SH24A-04:
Energetic Particle Measurements on Mars and in Lunar Orbit
Tuesday, 16 December 2014: 4:45 PM
Cary J Zeitlin1, Don Hassler2, Nathan Schwadron3, Harlan E. Spence4, R F Wimmer-Schweingruber5, Jan Kristoffer Appel5, Eckhard Boehm5, Stefan S Boettcher5, David E Brinza6, Sönke Burmeister7, Bent Ehresmann2, Jingnan Guo5, Jan Kohler5, Henning Lohf5, Cesar Martin-Garcia5, Arik Posner8, Scot CR Rafkin2, Gerald Weigle9, Javier Martín-Torres10 and Maria-Paz Zorzano10, (1)Southwest Research Institute Boulder, Earth, Oceans & Space Department, Boulder, CO, United States, (2)Southwest Research Institute Boulder, Boulder, CO, United States, (3)University of New Hampshire, Durham, NH, United States, (4)University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States, (5)University of Kiel, Kiel, Germany, (6)Jet Propulsion Laboratory, Pasadena, CA, United States, (7)Christian-Albrechts-Universität zu Kiel, Institute for Experimental and Applied Physics, Extraterrestrial Physics, Kiel, Germany, (8)NASA Headquarters, Washington, DC, United States, (9)Big Head Endian, Burden, KS, United States, (10)Centro de Astrobiologia, Madrid, Spain
Abstract:
The Radiation Assessment Detector (RAD) aboard the Curiosity rover has been making measurements of energetic particles on the surface of Mars since the rover landed in August 2012. RAD also acquired data for most of the cruise to Mars, from Dec. 2011 through July 2012. In both cruise and on the surface, RAD is under considerable shielding, averaging 22 g cm-2 of CO2 during the surface mission, and ~ 16 g cm-2 during cruise. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) aboard the LRO spacecraft in lunar orbit has been making measurements since mid-2009. CRaTER contains three sets of detectors, of which one is unshielded, one is under 6 g cm-2 of tissue-equivalent plastic (TEP) shielding, and one is under 9 g cm-2 of TEP. Taken together, the two experiments provide a wealth of data concerning the effects of shielding on Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs). Comparison of data from the two instruments is complicated by their different locations in the heliosphere, which at most times causes them to be magnetically connected to different regions on the Sun. Variability of the atmospheric shielding above RAD, which is both diurnal and seasonal, also influences the comparison. During solar quiet time, when the energetic particle flux is due to GCRs, many similarities – and some small but significant differences – are seen in detailed time series data. In contrast, during SEP events, both the shielding and location disparities cause large differences in the measured particle fluxes.
