I.6.2.1. Jupiter

Three models are currently available, see Figure I-8:

• The Divine and Garett model which is constructed using data from Pioneer 10 and 11 and which extends to 10 jovian radii R_J for protons and more than 100 R_J for electrons [RD.20].

• GIRE (Galileo Interim Electron Environment) based on Galileo and Pioneer electron data between 8 to 16 R_J [RD.83] and developed at ONERA [RN.17] using a physical model. This model has been validated by comparing calculated synchroton radiation with that measured from the ground by the VLA telescope and extends to 10 R_J.

I.6.2.2. Internal charging

For internal charging see [RD.19].

I.6.2.3. Mars

For Mars the orbital environment is very similar to an interplanetary environment – as the planet has no significant magnetic field that can neither support trapped radiation, nor provide adequate geomagnetic shielding. The only significant deviation from the interplanetary environment is the solid angle subtended by the planet that can provide some shielding - particularly for low altitude orbits. The radiation environment on the surface of Mars largely derives from the secondary particles produced by cosmic rays and solar protons in the atmosphere and regolith. For manned missions to the planet the dominant particle species of concern is the neutron. Several software packages have been developed to calculate the ambient environment at Mars due to atmospheric interactions [RD.84],[RD.85],[RD.86]. Residual crustal magnetic fields do exists that may provide some form of magnetic shielding, the effectiveness of which can be evaluated using the PLANETOCOSMICS software [RD.86].