High-Fidelity Exploration Tour of Saturnian Moons using Manifold Dynamics

The Cassini-Huygens mission significantly advanced our understanding of Saturn and its complex lunar system. However, it also engendered new scientific questions that remain unanswered. Major space agencies, including ESA through its Voyage 2050 Program, are planning to shed light on unanswered aspects with dedicated missions, emphasizing the importance of the in-situ exploration of the Inner Large Moons (ILMs) of Saturn, particularly Enceladus, Mimas, and Dione, for astrobiological research. This has prompted investigation into efficient methods for exploring the ringed planet. This work addresses the design of a 3D, high-fidelity, fuel-efficient lunar tour of the ILMs of Saturn, using innovative methodologies that enable prolonged observational access to the several targets. The Circular Restricted Three-Body Problem (CR3BP) serves as the basis for the design of science orbits around the moons of Saturn. Many previous contributions focused on preliminary analyses in the two-dimensional CR3BP, a framework that is inadequate for the observation of the lunar polar regions, where phenomena of high scientific interest occur. A spatial model is employed, with halo orbits used as staging points for observation missions around the ILMs, due to their significant out-of-plane motion and periodic nature. The stable and unstable Hyperbolic Invariant Manifolds (HIMs) are leveraged as natural pathways for low-energy transfers, enabling heteroclinic and homoclinic connections that provide global surface visibility for detailed lunar exploration and mapping. The extension to 3D dynamics also applies to moon-to-moon transfers, overcoming the restriction of previous studies focused on planar inter-moon trajectories. Transfers between halo orbits of adjacent Saturn–moon systems are designed by propagating branches of HIMs to the respective spheres of influence (SOI), where low-thrust arcs lead to the SOI of the next moon in the tour. The low-power electric propulsion system required for the maneuvers is supported by radioisotope thermoelectric generators. The transition from a simplified framework to a high-fidelity dynamical model is also addressed, by incorporating the relevant perturbations. For the design of the science orbits, the dynamics include the combined effects of the oblateness of Saturn and the ILMs. In the moon-to-moon transfer segments, additional perturbations are considered, namely the continuous gravitational influences of all relevant bodies, modeled with the use of ephemeris data. The inclusion of these perturbations ensures the design of the mission in a realistic dynamical environment. The proposed methodology can be applied to multi-moon systems of other giant planets, which represent compelling targets for future scientific exploration.