urn:nasa:pds:context:instrument:ns.mess 1.1 1.10.1.0 Product_Context 2016-10-01 1.0 extracted metadata from PDS3 catalog and modified to comply with PDS4 Information Model 2018-06-05 1.1 Minor updates to support PDS3 to PDS4 migrations. Added DOI for reference, removed optional attributes with N/A as values, added intstrument subtype, and did minor edits to the description field. urn:nasa:pds:context:instrument_host:spacecraft.mess instrument_to_instrument_host https://doi.org/10.1007/s11214-007-9262-7 Goldsten, J.O., E.A. Rhodes,, W.V. Boynton, W.C. Feldman, D.J. Lawrence, J.I. Trombka, D.M. Smith, L.G. Evans, J. White, N.W. Madden, P.C. Berg, G.A. Murphy, R.S. Gurnee, K. Strohbehn, B.D. Williams, E.D. Schaefer, C.A. Monaco, C.P. Cork, J.D. Eckels, W.O. Miller, M.T. Burks, L.B. Hagler, S.J. Deteresa, and M.C. Witte, The MESSENGER Gamma-Ray and Neutron Spectrometer, Space Science Reviews, 131, 339-391, 2007. Neutron Spectrometer Spectrometer Neutron Spectrometer The Neutron Spectrometer (NS) instrument formed part of the geochemistry investigation of the MESSENGER mission and yielded information about the elemental composition of the planet's surface. NS measured the flux of ejected neutrons in three energy ranges and was particularly sensitive to the H content of a body. Neutron measurements were used to infer the composition of Mercury's surface over localized regions using established techniques, such as used recently on the Lunar Prospector and Mars Odyssey missions. The NS sensor consisted of three scintillators, each wrapped separately and coupled to separate photo-multiplier tubes. The three scintillators were sensitive to neutrons of different energies: thermal neutrons (0.025 - 1 eV), epithermal neutrons (1 eV - 500 keV), and fast neutrons (500 keV - 7 MeV). The first and third scintillators were lithium (6Li)-glass scintillators (LG1 and LG2) that respond to a combination of thermal and epithermal neutrons. The middle scintillator was a borated plastic (BP) scintillator that responded only to epithermal and fast neutrons due to its electronics setup. The interaction of galactic cosmic rays (GCR) with the surface of Mercury produces neutrons, some of which escape the surface and produce a neutron signal that can be measured by the orbiting NS sensor. The measured neutron energy spectrum reflects the transport properties of the surface composition and is sensitive to depths down to about 1 m. Thermal neutrons are sensitive to a variety of elements, including Fe, Ti, Gd, Sm, Cl, and C. Epithermal neutrons are mostly sensitive to H abundance. Fast neutrons can provide a good measure of average atomic mass. For the MESSENGER mission, the NS sensor mapped the abundance of H over most of the northern hemisphere of Mercury, providing significant new information regarding the potential presence of water ice within and near permanently shaded craters near the north pole.