lro/lend lend 1 lcross site selection workshop october 16 th 2006 lunar exploration neutron detector...
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LRO/LENDLEND 1
LCROSS Site Selection WorkshopOctober 16th 2006
Lunar Exploration Neutron Detector Evaluation of Potential LCROSS Impact Sites
Igor MitrofanovSpace Research Institute
Richard StarrThe Catholic University of America
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Igor Mitrofanov PI Russian Institute for Space Research
William Boynton CoI University of Arizona
Larry Evans CoI Computer Science Corporation
Alexandr Kozyrev CoI Russian Institute for Space Research
Maxim Litvak CoI Russian Institute for Space Research
Roald Sagdeev CoI University of Maryland
Anton Sanin CoI Russian Institute for Space Research
Vladislav Shevchenko CoI Sternberg Astronomical Institute
Valery Shvetsov CoI Joint Institute for Nuclear Research
Richard Starr CoI Catholic University
Vlad Tret’yakov CoI Russian Institute for Space Research
Jacob Trombka CoI NASA Goddard Space Flight center
LEND Team
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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.
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Cosmic Ray Induced Neutron flux
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LRO Spaccraft
LOLA
LEND
Mini-RF ANTENNA
LROC NAC (2)
LAMP
CRaTER
Diviner
X
ZY
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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.
Moon
Vorb
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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) Science 281, 1496-1500.
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LEND Collimators - 1
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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.
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LEND Collimators - 3
Polyethylenecollimator
10B powder collimator
3Hecounters
Scintillationdetector
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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.
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MinimumEnergyLunarTransfer~ 4 Days
LunarOrbitInsertionSequence,4 Maneuvers,2-4 Days
Commissioning Phase,
30 x 216 km Altitude
Quasi-Frozen Orbit,
Up to 60 Days
PolarMapping
Phase,50 km AltitudeCircular Orbit,At least 1 Year
Launch: October 31, 2008
Nominal End of Mission: February 2010
LRO Mission Overview
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South Pole Candidate Targets - 1
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South Pole Candidate Targets - 2
# Latitude LongitudeΔS, km2
Nameof crater
Detection limit (3σ) of hydrogen for LEND (in ppm)
Average content of hydrogen from
LP (in ppm)
12 -89.9 111.1 380 Shackleton 30.9 145
10 -88.5 220 400 - 75.8 136
4 -87.6 38 575 Shoemaker 80.1 154
6 -86.8 75.8 257 Faustini 141.3 159
8 -87.4 260.2 183 - 151.5 117
3 -84.4 54.8 140 Nobile 264.5 114
1 -83.7 84.7 140 Amundsen 282.3 107
5 -87.4 12.5 116 - 284.8 88
11 -85.2 48.1 99 - 294.4 136
2 -84.7 323 100 Cabeus 309.4 142
9 -85.1 184.5 58 - 403.7 86
7 -83.5 164.5 70 Vichert 426.4 131
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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.
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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.