 The Europa Jupiter System Mission ( <unk> ) was a joint NASA / ESA proposal for exploration of Jupiter and its moons . In February 2009 it was announced that both space agencies had given this mission priority ahead of the Titan Saturn System Mission . The proposal included a launch date of around <unk> and consists of the NASA @-@ led Jupiter Europa Orbiter , and the ESA @-@ led Jupiter Ganymede Orbiter . ESA 's contribution had encountered funding competition from other ESA projects . However , the Jupiter Europa Orbiter ( <unk> ) , NASA 's contribution , was considered by the Planetary <unk> Survey to be too expensive . The survey supported a cheaper alternative to <unk> . 
