ASU team releases high-resolution global topographic map of Moon


November 16, 2011

The Arizona State University team that oversees the imaging system on board NASA’s Lunar Reconnaissance Orbiter (LRO) has released the highest resolution near-global topographic map of the Moon ever created. This new topographic map shows the surface shape and features nearly the entire Moon with a pixel scale close to 100 meters (328 feet). A single measure of elevation (one pixel) is about the size of two football fields placed side-by-side. At this scale explorers can accurately investigate kilometer-scale and larger craters, volcanoes and mountains.

Although the Moon is our closest neighbor, knowledge of its morphology is still limited. Due to instrumental limitations of previous missions, a global map of the Moon’s topography at high resolution has not existed until now. With the LRO Wide Angle Camera (WAC) stereo imaging and the Lunar Orbiter Laser Altimeter (LOLA) scientists can now accurately portray the shape of the entire Moon at high resolution. Color Shaded Relief Download Full Image

“Our new topographic view of the Moon provides the dataset that lunar scientists have waited for since the Apollo era,” said Mark Robinson, principal investigator of the Lunar Reconnaissance Orbiter Camera (LROC). “We can now determine slopes of all major geologic terrains on the Moon at 100 meter scale. Determine how the crust has deformed, better understand impact crater mechanics, investigate the nature of volcanic features, and better plan future robotic and human missions to the Moon.”

Called the Global Lunar DTM 100 m topographic model (GLD100), this map was created based on data acquired by LRO’s WAC, which is part of the LROC imaging system. The LROC imaging system consists of two Narrow Angle Cameras (NACs) to provide high-resolution images, and the WAC to provide 100-meter resolution images in seven color bands over a 57-kilometer (35-mile) swath.

The WAC is a relatively small instrument, easily fitting into the palm of one’s hand; however, despite its diminutive size it maps nearly the entire Moon every month. Each month the Moon's lighting has changed so the WAC is continuously building up a record of how different rocks reflect light under different conditions, and adding to the LROC library of stereo observations.

The LROC (WAC) has a pixel scale of about 75 meters (246 feet), and at the average altitude of 50 km (31 miles) a WAC image swath is 70 km (43 miles) wide across the ground-track. Since the equatorial distance between orbits is about 30 km (18 miles) there is complete overlap all the way around the Moon in one month. The orbit-to-orbit WAC overlap provides a strong stereo effect. Using digital photogrammetric techniques, a terrain model can be computed from the stereo overlap.

The near-global topographic map was constructed from 69,000 WAC stereo models and covers the latitude range 79°S to 79°N, 98.2 percent of the entire lunar surface. Due to persistent shadows near the poles it is not possible to create a complete stereo based map at the highest latitudes. However, another instrument onboard LRO called LOLA excels at mapping topography at the poles. Since LOLA ranges to the surface with its own lasers, and the LRO orbits converge at the poles, a very high resolution topographic model is possible, and can be used to fill in the WAC “hole at the pole.” The WAC topography was produced by LROC team members at the German Aerospace Center.

“Collecting the data and creating the new topographic map was a huge collaborative effort between the LRO project, the LOLA team, the LROC team at ASU and in Germany at the DLR,” Robinson said. “I could not be more pleased with the quality of the map – it’s phenomenal! The richness of detail should inspire lunar geologists around the world for years to come.”

Shaded relief images can be created from the GLD100 by illuminating the “surface” (in this case the shape model) from a given Sun direction and elevation above the horizon. To convey an absolute sense of height the resulting grayscale pixels are painted with colors that represent the altitude. Visualizations like these allow scientists to view the surface from very different perspectives, providing a powerful tool for interpreting the geologic processes that have shaped the Moon.

Future versions
The current model incorporates the first year of stereo imaging; there is another year of data that can be added to the solution. These additional stereo images will not only improve the sharpness (resolution) of the model but also fill in very small gaps that exist in the current map. Also the LROC team has made small improvements to the camera distortion model and the LOLA team has improved our knowledge of the spacecraft position over time. These next generation steps will further improve the accuracy of the next version of the LROC GLD100 topographic model of the Moon.

Nikki Cassis

marketing and communications director, School of Earth and Space Exploration

Sun Devils fall to Pepperdine despite late push


November 16, 2011

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After battling back in the final minutes of the game, the Arizona State men's basketball team fell to Pepperdine 66-60 Tuesday night at Wells Fargo Arena despite a big game by junior guard Trent Lockett.

It did not take long for the Waves to find their groove as they hit their first six shots from the field and never relinquished the lead after taking it with 16:35 left in the first half. The lead extended to 12 points behind 4-4 three-point shooting and 7-13 shooting from the field.

Pepperdine scored 10 points off of Sun Devil turnovers in the first half. Lockett poured in 23 points, 17 of which came in the second half. He was 8-11 from the field and 2-4 from beyond the arc, also pulling down nine rebounds.

Pepperdine feasted off of consistency, with Joshua Lowery being the only player in double-digits. Eight other players scored five or more points, and their bench produced 27 points.

The Sun Devils struggled from three-point range, making only seven of their 27 attempts, while the Waves made eight of their 11 tries. ASU was 17-23 from the foul line while Pepperdine was 22-31, 25 of those attempts coming in the second half.

Arizona State will hope to get back in the win column Friday night as they host New Mexico night at 6:30 p.m. for James Harden Beard Night.

More to come...