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Chabot NL, Peplowski PN, Ernst CM, Nair H, Lucks M, Steele RJ, Lawrence DJ. MEGANE investigations of Phobos and the Small Body Mapping Tool. EARTH, PLANETS, AND SPACE : EPS 2021; 73:217. [PMID: 34970072 PMCID: PMC8666434 DOI: 10.1186/s40623-021-01509-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Accepted: 08/25/2021] [Indexed: 06/14/2023]
Abstract
The MEGANE instrument onboard the MMX mission will acquire gamma-ray and neutron spectroscopy data of Phobos to determine the elemental composition of the martian moon and provide key constraints on its origin. To produce accurate compositional results, the irregular shape of Phobos and its proximity to Mars must be taken into account during the analysis of MEGANE data. The MEGANE team is adapting the Small Body Mapping Tool (SBMT) to handle gamma-ray and neutron spectroscopy investigations, building on the demonstrated record of success of the SBMT being applied to scientific investigations on other spacecraft missions of irregularly shaped bodies. This is the first application of the SBMT to a gamma-ray and neutron spectroscopy dataset, and the native, three-dimensional foundation of the SBMT is well suited to MEGANE's needs. In addition, the SBMT will enable comparisons between the MEGANE datasets and other datasets of the martian moons, including data from previous spacecraft missions and MMX's multi-instrument suite.
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Affiliation(s)
- Nancy L. Chabot
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - Patrick N. Peplowski
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - Carolyn M. Ernst
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - Hari Nair
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - Michael Lucks
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - R. Josh Steele
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
| | - David J. Lawrence
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 USA
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2
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Norbury JW, Slaba TC, Aghara S, Badavi FF, Blattnig SR, Clowdsley MS, Heilbronn LH, Lee K, Maung KM, Mertens CJ, Miller J, Norman RB, Sandridge CA, Singleterry R, Sobolevsky N, Spangler JL, Townsend LW, Werneth CM, Whitman K, Wilson JW, Xu SX, Zeitlin C. Advances in space radiation physics and transport at NASA. LIFE SCIENCES IN SPACE RESEARCH 2019; 22:98-124. [PMID: 31421854 DOI: 10.1016/j.lssr.2019.07.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Revised: 06/20/2019] [Accepted: 07/03/2019] [Indexed: 06/10/2023]
Abstract
The space radiation environment is a complex mixture of particle types and energies originating from sources inside and outside of the galaxy. These environments may be modified by the heliospheric and geomagnetic conditions as well as planetary bodies and vehicle or habitat mass shielding. In low Earth orbit (LEO), the geomagnetic field deflects a portion of the galactic cosmic rays (GCR) and all but the most intense solar particle events (SPE). There are also dynamic belts of trapped electrons and protons with low to medium energy and intense particle count rates. In deep space, the GCR exposure is more severe than in LEO and varies inversely with solar activity. Unpredictable solar storms also present an acute risk to astronauts if adequate shielding is not provided. Near planetary surfaces such as the Earth, moon or Mars, secondary particles are produced when the ambient deep space radiation environment interacts with these surfaces and/or atmospheres. These secondary particles further complicate the local radiation environment and modify the associated health risks. Characterizing the radiation fields in this vast array of scenarios and environments is a challenging task and is currently accomplished with a combination of computational models and dosimetry. The computational tools include models for the ambient space radiation environment, mass shielding geometry, and atomic and nuclear interaction parameters. These models are then coupled to a radiation transport code to describe the radiation field at the location of interest within a vehicle or habitat. Many new advances in these models have been made in the last decade, and the present review article focuses on the progress and contributions made by workers and collaborators at NASA Langley Research Center in the same time frame. Although great progress has been made, and models continue to improve, significant gaps remain and are discussed in the context of planned future missions. Of particular interest is the juxtaposition of various review committee findings regarding the accuracy and gaps of combined space radiation environment, physics, and transport models with the progress achieved over the past decade. While current models are now fully capable of characterizing radiation environments in the broad range of forecasted mission scenarios, it should be remembered that uncertainties still remain and need to be addressed.
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Affiliation(s)
- John W Norbury
- NASA Langley Research Center, Hampton, Virginia 23681, USA.
| | - Tony C Slaba
- NASA Langley Research Center, Hampton, Virginia 23681, USA
| | - Sukesh Aghara
- University of Massachusetts, Lowell, Massachusetts 01854, USA
| | | | | | | | | | - Kerry Lee
- NASA Johnson Space Center, Houston, Texas 77058, USA
| | - Khin M Maung
- University of Southern Mississippi, Hattiesburg, Mississippi 39406, USA
| | | | - Jack Miller
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Ryan B Norman
- NASA Langley Research Center, Hampton, Virginia 23681, USA
| | | | | | - Nikolai Sobolevsky
- Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia
| | - Jan L Spangler
- Science and Technology Corporation, Hampton, Virginia 23666, USA
| | | | | | | | - John W Wilson
- Old Dominion University, Norfolk, Virginia 23529, USA
| | | | - Cary Zeitlin
- Leidos Innovations Corporation, Houston, Texas 77058, USA
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3
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Norbury JW, Slaba TC, Sobolevsky N, Reddell B. Comparing HZETRN, SHIELD, FLUKA and GEANT transport codes. LIFE SCIENCES IN SPACE RESEARCH 2017; 14:64-73. [PMID: 28887946 PMCID: PMC7757342 DOI: 10.1016/j.lssr.2017.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 03/27/2017] [Accepted: 04/17/2017] [Indexed: 06/07/2023]
Abstract
For the first time, the American (NASA) and Russian (ROSCOSMOS) space radiation transport codes, HZETRN and SHIELD respectively, are directly compared to each other. Calculations are presented for Galactic Cosmic Ray (GCR) minimum Hydrogen, Oxygen and Iron projectiles incident on a uniform Aluminum cylinder of varying thickness. Comparisons are made for the flux spectra of neutrons, light ions (Z≤ 2), heavy ions (Z> 2) and pions emitted from the back of the Aluminum cylinder. In order to provide more benchmark comparisons, some calculations with the GEANT and FLUKA transport codes are also shown.
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Affiliation(s)
- John W Norbury
- NASA Langley Research Center, Hampton, Virginia 23681, USA.
| | - Tony C Slaba
- NASA Langley Research Center, Hampton, Virginia 23681, USA
| | - Nikolai Sobolevsky
- Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia
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4
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LIM LF, STARR RD, EVANS LG, PARSONS AM, ZOLENSKY ME, BOYNTON WV. Modeling orbital gamma-ray spectroscopy experiments at carbonaceous asteroids. METEORITICS & PLANETARY SCIENCE 2017; 52:174-190. [PMID: 32661458 PMCID: PMC7357204 DOI: 10.1111/maps.12786] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
To evaluate the feasibility of measuring differences in bulk composition among carbonaceous meteorite parent bodies from an asteroid or comet orbiter, we present the results of a performance simulation of an orbital gamma-ray spectroscopy (GRS) experiment in a Dawn-like orbit around spherical model asteroids with a range of carbonaceous compositions. The orbital altitude was held equal to the asteroid radius for 4.5 months. Both the asteroid gamma-ray spectrum and the spacecraft background flux were calculated using the MCNPX Monte-Carlo code. GRS is sensitive to depths below the optical surface (to ≈20-50 cm depth depending on material density). This technique can therefore measure underlying compositions beneath a sulfur-depleted (e.g., Nittler et al. 2001) or desiccated surface layer. We find that 3σ uncertainties of under 1 wt% are achievable for H, C, O, Si, S, Fe, and Cl for five carbonaceous meteorite compositions using the heritage Mars Odyssey GRS design in a spacecraft-deck-mounted configuration at the Odyssey end-of-mission energy resolution, FWHM = 5.7 keV at 1332 keV. The calculated compositional uncertainties are smaller than the compositional differences between carbonaceous chondrite subclasses.
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Affiliation(s)
- Lucy F. LIM
- NASA Goddard Space Flight Center, Code 691, Greenbelt, Maryland 20771, USA
| | - Richard D. STARR
- NASA Goddard Space Flight Center, Code 691, Greenbelt, Maryland 20771, USA
- Catholic University of America, Washington, District of Columbia 20064, USA
| | - Larry G. EVANS
- NASA Goddard Space Flight Center, Code 691, Greenbelt, Maryland 20771, USA
- Computer Sciences Corporation, Lanham-Seabrook, Maryland 20706, USA
| | - Ann M. PARSONS
- NASA Goddard Space Flight Center, Code 691, Greenbelt, Maryland 20771, USA
| | | | - William V. BOYNTON
- Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA
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5
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Mitrofanov IG, Litvak ML, Nikiforov SY, Jun I, Bobrovnitsky YI, Golovin DV, Grebennikov AS, Fedosov FS, Kozyrev AS, Lisov DI, Malakhov AV, Mokrousov MI, Sanin AB, Shvetsov VN, Timoshenko GN, Tomilina TM, Tret'yakov VI, Vostrukhin AA. The ADRON-RM Instrument Onboard the ExoMars Rover. ASTROBIOLOGY 2017; 17:585-594. [PMID: 28731818 DOI: 10.1089/ast.2016.1566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
This overview presents the physical principles, design, measurement capabilities, and summary of planned operations of the autonomous detector of radiation of neutrons onboard rover at Mars (ADRON-RM) on the surface of Mars. ADRON-RM is a Russian project selected for the joint European Space Agency-Roscosmos ExoMars 2020 landing mission. A compact passive neutron spectrometer, ADRON-RM, was designed to study the abundance and distribution of water and neutron absorption elements (such as Cl, Fe, and others) in the martian subsurface along the path of the ExoMars rover. Key Words: Mars exploration-Surface-Neutron Spectroscopy-Water. Astrobiology 17, 585-594.
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Affiliation(s)
- I G Mitrofanov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - M L Litvak
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - S Y Nikiforov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - I Jun
- 2 Jet Propulsion Laboratory, California Institute of Technology , Pasadena, California
| | - Y I Bobrovnitsky
- 3 A.A. Blagonravov Institute of Mechanical Engineering , Russian Academy of Sciences, Moscow, Russia
| | - D V Golovin
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - A S Grebennikov
- 3 A.A. Blagonravov Institute of Mechanical Engineering , Russian Academy of Sciences, Moscow, Russia
| | - F S Fedosov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - A S Kozyrev
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - D I Lisov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - A V Malakhov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - M I Mokrousov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - A B Sanin
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - V N Shvetsov
- 4 Joint Institute of Nuclear Research , Dubna, Russia
| | | | - T M Tomilina
- 3 A.A. Blagonravov Institute of Mechanical Engineering , Russian Academy of Sciences, Moscow, Russia
| | - V I Tret'yakov
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
| | - A A Vostrukhin
- 1 Institute for Space Research , Russian Academy of Sciences, Moscow, Russia
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6
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Prettyman TH, Yamashita N, Toplis MJ, McSween HY, Schörghofer N, Marchi S, Feldman WC, Castillo-Rogez J, Forni O, Lawrence DJ, Ammannito E, Ehlmann BL, Sizemore HG, Joy SP, Polanskey CA, Rayman MD, Raymond CA, Russell CT. Extensive water ice within Ceres' aqueously altered regolith: Evidence from nuclear spectroscopy. Science 2016; 355:55-59. [PMID: 27980087 DOI: 10.1126/science.aah6765] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2016] [Accepted: 11/23/2016] [Indexed: 11/03/2022]
Abstract
The surface elemental composition of dwarf planet Ceres constrains its regolith ice content, aqueous alteration processes, and interior evolution. Using nuclear spectroscopy data acquired by NASA's Dawn mission, we determined the concentrations of elemental hydrogen, iron, and potassium on Ceres. The data show that surface materials were processed by the action of water within the interior. The non-icy portion of Ceres' carbon-bearing regolith contains similar amounts of hydrogen to those present in aqueously altered carbonaceous chondrites; however, the concentration of iron on Ceres is lower than in the aforementioned chondrites. This allows for the possibility that Ceres experienced modest ice-rock fractionation, resulting in differences between surface and bulk composition. At mid-to-high latitudes, the regolith contains high concentrations of hydrogen, consistent with broad expanses of water ice, confirming theoretical predictions that ice can survive for billions of years just beneath the surface.
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Affiliation(s)
- T H Prettyman
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA.
| | - N Yamashita
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - M J Toplis
- Institut de Recherche d'Astrophysique et Planétologie, CNRS, Université Paul Sabatier, Toulouse 31400, France
| | - H Y McSween
- Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
| | - N Schörghofer
- University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
| | - S Marchi
- Southwest Research Institute, Boulder, CO 80302, USA
| | - W C Feldman
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - J Castillo-Rogez
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - O Forni
- Institut de Recherche d'Astrophysique et Planétologie, CNRS, Université Paul Sabatier, Toulouse 31400, France
| | - D J Lawrence
- Johns Hopkins University, Applied Physics Laboratory, Laurel, MD 20723, USA
| | - E Ammannito
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
| | - B L Ehlmann
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA.,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - H G Sizemore
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA
| | - S P Joy
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
| | - C A Polanskey
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - M D Rayman
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C A Raymond
- Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA 91109-8099, USA
| | - C T Russell
- Earth Planetary and Space Sciences, University of California, Los Angeles, Los Angeles, CA 90095-1567, USA
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7
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Peplowski PN, Beck AW, Lawrence DJ. Geochemistry of the lunar highlands as revealed by measurements of thermal neutrons. JOURNAL OF GEOPHYSICAL RESEARCH. PLANETS 2016; 121:388-401. [PMID: 27830110 PMCID: PMC5076490 DOI: 10.1002/2015je004950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 02/26/2016] [Accepted: 02/29/2016] [Indexed: 06/02/2023]
Abstract
Thermal neutron emissions from the lunar surface provide a direct measure of bulk elemental composition that can be used to constrain the chemical properties of near-surface (depth <1 m) lunar materials. We present a new calibration of the Lunar Prospector thermal neutron map, providing a direct link between measured count rates and bulk elemental composition. The data are used to examine the chemical and mineralogical composition of the lunar surface, with an emphasis on constraining the plagioclase concentration across the highlands. We observe that the regions of lowest neutron absorption, which correspond to estimated plagioclase concentrations of >85%, are generally associated with large impact basins and are colocated with clusters of nearly pure plagioclase identified with spectral reflectance data.
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Affiliation(s)
| | - Andrew W Beck
- The Johns Hopkins University Applied Physics Laboratory Laurel Maryland USA
| | - David J Lawrence
- The Johns Hopkins University Applied Physics Laboratory Laurel Maryland USA
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8
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Lawrence DJ, Feldman WC, Peplowski PN, Solomon SC. The 4 June 2011 neutron event at Mercury: A defense of the solar origin hypothesis. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2015; 120:5284-5289. [PMID: 26937331 PMCID: PMC4758620 DOI: 10.1002/2015ja021069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 06/01/2015] [Accepted: 06/03/2015] [Indexed: 06/05/2023]
Abstract
We address claim that neutrons from a 4 June 2011 event at Mercury are nonsolarThe claim is based on an erroneous assumption about instrument singles countsThe best interpretation of the neutron event is that the neutrons have a solar origin.
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Affiliation(s)
- David J Lawrence
- The Johns Hopkins University Applied Physics Laboratory Laurel Maryland USA
| | | | | | - Sean C Solomon
- Department of Terrestrial Magnetism Carnegie Institution of Washington Washington District of Columbia USA; Lamont-Doherty Earth Observatory Columbia University Palisades New York USA
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9
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Aghara SK, Sriprisan SI, Singleterry RC, Sato T. Shielding evaluation for solar particle events using MCNPX, PHITS and OLTARIS codes. LIFE SCIENCES IN SPACE RESEARCH 2015; 4:79-91. [PMID: 26177623 DOI: 10.1016/j.lssr.2014.12.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 12/17/2014] [Accepted: 12/23/2014] [Indexed: 06/04/2023]
Abstract
Detailed analyses of Solar Particle Events (SPE) were performed to calculate primary and secondary particle spectra behind aluminum, at various thicknesses in water. The simulations were based on Monte Carlo (MC) radiation transport codes, MCNPX 2.7.0 and PHITS 2.64, and the space radiation analysis website called OLTARIS (On-Line Tool for the Assessment of Radiation in Space) version 3.4 (uses deterministic code, HZETRN, for transport). The study is set to investigate the impact of SPEs spectra transporting through 10 or 20 g/cm(2) Al shield followed by 30 g/cm(2) of water slab. Four historical SPE events were selected and used as input source spectra particle differential spectra for protons, neutrons, and photons are presented. The total particle fluence as a function of depth is presented. In addition to particle flux, the dose and dose equivalent values are calculated and compared between the codes and with the other published results. Overall, the particle fluence spectra from all three codes show good agreement with the MC codes showing closer agreement compared to the OLTARIS results. The neutron particle fluence from OLTARIS is lower than the results from MC codes at lower energies (E<100 MeV). Based on mean square difference analysis the results from MCNPX and PHITS agree better for fluence, dose and dose equivalent when compared to OLTARIS results.
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Affiliation(s)
- S K Aghara
- University of Massachusetts Lowell, Chemical Engineering, 1 University Avenue, Lowell, MA 01854, United States.
| | - S I Sriprisan
- University of Massachusetts Lowell, Chemical Engineering, 1 University Avenue, Lowell, MA 01854, United States
| | - R C Singleterry
- NASA Langley Research Center, 2 West Reid Street, MS 188E, Hampton, VA 23681, United States
| | - T Sato
- Japan Atomic Energy Agency, 2-4, Shirakata-Shirane, Tokai, Ibaraki 319-1195, Japan
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10
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Prettyman TH, Mittlefehldt DW, Yamashita N, Lawrence DJ, Beck AW, Feldman WC, McCoy TJ, McSween HY, Toplis MJ, Titus TN, Tricarico P, Reedy RC, Hendricks JS, Forni O, Le Corre L, Li JY, Mizzon H, Reddy V, Raymond CA, Russell CT. Elemental mapping by Dawn reveals exogenic H in Vesta's regolith. Science 2012; 338:242-6. [PMID: 22997135 DOI: 10.1126/science.1225354] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Using Dawn's Gamma Ray and Neutron Detector, we tested models of Vesta's evolution based on studies of howardite, eucrite, and diogenite (HED) meteorites. Global Fe/O and Fe/Si ratios are consistent with HED compositions. Neutron measurements confirm that a thick, diogenitic lower crust is exposed in the Rheasilvia basin, which is consistent with global magmatic differentiation. Vesta's regolith contains substantial amounts of hydrogen. The highest hydrogen concentrations coincide with older, low-albedo regions near the equator, where water ice is unstable. The young, Rheasilvia basin contains the lowest concentrations. These observations are consistent with gradual accumulation of hydrogen by infall of carbonaceous chondrites--observed as clasts in some howardites--and subsequent removal or burial of this material by large impacts.
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Affiliation(s)
- Thomas H Prettyman
- Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ 85719-2395, USA.
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11
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Abstract
The radiation environment on the Moon includes albedo neutrons produced by primary particles interacting with the lunar surface. In this work, HZETRN2010 is used to calculate the albedo neutron contribution to effective dose as a function of shielding thickness for four different space radiation environments and to determine to what extent various factors affect such estimates. First, albedo neutron spectra computed with HZETRN2010 are compared to Monte Carlo results in various radiation environments. Next, the impact of lunar regolith composition on the albedo neutron spectrum is examined, and the variation on effective dose caused by neutron fluence-to-effective dose conversion coefficients is studied. A methodology for computing effective dose in detailed human phantoms using HZETRN2010 is also discussed and compared. Finally, the combined variation caused by environmental models, shielding materials, shielding thickness, regolith composition and conversion coefficients on the albedo neutron contribution to effective dose is determined. It is shown that a single percentage number for characterizing the albedo neutron contribution to effective dose can be misleading. In general, the albedo neutron contribution to effective dose is found to vary between 1-32%, with the environmental model, shielding material and shielding thickness being the driving factors that determine the exact contribution. It is also shown that polyethylene or other hydrogen-rich materials may be used to mitigate the albedo neutron exposure.
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Affiliation(s)
- Tony C Slaba
- NASA Langley Research Center, 2 West Reid St., MS 188E, Hampton, Virginia 23681, USA.
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12
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Lawrence DJ, Elphic RC, Feldman WC, Funsten HO, Prettyman TH. Performance of orbital neutron instruments for spatially resolved hydrogen measurements of airless planetary bodies. ASTROBIOLOGY 2010; 10:183-200. [PMID: 20298147 PMCID: PMC2956572 DOI: 10.1089/ast.2009.0401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Accepted: 12/28/2009] [Indexed: 05/29/2023]
Abstract
Orbital neutron spectroscopy has become a standard technique for measuring planetary surface compositions from orbit. While this technique has led to important discoveries, such as the deposits of hydrogen at the Moon and Mars, a limitation is its poor spatial resolution. For omni-directional neutron sensors, spatial resolutions are 1-1.5 times the spacecraft's altitude above the planetary surface (or 40-600 km for typical orbital altitudes). Neutron sensors with enhanced spatial resolution have been proposed, and one with a collimated field of view is scheduled to fly on a mission to measure lunar polar hydrogen. No quantitative studies or analyses have been published that evaluate in detail the detection and sensitivity limits of spatially resolved neutron measurements. Here, we describe two complementary techniques for evaluating the hydrogen sensitivity of spatially resolved neutron sensors: an analytic, closed-form expression that has been validated with Lunar Prospector neutron data, and a three-dimensional modeling technique. The analytic technique, called the Spatially resolved Neutron Analytic Sensitivity Approximation (SNASA), provides a straightforward method to evaluate spatially resolved neutron data from existing instruments as well as to plan for future mission scenarios. We conclude that the existing detector--the Lunar Exploration Neutron Detector (LEND)--scheduled to launch on the Lunar Reconnaissance Orbiter will have hydrogen sensitivities that are over an order of magnitude poorer than previously estimated. We further conclude that a sensor with a geometric factor of approximately 100 cm(2) Sr (compared to the LEND geometric factor of approximately 10.9 cm(2) Sr) could make substantially improved measurements of the lunar polar hydrogen spatial distribution.
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Affiliation(s)
- David J Lawrence
- Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723, USA.
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13
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Feldman WC, Lawrence DJ, Goldsten JO, Gold RE, Baker DN, Haggerty DK, Ho GC, Krucker S, Lin RP, Mewaldt RA, Murphy RJ, Nittler LR, Rhodes EA, Slavin JA, Solomon SC, Starr RD, Vilas F, Vourlidas A. Evidence for extended acceleration of solar flare ions from 1-8 MeV solar neutrons detected with the MESSENGER Neutron Spectrometer. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009ja014535] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - David J. Lawrence
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - John O. Goldsten
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - Robert E. Gold
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - Daniel N. Baker
- Laboratory for Atmospheric and Space Physics; University of Colorado; Boulder Colorado USA
| | - Dennis K. Haggerty
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - George C. Ho
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | - Säm Krucker
- Space Sciences Laboratory, Physics Department; University of California; Berkeley California USA
- School of Space Research; Kyung Hee University; Yongin, Geonggi Korea
| | - Robert P. Lin
- Space Sciences Laboratory, Physics Department; University of California; Berkeley California USA
- School of Space Research; Kyung Hee University; Yongin, Geonggi Korea
| | - Richard A. Mewaldt
- Physics Department; California Institute of Technology; Pasadena California USA
| | | | - Larry R. Nittler
- Department of Terrestrial Magnetism; Carnegie Institution of Washington; Washington D. C. USA
| | - Edgar A. Rhodes
- Johns Hopkins University Applied Physics Laboratory; Laurel Maryland USA
| | | | - Sean C. Solomon
- Department of Terrestrial Magnetism; Carnegie Institution of Washington; Washington D. C. USA
| | - Richard D. Starr
- Department of Physics; Catholic University of America; Washington D. C. USA
| | - Faith Vilas
- MMT Observatory; University of Arizona; Tucson Arizona USA
| | - Angelos Vourlidas
- Physics Department; California Institute of Technology; Pasadena California USA
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Banerjee D, Dewangan A. Simulation of the cosmic-ray induced dose-rate within a Martian soil profile. RADIAT MEAS 2008. [DOI: 10.1016/j.radmeas.2008.02.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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15
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Hayatsu K, Hareyama M, Kobayashi S, Yamashita N, Miyajim M, Sakurai K, Hasebe N. Radiation Doses for Human Exposed to Galactic Cosmic Rays and Their Secondary Products on the Lunar Surface. ACTA ACUST UNITED AC 2008. [DOI: 10.2187/bss.22.59] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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16
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Boynton WV, Taylor GJ, Evans LG, Reedy RC, Starr R, Janes DM, Kerry KE, Drake DM, Kim KJ, Williams RMS, Crombie MK, Dohm JM, Baker V, Metzger AE, Karunatillake S, Keller JM, Newsom HE, Arnold JR, Brückner J, Englert PAJ, Gasnault O, Sprague AL, Mitrofanov I, Squyres SW, Trombka JI, d'Uston L, Wänke H, Hamara DK. Concentration of H, Si, Cl, K, Fe, and Th in the low- and mid-latitude regions of Mars. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2007je002887] [Citation(s) in RCA: 234] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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17
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Prettyman TH, Hagerty JJ, Elphic RC, Feldman WC, Lawrence DJ, McKinney GW, Vaniman DT. Elemental composition of the lunar surface: Analysis of gamma ray spectroscopy data from Lunar Prospector. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002656] [Citation(s) in RCA: 283] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
| | - J. J. Hagerty
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - R. C. Elphic
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - W. C. Feldman
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - D. J. Lawrence
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - G. W. McKinney
- Los Alamos National Laboratory; Los Alamos New Mexico USA
| | - D. T. Vaniman
- Los Alamos National Laboratory; Los Alamos New Mexico USA
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18
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Lawrence DJ, Feldman WC, Elphic RC, Hagerty JJ, Maurice S, McKinney GW, Prettyman TH. Improved modeling of Lunar Prospector neutron spectrometer data: Implications for hydrogen deposits at the lunar poles. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002637] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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