TY - JOUR
T1 - Observed diurnal variations in Mars Science Laboratory Dynamic Albedo of Neutrons passive mode data
AU - Tate, C. G.
AU - Moersch, J.
AU - Jun, I.
AU - Mitrofanov, I.
AU - Litvak, M.
AU - Boynton, W. V.
AU - Drake, D.
AU - Fedosov, F.
AU - Golovin, D.
AU - Hardgrove, Craig
AU - Harshman, K.
AU - Kozyrev, A. S.
AU - Kuzmin, R.
AU - Lisov, D.
AU - Maclennan, E.
AU - Malakhov, A.
AU - Mischna, M.
AU - Mokrousov, M.
AU - Nikiforov, S.
AU - Sanin, A. B.
AU - Starr, R.
AU - Vostrukhin, A.
N1 - Funding Information:
This work was financially supported by J. Moersch’s Mars Data Analysis Program award ( NASA 80NSSC17K0508 ). We would also like to thank the MSL operations and science teams for helping acquire these data.
PY - 2018/6/1
Y1 - 2018/6/1
N2 - The Mars Science Laboratory Dynamic Albedo of Neutrons (DAN) experiment measures the martian neutron leakage flux in order to estimate the amount of water equivalent hydrogen present in the shallow regolith. When DAN is operating in passive mode, it is sensitive to neutrons produced through the interactions of galactic cosmic rays (GCR) with the regolith and atmosphere and neutrons produced by the rover's Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). During the mission, DAN passive mode data were collected over the full diurnal cycle at the locations known as Rocknest (sols 60–100) and John Klein (sols 166–272). A weak, but unexpected, diurnal variation was observed in the neutron count rates reported at these locations. We investigate different hypotheses that could be causing these observed variations. These hypotheses are variations in subsurface temperature, atmospheric pressure, the exchange of water vapor between the atmosphere and regolith, and instrumental effects on the neutron count rates. Our investigation suggests the most likely factors contributing to the observed diurnal variations in DAN passive data are instrumental effects and time-variable preferential shielding of alpha particles, with other environmental effects only having small contributions.
AB - The Mars Science Laboratory Dynamic Albedo of Neutrons (DAN) experiment measures the martian neutron leakage flux in order to estimate the amount of water equivalent hydrogen present in the shallow regolith. When DAN is operating in passive mode, it is sensitive to neutrons produced through the interactions of galactic cosmic rays (GCR) with the regolith and atmosphere and neutrons produced by the rover's Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). During the mission, DAN passive mode data were collected over the full diurnal cycle at the locations known as Rocknest (sols 60–100) and John Klein (sols 166–272). A weak, but unexpected, diurnal variation was observed in the neutron count rates reported at these locations. We investigate different hypotheses that could be causing these observed variations. These hypotheses are variations in subsurface temperature, atmospheric pressure, the exchange of water vapor between the atmosphere and regolith, and instrumental effects on the neutron count rates. Our investigation suggests the most likely factors contributing to the observed diurnal variations in DAN passive data are instrumental effects and time-variable preferential shielding of alpha particles, with other environmental effects only having small contributions.
KW - Dynamic Albedo of Neutrons
KW - Mars Science Laboratory
KW - Neutron spectrometer
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U2 - 10.1016/j.nima.2018.02.100
DO - 10.1016/j.nima.2018.02.100
M3 - Article
AN - SCOPUS:85043519438
SN - 0168-9002
VL - 892
SP - 70
EP - 83
JO - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
JF - Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
ER -