Galactic Cosmic Rays and Lunar Secondary Particles from Solar Minimum to Maximum: CRaTER Observations and Geant4 Modeling

Mark Dixon Looper, The Aerospace Corp, Los Angeles, United States, Joseph E Mazur, The Aerospace Corporation, Chantilly, VA, United States, J Bernard Blake, The Aerospace Corp, Los Angeles, CA, United States, Harlan E Spence, University of New Hampshire Main Campus, Durham, NH, United States, Nathan Schwadron, Los Alamos National Laboratory, Los Alamos, United States, Michael Joseph Golightly, Assurance Technology Corporation, Carlisle, MA, United States, Anthony W Case, Smithsonian Astrophysical Observatory, Cambridge, MA, United States, Justin Christophe Kasper, University of Michigan, Climate and Space Sciences and Engineering, Ann Arbor, United States, Lawrence W Townsend, University of Tennessee Knoxville, Knoxville, TN, United States and Jody Keith Wilson, University of New Hampshire Main Campus, Space Science Center, Durham, United States
Abstract:
The Lunar Reconnaissance Orbiter mission was launched in 2009 during the recent deep and extended solar minimum, with the highest galactic cosmic ray (GCR) fluxes observed since the beginning of the space era. Its Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument was designed to measure the spectra of energy deposits in silicon detectors shielded behind pieces of tissue equivalent plastic, simulating the self-shielding provided by an astronaut's body around radiation-sensitive organs. The CRaTER data set now covers the evolution of the GCR environment near the moon during the first five years of development of the present solar cycle. We will present these observations, along with Geant4 modeling to illustrate the varying particle contributions to the energy-deposit spectra. CRaTER has also measured protons traveling up from the lunar surface after their creation during GCR interactions with surface material, and we will report observations and modeling of the energy and angular distributions of these “albedo” protons.
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