Searching for Cold Trapped Resources in the Lunar RegolithSearching for Cold Trapped Resources in the Lunar RegolithN L S ILunar Polar

Science & ExplorationSearching for Cold Trapped Resources in the Lunar Regolith

J. Andrew McGovern1, D. Benjamin J. Bussey1, Benjamin T. Greenhagen2, David A. Paige3, and Joshua T.S. Cahill1

1Johns Hopkins University Applied Physics Lab, Laurel, MD, USA Johns Hopkins University Applied Physics Lab, Laurel, MD, USA 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

3University of California, Los Angeles, CA, USA

North1 Introduction 4 Performance ComparisonNorth1 Introduction 4 Performance Comparison� Finding in-situ resources on the Moon has the potential to make future exploration

North� Essentially identical ray tracing algorithms were implemented in Java, C++, and using � Finding in-situ resources on the Moon has the potential to make future exploration

much less expensive and drastically improve sustainability.

� The angle between the Moon’s spin axis and the normal to the ecliptic plane has been

� Essentially identical ray tracing algorithms were implemented in Java, C++, and using

CUDA.

� The Java and C++ host code was run on a quad-core Intel I7 processor. The CUDA code � The angle between the Moon’s spin axis and the normal to the ecliptic plane has been

less than 1.6o for millions of years.

� This results in permanently low Sun elevation angles at the lunar poles; and many polar

crater interiors are in perpetual shadow.

� The Java and C++ host code was run on a quad-core Intel I7 processor. The CUDA code

was executed on an NVidia Quadro 6000, Quadro 4000, and also on a GeForce GTX

560Ti.

� The speed improvements of the GPU make this kind of analysis practical on a desktop crater interiors are in perpetual shadow.

� Surfaces in permanent shadow are much colder than occasionally sunlit surfaces on

the Moon. Some permanent shadows are the right temperature to cold-trap volatiles.

� The speed improvements of the GPU make this kind of analysis practical on a desktop

workstation. Without a GPU only low resolution analysis in limited regions is practical

on a desktop workstation. In other words the GPU enables a capability with the Moon. Some permanent shadows are the right temperature to cold-trap volatiles.

� We wanted to know where all the permanent shadows were located, which ones were

good cold traps, and what it might take to explore these regions.

on a desktop workstation. In other words the GPU enables a capability with

tremendous savings to our project.

500Figure 7. Runtime (in seconds) on several

devices plotted for several DTM image good cold traps, and what it might take to explore these regions.

� Recently released science data products from the instruments on the Lunar

Reconnaissance Orbiter (LRO) provide accurate global digital terrain models (DTM) at

100 meters per pixel. We used the Lunar Orbiter Laser Altimeter (LOLA), the Lunar

350

400

450devices plotted for several DTM image

dimensions that were used in our analysis.

Like other images the number of pixels

increases as the square of the image

Reconnaissance Orbiter (LRO) provide accurate global digital terrain models (DTM) at

100 meters per pixel. We used the Lunar Orbiter Laser Altimeter (LOLA), the Lunar

Orbiter Reconnaissance Camera (LROC), and the Diviner mid-infrared sensor.

� The Diviner instrument collects surface brightness temperature readings in day and 150

200

250

300

Quad-Core CPU

GTX 560Ti

Quadro 6000

increases as the square of the image

dimension. The GTX 560Ti does not have

enough memory to store DTMs greater than

7760x7760. The Quadro 6000 is roughly 70 � The Diviner instrument collects surface brightness temperature readings in day and

night using a mid-infrared detector. Diviner data validates our permanent shadow

findings.0

50

100

1507760x7760. The Quadro 6000 is roughly 70

times faster than the CPU for simulating

illumination on large DTMs. We used an Intel

Core I7 CPU running at 2.67 GHz with 3 GB of findings.

0

3500 5500 7500 9500 11500 13500 15500Core I7 CPU running at 2.67 GHz with 3 GB of

memory.

2 Methods 5 Future Work2 Methods 5 Future Work� We simulated the Sun at 1440 longitudes (1/4o increments) around each pole, holding � Future implementations may query the laser shot data directly to improve � We simulated the Sun at 1440 longitudes (1/4o increments) around each pole, holding

the Sun at the closest sub-solar latitude at all longitudes.

� The idea is that over billions of years the Sun will eventually reach the “best”

� Future implementations may query the laser shot data directly to improve

accuracy and resolution; currently we pull surface radius values from a model

derived from shot data.� The idea is that over billions of years the Sun will eventually reach the “best”

illumination (i.e. closest sub-solar latitude) position at all longitudes.

� We ran an extended source ray tracing algorithm at each simulated Sun position over

the best available digital elevation models for the lunar surface.

Figure 5. Polar stereographic shaded relief rendering of the north polar topography (65o to 90o N) with

permanent shadows in red. The color scale maps color to surface radius values in kilometers.

derived from shot data.

� There is a wealth of science data coming from the instruments on board the

Lunar Reconnaissance Orbiter. Folding data from other instruments into our

analysis is a priority.the best available digital elevation models for the lunar surface.

� Model pixels unable to see even a small portion of the Sun in any of the simulations

were presumed to be in permanent shadow.

analysis is a priority.

� Apply Diviner radiometer data to more many more craters across the full

range of latitudes.Surface

were presumed to be in permanent shadow. range of latitudes.

� Currently we model the Sun as an extended source in the plane of the terrain

path. Modeling the full disk of the Sun in two dimensions would make our

SunFigure 1. Depiction of the basic ray tracing procedure

used to simulate a Sun position applied to a single

terrain path. The digital terrain model is first split into

path. Modeling the full disk of the Sun in two dimensions would make our

simulations more accurate.

� Add a camera model to simulate photorealistic science images for mission

concepts.

lit

lit

not lit

terrain path. The digital terrain model is first split into

separate terrain paths then each terrain path can be ray

traced independently in a separate computing core on

the GPU.

concepts.

Moon Centerlit

lit

not lit

not lit

surface points

the GPU.

3 Science Results 6 References

lit surface points

projected rays

3 Science Results 6 References� Arnold, J. R. (1979), Ice in the lunar polar regions, Journal of Geophysical Research, 84(B10), 5659-5668.

� Bussey, D. B. J., P. G. Lucey, D. Steutel, M. S. Robinson, P. D. Spudis, and K. D. Edwards (2003), Permanent shadow in simple craters near the

lunar poles (vol 30, pg 1278, 2003), Geophys Res Lett, 30(9), -.

� There are hundreds of permanent shadows north of 58o

N (Fig. 5) and south of 58o S (Fig. 6).

� Non-polar cold traps raise the possibility of greater lunar poles (vol 30, pg 1278, 2003), Geophys Res Lett, 30(9), -.

� Bussey, D. B. J., J. A. McGovern, P. D. Spudis, C. D. Neish, H. Noda, Y. Ishihara, and S. A. Sorensen (2010), Illumination conditions of the south pole of the

Moon derived using Kaguya topography, Icarus, 208(2), 558-564.

� Non-polar cold traps raise the possibility of greater

availability of lunar resources and could potentially

make it easier to live off the land.� Colaprete, A., et al. (2010), Detection of water within the LCROSS ejecta plume, Science, 330, 463-468.

� Feldman, W. C., et al. (2001), Evidence for water ice near the lunar poles, Journal of Geophysical Research-Planets, 106(E10), 23231-23251.Figure 3. A three-dimensional rendering from LOLA

make it easier to live off the land.

� Mazarico, E., G. A. Neumann, D. E. Smith, M. T. Zuber, and M. H. Torrance (2010), Illumination Conditions of the Lunar Polar Regions Using LOLA

Topography, Icarus, doi: 10.1016/j.icarus.2010.10.030.

� Paige, D. A., and e. al (2010), The Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment, Space Science Reviews, 150(1-4), 125-160.

Figure 3. A three-dimensional rendering from LOLA

topography of Dugan J crater. This is an example of a

non-polar permanent shadow (in red) on the north

facing interior crater wall (61.35N, 107.88E).

� Paige, D. A., et al. (2010), Diviner Lunar Radiometer Observations of Cold Traps in the Moon's south polar region, Science, 330, 479-482.

� Robinson, M. S., et al. (2010), Lunar Reconnaissance Orbiter Camera (LROC) Instrument Overview, Space Science Reviews, 150, 81-124.350

facing interior crater wall (61.35N, 107.88E).

� Scholten, F. (2011), GLD100 - Lunar topography from LROC WAC stereo, paper presented at EPSC-DPS Joint Meeting, Nantes, France, October 2-7.

� Siegler, M. A., B. G. Bills, and D. A. Paige (2011), Effects of orbital evolution on lunar ice stability, Journal of Geophysical Research-Planets, 116(E03010),

doi: 10.1029/2010JE003652.200

250

300

Figure 4. Diurnal surface temperature variation for a

point in permanent shadow (blue) compared to a

Southdoi: 10.1029/2010JE003652.

� Smith, D. E., and e. al (2010), The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission, Space Science Reviews,

150(1-4), 209-241.

� Spudis, P. D. (1996), The once and future Moon, 308 pp., Smithsonian Institution Press, Washington, D.C.

100

150

200point in permanent shadow (blue) compared to a

nearby illuminated point (red). The mid-day

temperatures for the shadowed point are 100 to 120 K

less than the comparison point with normal diurnal South� Spudis, P. D. (1996), The once and future Moon, 308 pp., Smithsonian Institution Press, Washington, D.C.

� Watson, K., B. C. Murray, and H. Brown (1961), The behavior of volatiles on the lunar surface, Journal of Geophysical Research, 66(9), 3033-3045.Figure 6. Polar stereographic shaded relief rendering of the south polar topography (65o to 90o S) with

permanent shadows in red.

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0 3 6 9 12 15 18 21 24

less than the comparison point with normal diurnal

illumination pattern. This data was supplied by the

Diviner instrument team.

Southpermanent shadows in red.

Lunar Local Time