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GCR Environmental Models I: Sensitivity Analysis for GCR EnvironmentsAccurate galactic cosmic ray (GCR) models are required to assess crew exposure during long-duration missions to the Moon or Mars. Many of these models have been developed and compared to available measurements, with uncertainty estimates usually stated to be less than 15%. However, when the models are evaluated over a common epoch and propagated through to effective dose, relative differences exceeding 50% are observed. This indicates that the metrics used to communicate GCR model uncertainty can be better tied to exposure quantities of interest for shielding applications. This is the first of three papers focused on addressing this need. In this work, the focus is on quantifying the extent to which each GCR ion and energy group, prior to entering any shielding material or body tissue, contributes to effective dose behind shielding. Results can be used to more accurately calibrate model-free parameters and provide a mechanism for refocusing validation efforts on measurements taken over important energy regions. Results can also be used as references to guide future nuclear cross-section measurements and radiobiology experiments. It is found that GCR with Z>2 and boundary energies below 500 MeV/n induce less than 5% of the total effective dose behind shielding. This finding is important given that most of the GCR models are developed and validated against Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer (ACE/CRIS) measurements taken below 500 MeV/n. It is therefore possible for two models to very accurately reproduce the ACE/CRIS data while inducing very different effective dose values behind shielding.
Document ID
20140006233
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Slaba, Tony C.
(NASA Langley Research Center Hampton, VA, United States)
Blattnig, Steve R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
May 27, 2014
Publication Date
April 7, 2014
Publication Information
Publication: Space Weather
Volume: 12
Issue: 4
Subject Category
Aerospace Medicine
Space Radiation
Report/Patent Number
NF1676L-17812
Funding Number(s)
WBS: WBS 651549.02.07.10
Distribution Limits
Public
Copyright
Other

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