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Lunar Exploration Neutron Detector Evaluation of Potential LCROSS Impact Sites

Lunar Exploration Neutron Detector Evaluation of Potential LCROSS Impact Sites. Igor Mitrofanov Space Research Institute imitrofa@space.ru and Richard Starr The Catholic University of America richard.starr@gsfc.nasa.gov. LEND Team. Lunar Exploration Neutron Detector.

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Lunar Exploration Neutron Detector Evaluation of Potential LCROSS Impact Sites

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  1. Lunar Exploration Neutron Detector Evaluation of Potential LCROSS Impact Sites Igor Mitrofanov Space Research Institute imitrofa@space.ru and Richard Starr The Catholic University of America richard.starr@gsfc.nasa.gov

  2. LEND Team

  3. Lunar Exploration Neutron Detector • LEND is one of six science instruments (plus one tech demo) that make up the science payload on NASA’s Lunar Reconnaissance Orbiter (LRO) mission. • LEND is a contributed instrument of the Federal Space Agency of Russia. • LEND will determine hydrogen distribution in the lunar subsurface to depths of 1-2 meters.

  4. Cosmic Ray Induced Neutron flux

  5. LRO Spaccraft X Z Y CRaTER LAMP Mini-RF ANTENNA LOLA Diviner LROC NAC (2) LEND

  6. Moon Vorb General Description of LEND • Eight 3He counters for detection of thermal and epithermal neutrons. • Four of the 3He counters are collimated with a combination of polyethylene and 10B powder. • Collimated detectors are also surrounded by Cd shields to filter out thermal neutrons with energies below ~0.4 eV so they are primarily sensitive to epithermal neutrons. • One stylbene scintillation spectrometer for detection of fast neutrons.

  7. Epithermal Neutrons • The first global mapping of neutron emission from the Moon was performed in 1998 by the Neutron Spectrometer on NASA’s Lunar Prospector mission. • Epithermal neutron flux decreased in polar regions of the Moon as compared with lower latitudes. • These regions of reduced epithermal flux correspond to floors of craters that are permanently shadowed suggesting water ice as a possible source of the signal. Feldman W.C. et al. (1998) Science281, 1496-1500.

  8. LEND Collimators - 1

  9. LEND Collimators - 2 LEND sensitivity to hydrogen depends on the collimator length and radius of its opening. These two parameters must be optimized without violating mass constraints.

  10. LEND Collimators - 3 Polyethylene collimator 10B powder collimator Scintillation detector 3He counters

  11. LEND Collimators - 4 Total counting rate: 2.1 s-1 Field of view: 5.7° NFOV: 0.9 s-1 Nbgd: 1.2 s-1 Nbgd / NFOV: 1.3 The modeled instrument sensitivity to hydrogen in a polar spot with 10 km diameter is ~70 ppm after 1 year of orbital operations.

  12. LRO Mission Overview Launch: October 31, 2008 Lunar OrbitInsertion Sequence, 4 Maneuvers, 2-4 Days Polar Mapping Phase, 50 km Altitude Circular Orbit, At least 1 Year Minimum Energy Lunar Transfer ~ 4 Days Commissioning Phase, 30 x 216 km Altitude Quasi-Frozen Orbit, Up to 60 Days Nominal End of Mission: February 2010

  13. South Pole Candidate Targets - 1

  14. South Pole Candidate Targets - 2

  15. Shoemaker - 1 LEND sensitivity vs. time for integration over entire are of Shoemaker crater. Bar at 60 days indicates how sensitivity may vary if exposure time increases or decreases by a factor of 2.

  16. Shoemaker - 2 Assumptions in Shoemaker Sensitivity Calculation: • Used the current model of the 50 km circular science orbit. • Used only direct projection criteria for accumulation of exposure time, when nadir direction crosses the target.

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