Nicolas André

RPWI Kick-Off Meeting, Uppsala, Sweden, November 26-27 2009

JupiterRadiation Environment

Jupiter Radiation Environments

• Radiation effects

• 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

• 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

From Insoo Jun, JPL

Jupiter Radiation Environments

From Hank Garrett, JPL

Jupiter Radiation Environments

Jupiter Radiation Environments

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

In orbit aroundGanymede

Courtesy of Arnaud Boutonnet, ESOC (27/05/2008)

The JGO will always orbit beyond ~12 Rj

Mission requirement: total radiation dose below 150 krad behind 8 mm Al shielding

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 approachesb) different input parameters (e.g., magnetic field models)c) different spatial coveraged) 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

Jupiter Radiation Environments

• Implications for the design of JGO

From Arno Wielders, ESTECFrom Karla Clark, JPL

Mission analysis

Jupiter Radiation Environments

• Implications for the design of JGO

Jun et al., 2005 (GIRE)

Jupiter Radiation Environments

• The local radiation environment around Ganymede

Khurana et al., Icarus, 2007

Shielding effect from the moon not yet modelled (it will decrease the dose)

When in orbit around Ganymede:

The JGO spacecraft (assumed ~POLAR) will encounter different field lines topology and, hence, different radiation doses

Jupiter Radiation Environments

• The local radiation environment around Ganymede

Ganymede’s polar regions are brightened in response to being open to jovian plasma

Leading/trailing hemispheric asymmetries at lower latitudes (closed field lines)

Khurana et al., Icarus, 2007

Jupiter Radiation Environments

• The local radiation environment around Ganymede

In blue: The counts correspondingto the Jovian plasma

In red:Inside Ganymede’s magnetosphere

Spike-like decreases observedfor ions and electrons:

=> We were on field lines connected to both Ganymede and jupiter

Clear decrease observedinside Ganymede’s magnetosphereby 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 resultsNecessary 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