Automated Design Architecture for Lunar Constellations

Missions to the Moon are actively being developed for its scientific and engineering values. The Lunar Exploration Analysis Group (LEAG) has identified at least twenty enabling and enhancing goals to fulfill the existing lunar exploration Strategic Knowledge Gaps (SKG). Several of these goals will require multi-asset missions to the surface of the Moon involving human and machine interaction, as well as access to a ground station on Earth. Therefore, a communication enabling constellation deployed around the moon will serve as a crucial enabling technology for such missions. However, the limited orbital stability of lunar orbits constrains the use of traditional central body orbits for designing these constellations. The Earth-Moon Lagrange points, on the other hand, offer a viable location to deploy these constellations. The stationarity of the Lagrange points coupled with the fact that they have a large line of sight access area to the Moon's surface makes them a viable candidate for deploying constellations with a minimal number of spacecraft. However, the design of a Lagrange point constellation mission is not straight forward. This involves selecting the Lagrange points that offer the optimal coverage, optimal quasi-stationary trajectories around these Lagrange points, the optimal transfer to these trajectories, and the design of the constituent spacecraft. Clearly, this multi-disciplinary problem can benefit from a unifying mission design architecture that simultaneously handles the above-mentioned challenges. In our previous work, we developed the Integrated Design Engineering and Automation of Swarms (IDEAS) software do design swarm missions to solar system small bodies. This work will focus on extending the capability of the IDEAS architecture to design optimal constellations deployed at the Earth-Moon Lagrange points. The constellation will be designed to act as a relay network to Earth with a minimum number of spacecraft. The performance of the constellation will be noted by studying the accessible regions on the surface of the moon. The approach taken by this work is as follows. We begin by modeling the coverage of spacecraft antenna by studying the accessible areas. The spacecraft will be assumed to be in halo orbits about the colinear Lagrange points. A selection scheme for the halo orbits is then discussed in order to coverage, synchronization, and stability requirements. Finally, the principles described are demonstrated by designing a Lagrange point constellation with three spacecraft that have access to at least 85 % of the Moon's surface and can communicate with at least 70 % of the surface at any given instant. The requirements and performance of this constellation are then evaluated assuming state-of-the-art hardware capabilities. The results indicate successful performance of the developed algorithms thus enabling the IDEAS architecture to generate holistic optimal designs which will greatly increase the returns of the future missions to the Moon.