Two options for the Callisto's exploration

Laplace (or Europa–Jupiter System Mission) is an L-class candidate mission for the Cosmic Vision 2015–2025 Program. It would be a joint project carried on by ESA, NASA and JAXA, aiming at the study of the Jupiter environment and its Galilean moons. ESA is coordinating the outer moons exploration phase, whose primary scientific goal is represented by Ganymede. Concerning Callisto, the secondary scientific target, the available propellant does not allow to insert into an orbit around it. In this study a pseudo-orbiter solution, which takes advantage of resonances and swing-bys at Callisto, and a gravitational capture solution, both adopted in order to obtain zero-cost observational data of Callisto, are implemented and compared pointing out benefits and drawbacks. The pseudo-orbiter solution relies on the classical Two-Body Problem dynamics, whereas the gravitational capture exploits the Circular Restricted Three-Body Problem and low-energy trajectories associated with this model. While the pseudo-orbiter solution requires a constrained global search among multiple possibilities, the most crucial point of the gravitational capture consists in the low value of velocity with respect to the moon, say V∞V∞, that the probe must meet for being captured. We demonstrate how this constraint can be fulfilled, thanks to subsequent gravitational perturbations of Callisto on the spacecraft. This means that starting from a perijove as low as the Ganymede–Jupiter distance and a V∞V∞ of about 1.5 km/s, we are able to increase the perijove and decrease V∞V∞ up to a suitable range to achieve a weak capture.

► Pseudo-orbiter and weak capture as two innovative solutions for Callisto exploration. ► An effective automatic sequence generation tool implemented for the pseudo-orbiter. ► Scientific requirements coded into a merit function minimised by of a global search. ► Weak capture at Callisto obtained with different methodologies and characteristics. ► T–P map implementation of the endgame to achieve gravitational capture.