Investigating Europa’s Radiation Environment with the Europa Clipper Radiation Monitor

Abstract

Abstract We present an overview of the radiation environment monitoring program planned for the Europa Clipper mission. The harsh radiation environment of Jupiter will be measured by a dedicated Radiation Monitor (RadMon) subsystem, yielding mission accumulative Total Ionizing Dose (TID) and instantaneous electron flux measurements with a 1-Hz cadence. The radiation monitoring subsystem is comprised of a stand alone sensor assembly along with distributed TID assemblies at various locations on the spacecraft. The sensor assembly itself is made of a TID sensor stack using the Metal-Oxide Semiconducting Field-Effect Transistor (MOSFET) and a Charge Rate Monitor (CRM) that uses a stack of bulk charge collection plates. The TID measurements will provide the critical information about the overall radiation levels relevant to the degradation of electronics over time, and the electron flux data can serve as a proxy for the Internal ElectroStatic Discharge (IESD) environment by measuring the >∼1 MeV electron environment. In addition, the radiation monitoring subsystem data will be augmented by serendipitous radiation data from science instruments onboard. This will be enabled by careful modeling and analysis of opportunistic background data from potentially the following instruments: Europa Imaging System (EIS), Europa-Ultraviolet Spectrograph (Europa-UVS), Mapping Imaging Spectrometer for Europa (MISE), MAss Spectrometer for Planetary EXploration (MASPEX), Plasma Instrument for Magnetic Sounding (PIMS), and SUrface Dust Analyzer (SUDA). Based on the current analysis, these instruments will be most sensitive to >1 MeV electrons. As such, the high-energy electron data obtained by the radiation monitoring subsystem will be qualitatively and quantitatively enhanced by the high-energy electron data acquired by the instruments. The holistic radiation monitoring program for the mission will be an extensive collaboration among many teams across the flight and payload systems. Although the radiation monitoring subsystem itself is an engineering resource for the mission, the collective data from the mission can also be used to improve the scientific understanding of the Jovian magnetosphere and the high-energy electron environment near Europa, where the motion of charged particles is perturbed by the local electromagnetic environment. The data could also help in the understanding of the radiation modification of Europa surface compounds, which could subsequently help guide lab experiments to aid in understanding the origin and evolution of surface materials and in constraining the interpretation of observational data. To this end, the radiation monitoring subsystem is a useful resource for helping address the Europa Clipper mission’s primary goal of assessing the habitability of Europa.