Lunar Exploration Neutron Detector for NASA’s LRO mission: instrument concept and first data
Abstract
Results from the Lunar Exploration Neutron Detector (LEND) instrument on board the Lunar Reconnaissance Orbiter (LRO) spacecraft will be presented. This instrument can measure both the neutron emission from the lunar surface and the local neutron background in orbit. Since neutron emission from the Moon is strongly affected by the presence of hydrogen in the regolith, analysis of these data will make a significant contribution to the search for possible water bearing regions. The measurement of the lunar neutron flux will also help to determine the lunar neutron radiation environment, which is of great importance in the planning and operation of future human missions to the Moon. To provide neutron data with high spatial resolution, the instrument has four high pressure 3He proportional counters each with a Cd foil cover (CSETN1 - 4) inside four holes of the Module of Collimation (MC). The fifth collimated sensor with stilbene (organic crystal scintillator) measures high energy neutrons (SHEN). It is placed within the central hole of the MC. The collimator is constructed from polyethylene and boron isotope, 10B. The physical design is such that the collimator defines a surface footprint of 10 km diameter (FWHM) for a spacecraft mapping orbit of 50 km. To characterize the neutron environment at the spacecraft in orbit, the LEND also carries four additional 3He detectors external to MC: one sensor of epithermal neutrons (SETN) and three sensors of thermal neutrons (STN 1 - 3). The sensors STN 1 and 2 measure thermal neutrons with velocity vectors parallel and anti-parallel to the LRO flight direction and analysis of these data will be performed using the Doppler filter method for distinguishing the local background of the spacecraft from neutron emission of the Moon. The first mapping data of Moon neutron emission will be presented from observations on the commissioning orbit. Results of neutron measurements will be discussed for the representative sample of about 40 permanently shadowed regions (PSRs) around the south pole with sufficiently large areas of >100 km2. Statistics of these PSRs is enough for testing the signature of enhancement of hydrogen in the regolith of these regions in comparison with illuminated surface around them. LEND data for hydrogen content will be discussed in more details for the site of LCROSS impact in comparison with measurements by another space instruments and Earth-based observatories.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.U22A..03M
- Keywords:
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- 5494 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Instruments and techniques;
- 6250 PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS / Moon