From Earth To Moon: Satellite Constellation For Future Lunar Exploration

The present work investigates the requirements and capability of a lunar satellite constellation designed to meet communication and coverage needs, connecting Earth and strategically significant lunar regions, such as the South Pole and the Equatorial Near-Earth side. These are viewed as potential locations for future human return missions, robotic exploration, and the establishment of stable habitats. Developing such a communication network poses several remarkable challenges. First, the considerable distance between Moon and Earth results in signal propagation delays and losses, that can lead to the necessity of high-power subsystems for the spacecrafts. The latter are more exposed to cosmic radiation than their Earth-based counterparts, which can substantially impact the operational lifetime. Furthermore, the lunar orbits selection is a complex task due to their instability which introduce additional difficulties in the design. Finally, the launch costs and complexity for big constellations of large satellites in the lunar environment can be prohibitively expensive and intricate. Possible solutions for the aforementioned problems include the use of specific stable orbits that minimize the need for orbital maintenance while enabling spacecraft to achieve their communication goals. This approach can reduce fuel requirements, decreases the overall system size, and extends the operational lifetime. Consequently, it becomes feasible to use smaller satellites deployed in a single launch, utilizing them as piggyback payloads of larger exploration missions, creating a more flexible, agile, and less customized system. Along with this, one can consider the possibility to use the expected lunar outpost as relay terminals to communicate with Earth reducing the workload and power requirements for the constellation. Two main architectures have been conceived and analysed to achieve the objectives proposed by the study. In one case, larger satellites are employed to cover all the necessary links, while in the other, small CubeSat-sized are used, supported in relaying data to Earth by communication terminals placed on the lunar sites. The work started from an examination on several orbits through researches that helped making a choice and focused the analysis on particular Keplerian ones, known as ‘Frozen Orbits’. Using simulations conducted in AGI System Tool Kit (STK), it was evaluated the necessary number, types, and behaviour of satellites in those trajectories under the influence of gravitational fields of Moon, Earth and Sun, as well as the impact of solar radiation pressure. The study proceeded assessing satellites of various sizes, originating from existing Earth-based communication constellations with a special attention to their communication subsystems, frequencies, power requirements, mass, and antenna configurations. These satellite formats represent promising solutions to ensure the anticipated performance. Both the analysis performed, converged in a second simulation that allowed to define the two satellite platforms previously highlighted and so the related architectures or Concept of Operations, able to guarantee the necessary communication requirements. Lastly, a trade-off was made to define which architecture, with its combination of spacecraft numbers, orbits configuration and communication subsystem represented the best option, considering also the propulsive ΔV that should be spent to perform station keeping manoeuvres.