Using the Galileo Solid-State Imaging Instrument as a Sensor of Jovian Energetic Electrons

We develop a technique to quantitatively characterize the high-energy electron environment using the Galileo spacecraft solid-state imaging (SSI) instrument and results from 3-D Monte Carlo particle transport simulations in Geant4, validating our findings with the Galileo energetic particle detector (EPD). We postprocess raw SSI images to obtain frames with only the radiation contribution. The camera settings (gain state, filter, and so on) are used to compute the intensity of the observed radiation hits. Simulating the response of the SSI instrument to mono-energetic electron environments, we find that the SSI is capable of detecting ≥10-MeV electrons (>90% of <;10-MeV particles are stopped with 95% confidence). Using geometric factors computed for the SSI, we calculate the environment particle flux given a number of pixels with radiation hits. We compare the SSI results to measurements from the Galileo EPD, examining the electron fluxes from the EPD >11-MeV integral flux channel. We find agreement within 3σ of the EPD data for 43 out of 43 (100%) of the SSI images evaluated. 62% of fluxes are also within 1σ of the EPD data. This approach can be applied to other sets of imaging data (star trackers) in energetic electron environments, such as those found in geostationary Earth orbit.