Radiation Environment Jupiter Radiation Environment Nicolas André RPWI Kick-Off Meeting, Uppsala, Sweden, November 26-27 2009

Jupiter Radiation Environments Radiation effects Radiation environments Total Ionizing Dose (TID) - Cumulative long-term ionizing damage mainly due to protons and electrons Displacement Damage Dose (DDD) - Cumulative long term non-ionizing damage mainly due to protons, electrons, and neutrons Single Event Effects (SEE) - Event caused by a single charged particle (heavy ion and/or protons) traversing the active volume of microelectronic device Charging - Internal charging, surface charging Material degradation Noise in science instrument Solar Energetic Particles (SEP) - TID, DDD, SEE Galactic Cosmic Rays (GCR) - SEE Low-energy (<100 keV) Jovian trapped particles - surface charging, material degradation High-energy (>100 keV) Jovian trapped particles - TID, DDD, SEE, IESD From Insoo Jun, JPL

Jupiter Radiation Environments From Hank Garrett, JPL

Jupiter Radiation Environments

Jupiter Radiation Environments

Salammbô “Family” of Radiation Models Jupiter Radiation Environments Salammbô “Family” of Radiation Models Jupiter radiation physical modeling - At ONERA, Toulouse, France (A. Sicard, S. Bourdarie) At SwRI, San Antonio, USA (D. Santos-Costa) Diffusion theory, Fokker-Planck transport equation Boundary conditions based on spacecraft observations Averaged trapped particle populations deduced from simulations Comparison with spacecraft and synchrotron data Various physical processes included

Jupiter Radiation Environments ESA Approach #1 (2006-2009) Philosophy: Take advantage of all these pre-existing models by combining them together and then get the best specification we could obtain at the present time for any spacecraft which will fly in the Jovian magnetosphere In practice: (e.g., electron model) The model currently available at ESA allows to combine D&G83, plus GIRE plus Salammbô. The selection from one model to the other is done first according to L and then according to the energy. => JOP/JOE model provided by ONERA On-going contract with Qinetiq (ONERA) to improve the model and implement it in SPENVIS (engineering model)

Jupiter Radiation Environments NASA/ESA Approach (2008-…) The end results of the models are used to constrain potential mission scenarios and estimate the total radiation dose. It is therefore critical to have a good and robust understanding of the radiation environment of Jupiter. => Radiation Working Group set up (Dec. 2010) Recommandations only !

Jupiter Radiation Environments JGO Mission Profile Courtesy of Arnaud Boutonnet, ESOC (27/05/2008) The JGO will always orbit beyond ~12 Rj In orbit around Ganymede Mission requirement: total radiation dose below 150 krad behind 8 mm Al shielding

Jupiter Radiation Environments Implications for the design of JGO Jupiter Radiation Environments Jovian radiation belts (electron, protons) have been modelled empirically (D&G, GIRE) and physically (Salammbô) by various groups in the United States (JPL, SwRI) and in Europe (ONERA): a) different approaches b) different input parameters (e.g., magnetic field models) c) different spatial coverage d) different energy coverage Courtesy of Sébastien Bourdarie, ONERA EPD data The JGO will always orbit beyond ~12 Rj => use of the GIRE or D&G models

Jupiter Radiation Environments Implications for the design of JGO Mission analysis From Arno Wielders, ESTEC From Karla Clark, JPL

Jupiter Radiation Environments Implications for the design of JGO Jun et al., 2005 (GIRE)

Jupiter Radiation Environments The local radiation environment around Ganymede Jupiter Radiation Environments Khurana et al., Icarus, 2007 When in orbit around Ganymede: The JGO spacecraft (assumed ~POLAR) will encounter different field lines topology and, hence, different radiation doses Shielding effect from the moon not yet modelled (it will decrease the dose)

Jupiter Radiation Environments The local radiation environment around Ganymede Khurana et al., Icarus, 2007 Ganymede’s polar regions are brightened in response to being open to jovian plasma Leading/trailing hemispheric asymmetries at lower latitudes (closed field lines)

Jupiter Radiation Environments The local radiation environment around Ganymede In blue: The counts corresponding to the Jovian plasma In red: Inside Ganymede’s magnetosphere Spike-like decreases observed for ions and electrons: => We were on field lines connected to both Ganymede and jupiter Clear decrease observed inside Ganymede’s magnetosphere by a factor up to 10 ! Williams et al., JGR, 1998

Jupiter Radiation Environments A lot of (very) useful information exist on the web (Use it !!!) : Adopt a coordinated strategy wrt models and tools used btw all RPWI teams Necessary to understand/compare our results Necessary dialogue with ESA (both way): our needs / their needs Recommendations http://opfm.jpl.nasa.gov/library/2009opfminstrumentworkshop/ http://www.openchannelfoundation.org/projects/GIRE/

Jupiter Radiation Environments ESA Approach #2 (under QinetiQ contract) Disadvantages of combining all existing models together: discontinuities … Re-analysis of all existing data, empricial fits proposed under various assumptions Far from being mature and totally agreed, but could be the reference model (ESA) in a few months (not before end of assessment phase …) => New Radiation model currently built by ONERAand reviewed by ESA and Radiation Working Group