LEND neutron data processing for the mapping of the Moon

Litvak, M. L.; Митрофанов, И. Г.; Санин, А. Б.; Golovin, D. V.; Malakhov, A.; Boynton, W. V.; Droege, G.; Harshman, K.; Starr, R.; Milikh, G. M.; Sagdeev, R. Z.

doi:10.1029/2011je004035

Cited by 20 publications

(50 citation statements)

References 43 publications

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“…Each channel corresponds to the energy deposited in the 3 He detector volume due to neutron reactions with 3 He. Figure a is a typical raw (i.e., not processed) plot of passive data from sol 36, which shows an asymptotic count rate increase after the detector turns on—a so‐called “efficiency curve.” This effect is also seen in data from similar 3 He counters used by the lunar exploration neutron detector on board the lunar reconnaissance orbiter [ Litvak et al , ]. It is believed that the gradual increase of the count rates is due to the fact that the effective volume of the active 3 He gas in the counter participating in neutron reactions also increases as a function of time after the high‐voltage power turn on, eventually reaching a saturation level in an hour or so.…”

Section: Dan Passive Data Up To Sol 100mentioning

confidence: 77%

Neutron background environment measured by the Mars Science Laboratory's Dynamic Albedo of Neutrons instrument during the first 100 sols

et al. 2013

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[1] The Dynamic Albedo of Neutrons (DAN) instrument on board Mars Science Laboratory has been operating successfully since the landing and has been making measurements regularly along Curiosity's traverse at the surface. DAN measures thermal (E < 0.4 eV) and epithermal neutrons (0.4 eV < E <~1 keV) while operating in two different modes: active and passive. The active mode uses a pulsed neutron generator (PNG) to study the geological characteristics of the subsurface. In the passive mode, DAN measures the background neutron environment. This paper presents results of measurements in the passive mode from landing through to sol 100 and provides an interpretation of the data based on extensive Monte Carlo simulations. The main observations are summarized as follows: (1) the thermal neutron counts vary strongly along the rover traverse while the epithermal counts do not show much variation; (2) the neutrons from the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) are a larger contributor to the DAN passive data than the Galactic Cosmic Ray (GCR)-induced neutrons; (3) for the MMRTG neutrons, both the thermal and the epithermal counts increase as a function of the subsurface water content; (4) on the other hand, for the GCR-induced neutrons, the thermal counts increase but the epithermal counts decrease as a function of the subsurface water content; and (5) relative contributions by the MMRTG and GCR to the DAN thermal neutron counts at the Rocknest site, where the rover was stationed from sol 59 to sol 100, are estimated to be~60% and~40%, respectively.

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Section: Dan Passive Data Up To Sol 100mentioning

confidence: 77%

Neutron background environment measured by the Mars Science Laboratory's Dynamic Albedo of Neutrons instrument during the first 100 sols

et al. 2013

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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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“…In this paper we did not discuss these measurements in details and did not use it as part of the data reduction process.” In short, the commissioning data provide a valuable way to assess the performance of the LEND CSETN. Yet, neither Litvak et al [] nor any of the other papers in this set report any results from the commissioning orbit data.…”

Section: Other Evidencementioning

confidence: 86%

“…The recent set of papers claiming that the LEND CSETN has a 10 km footprint do not explain the altitude dependence of the observed count rate. The nearest these authors come to discussing the altitude dependence is in Litvak et al [], who state that “Data from the commissioning orbit is the important part of the instrument in‐flight calibration because it measured at the variable altitude above the Moon.... In this paper we did not discuss these measurements in details and did not use it as part of the data reduction process.” In short, the commissioning data provide a valuable way to assess the performance of the LEND CSETN.…”

Section: Other Evidencementioning

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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LEND neutron data processing for the mapping of the Moon

Cited by 20 publications

References 43 publications

Neutron background environment measured by the Mars Science Laboratory's Dynamic Albedo of Neutrons instrument during the first 100 sols

Neutron background environment measured by the Mars Science Laboratory's Dynamic Albedo of Neutrons instrument during the first 100 sols

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

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

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