Experiment LEND of the NASA Lunar Reconnaissance Orbiter for High-Resolution Mapping of Neutron Emission of the Moon

Митрофанов, И. Г.; Санин, А. Б.; Golovin, D. V.; Litvak, M. L.; Коновалов, А. А.; Kozyrev, A.; Malakhov, A.; Мокроусов, М. И.; Tretyakov, V. I.; Troshin, V. S.; Uvarov, Vladimir; Varenikov, A.; Vostrukhin, A.; Шевченко, В. В.; Швецов, В. Н.; Krylov, A. R.; Тимошенко, Г. Н.; Bobrovnitsky, Yu. I.; Tomilina, T. M.; Grebennikov, Alexandre; Kazakov, L. L.; Sagdeev, R. Z.; Milikh, G. M.; Bartels, A.; Chin, G.; Floyd, S. R.; Garvin, J. B.; Keller, John W.; McClanahan, T. P.; Trombka, J. I.; Boynton, W. V.; Harshman, K.; Starr, R.; Evans, L. G.

doi:10.1089/ast.2007.0158

Cited by 38 publications

(58 citation statements)

References 16 publications

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“…Details of the LEND instrument are described in Mitrofanov et al (2005Mitrofanov et al ( , 2008. We use these details to estimate LEND's sensitivity to hydrogen at its optimum proposed spatial resolution, using the SNASA framework.…”

Section: Spatially Resolved Hydrogen Measurements In Lunar Polar Regionsmentioning

confidence: 99%

“…Fast neutrons carry information about iron and titanium (or, alternatively, average atomic mass) for nonhydrous silicate bodies Gasnault et al, 2001) as well as hydrogen at the Moon and Mars (Feldman et al, 2000a(Feldman et al, , 2002a. New planetary neutron measurements are planned for the asteroids Ceres and Vesta on the NASA Dawn spacecraft , for Mercury on the NASA MESSENGER spacecraft (Goldsten et al, 2007), and for the Moon with the Lunar Reconnaissance Orbiter (LRO) spacecraft (Mitrofanov et al, 2005(Mitrofanov et al, , 2008. More details about specific orbital neutron spectroscopy measurements can be found in the above references.…”

Section: Introductionmentioning

confidence: 99%

“…However, the spatial resolution of the LP data is too broad to resolve individual craters or deposits, all of which are smaller than 30 km in diameter. In response to this need, the LRO spacecraft is carrying a neutron sensor that will collimate the incoming epithermal neutrons in order to improve the spatial resolution of epithermal neutron measurements (Mitrofanov et al, 2005(Mitrofanov et al, , 2008.…”

Section: Introductionmentioning

confidence: 99%

“…The collimator technique is straightforward to understand and can be well applied to the SNASA technique. It is also the basis for several recently proposed neutron instruments and will be flown in lunar orbit on LRO (Mitrofanov et al, 2005(Mitrofanov et al, , 2008. Figure 2 shows the general concept for a neutron spectrometer with a collimated FOV for epithermal neutrons.…”

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confidence: 99%

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Performance of Orbital Neutron Instruments for Spatially Resolved Hydrogen Measurements of Airless Planetary Bodies

Lawrence

Elphic²,

Feldman³

et al. 2010

Astrobiology

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Orbital neutron spectroscopy has become a standard technique for measuring planetary surface compositions from orbit. While this technique has led to important discoveries, such as the deposits of hydrogen at the Moon and Mars, a limitation is its poor spatial resolution. For omni-directional neutron sensors, spatial resolutions are 1-1.5 times the spacecraft's altitude above the planetary surface (or 40-600 km for typical orbital altitudes). Neutron sensors with enhanced spatial resolution have been proposed, and one with a collimated field of view is scheduled to fly on a mission to measure lunar polar hydrogen. No quantitative studies or analyses have been published that evaluate in detail the detection and sensitivity limits of spatially resolved neutron measurements. Here, we describe two complementary techniques for evaluating the hydrogen sensitivity of spatially resolved neutron sensors: an analytic, closed-form expression that has been validated with Lunar Prospector neutron data, and a three-dimensional modeling technique. The analytic technique, called the Spatially resolved Neutron Analytic Sensitivity Approximation (SNASA), provides a straightforward method to evaluate spatially resolved neutron data from existing instruments as well as to plan for future mission scenarios. We conclude that the existing detector-the Lunar Exploration Neutron Detector (LEND)-scheduled to launch on the Lunar Reconnaissance Orbiter will have hydrogen sensitivities that are over an order of magnitude poorer than previously estimated. We further conclude that a sensor with a geometric factor of * 100 cm 2 Sr (compared to the LEND geometric factor of * 10.9 cm 2 Sr) could make substantially improved measurements of the lunar polar hydrogen spatial distribution.

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Section: Spatially Resolved Hydrogen Measurements In Lunar Polar Regionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Performance of Orbital Neutron Instruments for Spatially Resolved Hydrogen Measurements of Airless Planetary Bodies

Lawrence

Elphic²,

Feldman³

et al. 2010

Astrobiology

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“…T he major advantage of the collimated neutron telescope Lunar Exploration Neutron Detector (LEND) on board NASA's Lunar Reconnaissance Orbiter (LRO) compared with the previous neutron spectrometer (NS) on Lunar Prospector is the ability of LEND to measure spatial variations of lunar neutrons within a narrow field of view (FOV) (1,2). The count rate of neutrons within the FOV is our "signal" for such lunar mapping, and all other counts in the collimated sensors are "background" (1, 2).…”

mentioning

confidence: 99%

Response to Comment on “Hydrogen Mapping of the Lunar South Pole Using the LRO Neutron Detector Experiment LEND”

Митрофанов

Boynton

Litvak

et al. 2011

Science

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Critical comments from Lawrence et al. are considered on the capability of the collimated neutron telescope Lunar Exploration Neutron Detector (LEND) on NASA's Lunar Reconnaissance Orbiter (LRO) for mapping lunar epithermal neutrons, as presented in our paper. We present two different analyses to show that our previous estimated count rates are valid and support the conclusions of that paper.T he major advantage of the collimated neutron telescope Lunar Exploration Neutron Detector (LEND) on board NASA's Lunar Reconnaissance Orbiter (LRO) compared with the previous neutron spectrometer (NS) on Lunar Prospector is the ability of LEND to measure spatial variations of lunar neutrons within a narrow field of view (FOV) (1, 2). The count rate of neutrons within the FOV is our "signal" for such lunar mapping, and all other counts in the collimated sensors are "background" (1, 2). According to our paper (3), the count rate of the collimated sensors is about 5 counts per second (cps), with a signal about 1.5 to 1.9 cps and a background about 3.1 to 3.5 cps. The main criticism of our paper by Lawrence et al. (4) is based on the estimation of a much larger background that was nearly equal to the total count rate of the collimated sensors. If that were the case, LEND could not detect a significant number of neutrons within its FOV, and it would not be able to map neutrons with the required spatial resolution.In our analysis of the LEND mapping capabilities (1, 2), we took into account neutrons at all energies corresponding to the collimated signal and all the components of background on lunar orbit. Lawrence et al. (4) have focused on one particular component of background, which is associated with the partial transparency of the collimator for high-energy epithermal (HEE) neutrons from the Moon. This component was presented in (4) as a new background that was missed in our paper (3), but that is not correct. We estimated a count rate about 0.3 cps for neutrons of all energies, including the HEE.In (4), the count rate for freely propagating HEE neutrons was estimated as 2.25 cps, which is about 7 times higher than our estimation. To get this value, Lawrence et al. (4) performed a numerical simulation of LEND-type sensors for HEE neutrons from soils with different atomic mass. They found that the count rate of HEE neutrons should be about 10% higher for maria than for highlands. Then, using NASA Planetary Data System (PDS) data, they found a difference of about 0.25 cps between the maximum count rate of maria and the mean count rate for highlands. Using these values, they found 2.25 cps for the background from propagating HEE neutrons.We disagree with two statements in (4). The first one is related to the count-rate values they used. The statistics of the counts are low, and one must average data over large areas to properly estimate the difference between maria and highlands. However, Lawrence et al. (4) compared the maximum count rate in one area with the mean count rate in another. We found the difference between mean c...

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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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Experiment LEND of the NASA Lunar Reconnaissance Orbiter for High-Resolution Mapping of Neutron Emission of the Moon

Cited by 38 publications

References 16 publications

Performance of Orbital Neutron Instruments for Spatially Resolved Hydrogen Measurements of Airless Planetary Bodies

Performance of Orbital Neutron Instruments for Spatially Resolved Hydrogen Measurements of Airless Planetary Bodies

Response to Comment on “Hydrogen Mapping of the Lunar South Pole Using the LRO Neutron Detector Experiment LEND”

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

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