Depth Dose Exposures in the Magnetosphere of Jupiter at the Icy Moons: Callisto, Ganymede, and Europa

The highly successful Galileo mission made a number of startling and remarkable discoveries during its eight-year tour in the harsh Jupiter radiation environment. Two of these revelations were: 1) salty oceans lying under an icy crust of the Galilean moons: Europa, Ganymede and Callisto, and 2) the possible existence or remnants of life, especially on Europa, which has a very tenuous atmosphere of oxygen. Galileo radiation measurement data from the Energetic Particle Detector (EPD) have been used (Garrett et al., 2003) to update the trapped electron environment model, GIRE: Galileo Interim Radiation Environment, in the range of L (L: McIlwain parameter – see ref. 6) = 8–16 Rj (Rj: radius of Jupiter ≈ 71,400 km) with plans to extend the model for both electrons and protons as more data are reduced and analyzed. In this paper the current GIRE model and high-energy transport codes have been used to compute depth dose exposures as a function of spacecraft shielding thickness for specified times in orbit at Callisto (Rj ≈ 26.6), Ganymede (Rj ≈ 15), and Europa (Rj ≈ 9.47). During its mission, Galileo encountered a number of radiation-induced anomalies; in fact, few Galileo spacecraft systems were unaffected by the radiation environment. The results presented in this paper can be applied to utilize shielding effectively and possibly minimize potential radiation-induced anomalies on future Jupiter spacecraft.