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J.w. Head - One of the best experts on this subject based on the ideXlab platform.
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new evidence for surface water ice in small scale cold traps and in three large craters at the north polar region of mercury from the mercury Laser Altimeter
Geophysical Research Letters, 2017Co-Authors: Ariel N Deutsch, Gregory A Neumann, J.w. HeadAbstract:The Mercury Laser Altimeter (MLA) measured surface reflectance, rs, at 1064 nm. On Mercury, most water-ice deposits have anomalously low rs values indicative of an insulating layer beneath which ice is buried. Previous detections of surface water ice (without an insulating layer) were limited to seven possible craters. Here we map rs in three additional permanently shadowed craters that host radar-bright deposits. Each crater has a mean rs value > 0.3, suggesting that water ice is exposed at the surface without an overlying insulating layer. We also identify small-scale cold traps ( 0.3 and permanent shadows have biannual maximum surface temperatures < 100 K. We suggest that a substantial amount of Mercury's water ice is not confined to large craters, but exists within micro-cold traps, within rough patches and inter-crater terrain.
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summary of the results from the lunar orbiter Laser Altimeter after seven years in lunar orbit
Icarus, 2017Co-Authors: D. E. Smith, Erwan Mazarico, M S Robinson, F G Lemoine, J.w. Head, Paul G Lucey, O Aharonson, Xiaoli SunAbstract:In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.
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the steepest slopes on the moon from lunar orbiter Laser Altimeter lola data spatial distribution and correlation with geologic features
Icarus, 2016Co-Authors: M A Kreslavsky, J.w. HeadAbstract:Abstract We calculated topographic gradients over the surface of the Moon at a 25 m baseline using data obtained by the Lunar Orbiter Laser Altimeter (LOLA) instrument onboard the Lunar Reconnaissance Orbiter (LRO) spacecraft. The relative spatial distribution of steep slopes can be reliably obtained, although some technical characteristics of the LOLA dataset preclude statistical studies of slope orientation. The derived slope-frequency distribution revealed a steep rollover for slopes close to the angle of repose. Slopes significantly steeper than the angle of repose are almost absent on the Moon due to (1) the general absence of cohesion/strength of the fractured and fragmented megaregolith of the lunar highlands, and (2) the absence of geological processes producing steep-slopes in the recent geological past. The majority of slopes steeper than 32°–35° are associated with relatively young large impact craters. We demonstrate that these impact craters progressively lose their steepest slopes. We also found that features of Early Imbrian and older ages have almost no slopes steeper than 35°. We interpret this to be due to removal of all steep slopes by the latest basin-forming impact (Orientale), probably by global seismic shaking. The global spatial distribution of the steepest slopes correlates moderately well with the predicted spatial distribution of impact rate; however, a significant paucity of steep slopes in the southern farside remains unexplained.
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the transition from complex craters to multi ring basins on the moon quantitative geometric properties from lunar reconnaissance orbiter lunar orbiter Laser Altimeter lola data
Journal of Geophysical Research, 2012Co-Authors: David M H Baker, J.w. HeadAbstract:United States. National Aeronautics and Space Administration (NASA Lunar Reconnaissance Orbiter Lunar Orbiter Laser Altimeter (LOLA) experiment (NNX09AM54G)
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Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment
2012Co-Authors: Caleb I Fassett, Erwan Mazarico, D. E. Smith, J.w. Head, Seth J Kadish, G. A. Neumann, M. T. ZuberAbstract:New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.
S B Luthcke - One of the best experts on this subject based on the ideXlab platform.
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the transmitter pointing determination in the geoscience Laser Altimeter system
Geophysical Research Letters, 2005Co-Authors: Marcos J Sirota, Sungkoo Bae, Pamela S Millar, David Mostofi, Charles E Webb, Bob E Schutz, S B LuthckeAbstract:[1] The determination of accurate elevation data using Laser altimetry relies on accurate knowledge of the instrument pointing angle. The Geoscience Laser Altimeter System (GLAS) on the Ice, Cloud and land Elevation Satellite (ICESat) uses a novel system for determination of the Laser pointing vector. In this paper we describe this system, as well as the method used to process its data, which are required to meet ICESat's science objectives. We discuss the necessary modifications to processing techniques, implemented to optimize accuracy for the various operating conditions. Results to date are compared to calibration/validation data to assess their accuracy. We show that the stated requirements have been met for near nominal operating conditions.
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enhanced geolocation of spaceborne Laser Altimeter surface returns parameter calibration from the simultaneous reduction of Altimeter range and navigation tracking data
Journal of Geodynamics, 2002Co-Authors: S B Luthcke, C C Carabajal, D D RowlandsAbstract:Abstract The accurate geolocation of a Laser Altimeter’s surface return, the spot from which the Laser energy reflects on the Earth’s surface, is a critical issue in the scientific application of these data. Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate these data. Detailed Laser Altimeter measurement models have been developed and implemented within precision orbit determination software providing the capability to simultaneously estimate the orbit and geolocation parameters from a combined reduction of Altimeter range and spacecraft tracking data. In preparation for NASA’s future dedicated Earth observing spaceborne Laser Altimeter missions, the Vegetation Canopy Lidar (VCL) and the Ice, Cloud and land Elevation Satellite (ICESat), data from two Shuttle Laser Altimeter (SLA) missions have been reprocessed to test and refine these algorithms and to develop the analysis methodologies for the production and verification of enhanced geolocation products. Both direct altimetry and dynamic crossover data have been reduced in combination with navigation tracking data to obtain significant improvement in SLA geolocation accuracy. Residual and overlap precision tests indicate a factor of two improvement over the previously released SLA Standard Data Products, showing 40-m RMS horizontal and 26-cm RMS elevation geolocation precision for the long SLA-01 arcs. Accuracy estimates by comparing SLA profiles to Digital Elevation Models show horizontal positioning accuracy at the 60-m (1σ) level. Vertical accuracies, on the order of 1 m (1σ) for low slope surfaces are now dominated by the ±75-cm one-way range resolution of the instrument. Comparable relative improvements are also observed in the analysis of the SLA-02 data. The analyses show that complex temporal variations in parameters (i.e., pointing) can be recovered and not just simple biases. The methodology and results obtained from the detailed analysis are discussed in this paper, along with their applicability to VCL and ICESat.
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enhanced geolocation of spaceborne Laser Altimeter surface returns parameter calibration from the simultaneous reduction of Altimeter range and navigation tracking data
Journal of Geodynamics, 2002Co-Authors: S B Luthcke, C C Carabajal, David D RowlandsAbstract:Abstract The accurate geolocation of a Laser Altimeter’s surface return, the spot from which the Laser energy reflects on the Earth’s surface, is a critical issue in the scientific application of these data. Pointing, ranging, timing and orbit errors must be compensated to accurately geolocate these data. Detailed Laser Altimeter measurement models have been developed and implemented within precision orbit determination software providing the capability to simultaneously estimate the orbit and geolocation parameters from a combined reduction of Altimeter range and spacecraft tracking data. In preparation for NASA’s future dedicated Earth observing spaceborne Laser Altimeter missions, the Vegetation Canopy Lidar (VCL) and the Ice, Cloud and land Elevation Satellite (ICESat), data from two Shuttle Laser Altimeter (SLA) missions have been reprocessed to test and refine these algorithms and to develop the analysis methodologies for the production and verification of enhanced geolocation products. Both direct altimetry and dynamic crossover data have been reduced in combination with navigation tracking data to obtain significant improvement in SLA geolocation accuracy. Residual and overlap precision tests indicate a factor of two improvement over the previously released SLA Standard Data Products, showing 40-m RMS horizontal and 26-cm RMS elevation geolocation precision for the long SLA-01 arcs. Accuracy estimates by comparing SLA profiles to Digital Elevation Models show horizontal positioning accuracy at the 60-m (1σ) level. Vertical accuracies, on the order of 1 m (1σ) for low slope surfaces are now dominated by the ±75-cm one-way range resolution of the instrument. Comparable relative improvements are also observed in the analysis of the SLA-02 data. The analyses show that complex temporal variations in parameters (i.e., pointing) can be recovered and not just simple biases. The methodology and results obtained from the detailed analysis are discussed in this paper, along with their applicability to VCL and ICESat.
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improvements in spaceborne Laser Altimeter data geolocation
Surveys in Geophysics, 2001Co-Authors: S B Luthcke, C C Carabajal, D D Rowlands, D E PavlisAbstract:For many science applications of Laser altimetry, the preciselocation of the point on the Earth's surface from which the Laser energy reflects is required.The Laser surface return geolocation is computed from the Laser Altimeter's range observation in combinationwith precise knowledge of spacecraft position, instrument tracking points referenced to thespacecraft center of mass, spacecraft attitude, Laser orientation, observation and attitude data timetags. An approach that simultaneously estimates the geometric and dynamic parameters of the orbit andLaser range measurement model by a combined reduction of both spacecraft tracking and LaserAltimeter surface range residuals is applied to produce improved pointing, orbit and range bias solutionsand therefore improved geolocation. The data acquired by the Shuttle Laser Altimeter (SLA)-01 and 02missions constitute a valuable pathfinder data set to test algorithms in preparation for the upcoming VCL(Vegetation Canopy Lidar) and ICESat (Ice, Cloud and Elevation Satellite) missions. Results from apreliminary SLA-01 data analysis are presented along with a brief description of the methodology and itsapplication to future spaceborne missions.
Xiaoli Sun - One of the best experts on this subject based on the ideXlab platform.
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summary of the results from the lunar orbiter Laser Altimeter after seven years in lunar orbit
Icarus, 2017Co-Authors: D. E. Smith, Erwan Mazarico, M S Robinson, F G Lemoine, J.w. Head, Paul G Lucey, O Aharonson, Xiaoli SunAbstract:In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.
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calibration of the mercury Laser Altimeter on the messenger spacecraft
IEEE Transactions on Geoscience and Remote Sensing, 2015Co-Authors: Xiaoli SunAbstract:This paper gives a detailed description of the prelaunch and in-orbit calibrations of the Mercury Laser Altimeter (MLA) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, which was launched on August 3, 2004 and has been operating in orbit about Mercury since March 2011. A brief summary of the MLA instrument is given, followed by the instrument measurement model and calibration formulas. The prelaunch tests used to determine the values of various calibration coefficients are described. The boresight alignment parameters were verified and recalibrated by special tests, with the MESSENGER spacecraft en route to Mercury. The MLA instrument model and the calibration methods were largely derived from airborne and spaceborne lidar for Earth science observation at the NASA Goddard Space Flight Center and will benefit future space lidar developments for Earth and space science.
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the mercury Laser Altimeter instrument for the messenger mission
Space Science Reviews, 2007Co-Authors: John F. Cavanaugh, Jan F. Mcgarry, Luis Ramosizquierdo, Xiaoli Sun, Danny J Krebs, Annemarie Novogradac, James C Smith, A E Bartels, Raymond Trunzo, Jamie BrittAbstract:The Mercury Laser Altimeter (MLA) is one of the payload science instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, which launched on August 3, 2004. The Altimeter will measure the round-trip time of flight of transmitted Laser pulses reflected from the surface of the planet that, in combination with the spacecraft orbit position and pointing data, gives a high-precision measurement of surface topography referenced to Mercury’s center of mass. MLA will sample the planet’s surface to within a 1-m range error when the line-of-sight range to Mercury is less than 1,200 km under spacecraft nadir pointing or the slant range is less than 800 km. The Altimeter measurements will be used to determine the planet’s forced physical librations by tracking the motion of large-scale topographic features as a function of time. MLA’s Laser pulse energy monitor and the echo pulse energy estimate will provide an active measurement of the surface reflectivity at 1,064 nm. This paper describes the instrument design, prelaunch testing, calibration, and results of postlaunch testing.
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Laser ranging between the mercury Laser Altimeter and an earth based Laser satellite tracking station over a 24 million km distance
Frontiers in Optics, 2005Co-Authors: Xiaoli Sun, Jan F. Mcgarry, John F. Cavanaugh, Thomas W Zagwodzki, John J Degnan, Barry D Coyle, David R Skillman, David E SmithAbstract:Using the Mercury Laser Altimeter, a 10-cm Laser ranging precision was demonstrated between Earth and the MESSENGER spacecraft over a 24-million-km distance in space.
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mars orbiter Laser Altimeter receiver model and performance analysis
Applied Optics, 2000Co-Authors: James B. Abshire, Xiaoli Sun, Robert S AfzalAbstract:The design, calibration, and performance of the Mars Orbiter Laser Altimeter (MOLA) receiver are described. The MOLA measurements include the range to the surface, which is determined by the Laser-pulse time of flight; the height variability within the footprint determined by the Laser echo pulse width; and the apparent surface reflectivity determined by the ratio of the echo to transmitted pulse energies.
Kelly M Brunt - One of the best experts on this subject based on the ideXlab platform.
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land ice height retrieval algorithm for nasa s icesat 2 photon counting Laser Altimeter
Remote Sensing of Environment, 2019Co-Authors: Benjamin Smith, H A Fricker, Nicholas Holschuh, Alex S Gardner, Susheel Adusumilli, Kelly M Brunt, Beata Csatho, Kaitlin Harbeck, Alexander HuthAbstract:Abstract The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) and its sole scientific instrument, the Advanced Topographic Laser Altimeter System (ATLAS), was launched on 15 September 2018 with a primary goal of measuring changes in the surface of the Earth's land ice (glaciers and ice sheets). ATLAS is a photon-counting Laser Altimeter, which records the transit time of individual photons in order to reconstruct surface height along track. The ground-track pattern repeats every 91 days such that changes in ice sheet surface height can be estimated through time. In this paper, we describe the set of algorithms that have been developed for ICESat-2 to retrieve ice sheet surface height from the geolocated photons for the Land Ice Along-Track Height Product (ATL06), and demonstrate their output and performance using a synthetic dataset over various land-ice surfaces and under different cloud conditions. We show that the ATL06 algorithm is expected to perform at the level required to meet the ICESat-2 science objectives for land ice.
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the ice cloud and land elevation satellite 2 mission a global geolocated photon product derived from the advanced topographic Laser Altimeter system
Remote Sensing of Environment, 2019Co-Authors: Thomas A Neumann, John F. Cavanaugh, Anita C Brenner, Kelly M Brunt, Sungkoo Bae, Anthony J Martino, Thorsten Markus, Megan R Bock, Stanley T FernandesAbstract:Abstract The Ice, Cloud, and land Elevation Satellite – 2 (ICESat-2) observatory was launched on 15 September 2018 to measure ice sheet and glacier elevation change, sea ice freeboard, and enable the determination of the heights of Earth's forests. ICESat-2's Laser Altimeter, the Advanced Topographic Laser Altimeter System (ATLAS) uses green (532 nm) Laser light and single-photon sensitive detection to measure time of flight and subsequently surface height along each of its six beams. In this paper, we describe the major components of ATLAS, including the transmitter, the receiver and the components of the timing system. We present the major components of the ICESat-2 observatory, including the Global Positioning System, star trackers and inertial measurement unit. The ICESat-2 Level 1B data product (ATL02) provides the precise photon round-trip time of flight, among other data. The ICESat-2 Level 2A data product (ATL03) combines the photon times of flight with the observatory position and attitude to determine the geodetic location (i.e. the latitude, longitude and height) of the ground bounce point of photons detected by ATLAS. The ATL03 data product is used by higher-level (Level 3A) surface-specific data products to determine glacier and ice sheet height, sea ice freeboard, vegetation canopy height, ocean surface topography, and inland water body height.
Erwan Mazarico - One of the best experts on this subject based on the ideXlab platform.
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summary of the results from the lunar orbiter Laser Altimeter after seven years in lunar orbit
Icarus, 2017Co-Authors: D. E. Smith, Erwan Mazarico, M S Robinson, F G Lemoine, J.w. Head, Paul G Lucey, O Aharonson, Xiaoli SunAbstract:In June 2009 the Lunar Reconnaissance Orbiter (LRO) spacecraft was launched to the Moon. The payload consists of 7 science instruments selected to characterize sites for future robotic and human missions. Among them, the Lunar Orbiter Laser Altimeter (LOLA) was designed to obtain altimetry, surface roughness, and reflectance measurements. The primary phase of lunar exploration lasted one year, following a 3-month commissioning phase. On completion of its exploration objectives, the LRO mission transitioned to a science mission. After 7 years in lunar orbit, the LOLA instrument continues to map the lunar surface. The LOLA dataset is one of the foundational datasets acquired by the various LRO instruments. LOLA provided a high-accuracy global geodetic reference frame to which past, present and future lunar observations can be referenced. It also obtained high-resolution and accurate global topography that were used to determine regions in permanent shadow at the lunar poles. LOLA further contributed to the study of polar volatiles through its unique measurement of surface brightness at zero phase, which revealed anomalies in several polar craters that may indicate the presence of water ice. In this paper, we describe the many LOLA accomplishments to date and its contribution to lunar and planetary science.
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a new lunar digital elevation model from the lunar orbiter Laser Altimeter and selene terrain camera
Icarus, 2016Co-Authors: M K Barker, Erwan Mazarico, Junichi HaruyamaAbstract:Abstract We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512 pixels per degree (∼60 m at the equator) and a typical vertical accuracy ∼3 to 4 m. This DEM is constructed from ∼ 4.5 × 10 9 geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1 ° × 1 ° ) from the SELENE Terrain Camera (TC) (∼1010 pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of
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detection of the lunar body tide by the lunar orbiter Laser Altimeter
Geophysical Research Letters, 2014Co-Authors: Erwan Mazarico, M K BarkerAbstract:The Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter spacecraft collected more than 5 billion measurements in the nominal 50 km orbit over ~10,000 orbits. The data precision, geodetic accuracy, and spatial distribution enable two-dimensional crossovers to be used to infer relative radial position corrections between tracks to better than ~1 m. We use nearly 500,000 altimetric crossovers to separate remaining high-frequency spacecraft trajectory errors from the periodic radial surface tidal deformation. The unusual sampling of the lunar body tide from polar lunar orbit limits the size of the typical differential signal expected at ground track intersections to ~10 cm. Nevertheless, we reliably detect the topographic tidal signal and estimate the associated Love number h2 to be 0.0371 ± 0.0033, which is consistent with but lower than recent results from lunar Laser ranging.
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Stratigraphy, Sequence, and Crater Populations of Lunar Impact Basins from Lunar Orbiter Laser Altimeter (LOLA) Data: Implications for the Late Heavy Bombardment
2012Co-Authors: Caleb I Fassett, Erwan Mazarico, D. E. Smith, J.w. Head, Seth J Kadish, G. A. Neumann, M. T. ZuberAbstract:New measurements of the topography of the Moon from the Lunar Orbiter Laser Altimeter (LOLA)[1] provide an excellent base-map for analyzing the large crater population (D.20 km)of the lunar surface [2, 3]. We have recently used this data to calculate crater size-frequency distributions (CSFD) for 30 lunar impact basins, which have implications for their stratigraphy and sequence. These data provide an avenue for assessing the timing of the transitions between distinct crater populations characteristic of ancient and young lunar terrains, which has been linked to the late heavy bombardment (LHB). We also use LOLA data to re-examine relative stratigraphic relationships between key lunar basins.
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global surface slopes and roughness of the moon from the lunar orbiter Laser Altimeter
Journal of Geophysical Research, 2011Co-Authors: M A Rosenburg, Erwan Mazarico, J.w. Head, David E Smith, Gregory A Neumann, O Aharonson, M A KreslavskyAbstract:[1] The acquisition of new global elevation data from the Lunar Orbiter Laser Altimeter, carried on the Lunar Reconnaissance Orbiter, permits quantification of the surface roughness properties of the Moon at unprecedented scales and resolution. We map lunar surface roughness using a range of parameters: median absolute slope, both directional (along‐track) and bidirectional (in two dimensions); median differential slope; and Hurst exponent, over baselines ranging from ∼17 m to ∼2.7 km. We find that the lunar highlands and the mare plains show vastly different roughness properties, with subtler variations within mare and highlands. Most of the surface exhibits fractal‐like behavior, with a single or two different Hurst exponents over the given baseline range; when a transition exists, it typically occurs near the 1 km baseline, indicating a significant characteristic spatial scale for competing surface processes. The Hurst exponent is high within the lunar highlands, with a median value of 0.95, and lower in the maria (with a median value of 0.76). The median differential slope is a powerful tool for discriminating between roughness units and is useful in characterizing, among other things, the ejecta surrounding large basins, particularly Orientale, as well as the ray systems surrounding young, Copernican‐age craters. In addition, it allows a quantitative exploration on mare surfaces of the evolution of surface roughness with age.
