Global maps of lunar neutron fluxes from the LEND instrument

Litvak, M. L.; Митрофанов, И. Г.; Санин, А. Б.; Malakhov, A.; Boynton, W. V.; Chin, G.; Droege, G.; Evans, L. G.; Garvin, J. B.; Golovin, D. V.; Harshman, K.; McClanahan, T. P.; Мокроусов, М. И.; Mazarico, E.; Milikh, G. M.; Neumann, Gregory A.; Sagdeev, R. Z.; Smith, David E.; Starr, R.; Zuber, M. T.

doi:10.1029/2011je003949

Cited by 39 publications

(52 citation statements)

References 31 publications

(64 reference statements)

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“…The detailed procedure to convert maps of neutron count rates to H/H 2 O concentrations is described in Mitrofanov et al (2008) and Mitrofanov et al (2010b). Detailed procedures for the calibration and processing of the LEND data are described in Mitrofanov et al (2012), Boynton et al (2012), and Litvak et al (2012aLitvak et al ( , 2012b.…”

Section: Introductionmentioning

confidence: 99%

Evidence for the sequestration of hydrogen-bearing volatiles towards the Moon’s southern pole-facing slopes

McClanahan

Митрофанов

Boynton

et al. 2015

Icarus

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a b s t r a c tThe Lunar Exploration Neutron Detector (LEND) onboard the Lunar Reconnaissance Orbiter (LRO) detects a widespread suppression of the epithermal neutron leakage flux that is coincident with the pole-facing slopes (PFS) of the Moon's southern hemisphere. Suppression of the epithermal neutron flux is consistent with an interpretation of enhanced concentrations of hydrogen-bearing volatiles within the upper meter of the regolith. Localized flux suppression in PFS suggests that the reduced solar irradiation and lowered temperature on PFS constrains volatility to a greater extent than in surrounding regions. Epithermal neutron flux mapped with LEND's Collimated Sensor for Epithermal Neutrons (CSETN) was analyzed as a function of slope geomorphology derived from the Lunar Orbiting Laser Altimeter (LOLA) and the results compared to co-registered maps of diurnally averaged temperature from the Diviner Lunar Radiometer Experiment and an averaged illumination map derived from LOLA. The suppression in the average south polar epithermal neutron flux on equator-facing slopes (EFS) and PFS (85-90°S) is 3.3 ± 0.04% and 4.3 ± 0.05% respectively (one-sigma-uncertainties), relative to the average count-rate in the latitude band 45-90°S. The discrepancy of 1.0 ± 0.06% between EFS and PFS neutron flux corresponds to an average of $23 parts-per-million-by-weight (ppmw) more hydrogen on PFS than on EFS. Results show that the detection of hydrogen concentrations on PFS is dependent on their spatial scale. Epithermal flux suppression on large scale PFS was found to be enhanced to 5.2 ± 0.13%, a discrepancy of $45 ppmw hydrogen relative to equivalent EFS. Enhanced poleward hydration of PFS begins between 50°S and 60°S latitude. Polar regolith temperature contrasts do not explain the suppression of epithermal neutrons on pole-facing slopes. The Supplemental on-line materials include supporting results derived from the uncollimated Lunar Prospector Neutron Spectrometer and the LEND Sensor for Epithermal Neutrons. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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Section: Introductionmentioning

confidence: 99%

Evidence for the sequestration of hydrogen-bearing volatiles towards the Moon’s southern pole-facing slopes

McClanahan

Митрофанов

Boynton

et al. 2015

Icarus

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“…While the interpretation of the LEND measurements remains controversial, at a minimum the existing literature demonstrates that there is significant uncertainty regarding the actual spatial resolution of the collimated data. Further, there is general agreement that background from uncollimated high-energy epithermal neutrons is a significant source of uncertainties, and a proper accounting for such background is required to understand the collimated LEND data [21,22,36,37].…”

Section: Planetary Neutron Spectroscopy and Lunar Polar Hydrogen Measmentioning

confidence: 98%

High-resolution mapping of lunar polar hydrogen with a low-resource orbital mission

et al. 2015

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a b s t r a c tLunar permanently shaded regions (PSRs) are unique solar-system environments. Their low temperatures ( o 100 K) facilitate cold trapping of volatile materials over timescales comparable to the lifetime of the solar system. While much has been learned about these regions from orbital spacecraft, important missing information includes the spatial and depth-dependent distribution of bulk hydrogen concentrations in and around PSRs. We present two complementary mission scenarios where orbital neutron spectroscopy will provide significantly improved understanding of lunar polar bulk hydrogen concentrations. In the first mission concept, a six-month orbital mission will measure bulk hydrogen concentrations with sensitivity better than 50 ppm and a spatial resolution of order 20 km over the entire lunar South Polar region (poleward of 80ºS). Spatial reconstruction analyses of the returned data will improve the final spatial resolution to better than 10 km. The presence and burial depth (o 25 cm) of subsurface deposits will be quantified with latitude-dependent sensitivities ranging from 50 to 350 ppm. The second concept envisions a few, very low altitude ( $ 5 km) flyovers of one or more PSRs to quantify the hydrogen concentrations and spatial heterogeneities with a hydrogen sensitivity less than 200 and spatial scale size of 5 km. Both concepts can be combined in a single mission where full-coverage polar measurements are made with a hydrogen spatial resolution of 20 km, and higher spatial resolution measurements are made for a few strategically selected PSRs at the end of the mission. & 2015 IAA. Published by Elsevier Ltd. on behalf of IAA. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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“…Thus, no substantive evidence to support claims about the functioning of the collimator in the LEND CSETN can be drawn from the paper by Sanin et al [2012]. Litvak et al [2012a] use the orbital phase profile to conclude that the collimated count rate into the LEND CSETN is 1.7 neutrons per second. The orbital phase profile involves averaging over narrow latitude bands either on the near or far side of the Moon.…”

Section: The Lunar Uncollimated Backgroundmentioning

confidence: 99%

“…All Rights Reserved. Recently, a number of papers have appeared [Litvak et al, 2012a;Sanin et al, 2012;Mitrofanov et al, 2012;Litvak et al, 2012b;Boynton et al, 2012] that contain assertions to the effect that the LEND CSETN is producing a map with 10 km spatial resolution. Given the importance for the planning of future missions, it is imperative that the performance of the LEND CSETN is clarified for decision-makers outside the field of planetary neutron studies.…”

Section: 1002/2013je004421mentioning

confidence: 99%

How well do we know the polar hydrogen distribution on the Moon?

et al. 2014

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A detailed comparison is made of results from the Lunar Prospector Neutron Spectrometer (LPNS) and the Lunar Exploration Neutron Detector Collimated Sensors for Epithermal Neutrons (LEND CSETN). Using the autocorrelation function and power spectrum of the polar count rate maps produced by these experiments, it is shown that the LEND CSETN has a footprint that is at least as big as would be expected for an omnidirectional detector at an orbital altitude of 50 km. The collimated flux into the field of view of the collimator is negligible. A dip in the count rate in Shoemaker crater is found to be consistent with being a statistical fluctuation superimposed on a significant, larger-scale decrease in the count rate, providing no evidence for high spatial resolution of the LEND CSETN. The maps of lunar polar hydrogen with the highest contrast, i.e., spatial resolution, are those resulting from pixon image reconstructions of the LPNS data. These typically provide weight percentages of water-equivalent hydrogen that are accurate to 30% within the polar craters.

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Global maps of lunar neutron fluxes from the LEND instrument

Cited by 39 publications

References 31 publications

Evidence for the sequestration of hydrogen-bearing volatiles towards the Moon’s southern pole-facing slopes

Evidence for the sequestration of hydrogen-bearing volatiles towards the Moon’s southern pole-facing slopes

High-resolution mapping of lunar polar hydrogen with a low-resource orbital mission

How well do we know the polar hydrogen distribution on the Moon?

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