Optical measurements of the Moon as a tool to study its surface

Shkuratov, Yuriy; Kaydash, V. G.; Korokhin, V. V.; Velikodsky, Yu. I.; Opanasenko, N. V.; Videen, Gorden

doi:10.1016/j.pss.2011.06.011

Cited by 211 publications

(203 citation statements)

References 219 publications

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“…To correct for brightness changes due to local topography within the image and brightness changes due to differences in phase angle between images, we used a photometric adjustment based on the disk function for the former and a phase function for the latter Schröder et al, 2013b). Schröder et al (2013b) used an approach based on models in which the explicit dependence of reflectance on phase angle is decoupled from the effects of local topography (Kaasalainen et al, 2001;Shkuratov et al, 2011). Their approach separates the disk function from the phase function, and is well suited to facilitate photometric correction by combining the best-fit disk function of Vesta with a polynomial to describe the phase function.…”

Section: Data Base and Methodsmentioning

confidence: 99%

The geological nature of dark material on Vesta and implications for the subsurface structure

Jaumann

Naß

Otto

et al. 2014

Icarus

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a b s t r a c tDeposits of dark material appear on Vesta's surface as features of relatively low-albedo in the visible wavelength range of Dawn's camera and spectrometer. Mixed with the regolith and partially excavated by younger impacts, the material is exposed as individual layered outcrops in crater walls or ejecta patches, having been uncovered and broken up by the impact. Dark fans on crater walls and dark deposits on crater floors are the result of gravity-driven mass wasting triggered by steep slopes and impact seismicity. The fact that dark material is mixed with impact ejecta indicates that it has been processed together with the ejected material. Some small craters display continuous dark ejecta similar to lunar dark-halo impact craters, indicating that the impact excavated the material from beneath a higher-albedo surface. The asymmetric distribution of dark material in impact craters and ejecta suggests non-continuous distribution in the local subsurface. Some positive-relief dark edifices appear to be impact-sculpted hills with dark material distributed over the hill slopes. Dark features inside and outside of craters are in some places arranged as linear outcrops along scarps or as dark streaks perpendicular to the local topography. The spectral characteristics of the dark material resemble that of Vesta's regolith. Dark material is distributed unevenly across Vesta's surface with clusters of all types of dark material exposures. On a local scale, some craters expose or are associated with dark material, while others in the immediate vicinity do not show evidence for dark material. While the variety of surface exposures of dark material and their different geological correlations with surface features, as well as their uneven distribution, indicate a globally inhomogeneous distribution in the subsurface, the dark material seems to be correlated with the rim and ejecta of the older Veneneia south polar basin structure. The origin of the dark material is still being debated, however, the geological analysis suggests that it is exogenic, from carbon-rich low-velocity impactors, rather than endogenic, from freshly exposed mafic material or melt, exposed or created by impacts.

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Section: Data Base and Methodsmentioning

confidence: 99%

The geological nature of dark material on Vesta and implications for the subsurface structure

Jaumann

Naß

Otto

et al. 2014

Icarus

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“…If we fit a straight line for the radiance factor of facets observed with phase angle larger than 20 • , we measure a increase of the radiance factor of 0.11 due to the non-linear enhancement, which is ∼ 50% of the albedo at zero phase angle (0.19 ± 0.02, the geometric albedo according to Sierks et al, 2011). The spread of points is due to geometric condition only, the so-called disk profile (Shkuratov et al, 2011), were facets close to limb are obscured in the extreme values of incidence and emergence angles. On Figure 2.2b, we observe a concentration of radiance factor along diagonal that results from the specular behavior of the opposition effect, and outside of it, the diffusive scattering component.…”

Section: Then It Providesmentioning

confidence: 99%

“…This component is related to limb darkening, topography and also the global surface scattering properties. Further mathematical and qualitative description of photometric definitions was reviewed by Shkuratov et al (2011). In what follows, the equigonal albedo is also decomposed in two terms:…”

Section: Then It Providesmentioning

confidence: 99%

“…Moving further from the RTE models, there is a class of empirical models that decouples the reflectance dependence of phase angles, the phase function, from the gradient behavior due to local topography, called disk function (e.g., Shkuratov et al 2011). Generally, those models neglect or roughly describe the multiple-scattering and the macroscopic roughness, making their application restricted to dark smooth surfaces on limited phase angle coverage.…”

Section: Introductionmentioning

confidence: 99%

“…First, for normalizing images of undersampled filters to a standard illumination condition, we tested five scattering laws to find the most suitable one for the photometric correction of topography, in same manner as Schröder et al (2013). Since the phase dependence can vary throughout (21) Lutetia's surface, the individual fitting of Akimov phase function (Akimov, 1988;Shkuratov et al, 2011) was obtained for each surface element of the shape model, called facet. The spectro-photometry of each facet is derived through the normalization to same a phase angle, allowing a spectral slope map to be obtained.…”

Section: Introductionmentioning

confidence: 99%

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Asteroid (21) Lutetia: Disk-resolved photometric analysis of Baetica region

Hasselmann

Fornasier

Leyrat

et al. 2016

Icarus

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ABSTRACT. (21) Lutetia has been visited by Rosetta mission on July 2010 and observed with a phase angle ranging from 0.15 to 156.8 degrees. The Baetica region, located at the north pole has been extensively observed by OSIRIS cameras system. Baetica encompass a region called North Pole Crater Cluster (NPCC), shows a cluster of superposed craters which presents signs of variegation at the small phase angle images. For studying the location, we used 187 images distributed throughout 14 filter recorded by the NAC (Narrow Angle Camera) and WAC (Wide Angle Camera) of the OSIRIS system on-board Rosetta taken during the fly-by. Then, we photometrically modeled the region using Minnaert diskfunction and Akimov phase function to obtain a resolved spectral slope map at phase angles of 5 • and 20 • . We observed a dicothomy between Gallicum and Danuvius-Sarnus Labes in the NPCC, but no significant phase reddening (−0.04 ± 0.045% · microns −1 deg −1 ). In the next step, we applied the Hapke (2008Hapke ( ,2012 model for the NAC F82+F22 (649.2 nm), WAC F13 (375 nm) and WAC F17 (631.6 nm) and we obtained normal albedo maps and Hapke parameter maps for NAC F82+F22. On Baetica, at 649.2 nm, the geometric albedo is 0.205 ± 0.005, the average single-scattering albedo is 0.181 ± 0.005, the average asymmetric factor is −0.342 ± 0.003, the average shadow-hiding opposition effect amplitude and width are 0.824 ± 0.002 and 0.040 ± 0.0007, the average roughness slope is 11.45 • ± 3 • and the average porosity is 0.85 ± 0.002. We are unable to confirm the presence of coherent-backscattering mechanism. In the NPCC, the normal albedo variegation among the craters walls reach 8% brighter for Gallicum Labes and 2% fainter for Danuvius Labes. The Hapke parameter maps also show a dicothomy at the opposition effect coefficients, single-scattering albedo and asymmetric factor, that may be attributed to the maturation degree of the regolith or to compositonal variation. In addition, we compared the Hapke (2008Hapke ( , 2012 and Hapke (1993) parameters with laboratory samples and other small-solar system bodies visited by space missions.

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Ilmenite mapping of the lunar regolith over Mare Australe and Mare Ingenii regions: An optimized multisource approach based on Hapke radiative transfer theory

et al. 2013

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[1] We model lunar ilmenite abundances over Mare Australe and Mare Ingenii regions using a new approach; we integrate Lunar Reconnaissance Orbiter Wide Angle Camera (WAC) and Clementine UV-visible/near-infrared (UVVIS/NIR) data to obtain a 14-band mosaic (320-2000 nm). We use Hapke's radiative transfer equations to compute spectra for various mixtures of orthopyroxene, clinopyroxene, plagioclase, olivine, and ilmenite, with varying grain size, chemistry, and degree of maturity, and find the closest match between the modeled spectra and the spectra of the less mature pixels (optical maturity ≥ 0.2) in the 14-band mosaic. We calculate a "maximum stoichiometrically possible ilmenite content", using Clementine-derived TiO 2 abundances and the amount of TiO 2 in stoichiometric ilmenite, and use it as a constraint in our model. We validate our methodology with lunar soil spectra of known composition. Our results show that the integrated WAC-UVVIS/ NIR data and the UVVIS/NIR data overestimate ilmenite abundances by 8.80 wt % and 7.97 wt %, respectively, when a fixed maximum of 20 wt % ilmenite is used. When the maximum stoichiometrically possible ilmenite content is used as a constraint, the integrated WAC-UVVIS/NIR data give slightly more accurate ilmenite abundance estimation (±2.87 wt %) than when using only UVVIS/NIR data (± 3.04 wt %). We find ilmenite concentrations of 0À11 wt % in Mare Australe and 0À6 wt % in Mare Ingenii region. Ilmenite abundances between 4 and 7 wt % are exposed in Mare Australe, whereas ilmenite abundances between 7 and 11 wt % are found on the walls of 0.6-11.8 km diameter craters within Mare Australe.

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Optical measurements of the Moon as a tool to study its surface

Cited by 211 publications

References 219 publications

The geological nature of dark material on Vesta and implications for the subsurface structure

The geological nature of dark material on Vesta and implications for the subsurface structure

Asteroid (21) Lutetia: Disk-resolved photometric analysis of Baetica region

Ilmenite mapping of the lunar regolith over Mare Australe and Mare Ingenii regions: An optimized multisource approach based on Hapke radiative transfer theory

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