The MESSENGER Gamma-Ray and Neutron Spectrometer

Goldsten, J.; Rhodes, E. A.; Boynton, W. V.; Feldman, W. C.; Lawrence, D. J.; Trombka, J. I.; Smith, David M.; Evans, L. G.; White, Jack; Madden, N.; Berg, Peter C.; Murphy, G. A.; Gurnee, R. S.; Strohbehn, K.; Williams, Bruce D.; Schaefer, Edward D.; Monaco, Christopher A.; Cork, C.; Eckels, J.D.; Miller, W. Thomas; Burks, M.; Hagler, L.; DeTeresa, Steven J.; Witte, Monika C.

doi:10.1007/s11214-007-9262-7

Cited by 172 publications

(151 citation statements)

References 47 publications

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“…1) consists of three scintillators that are each separately read out with photomultiplier tubes (PMTs) (Goldsten et al, 2007). The center block, a borated plastic (BP) scintillator, is sensitive to epithermal (0.4 eV to 500 keV) and fast neutrons (500 keV to few MeV), and the two planar lithium glass (LG) scintillators are sensitive to thermal (<0.4 eV) and epithermal neutrons.…”

Section: Neutron Spectrometer On the Messenger Spacecraftmentioning

confidence: 99%

“…2). Except for excess counts at low-energy channels that are likely due to planetary gamma-rays, the net counts are well fit by a Gaussian function (dashed blue curve) that is similar in width to pre-launch calibration data (Goldsten et al, 2007). To avoid including any counts from the gamma-ray background in the summed neutron counts, we define the total measured neutron counts in each sensor as the total counts above channel 17.…”

Section: Neutron Spectrometer Data From Three Mercury Flybysmentioning

confidence: 99%

“…We utilize observations by MESSENGER's Neutron Spectrometer (NS), which is part of the Gamma-Ray and Neutron Spectrometer (GRNS) instrument (Goldsten et al, 2007). Neutrons are produced on airless or nearly airless planetary bodies when galactic cosmic rays (GCRs) hit the surface, which occurs when any atmosphere is too thin to absorb the GCRs and the magnetic field is too low in magnitude to deflect them.…”

Section: Introductionmentioning

confidence: 99%

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Identification and measurement of neutron-absorbing elements on Mercury’s surface

Lawrence

Feldman

Goldsten

et al. 2010

Icarus

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Section: Neutron Spectrometer On the Messenger Spacecraftmentioning

confidence: 99%

Section: Neutron Spectrometer Data From Three Mercury Flybysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identification and measurement of neutron-absorbing elements on Mercury’s surface

Lawrence

Feldman

Goldsten

et al. 2010

Icarus

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“…The GRS system consists of two sensors: a high purity germanium (HpGe) gamma‐ray sensor, which was cryocooled and was sensitive to gamma rays from 50 keV to 10 MeV, and a borated plastic ACS to actively reject background charged particles from the germanium detector (Goldsten et al, 2007). The ACS is sensitive to electrons with energies greater than 50 keV up to several hundreds of keV through bremsstrahlung photon production by impact of energetic electrons on the sensor housing and nearby materials (Lawrence et al, 2015).…”

Section: Ee Observationsmentioning

confidence: 99%

“…Because the sensor area of these instruments was significantly larger than that of the EPS (Goldsten et al, 2007), the NS, GRS, and XRS were over an order of magnitude more sensitive than the EPS for detecting energetic electrons. For the GRS, both the main Ge gamma‐ray sensor and the scintillator anticoincidence shield (ACS) were sensitive to EE events.…”

Section: Introductionmentioning

confidence: 99%

Statistical Study of Mercury's Energetic Electron Events as Observed by the Gamma‐Ray and Neutron Spectrometer Instrument Onboard MESSENGER

et al. 2018

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We present results from a statistical analysis of Mercury's energetic electron (EE) events as observed by the gamma‐ray and neutron spectrometer instrument onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. The main objective of this study is to investigate possible anisotropic behavior of EE events using multiple data sets from MESSENGER instruments. We study the data from the neutron spectrometer (NS) and the gamma‐ray spectrometer anticoincidence shield (ACS) because they use the same type of borated plastic scintillator and, hence, they have very similar response functions, and their large surface areas make them more sensitive to low‐intensity EE events than MESSENGER's particle instrumentation. The combined analysis of NS and ACS data reveals two different classes of energetic electrons: “Standard” events and “ACS‐enhanced” events. Standard events, which comprise over 90% of all events, have signal sizes that are the same in both the ACS and NS. They are likely gyrating particles about Mercury's magnetic field following a 90° pitch angle distribution and are located in well‐defined latitude and altitude regions within Mercury's magnetosphere. ACS‐enhanced events, which comprise less than 10% of all events, have signal sizes in the ACS that are 10 to 100 times larger than those observed by the NS. They follow a beam‐like distribution and are observed both inside and outside Mercury's magnetosphere with a wider range of latitudes and altitudes than Standard events. The difference between the Standard and ACS‐enhanced event characteristics suggests distinct underyling acceleration mechanisms.

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Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

et al. 2014

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[1] Data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) Neutron Spectrometer (NS) have been used to identify energetic neutrons (0.5-8 MeV energy) associated with solar events that occurred on 4 June 2011. Multiple lines of evidence, including measurements from the NS and the MESSENGER Gamma-Ray Spectrometer, indicate that the detected neutrons have a solar origin. This evidence includes a lack of time-coincident, energetic (>45 MeV) charged particles that could otherwise create local neutrons from nearby spacecraft material and a lack of proton-induced gamma rays that should be seen if energetic protons were present. NS data cannot rule out the presence of lower-energy ions (<30 MeV) that can produce local neutrons. However, the ion spectral shape required to produce the measured neutron count rate locally is softer than any known ion spectral shape. The neutron energy spectrum shows a relative enhancement in the energy range 0.8-3 MeV compared with cosmic-ray-generated neutrons from the spacecraft or Mercury. The spectral shape of the measured neutron fluence spectrum is consistent with a previously modeled fluence spectrum of neutrons that originate at the Sun and are propagated through the MESSENGER spacecraft to the NS. These measurements provide strong evidence for a solar origin of the detected neutrons and suggest that a large number of low-energy threshold ion evaporation reactions were taking place on the Sun during the neutron event.

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The MESSENGER Gamma-Ray and Neutron Spectrometer

Cited by 172 publications

References 47 publications

Identification and measurement of neutron-absorbing elements on Mercury’s surface

Identification and measurement of neutron-absorbing elements on Mercury’s surface

Statistical Study of Mercury's Energetic Electron Events as Observed by the Gamma‐Ray and Neutron Spectrometer Instrument Onboard MESSENGER

Detection and characterization of 0.5–8 MeV neutrons near Mercury: Evidence for a solar origin

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