With lunar exploration attracting global attention, there is a growing interest in the design of relay satellite constellations for future lunar communication systems which is challenged by the huge distance between earth and moon. In this paper, we propose a novel hybrid combined Earth-Moon constellation network structure with Earth-Moon Libration 1/2 (EML1/L2) points Halo orbits, ordinary lunar orbits, and Geostationary Earth Orbit (GEO) to minimize both the total number of satellites and the average per-device Age of Information (AoI) as well as maximizing the coverage ratio of specific lunar surface regions to improve information freshness. This is formulated as a multiobjective optimization problem solved by the Nondominated Sorting Genetic Algorithm-II (NSGA-II). By simulating various constellation configurations, we can obtain the optimal configuration parameters for different total numbers of satellites. The simulation results show that our proposed combined constellation significantly outperforms traditional Walker Star and Delta constellations in both AoI and coverage performance.

With the ever-increasing lunar missions, a growing interest develops in designing data relay satellite constellations for cislunar communications, which is challenged by the constrained visibility and huge distance between the earth and moon in pursuit of establishing real-time communication links. In this work, therefore, we propose an age and coverage optimal relay satellite constellation for cislunar communication by considering the self-rotation of the earth as well as the orbital motion of the moon, which consists of hybrid Earth-Moon Libration 1/2 (EML1/L2) points Halo orbits, ordinary lunar orbits, and Geostationary Earth Orbit (GEO) satellites. In particular, by minimizing both the number of satellites and the average per-device Age of Information (AoI) while maximizing the coverage ratio of specific lunar surface regions, a multi-objective optimization problem is formulated and solved by using a well-designed Nondominated Sorting Genetic Algorithm-II (NSGA-II). The simulation results demonstrate that our proposed hybrid constellation significantly outperforms traditional Walker Star and Delta constellations in terms of both AoI and the coverage of communication.

With the proliferation of massive explorations on Lunar Far-side Surface (LFS), deployments of scientific infrastructures have drawn substantial attentions with the aids of relay satellites for the moon, i.e., China’s "Queqiao", which allows real-time reporting for current status information from the landing equipment and space vehicles. Without suitable constellation with well designed scheduling scheme, it would be very difficult to get timely information if depending only on single Halo relay satellite due to large coverage gap and limited energy budget for the communication links. In this paper, we design a hybrid circular-Halo orbital multi-relay constellation system for the LFS communication by minimizing the average per-device Age of Information (AoI) of users in the earth. In particular, we develop an age-optimal scheduling strategy with constellation design for accessing different relay satellite of constellation by solving a Constrained Markov Decision Process (CMDP) optimization problem to significantly reduce the average coverage gap in LFS area. Simulation results show that the average per-device AoI of the proposed scheduling algorithm with the well-designed constellation could achieve 16.20% less in time than that of single Halo satellite relay system compared with typical algorithms.