Using proton radiation from the moon to search for diurnal variation of regolith hydrogenation

Schwadron, N. A.; Wilson, J. K.; Jordan, A. P.; Looper, M. D.; Zeitlin, C.; Townsend, Lawrence W.; Spence, H. E.; Legere, Jason S.; Bloser, Peter F.; Farrell, W. M.; Hurley, D. M.; Petro, N. E.; Stubbs, T. J.; Pieters, C. M.

doi:10.1016/j.pss.2017.09.012

Cited by 10 publications

(13 citation statements)

References 45 publications

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“…If “albedo” protons were present in significant numbers, a mirror image band reflected about the 45° line in the scatter plot would be visible. Such protons are clearly seen (Schwadron et al, ) in analysis of D4·D6 coincidence data, for which the energy threshold is much lower, ∼65 MeV compared to ∼115 MeV. But here, no evidence of these protons is seen, likely because the large majority of them do not have sufficient kinetic energy to penetrate the stack and cause a threefold coincidence of the thick detectors.…”

Section: Previous Flux Results and Refinement Of Helium Identificatiomentioning

confidence: 99%

Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER

et al. 2019

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We report updated measurements of the integral fluxes of energetic protons, helium ions, and heavier ions as measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER). CRaTER is a particle telescope that has been operating aboard the Lunar Reconnaissance Orbiter since 2009. In an earlier report, we presented the methodology used to extract linear energy transfer spectra and integral fluxes for particles with sufficient energies to fully penetrate the telescope. Results were presented for the time span from late 2009 to the end of calendar year 2014, a period that encompassed the rise of solar activity from deep solar minimum to the weak maximum of Cycle 24. Here, we update the results with data obtained from that point in time through the end of 2018, in the declining phase of Cycle 24. Fluxes obtained in the most recent data are approaching the peak levels observed in late 2009 and early 2010. The results can be used as input to models of solar modulation of galactic cosmic rays and are also relevant to human exploration of deep space.

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Section: Previous Flux Results and Refinement Of Helium Identificatiomentioning

confidence: 99%

Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER

et al. 2019

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“…Finally, as noted in section 1, CRaTER does not see many “albedo” secondary particles coming up from the Moon that have enough energy to penetrate the stack and trigger all three thick detectors, which means that the ones we do detect give at most two energy‐deposit measurements and thus we have less information to devise cuts to separate, for example, the albedo proton track from its background. We have devised a method akin to the statistical procedure outlined above to perform background subtraction for these observations (Schwadron, Wilson, et al, 2018), and we plan to improve that algorithm and apply it to our measurements of lunar albedo protons.…”

Section: Discussionmentioning

confidence: 99%

Long‐Term Observations of Galactic Cosmic Ray LET Spectra in Lunar Orbit by LRO/CRaTER

et al. 2020

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The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) has been orbiting the Moon since 2009 aboard the Lunar Reconnaissance Orbiter (LRO). From this vantage point, it samples the interplanetary energetic particle population outside the shielding of the Earth's magnetosphere. We report the sensor's observations of galactic cosmic rays (GCRs) over a complete solar activity cycle. CRaTER is designed primarily to measure not the spectra of GCR particles outside the sensor but rather their effects on matter, and in particular, it measures the linear energy transfer (LET) or energy-deposit spectrum in its silicon detectors. We have used the Geant4 radiation-transport code to devise a background-rejection algorithm to improve these measurements of LET under 9.9 g/cm 2 of shielding, and the resulting observations show the changing radiation effects of GCRs as their intensity and spectrum vary with solar modulation. As of 2020 this intensity, after declining during solar maximum activity, has recovered to a level that exceeds by a few percent the historically high values seen during the deep solar minimum at the start of the LRO mission in 2009. Plain Language Summary Energetic particle radiation consists of fast-moving atomic fragments traveling in space. The particles with the highest energy, called cosmic rays, can penetrate even thick shielding and deposit their energy into astronauts or electronics, causing radiation damage. A sensor aboard the Lunar Reconnaissance Orbiter satellite has been measuring cosmic rays in orbit around the Moon since 2009, monitoring the varying intensity of their radiation effects, and this paper reports improvements we have made to these measurements. The Sun's output of energetic particles, magnetic fields, and so forth varies on an 11-year cycle, and this activity affects the intensity of cosmic rays coming into the solar system. Our measurements of cosmic ray radiation effects show that, after a decline during the middle of the solar activity cycle, as of 2020 their intensity has risen back to exceed the historically high levels seen at the start of the mission. Unlike many spaceborne charged-particle telescopes, CRaTER is not primarily designed to measure the particle environment outside the sensor, though it has been used for that purpose (e.g., Wilson et al., 2019; Zeitlin et al., 2019, and references cited therein). Rather, it is designed to measure the effects of that

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“…While all previous lunar mapping with CRaTER data used analysis that focused on albedo protons (Schwadron et al, 2016(Schwadron et al, , 2018Wilson et al, 2012Wilson et al, , 2014, we use here singles rates to derive the SEP Index and map the Moon. This means that we are probably seeing map features from more than one type of albedo particle.…”

Section: Candidate Albedo Particles In the Sepi Mapmentioning

confidence: 99%

“…(A similar method with a related limitation is used by the GOES team to identify SEP events in their data; they use a high event detection threshold due to the varying GCR background.) More recent work by Schwadron et al () used only ~500 hr of CRaTER data, so it could rely on the visual identification of three small SEP events to manually isolate periods where only the GCR background was present. This, however, is impractical for multiyear analysis and might suffer from a lack of consistency.…”

Section: Identifying Sep Events In Crater Datamentioning

confidence: 99%

“…Schwadron et al () binned several years of CRaTER data by lunar latitude and found a latitudinal trend in the albedo proton yield, suggesting a detection of high‐latitude (polar) hydrogen or H‐bearing molecules. Also, an improved data analysis technique tentatively discerned a sunrise‐versus‐sunset contrast in the albedo proton yield using only a small fraction of the CRaTER data set (Schwadron et al, ), suggesting a diurnal variation in the hydrogenation of the lunar regolith.…”

Section: Introductionmentioning

confidence: 99%

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Precise Detections of Solar Particle Events and a New View of the Moon

Wilson

Spence

Schwadron

et al. 2020

Geophysical Research Letters

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We have invented a new method for detecting solar particle events using data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Using a simple function of the total particle detection rates from four of CRaTER's six detectors, we can precisely identify solar energetic particle event periods in the CRaTER data archive. During solar quiet periods we map the distribution of a mare‐associated mixture of elements in the lunar regolith using this new method. The new map of the moon probably reflects an as‐yet unknown combination of lunar albedo protons, neutrons, and gamma rays, and most closely resembles Lunar Prospector maps of gamma rays characteristic of thorium and iron. This result will lead to multiple follow‐up studies of lunar albedo particles and may also contribute to the study of diurnally varying hydrogenation of the lunar regolith.

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Using proton radiation from the moon to search for diurnal variation of regolith hydrogenation

Cited by 10 publications

References 45 publications

Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER

Update on Galactic Cosmic Ray Integral Flux Measurements in Lunar Orbit With CRaTER

Long‐Term Observations of Galactic Cosmic Ray LET Spectra in Lunar Orbit by LRO/CRaTER

Precise Detections of Solar Particle Events and a New View of the Moon

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