Europa Orbiter tour design with Io gravity assists

For a Europa Orbiter mission, the strategy for designing Jovian System tours that include Io flybys differs significantly from schemes developed for previous versions of the mission. Assuming that the closest approach distance of the incoming hyperbola at Jupiter is below the orbit of Io, then an Io gravity assist gives the greatest energy pump-down for the least decrease in perijove radius. Using Io to help capture the spacecraft can increase the savings in Jupiter orbit insertion ΔVΔV over a Ganymede-aided capture. The tour design is guided by Tisserand graphs overlaid with a simple and accurate radiation model so that tours including Io flybys can maintain an acceptable radiation dosage. While Io flybys increase the duration of tours that are ultimately bound for Europa, they offer ΔVΔV savings and greater scientific return, including the possibility of flying through the plume of one of Io's volcanoes.