The present paper studies the lifetime of orbits around a moon that is in orbit around its mother planet. In the context of the inner restricted three-body problem, the dynamical model considered in the present study uses the double-averaged dynamics of a spacecraft moving around a moon under the gravitational pulling of a disturbing third body in an elliptical orbit. The non-uniform distribution of the mass of the moon is also considered. Applications are performed using numerical experiments for the Callistospacecraft-Jupiter system, and lifetime maps for different values of the eccentricity of the disturbing body (Jupiter) are presented, in order to investigate the role of this parameter in these maps. The idea is to simulate a system with the same physical parameters as the Jupiter-Callisto system, but with larger eccentricities. These maps are also useful for validation and improvements in the results available in the literature, such as to find conditions to extend the available time for a massless orbiting body to be in highly inclined orbits under gravitational disturbances coming from the other bodies of the system.
Abstract. Space missions intending to visit Europa, one of the famous Galilean's moons of Jupiter, are among the most important topics in space activities today. There is an increasing interest in the scientific community to send spacecrafts to be inserted into Europa's orbit, with goals like mapping its surface and gravitational field. From the quality of the observations until the orbital maneuvers, the required aspects for the success of the mission will depend on the orbits used by the spacecraft. The present work searches for less perturbed elliptical orbits around Europa, because they are very important, since these orbits are expected to be more stable to place the spacecraft. The development of the study is based on the net effects of the perturbing forces over the time, evaluated by the integral of those forces with respect to the time. The value of this integral depends both on the dynamical model and the orbit of the spacecraft. Jupiter's third-body perturbation and the J2 and J3 terms of the gravitational potential of Europa are the perturbing forces considered. The results presented here are obtained by performing numerical integrations of the perturbing forces, and they show the locations of the less perturbed orbits.
IntroductionCurrently, there exist plans to send spacecrafts to study the planetary moons of our Solar System. Europa is among the group of bodies with greater potential to receive scientific missions in the next decade 1 . The possibilities to explore the inner oceans and the search for organic molecules to better understand the complexity of the existence of life in the universe are among the most important objectives. Nowadays, the most advanced project under development for this purpose is the Jupiter Icy Moon Explorer (JUICE). This one and other similar types of missions require near-circular, near-polar orbits [1].The present paper has the objective of mapping elliptical orbits around Europa, in order to search for the less perturbed ones, which can be used in some types of missions. Less perturbed orbits have smaller variations of Keplerian elements. In the majority of the cases, they demand less station keeping maneuvers for these types of space missions. The search is based on the integral of the perturbing forces over the time, because this quantity can express the net velocity variation that the spacecraft received from the perturbation forces. Several previous works in the literature used this technique to study problems related to orbital maneuvers, fuel consumption, maneuvering time, and so forth [2][3][4][5][6][7][8][9][10].
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