In view of the shortcomings of existing satellite navigation systems in deep-space performance, candidate architectures which utilise libration point orbits in the Earth-Moon system are proposed to create an autonomous satellite navigation system for lunar missions. Three candidate constellations are systematically studied in order to achieve continuous global coverage for lunar orbits: the Earth-Moon L_1,2 two-satellite constellation, the Earth-Moon L_2,4,5 three-satellite constellation and the Earth-Moon L_1,2,4,5 four-satellite constellation. After a thorough search for possible configurations, the latter two constellations are found to be the simplest feasible architectures for lunar navigation. Finally, an autonomous orbit determination simulation is performed to verify the autonomy of the system and two optimal configurations are obtained in a comprehensive consideration of coverage and autonomous orbit determination performance.

Based on the candidate architectures of the libration point satellite navigation system proposed in our previous work, a navigation performance study is conducted in this paper to verify the cislunar navigation ability of the proposed system. Using scalar satellite-to-satellite range measurement between the user and libration point navigation satellites, a virtual lunar exploration mission scenario is developed to verify the navigation performance of the candidate Earth-Moon L_1,2,4,5 four-satellite constellations. The simulation results indicate that the libration point satellite navigation system is available for cislunar navigation and the navigation accuracy of a few tens of metres can be achieved for both the trans-lunar cruise and lunar orbit phase. Besides that, it is also found that the navigation accuracy of the libration point satellite navigation system is sensitive to the orbit of the L₁ satellite. Once the L₁ navigation satellite is located in the Halo orbit or vertical Lyapunov orbit, the proposed system can present a better navigation performance in cislunar space.

A combination of experiments and first-principles method calculations has been applied to investigate the influence of the hydrostatic pressure on the electrical properties of the phase-change material hexagonal ${\text{Ge}}_2{\text{Sb}}_2{\text{Te}}_5$ (h-GST). Experimentally, it is found that the resistance of h-GST declines monotonically with increasing hydrostatic pressure up to 0.7 GPa. Theoretically, the band-structure calculations revealed that the electronic band gap also decreases with the pressure. The hydrostatic pressure increases the conductivity of h-GST by reducing the electronic band gap. The $d{E}_g/dP$ obtained from theoretical calculations and the $d\text{ln}\rho /dP$ by experimental result are in the same order of magnitude.