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Clark R.N.,U.S. Geological Survey | Pieters C.M.,Brown University | Green R.O.,Jet Propulsion Laboratory | Boardman J.W.,Analytical Imaging and Geophysics LLC | Petro N.E.,NASA
Journal of Geophysical Research E: Planets | Year: 2011

In the near-infrared from about 2 μm to beyond 3 μm, the light from the Moon is a combination of reflected sunlight and emitted thermal emission. There are multiple complexities in separating the two signals, including knowledge of the local solar incidence angle due to topography, phase angle dependencies, emissivity, and instrument calibration. Thermal emission adds to apparent reflectance, and because the emission's contribution increases over the reflected sunlight with increasing wavelength, absorption bands in the lunar reflectance spectra can be modified. In particular, the shape of the 2 μm pyroxene band can be distorted by thermal emission, changing spectrally determined pyroxene composition and abundance. Because of the thermal emission contribution, water and hydroxyl absorptions are reduced in strength, lowering apparent abundances. It is important to quantify and remove the thermal emission for these reasons. We developed a method for deriving the temperature and emissivity from spectra of the lunar surface and removing the thermal emission in the near infrared. The method is fast enough that it can be applied to imaging spectroscopy data on the Moon. Copyright © 2011 by the American Geophysical Union.

Boardman J.W.,Analytical Imaging and Geophysics LLC | Kruse F.A.,Naval Postgraduate School, Monterey
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011

Imaging spectrometers collect unique data sets that are simultaneously a stack of spectral images and a spectrum for each image pixel. While these data can be analyzed using approaches designed for multispectral images, or alternatively by looking at individual spectra, neither of these takes full advantage of the dimensionality of the data. Imaging spectrometer spectral radiance data or derived apparent surface reflectance data can be cast as a scattering of points in an n-dimensional Euclidean space, where n is the number of spectral channels and all axes of the n-space are mutually orthogonal. Every pixel in the data set then has a point associated with it in the n- d space, with its Cartesian coordinates defined by the values in each spectral channel. Given n-dimensional data, convex and affine geometry concepts can be used to identify the purest pixels in a given scene (the endmembers). N-dimensional visualization techniques permit human interpretation of all spectral information of all image pixels simultaneously and projection of the endmembers back to their locations in the imagery and to their spectral signatures. Once specific spectral endmembers are defined, partial linear unmixing (mixture-tuned matched filtering or MTMF) can be used to spectrally unmix the data and to accurately map the apparent abundance of a known target material in the presence of a composite background. MTMF incorporates the best attributes of matched filtering but extends that technique using the linear mixed-pixel model, thus leading to high selectivity between similar materials and minimizing classification and mapping errors for analysis of imaging spectrometer data. © 2006 IEEE.

Besse S.,University of Maryland University College | Sunshine J.,University of Maryland University College | Staid M.,Planetary Science Institute | Boardman J.,Analytical Imaging and Geophysics LLC | And 6 more authors.
Icarus | Year: 2013

Observations of the Moon obtained by the Moon Mineralogy Mapper (M3) instrument were acquired at various local viewing geometries. To compensate for this, a visible near-infrared photometric correction for the M3 observations of the lunar surface has been derived. Images are corrected to the standard geometry of 30° phase angle with an incidence of 30° and an emission of 0°. The photometric correction is optimized for highland materials but is also a good approximation for mare deposits. The results are compared with ground-based observations of the lunar surface to validate the absolute reflectance of the M3 observations. This photometric model has been used to produce the v1.0 Level 2 delivery of the entire set of M3 data to the Planetary Data System (PDS). The photometric correction uses local topography, in this case derived from an early version of the Lunar Orbiter Laser Altimeter data, to more accurately determine viewing geometry. As desired, this photometric correction removes most of the topography of the M3 measurements. In this paper, two additional improvements of the photometric modeling are discussed: (1) an extrapolated phase function long ward of 2500nm to avoid possible misinterpretation of spectra in the wavelength region that includes possible OH/H2O absorptions and (2) an empirical correction to remove a residual cross-track gradient in the data that likely is an uncorrected instrumental effect. New files for these two effects have been delivered to PDS and can be applied to the M3 observations. © 2012 Elsevier Inc.

Ohtake M.,Japan Aerospace Exploration Agency | Pieters C.M.,Brown University | Isaacson P.,University of Hawaii at Manoa | Besse S.,European Space Agency | And 8 more authors.
Icarus | Year: 2013

Remote-sensing datasets obtained by each instrument aboard Selenological and Engineering Explorer (SELENE) and Chandrayaan-1 have not been compared directly, and the characteristics of each instrument's data, which may reflect the observation conditions of each instrument and/or residual error in instrument calibration, are unknown. This paper describes the basic characteristics of the data derived by each instrument, briefly describes the data-processing conversion from radiance to reflectance, and demonstrates what we can achieve by combining data obtained by different instruments on different missions (five remote-sensing instruments and an Earth-based telescope). The results clearly demonstrate that the spectral shapes of the instruments are comparable and thus enable us to estimate the composition of each geologic unit, although absolute reflectances differ slightly in some cases. © 2013 Elsevier Inc.

Klima R.L.,Johns Hopkins University | Pieters C.M.,Brown University | Boardman J.W.,Analytical Imaging and Geophysics LLC | Green R.O.,Jet Propulsion Laboratory | And 9 more authors.
Journal of Geophysical Research E: Planets | Year: 2011

Lunar geochemical groups such as Mg suite, ferroan anorthosite, and alkali suite rocks are difficult to distinguish from orbit because they are defined by both modal mineralogy and elemental composition of their constituent minerals. While modal mineralogy can be modeled, only specific minerals or elements can be directly detected. At near-infrared (NIR) wavelengths, pyroxenes are among the most spectrally distinctive minerals, and their absorption bands are sensitive to structure and composition. Pyroxenes thus provide important clues to distinguish these geochemical groups and to understand lunar crustal evolution. Using Moon Mineralogy Mapper data, we search for lithologies dominated by strong low-calcium pyroxene (LCP) signatures. We compare the NIR absorptions of 20 LCPs to a suite of synthetic pyroxenes to determine which lunar pyroxenes appear magnesian enough to be candidate Mg suite norites. We detail three prominent regions of LCP (1) in South Pole-Aitken Basin (SPA), (2) south of Mare Frigoris, and (3) north of Mare Frigoris. The absorption band positions suggest that the LCPs north of Mare Frigoris and those in SPA are compositionally similar to one another and of ∼Mg50-75, implying that the mafic material excavated by the SPA impact was relatively iron-rich. Modified Gaussian modeling results suggest that the Apollo basin may have tapped different composition material than is exposed in much of SPA. The LCPs located in the highlands south of Mare Frigoris exhibit absorption bands at short wavelengths consistent with Mg > ∼80. The coincidence of these Mg-rich LCPs with the thorium measured by Lunar Prospector make them good candidates for KREEP-related Mg suite pyroxenes. Copyright 2011 by the American Geophysical Union.

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