Earth-Jupiter-Earth trajectories and the Europa ice-clipper mission

The nature of optimized Earth-Jupiter-Earth trajectories is described in a search for a Europa Flyby that could return a gaseous sample from close proximity to Europa. Rights from four to ten years duration are considered, Long flight times are required in order to go around Jupiter in the same direction as Europa and ten-year flights are needed to be able to approach Europa. Trajectories are shown for launches in 2000, 2001, and 2003 that make use of two-year delta-V Earth gravity assists in order to avoid the high C3's required for direct launches to Jupiter, Total night times are thus twelve yean. Close approach to an asteroid can be obtained on each leg of these trajectories at an average cost of about 50 m/s delta-V.