Tour Design Techniques for the Europa Clipper Mission

Europa is one of the most scientifically interesting targets of the solar system, as it may possess what are thought to be the three necessary ingredients for life: an extensive ocean of liquid water, an energy source, and a suite of biogenic elements. To explore the habitability of Europa, NASA is developing the Europa Clipper mission, currently scheduled to be launched in 2023. Europa resides deep inside the gravity well of Jupiter, in a region of the magnetosphere with many trapped ionized particles that when accelerated to near relativistic speeds result in a radiation environment detrimental to spacecraft electronics; a Europa orbiter mission that would continuously reside in the same radiation environment as Europa would require a large amount of Delta V for an orbit insertion maneuver, and would only return limited science data before being critically exposed to radiation. To mitigate these issues, Europa Clipper will instead use a high number of Europa flybys, connected by resonant and nonresonant transfers. Science data are collected during high-radiation Europa flybys, and returned to Earth during the rest of the highly elliptical Jovian orbits, at a much lower radiation dose exposure. This paper will present several tour techniques developed for the design of the Europa Clipper flyby trajectory. In particular, this paper will describe different ways to perform fast line-of-apsides rotations; a new approach to improve the coverage of Europa's trailing and leading edges; parametric studies of the expected radiation dose and time of flight as function of the Europa resonance; and a quick way to estimate the radiation dose for complete Jovian tours. Other techniques, which were already presented in previous papers, will be reviewed for completeness. Then some of the new approaches will be implemented in the 18F17 tour.