Jovian radiation models for JUICE mission

Transcription

1 Jovian radiation models for JUICE mission Hugh Evans and David Rodgers 19/09/2016 ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 1 ESA UNCLASSIFIED - For Official Use

2 The Jovian Magnetosphere is BIG ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 2

3 JORE 2 M 2 Jovian Radiation Environment and Effects Models and Mitigation Project An ESA TRP project to develop radiation and plasma environment and effects models to support the JUICE mission. Contract #21290/08/NL/JK Outputs include: Jovian Space Environment Model (JOSE) - New Trapped electron and proton models based on all relevant data, calculated using a consistent magnetic field. Incorporates the HIC model. SHIELDOSE-2Q - Extension of SHIELDOSE-2 to treat Ti, Fe, Ta, CW80 and Al-Ta shields for a wider variety of target materials relevant to Laplace microelectronics and sensors. GARSO New genetic algorithm-based shield optimisation tool using Geant4/MULASSIS to identify improved radiation shields through natural selection processes. PLANETOCOSMICS-J - Extension to treat radiation environment in vicinity of Galilean moons JOSE: A New Jovian Specification Environment Model IEEE Transactions on Nuclear Science 58(3): July 2011 ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 3

4 GREET Ganymede Radiation Environment Engineering Tool An ESA TRP project to develop magnetic shielding models of the Ganymede Environment to support the JUICE mission. Contract # /09/NL/AF Tracking particles within the complex rotating magnetic fields of the planet and moon, and the probability of interactions with Ganymede s surface is a non-trivial calculation, and whilst the Monte Carlo PLANETOCOSMICS-J tool can be used for this application, simulations times make it impractical for general environment assessment required by the JUICE Project. GREET provides a rapid simulation of the shielding effects of Ganymede on the local Jovian trapped electron environment. The Ganymede Radiation Environment Engineering Tool (GREET) for JUICE Mission Environment Prediction, NSREC 2014 Paper H-1 ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 4

5 IEM Solar Interplanetary Electron Model An ESA TRP project to develop a model of the interplanetary electron environment through out the heliosphere Contract #22915/09/NL/AF df E = 21.8 E 1.57 This model is based on observations of electrons in interplanetary space (mainly near 1 AU). The most important contribution to interplanetary electrons arises from the intense emissions from the Sun during solar energetic particle events. However, at quiet times, Jupiter is the dominant source. Hence, IEM includes a model of Jovian electrons and takes into account the diffusion processes that transport electrons through the heliosphere. The IEM model was evaluated to give an estimate of the electron flux just outside the Jovian magnetosphere. The Interplanetary Electron Model (IEM), IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 58, NO. 6, DECEMBER 2011 ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 5

6 JUICE trajectory and Electron Belt Passages ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 6

7 JUICE trajectory and PROTON Belt Passages ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 7

8 JUICE: Dose accumulation over Mission ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 8

9 JUICE Trapped Electron Spectra (JOSE + IEM) ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 9

10 JUICE Trapped Proton Spectra (JOSE) ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 10

11 JUICE Mission Total Ionising Dose (SD2-Q) ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 11

12 JUICE Margin Policy LONG TERM (mission) 1. Assume a log-normal distribution at a particular location. 2. As the integration time increases, the variance decreases (regression to the mean). 3. Thus, for a given mission duration, the variance can be determined, and the probability of exceeding the dose estimated. For JUICE with ~95% confidence, this implies a margin of day orbit repeat Jovian Radiation Belt Models, Uncertainties and Margins, IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 60, NO. 4, AUGUST 2013 ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 12

13 JUICE Margin Policy: SHORT TERM (Worst fluxes) Highest fluxes are to be expected at lowest Radius, which for JUICE is radius of 9.5 Rj. The EPD DC2 data has saturated here, so to gauge the dynamic range of the measurements at 9.5 Rj, it was assumed the range at Rj was representative of the range at 9.5 Rj. From this scatter it was determined that a factor of 4 provided a reasonable envelope for instantaneous fluxes. ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 13

14 Conclusions To support the JUICE project ESA has funded the development of several radiation environment models for the Jovian environment and integrated them in the SPENVIS system: JOREM/JOSE models the Jovian trapped proton and electron belts IEM models the interplanetary regime SHIELDOSE-2Q extends SHIELDOSE-2 with more representative shielding materials and targets. PLANETOCOSMICS-J update provided the tool for evaluating the significant magnetic shielding around Ganymede, as used in the GREET project The JUICE environment specification has been produced using these models, and radiation design margins appropriate for the statistical uncertainties in the models and existing data have been determined. The Jovian radiation environment is considerably harsher than the terrestrial equivalent, far exceeding the normal engineering required for a GEO or SSO mission. ESA UNCLASSIFIED - For Official Use Hugh Evans ESTEC 19/09/2016 Slide 14