8,712 research outputs found
MarsLux: HI-Resolution Illumination Maps Generator for Mars
Illumination simulation codes for the Moon's surface have been thoroughly developed during the last years. Despite works done for the Moon, no studies have investigated the relation between sunlight illumination and the Martian surface applying those codes done for the Moon to Mars. The objective of this work is to describe the development of a surface illumination simulation code, called MarsLux, which allows users to make a detailed investigation of the illumination conditions on Mars, based on its topography and the relative position of the Sun. Our code can derive accurate illumination maps, form topographic data, showing areas that are fully illuminated, areas in total shadow, and areas with partial shade, in short computational times. Although the code does not take into account any atmospheric effect, the results proved to be of high accuracy. The maps generated are useful for geomorphological studies, to study gullies, thermal weathering, or mass wasting processes as well as for producing energy budget maps for future exploration missions.Fil: Spagnuolo, Mauro Gabriel. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Carballo, Federico Daniel. Servicio Geologico Minero Argentino; ArgentinaFil: Marco Figuera, R.. Jacobs University Bremen; AlemaniaFil: Rossi, A. P.. Jacobs University Bremen; Alemani
Enhancement of digital images through band ratio techniques for geological applications
The fundamentals in the use of band ratio techniques to enhance spectral signatures of geologic interest are discussed. The path radiance, additive term of the measured radiance at any given wavelength, is almost completely eliminated from LANDSAT images by subtracting the smallest value of the radiance measured in each channel, at shadows caused by topographic relief and clouds, and deep clear water bodies. By ratioing successive spectral channels the effect of solar angle of elevation is minimized and the product expresses, to a first approximation, a relationship between reflectances, which are intrinsic characteristics of the targets. Ratios between noncorrelated channels, such as R 7/4, R 7/5, and R 6/4 are useful to show variations in the vegetation cover, probably related to geobotanical associations
Simulated response of a multispectral scanner over wheat as a function of wavelength and view/illumination direction
The reflectance response with view angle of wheat, was analyzed. The analyses, which assumes there are no atmospheric effects, and otherwise simulates the response of a multispectral scanner, is based upon spectra taken continuously in wavelength from 0.45 to 2.4 micrometers at more than 1200 view/illumination directions using an Exotech model 20C spectra radiometer. Data were acquired six meters above four wheat canopies, each at a different growth stage. The analysis shows that the canopy reflective response is a pronounced function of illumination angle, scanner view angle and wavelength. The variation is greater at low solar elevations compared to high solar elevations
Water ice in the dark dune spots of Richardson crater on Mars
In this study we assess the presence, nature and properties of ices - in
particular water ice - that occur within these spots using HIRISE and CRISM
observations, as well as the LMD Global Climate Model. Our studies focus on
Richardson crater (72{\deg}S, 179{\deg}E) and cover southern spring and summer
(LS 175{\deg} - 17 341{\deg}). Three units have been identified of these spots:
dark core, gray ring and bright halo. Each unit show characteristic changes as
the season progress. In winter, the whole area is covered by CO2 ice with H2O
ice contamination. Dark spots form during late winter and early spring. During
spring, the dark spots are located in a 10 cm thick depression compared to the
surrounding bright ice-rich layer. They are spectrally characterized by weak
CO2 ice signatures that probably result from spatial mixing of CO2 ice rich and
ice free regions within pixels, and from mixing of surface signatures due to
aerosols scattering. The bright halo shaped by winds shows stronger CO2
absorptions than the average ice covered terrain, which is consistent with a
formation process involving CO2 re-condensation. According to spectral,
morphological and modeling considerations, the gray ring is composed of a thin
layer of a few tens of {\mu}m of water ice. Two sources/processes could
participate to the enrichment of water ice in the gray ring unit: (i) water ice
condensation at the surface in early fall (prior to the condensation of a CO2
rich winter layer) or during winter time (due to cold trapping of the CO2
layer); (ii) ejection of dust grains surrounded by water ice by the geyser
activity responsible for the dark spot. In any case, water ice remains longer
in the gray ring unit after the complete sublimation of the CO2. Finally, we
also looked for liquid water in the near-IR CRISM spectra using linear unmixing
modeling but found no conclusive evidence for it
S190 interpretation techniques development and application to New York State water resources
The author has identified the following significant results. The program has demonstrated that Skylab imagery can be utilized to regularly monitor eutrophication indices of lakes, such as chlorophyll concentration and photic zone depth. The relationship between the blue to green reflectance ratio and chlorophyll concentration was shown, along with changes in lake properties caused by chlorophyll, lignin, and humic acid using reflectance ratios and changes. A data processing technique was developed for detecting atmospheric fluctuations occurring over a large lake
Signature extension preprocessing for LANDSAT MSS data
There are no author-identified significant results in this report
Atmospheric effects on radiometry from zenith of a plane with dark vertical protrusions
Effects of an optically thin plane-parallel scattering atmosphere on radiometric imaging from the zenith of a specific surface-type are analyzed. The surface model was previously developed to describe arid steppe, where the sparse vegetation forms dark vertical protrusions from the bright soil-plane. The analysis is in terms of the surface reflectivity to the zenith r sub p for the direct beam, which is formulated as r sub p = r sub i exp (-s tan theta sub 0), where v sub i is the Lambert law reflectivity of the soil, the protrusions parameters s is the projection on a vertical plane of protrusions per unit area and theta sub 0 is the zenith angle. The surface reflectivity r sub p is approximately equal to that for the global irradiance (which is directly measured in the field) only for a narrow range of the solar zenith angles. The effects of the atmosphere when imaging large uniform areas of this type are comparable to those in imaging a Lambert surface with a reflectivity r sub p. Thus, the effects can be approximated by those in the case of a dark Lambert surface (analyzed previously), inasmuch as r sub p is smaller than the soil reflectivity r sub i for any off-zenith illumination. The surface becomes effectively darker with increasing solar zenith angle. Adjacency effects of a reflection from one area and scattering in the instantaneous field of view (object pixel) are analyzed as cross radiance and cross irradiance
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