Low-thrust approach and gravitational capture at mercury

ABSTRACT BepiColombo, an ESA science mission, will reach Mercury in early 2017. The complex nearly 5-year long transfer consists of 6 flybys and many extended thrust arcs where the spacecraft is accelerated by solar electric propulsion. The thrust level is too low for a capture from a hyperbolic approach. To avoid a single point failure of a classical chemical orbit insertion burn, a trajectory is proposed where the gravity of the Sun is exploited to weakly capture the spacecraft in a Mercury orbit. The arrival conditions are optimised taking into account the interplanetary delta-V and low-cost recovery options in case of a failed orbit insertion. Finally, the navigation aspects for this unusual approach trajectory are studied