.42%. Considering the LEO satellite launch maintenance cost for the enhancement effect of heterogeneous LEO constellations on CIT, this paper demonstrates that planA can effectively improve the accuracy of the 3D IED model.