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Volumn 340, Issue 6136, 2013, Pages 1080-1084

Measurements of energetic particle radiation in transit to mars on the mars science laboratory

Author keywords

[No Author keywords available]

Indexed keywords

ASSESSMENT METHOD; DATA SET; ENERGY EFFICIENCY; LABORATORY METHOD; LINEARITY; MARS; MEASUREMENT METHOD; PARTICULATE MATTER; RADIATION BALANCE;

EID: 84878352790     PISSN: 00368075     EISSN: 10959203     Source Type: Journal    
DOI: 10.1126/science.1235989     Document Type: Article
Times cited : (509)

References (39)
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    • note
    • The full spacecraft model contains thousands of components, hence the need for simplification. At present, only a subset of materials within the charged particle telescope's field of view is included in the shielding model, the current state of which is described in the supplementary materials.
  • 9
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  • 13
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    • note
    • Dose rates as measured by the RAD include particles originating from the MSL's power supply, a radioisotope thermoelectric generator that emits a steady background of neutrons and g rays. These contributions were measured during ground tests and were subtracted from the results presented here. More details about the background subtraction are given in the supplementary materials.
  • 14
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    • note
    • Before 27 January 2012, the RAD observed with a 465-s cadence and nearly 100% duty cycle. Subsequently, RAD observations were 929 s in duration, with a 50% duty cycle, reducing the data volume by a factor of 4 to accommodate steadily decreasing telemetry bandwidth. At the same time as the observing cadence was changed, the sensitivity of the plastic scintillator was increased, resulting in a slightly higher value of the GCR dose rate measured by that detector (~10%, visible in Fig. 1).
  • 15
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    • note
    • Simulations indicate that the average value of the ratio dE/dx in silicon and LET in water is 1.6 for GCRs, with an associated uncertainty of T15%. Proper calculation of the range of this ratio must account for the effects of straggling, which is a significant factor in thin silicon detectors such as those in the RAD. The LET conversion factor in turn yields a dose conversion factor of 1.45.
  • 16
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    • note
    • The spacecraft shielding was equal for both detectors, but the plastic scintillator is additionally shielded by 1.2 cm of plastic scintillator below and on the sides and 2.8 cm of cesium iodide on top. Proton energies required to penetrate these materials are about 35 and 95 MeV, respectively, as compared to about 10 MeV required for a particle in the telescope field of view to reach the silicon detector used for dosimetry.
  • 18
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    • note
    • The P7 channel measures the proton flux between 165 and 500 MeV. It was chosen for comparison because the reported ratio of peak flux to quiet-time flux was similar to the ratio of peak dose rate to quiet-time dose rate seen in the RAD in the 27 January event. This comparison is not intended to suggest that the P7 channel and the RAD (under shielding) had similar sensitivities in terms of their energy thresholds or ranges.
  • 19
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    • note
    • The use of the quiet-time flux of GOES differential proton flux channels is problematic, especially for the higher-energy channels. The differential fluxes are obtained by subtracting fluxes measured in the various integral channels. As there are by definition no negative fluxes, the algorithm used to obtain differential fluxes assumes a background level that cannot be crossed, as discussed in (20). Despite this caveat, the dearth of higher-energy proton data from other spacecraft sources led us to arbitrarily scale the GOES data for comparison to the RAD data.
  • 24
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    • Cucinotta, F.A.1    Chappell, L.2    Kim, M.Y.3
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    • For 2012, the average modulation potential derived from the Earth-based Oulu neutron monitor (38) was less than 700 MV, as compared to values of 1000 MV or greater seen in previous solar maximum periods. The full range of the modulation potential (F) during the cruise as measured by the Oulu neutron monitor is available at
    • For 2012, the average modulation potential derived from the Earth-based Oulu neutron monitor (38) was less than 700 MV, as compared to values of 1000 MV or greater seen in previous solar maximum periods. The full range of the modulation potential (F) during the cruise as measured by the Oulu neutron monitor is available at http://cosmicrays.oulu.fi/phi/Phi-mon.txt.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.