Operation of a 3He proportional counter in the Ganymede radiation environment

Abstract

Neutron spectroscopy has the potential to address many of the scientific objectives of the Jupiter Ganymede Orbiter mission. The most significant challenge is understanding the response of a neutron spectrometer to the intense radiation environment around Ganymede. This study uses data from the Lunar Prospector Neutron Spectrometer to benchmark simulations of the performance of a similar instrument in Ganymede orbit. A solar particle event observed by the Lunar Prospector Neutron Spectrometer serves as a surrogate for the charged particle environment around Ganymede, facilitating a study of the instrument response using data acquired in an environment very similar to the radiation environment found at Ganymede. Based on the conclusions of this study, modifications to a Lunar Prospector-style neutron spectrometer are suggested to allow for the operation of such an instrument in Ganymede orbit. Simulations of the expected signal, based on current models of the surface composition, show this instrument would be capable of compositionally characterizing the nature and extent of surface ice deposits.