"This dataset is being used to make digital elevation and terrain maps that will be a fundamental reference for future scientific and human exploration missions to the moon," said Dr. Gregory Neumann of NASA's Goddard Space Flight Center in Greenbelt, Md. "After about one year taking data, we already have nearly 3 billion data points from the Lunar Orbiter Laser Altimeter on board the LRO spacecraft, with near-uniform longitudinal coverage. We expect to continue to make measurements at this rate through the next two years of the science phase of the mission and beyond. Near the poles, we expect to provide near-GPS-like navigational capability as coverage is denser due to the spacecraft's polar orbit." Neumann will present the map at the American Geophysical Union meeting in San Francisco December 17.
The Lunar Orbiter Laser Altimeter (LOLA) works by propagating a single laser pulse through a Diffractive Optical Element that splits it into five beams. These beams then strike and are backscattered from the lunar surface. From the return pulse, the LOLA electronics determines the time of flight which, accounting for the speed of light, provides a precise measurement of the range from the spacecraft to the lunar surface. Range measurements, combined with accurate tracking of the spacecraft's location, are used to build a map revealing the contours of the lunar landscape. The five beams create a two-dimensional spot pattern that unambiguously reveals slopes. LOLA will also measure the spreading of the return pulse to get the surface roughness and the change in the transmitted compared to the return energy of the pulse to determine surface reflectance.
The new LOLA maps are more accurate and sample more places on the lunar surface than any available before. "The positional errors of image mosaics of the lunar far side, where direct spacecraft tracking – the most accurate -- is unavailable, have been one to ten kilometers (about 0.62 to 6.2 miles)," said Neumann. "We're beating these down to the level of 30 meters (almost 100 feet) or less spatially and one meter (almost 3.3 feet) vertically. At the poles, where illumination rarely provides more than a glimpse of the topography below the crater peaks, we found systematic horizontal errors of hundreds of meters (hundreds of yards) as well." In terms of coverage, the nearly three billion range measurements so far by LRO compare to about eight million to nine million each from three recent international lunar missions, according to Neumann. "They were limited to a mile or so between individual data points, whereas our measurements are spaced about 57 meters (about 187 feet) apart in five adjacent tracks separated by about 15 meters (almost 50 feet)."
"Recent papers have clarified some aspects of lunar processes based solely on the more precise topography provided by the new LOLA maps," adds Neumann, "such as lunar crater density and resurfacing by impacts, or the formation of multi-ring basins."
"The LOLA data also allow us to define the current and historical illumination environment on the moon," said Neumann. Lunar illumination history is important for discovering areas that have been shaded for long periods. Such places, typically in deep craters near the lunar poles, act like cold storage, and are capable of accumulating and preserving volatile material like water ice.
The landscape in polar craters is mysterious because their depths are often in shadow. The new LOLA dataset is illuminating details of their topography for the first time. "Until LRO and the recent Japanese Kaguya mission, we had no idea of what the extremes of polar crater slopes were," said Neumann. "Now, we find slopes of 36 degrees over several kilometers (several thousands of yards) in Shackleton crater, for example, which would make traverses quite difficult and apparently causes landslides. The LOLA measurements of shadowed polar crater slopes and their surface roughness take place at scales from lander size to kilometers. These measurements are helping the LRO science team model the thermal environment of these craters, and team members are developing temperature maps of them."
LRO and LOLA were built and are managed by NASA Goddard. The research was funded by NASA's Exploration Systems Mission Directorate at NASA Headquarters in Washington.
Nancy Neal-Jones | EurekAlert!
NASA finds newly formed tropical storm lan over open waters
17.10.2017 | NASA/Goddard Space Flight Center
The melting ice makes the sea around Greenland less saline
16.10.2017 | Aarhus University
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
17.10.2017 | Life Sciences
17.10.2017 | Life Sciences
17.10.2017 | Earth Sciences