Determining Charged Particle Flux Direction in MSL/RAD
Jan Kristoffer Appel1, Jan Kohler1, Jingnan Guo2, Bent Ehresmann3, Cary J Zeitlin4, Robert F Wimmer-Schweingruber5, Don Hassler6, Scot CR Rafkin7, Eckart Boehm1, Stephan I Boettcher5, Cesar Martin-Garcia8, David E Brinza9, Eddie Weigle10, Henning Lohf1, Soenke Burmeister1, Gunther Reitz11, Daniel Matthiae11, Arik Posner12, Javier Martín-Torres13 and María-Paz Zorzano13, (1)University of Kiel, Kiel, Germany, (2)University of Science and Technology of China, School of Earth and Space Sciences, Hefei, China, (3)Southwest Research Institute Boulder, Solar System Science & Exploration Division, Boulder, CO, United States, (4)Southwest Research Institute, Durham, NH, United States, (5)University of Kiel, Institute for Experimental and Applied Physics, Kiel, Germany, (6)Southwest Research Institute, Boulder, United States, (7)Southwest Research Institute Boulder, Boulder, CO, United States, (8)IEAP, University of Kiel, Kiel, Germany, (9)Jet Propulsion Laboratory, Pasadena, CA, United States, (10)Big Head Endian, Burden, KS, United States, (11)German Aerospace Center DLR Cologne, Cologne, Germany, (12)NASA Headquarters, SMD/Heliophysics Division, Washington, DC, United States, (13)Centro de Astrobiologia, Madrid, Spain
Abstract:
The Radiation Assessment Detector (RAD) is an instrument onboard the Mars Science Laboratory (MSL) rover Curiosity, currently characterizing the radiation environment on the surface of Mars. The radiation entering the instrument from above consists mostly of Galactic Cosmic Rays (GCRs) modulated by the Martian atmosphere. From below, the instrument is exposed to secondary radiation produced by the interactions of the GCR with the soil. This secondary radiation gets further modulated going through the rover body before entering RAD.
We developed a method of determining the direction of the charged particles measured by RAD. This method also extends the energy range possible for measurements with RAD beyond the intruments design limit. Using a combination of GEANT4 and Planetocosmics simulations, we reconstructed the expected charged particle spectra and intensities for upward and downward directed radiation which can be compared with observations. With the developed method, we are able to, for the first time, measure the upward charged particle flux with RAD both during the cruise phase and the surface science phase. Comparing the results of the simulations with the instrument data sets enables us to evaluate the simulation tools used to predict the Martian radiation envronment.
