CLPS TO2-AB: NSS (Neutron Spectrometer System)

The Neutron Spectrometer System is an instrument designed to measure the leakage flux of low-energy neutrons out of the lunar soil. A key determinant of leakage flux in the epithermal energy range (>0.5 eV – 500 keV) is abundance of hydrogen-bearing compounds. NSS gauges the fluxes of neutrons in two energy ranges: a) thermal neutrons, less than 0.5 eV, which respond to both abundance and burial depth of hydrogenous materials, and b) epithermal neutrons, which vary in a different way with hydrogen abundance and burial depth from the thermal neutron population. Together, these two measurements constrain not only water-equivalent hydrogen (WEH) abundance but permit a simple model of stratigraphy (burial depth and lower-layer WEH abundance, assuming the overburden is hydrogen-free). Water-equivalent hydrogen is the weight percent of water that a material would contain if all the detected hydrogen was in the form of H2O. For example, a material containing 1500 ppm H would have a water-equivalent hydrogen content of 1.35 wt.%. NSS consists of gas-proportional counter neutron detectors with a design based on the Lunar Prospector Neutron Spectrometer. NSS will measure any temporal variations of at least 0.5 wt.% water-equivalent hydrogen (WEH) at the lander's location. NSS measurements are also used to infer the probable burial depth and WEH wt.% of a buried layer below otherwise desiccated regolith.

Collections in the NSS Archive Bundle

Documentation

See the NSS User Guide for details about this bundle.

Tools

PDS4 Viewer - This standalone tool displays PDS4-labeled images and tables. Available for Windows, Mac, and Linux platforms. Source code and Python library also available.