Investigating Jovian Radiation Environment by the Europa Clipper Mission

Abstract

<p>For the Europa Clipper mission, the radiation environment of Jupiter will be measured by a dedicated Radiation Monitoring (RadMon) subsystem, which will provide mission accumulated Total Ionizing Dose (TID) and instantaneous electron flux measurements at a 1-Hz cadence in multiple energy ranges. The radiation monitoring subsystem is comprised of a stand-alone sensor assembly along with distributed TID assemblies at various locations on the spacecraft. The TID measurements will provide the critical information about the overall radiation levels relevant to the electronic’s degradation 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 made possible by careful modeling and analysis of opportunistic background data from the following instruments (as we envisioned now): 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 understanding, these instruments would be most sensitive to > 1 MeV electrons. As such, the high energy electron data obtained by the radiation monitoring subsystem will be qualitatively and quantitively 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.</p> <p> </p> <p>Although the radiation monitoring subsystem itself is an engineering resource for the mission, the collective data from the mission can be also 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 will also help understand the radiation modification of surface compounds, which will subsequently help guide lab experiments to aid in understanding the origin and evolution of surface materials. In this paper, we will discuss the science made possible by these high energy electron measurements. Examples of potential science from the Europa Clipper mission include:</p> <ul> <li>Quantification of trapped electron fluxes spatially (e.g., by R, lat, and LT)</li> <li>Assessment of time variations of the radiation belts of Jupiter</li> <li>High-energy (>10 MeV) electron populations and physical mechanism for energization</li> <li>Physical mechanism for a C-22 like storm</li> <li>Radiation level range in stretched field line region of Jupiter (outward of Ganymede's orbit)</li> <li>Level of precipitation of electron flux and dose into Europa as a function of surface region</li> <li>Role of energetic electrons in surface modifications, e.g., radiolysis, sputtering, etc.</li> </ul>