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E. Chassefiere, F. Leblanc, A. Sarkissian (SA/CNRS), J.-J. Berthelier (CETP/CNRS), A. Jambon (MAGIE/University Paris 6), M. Chaussidon (CRPG/CNRS), R. Johnson (University of Virginia)
A neutral and charged particle spectrometer, called NIS (Neutral and Ion Spectrometer), is proposed to be boarded on the MSE element of the BepiColombo mission, together with a laser-induced desorption system (LID). LID consists of a laser diode and an optics focusing the laser beam on a preselected zone of the surface. NIS will measure both the atmospheric composition (ambient and laser-induced) and the flux of solar wind (and/or pick-up) particles reaching the surface. LID will be used to remove volatiles contained in the regolith through adequate step-heating from ambient temperature to 1500-2000°C. Species outgassed by laser desorption form a transient local component to the atmosphere, to be analyzed by NIS in the same way as the background atmosphere. The LIDNIS experiment is therefore devoted to the study of gas-surface interaction, and is complementary of the measurements of atmospheric species planned to be made from MPO, by UV spectroscopy and/or in-situ mass spectrometry. Note that orbital measurements of energetic particles and more generally magnetospheric dynamics, together with orbital measurements of atmospheric species, will provide the global view required for interpreting local data obtained by LIDNIS in a global scale perspective.
NIS will have the capability of measuring the composition of the neutral and ionized particles originating from the surface and of detecting the solar wind or magnetospheric particles impinging on the surface. These are responsible in part of the removal of volatiles and sputtering of the surface. For thermal particles, the NIS mass range is 1 to 64 amu, for a mass resolving power of about 100. For hot neutrals the mass resolution will be somewhat lower than about 30 and for energetic particles, NIS has a range of about 1 keV/charge and a resolution of approximately 5