Towards end-to-end design of spacecraft swarms for small-body reconnaissance

The exploration of small bodies in the Solar System is a high priority planetary science. Asteroids, comets, and planetary moons yield important information about the evolution of the Solar System. Additionally, they could provide resources for a future space economy. While much research has gone into exploring asteroids and comets, dedicated spacecraft missions to planetary moons are few and far between. There are three fundamental challenges of a spacecraft mission to the planetary moons: The first challenge is that the spheres of influence of most moons (except that of Earth) are small and, in many cases, virtually absent. The second is that many moons are tidally locked to their planets, which means that an observer on the planet will have an entire hemisphere, which is always inaccessible. The third challenge is that at a given time about half of the region will be in the Sun's shadow. Therefore, a single spacecraft mission to observe the planetary moon cannot provide complete coverage. Such a complex task can be solved using a swarm approach, where the mapping task is delegated to multiple low-cost spacecraft. Clearly, the design of a swarm mission for such a dynamic environment is challenging. For this reason, we have proposed the Integrated Design Engineering & Automation of Swarms (IDEAS) software to perform automated end-to-end design of swarm missions. Specifically, it will use a sub-module known as the Automated Swarm Designer module to find optimal swarm configurations suited for a given mission. In our previous work, we have developed the Automated Swarm Design module to find swarm configurations for asteroid mapping operations. In this work, we will evaluate the capability of the Automated Swarm module to design missions to planetary moons. We will explore the design space of resonant co-orbits where the spacecraft will have planned periodic encounters with the planetary moon due to the natural dynamics. However, the orientation of the mapping orbits will be a crucial design parameter. Since the arrival trajectories at the target planet do not support captures into any desired inclination, the mission designer should orient the science orbits using the obtained inclination. In this paper, we present a new algorithm to determine the final orientation of the resonant orbits. The proposed algorithm will use a sequence of principal angle rotations to place the apoapsis of the spacecraft's orbit at a desired latitude, longitude, and altitude above the planetary moon. Furthermore, we show that for polar orbits, the algorithm results in a compact solution that can easily determine the orientation of the target orbit. Finally, we will demonstrate the application of the developed algorithm through numerical simulations of a spacecraft swarm mission to map the surface of the Martian moon Deimos.