Instrument Overview
===================
 
A detailed description of the Lunar Prospector Neutron Spectrometer is
given in the article The Lunar Prospector gamma-ray and neutron
spectrometers, W. C. Feldman et al., Nuc. Inst. and Meth. A, 422, 562,
1999 [FELDMANETAL1999A]. For details not found herein, the reader is
referred to this article.
 
The Lunar Prospector Neutron Spectrometer (NS) consists of two
identical 5 cm diameter by 20 cm long helium-3 filled gas proportional
counters.  One counter is covered with a 0.75 mm thick Cd shield, and
is only sensitive to epithermal neutrons having energies above 0.25
eV.  The second counter is covered with a 0.75 mm thick Sn shield and
is sensitive to both thermal and epithermal neutrons.  The difference
in counting rates between the two counters is a measure of the flux of
thermal neutrons with energies between 0 and 0.25 eV.  Fast neutrons
will be measured using the ACS of the Gamma Ray Spectrometer. The NS
has a mass of 3.9 kg and uses about 2.5 w of power [BINDERETAL1998].
 
Science Objectives
==================
 
A major science objective of the Neutron Spectrometer is to search for
the existence of water ice located in permanently shadowed areas near
the lunar poles.  This requires separate measurements of thermal,
epithermal, and fast neutrons from the lunar surface [FELDMANETAL1991].
 
Platform Mounting Descriptions
==============================
 
The NS is mounted on one of the three Lunar Prospector booms. The
Neutron Spectrometer is mounted on a chassis that is shared with the
Alpha Particle Spectrometer.
 
Operational Considerations
==========================
 
Maps of hydrogen near the surface should be possible after 1 month of
observations at the poles and elsewhere after 6 months of data
collection.
 
Operation and Sampling Modes
============================
 
The Neutron Spectrometer is designed to operate continuously during
the Lunar Prospector Primary Mission.
 
Principal Investigator
======================
 
The Co-I and spectrometer group leader for the Lunar Prospector
Neutron Spectrometer experiment is Dr. William Feldman of Los Alamos
National Laboratory.