Observational properties of low-energy orbits around icy moons

摘要

The moons of the giant planets are getting into the focus of the next exploration missions to the outer solar system. The reason for this interest resides in their dynamical role within their respective systems and the signs of habitability suggested in some cases by surface and subsurface features. Flyby missions offer adequate recognition scenarios for the initial exploration phase of a celestial body, but they must be followed by orbiters if more extended observations are required. The dynamical structures of the Circular Restricted Three-Body Problem pave the way to such opportunities. In particular, libration point orbits around the two collinear equilibrium points L-1 and L-2 of a planet-moon-spacecraft system are characterized by low speeds relative to the moon. Heteroclinic and homoclinic connections built from these orbits allow close-up views of the moons. The aim of this work is to determine the observational performance of heteroclinic and homoclinic connections of planar Lyapunov orbits around L-1 and L-2 for three systems of scientific relevance: Jupiter-Europa, Uranus-Titania and Uranus-Oberon. Lunar surface coverage, repeat patterns, lunar distance ranges and speed profiles are derived and discussed for each case.