Jupiter Europa Orbiter
Ganymede orbiter. JEO would place a spacecraft equipped with remote sensing and radar investigations into a close orbit around Europa for a period of at least 1 year. Prior to insertion into Europa orbit, JEO would complete a 2-year tour of the jovian system using the Galilean satellites for gravity-assist flybys. Given the complex gravitational environments of the jovian system, the long-term stability of JEO’s orbit about Europa cannot be guaranteed. Therefore, to meet planetary protection requirements at the end of its mission, JEO would be either commanded to impact onto the surface of Europa in a controlled manner at a selected site, or ejected from Europa orbit and placed on a collision course with Jupiter. The combination of this controlled end-of-mission scenario, along with standard clean-assembly procedures, selective application of dry-heat microbial reduction, and the sterilizing effect of the jovian radiation environment, would allow JEO to meet planetary protection requirements. The integrated cost of these requirements, while not a primary driver of the mission budget, is nonetheless significant.
As of this writing, budget pressures have led to a descoping and replanning of JEO and probably of the entire EJSM program. Current studies are focused on developing less costly JEO mission concepts. Once those studies are complete and the budget picture is clarified, NASA will decide whether and how to proceed with Europa explora-