Energetic neutral particles detection in the environment of Jupiter’s icy moons: Ganymede’s and Europa’s neutral imaging experiment (GENIE)

• ENP observations relate the exosphere to surface and to plasma precipitation.
• Coordination with other instrument observations will lead to a full investigation.
• ENP is a new measurement for ice, thus it will produce a big science return.
• ENP observations are feasible, addressing the noise control.
• The concept of the ENP detector, GENIE, is well suited for a mission to the Jupiter's moons.

The detection of Energetic Neutral Particles (ENP) above 10 eV can unequivocally relate a surface-bound exosphere to surface features and can monitor instantaneously the effect of plasma precipitation onto the surface. In the framework of a mission to Jupiter's moons, 2D imaging of plasma precipitation will provide important information on the plasma circulation at the orbits of the moons. Furthermore, a joint measurement of precipitating ions will permit an estimation of the efficiency of the release process. Coupled measurements of ENP and gas composition will improve our knowledge of surface release mechanisms. Ganymede's and Europa's Neutral Imaging Experiment (GENIE) is a high-angular-resolution detector, based on the ToF (Time of Flight) technique, that can detect ENP (energy range >10 eV–few keV) in the Jupiter environment thanks to an innovative design and technology. Its objective is to map the sites of origin of the ENP of the icy moons’ exospheres to investigate the interaction between the surface and the environment. Finally, coupling GENIE with an ion sensor and a mass spectrometer will be an outstanding opportunity to better understand the magnetosphere–moon coupling within the Jupiter system and compare the surface interaction with plasma in the diverse moons. In this paper, the scientific objectives and requirements of ENP detection are summarized and the description of the innovative design concept of GENIE is given, together with the signal and background noise simulation.