Using the Galileo Solid State Imager as a Sensor of Jovian Energetic Electrons
Ashley Carlton
Massachusetts Institute of Technology
A. Carlton is a Ph.D. candidate in the Space, Telecommunications, Astronomy, and Radiation (STAR) Laboratory at MIT. She received BS degrees in physics and mathematics from Wake Forest University in 2011 and a MS in aeronautical engineering from MIT in 2014. In between undergraduate and graduate studies, A. Carlton was a Science Operations Team mission planner for the Chandra X-ray Observatory (2011-2014).
Abstract
We quantitatively describe the Jovian energetic electron environment using the Solid State Imager (SSI) on the Galileo spacecraft. We post-process raw SSI images by removing the target object and dark current to obtain frames... [ view full abstract ]
We quantitatively describe the Jovian energetic electron environment using the Solid State Imager (SSI) on the Galileo spacecraft. We post-process raw SSI images by removing the target object and dark current to obtain frames only with the radiation contribution. The camera settings (gain state, filter, etc.) are used to compute the energy deposited in each pixel, which corresponds to the intensity of the observed radiation hits (the actual measurements are expressed with the digital number (DN), from which the energy deposited can be computed).
Histograms of the number of pixels versus energy deposited by incident particles from processed SSI images are compared with the results from 3D Monte Carlo transport simulations of the SSI using Geant4. We use Geant4 to simulate the response of the SSI instrument to mono-energetic electron environments from 1 to 100 MeV. We fit the modeled instrument response to the SSI data using a linear combination of the simulated mono-energetic histograms to match the SSI observations. We then estimate the spectra of the energetic electron environment at Jupiter, or we estimate the integral flux when there is lower confidence in the spectra fits. We validate the SSI results by comparing the environment predictions to the observations from the Energetic Particle Detector (EPD) on the Galileo spacecraft, examining the electron differential fluxes from 10’s of keV to 11 MeV. For higher energies (up to 31.0 MeV), we compare our findings with the NASA GIRE model, which is based on measurements from the Pioneer spacecraft. This approach could be applied to other sets of imaging data in energetic electron environments, such as from star trackers in geostationary Earth orbits.
Authors
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Ashley Carlton
(Massachusetts Institute of Technology)
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Maria De Soria-santacruz Pich
(Jet Propulsion Laboratory, California Institute of Technology)
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Insoo Jun
(Jet)
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Wousik Kim
(Jet Propulsion Laboratory, California Institute of Technology)
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Kerri Cahoy
(Massachusetts Institute of Technology)
Topic Areas
Magnetosphere(s) , Radiation Effects (e.g., SEE, TID, DDD) , Radiation
Session
Session 7 » Instruments and Missions (13:30 - Wednesday, 17th May)
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