- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Reflectance variation in boreal landscape during the snow melting period using airborne imaging spectroscopy
摘要： We aim a better understanding of the effect of spring-time snow melt on the remotely sensed scene reflectance by using an extensive amount of optical spectral data obtained from an airborne hyperspectral campaign in Northern Finland. We investigate the behaviour of thin snow reflectance for different land cover types, such as open areas, boreal forests and treeless fells. Our results not only confirm the generally known fact that the reflectance of a melting thin snow layer is considerably lower than that of a thick snow layer, but we also present analyses of the reflectance variation over different land covers and in boreal forests as a function of canopy coverage. According to common knowledge, the highly variating reflectance spectra of partially transparent, most likely also contaminated thin snow pack weakens the performance of snow detection algorithms, in particular in the mapping of Fractional Snow Cover (FSC) during the end of the melting period. The obtained results directly support further development of the SCAmod algorithm for FSC retrieval, and can be likewise applied to develop other algorithms for optical satellite data (e.g. spectral unmixing methods), and to perform accuracy assessments for snow detection algorithms.
关键词： SCE,AISA,Scene reflectance,Boreal forest,Spectroscopy,FSC,Snow mapping,NDSI,MODIS,NDVI,Land cover classification,Snow melt,Fell,Reflectance
更新于2025-09-10 09:29:36
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Improving Remote Sensing of Aerosol Optical Depth over Land by Polarimetric Measurements at 1640 nm: Airborne Test in North China
摘要： An improved aerosol retrieval algorithm based on the Advanced Multi-angular Polarized Radiometer (AMPR) is presented to illustrate the utility of additional 1640-nm observations for measuring aerosol optical depth (AOD) over land using look-up table approaches. Spectral neutrality of the polarized surface reflectance over visible to short-wavelength infrared bands is verified, and the 1640-nm measurements corrected for atmospheric effects are used to estimate the polarized surface reflectance at shorter wavelengths. The AMPR measurements over the Beijing-Tianjin-Hebei region in north China reveal that the polarized surface reflectance of 670, 865 and 1640 nm are highly correlated with correlation slopes close to one (0.985 and 1.03) when the scattering angle is less than 145°. The 1640-nm measurements are then employed to estimate polarized surface reflectance at shorter wavelengths for each single viewing direction, which are then used to improve the retrieval of AOD over land. The comparison between AMPR retrievals and ground-based Sun-sky radiometer measurements during three experimental flights illustrates that this approach retrieves AOD at 865 nm with uncertainties ranging from 0.01 to 0.06, while AOD varies from 0.05 to 0.17.
关键词： airborne Advanced Multi-angle Polarized Radiometer (AMPR),aerosol optical depth (AOD),polarized surface reflectance,1640 nm
更新于2025-09-10 09:29:36
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Effect of pH Adjustment on Hydrothermal Synthesis of Aluminum Doped Zinc Oxide
摘要： Aluminum doped zinc oxide (AZO) was synthesized with various pH adjustments reagent (ammonia, TMAH, TEAH and TPAH) by hydrothermal reaction. Regardless of the pH adjustment, the main product of the synthesized powders with 5?mol% Al was zinc oxide. However, the diffraction peaks of gahnite (ZnAl2O4) were detected in the sample prepared from the precursor solutions with TMAH, TEAH and TPAH as pH adjustment. The excellent absorption property in near-infrared (NIR) region was obtained in the synthesized powder with about 2?mol% Al using ammonia. Based on these results, the initial state of Zn and Al ion in precursor solution is thought to affect the crystal phase of the product in hydrothermal synthesis. The NIR absorption property was highly enhanced by using urea as the pH-shift reagent during hydrothermal reaction process.
关键词： pH adjustment,Near-infrared reflectance,Hydrothermal synthesis,Aluminum doped zinc oxide
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Harmonization And Fusion of Global Scale Data
摘要： Remote sensing data provides scientists with synoptic coverage of the Earth's surface, allowing us to understand its system dynamics in a way that would be impossible with more direct observation. As more satellites have been deployed in recent years, imagery has become more readily available and diverse, encompassing a wider range of spatial, temporal, and spectral resolutions than ever before. While these data better inform our understanding of the Earth, anyone hoping to leverage this information is hampered by the large size and complexity of these datasets, a lack of easily accessible computing resources, and the broad expertise required to correctly interpret the imagery. To fully leverage the information in these disparate datasets, data fusion methods must be implemented that abstract access to them. Large scale fusion of geospatial data, using physically based and statistical methods, can be accomplished to create a living model of the earth. This presentation will discuss the Descartes Labs approach to data fusion and normalization as well as our effort to leverage these capabilities toward a synoptic earth model. Topics will include the current status of the physical normalization algorithms deployed into the Descartes Labs Platform as well as efforts to harmonize and abstract access to multi-vendor constellations.
关键词： cloud computing,data fusion,data normalization,surface reflectance
更新于2025-09-10 09:29:36
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Synthesis of green cool pigments (CoxZn1-xO) for application in NIR radiation reflectance
摘要： Reconciling green synthesis, sustainability and production of pigments for protection of solar radiation is a continuous topic of search for unique, versatile and environmental compatible methods. In this perspective, we present the green synthesis of inorganic pigments with reflective properties of infrared radiation in the NIR region. Green powder pigments described by CoxZn1-xO, were obtained via the gelatinization method of starch colloidal suspension with inorganic salts (zinc and cobalt), calcined at different temperatures. Structural, morphological and spectroscopic characterization showed the pigments present Wurtzite crystalline phase with compact hexagonal structure, and monophasic when obtained at a calcination temperature above 800 °C. Colorimetric measurements obtained by the CIE-L*a*b* method presented values related to green pigments attributed to cobalt ions, which replace the zinc ions in the Wurtzite matrix and corroborate the composition estimated by X-ray fluorescence analysis for Co0.1Zn0.9O. The pigments' NIR reflectivity increased with the calcination temperature increasing, with R% > 35%; and when the pigment is dispersed in a white paint the increase is R% > 50%. Therefore, our green pigments present great potential to be used as an active material in cold coatings and in solar devices.
关键词： Colorimetry,NIR reflectance,Cool pigments,Green synthesis
更新于2025-09-10 09:29:36
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In situ measurement of the spectral reflectance of mirror-like metallic surfaces during plasma exposition
摘要： Visible spectroscopy in fusion plasmas crucially depends on the optical properties of first mirrors withstanding a considerable amount of radiation and particle fluxes. As a result of this interaction the optical properties of the mirrors could be changed so that a cleaning of the mirror is regularly required. Thus the reflectance of the first mirror must be monitored in situ. The newly developed Doppler-Shifted Reflectance Measurement (DSRM) diagnostic provides the spectral reflectance of mirrors in the absence of any calibration sources. It is based on the emission of fast H/D atoms in a low density Ar-H plasma by applying a negative potential on the order of to the mirror surface. Until now, the experimental data were restricted to measure only the fast atoms emission at the Hα line. In this work we prove that the new technique also provides the mirror reflectance at the Hβ line (Cu) (486 nm) relevant for the charge-exchange recombination spectroscopy (CXRS) measurements of the He II line (468 nm) in ITER. Moreover, the DSRM diagnostic remains sensitive to the polarization of the reflected light of a W mirror. We present the first experimental data on the time-dependent regime of operation: in situ monitoring of the degradation of an Al mirror is shown as a function of the mirror temperature. The passive heating of the mirror was performed by the plasma itself, which makes the separation between the impact of high temperature and plasma erosion on the mirror reflectance for the temperatures above 500 K impossible. A very good agreement of the experimental and the theoretical data calculated using the Drude theory for the temperature below 500 K is found. For the temperatures above 500 K the degradation of the reflectance of the mirror is determined by the erosion of Al, which is confirmed by monitoring the Al I spectral lines in unison.
关键词： light polarization,CXRS,surface degradation,optical emission spectroscopy,fast neutral atoms,spectral reflectance
更新于2025-09-10 09:29:36
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UV-Vis spectroscopy
摘要： UV-Vis reflectance spectroscopy has been widely used as a non-invasive method for the study of cultural heritage materials for several decades. In particular, FORS, introduced in the 1980s, allows to acquire hundreds of reflectance spectra in situ in a short time, contributing to the identification of artist’s materials. More recently, microspectrofluorimetry has also been proposed as a powerful non-invasive method for the identification of dyes and lake pigments that provides high sensitivity and selectivity. In this chapter, the concepts behind these spectroscopic methodologies will be discussed, as well as the instrumentation and measurement modes used. Case studies related with different cultural heritage materials (paintings and manuscripts, textiles, carpets and tapestries, glass, metals, and minerals), which show the usefulness of UV-Vis reflectance spectroscopy and microspectrofluorimetry applied to the study of artworks, will also be presented.
关键词： glass,reflectance,microspectrofluorimetry,textiles,FORS,carpets and tapestries,paintings and manuscripts,minerals,non-invasive,metals,UV-Vis spectroscopy
更新于2025-09-10 09:29:36
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A soft x-ray-ultraviolet (SUV) beamline and diffractometer for resonant elastic scattering and ultraviolet-vacuum ultraviolet reflectance at the Singapore synchrotron light source
摘要： A new beamline and a six-circle UHV diffractometer have been constructed at the Singapore Synchrotron Light Source with a broad energy coverage from 3.5 to 1500 eV. The beamline is optimized for ultraviolet-vacuum-ultraviolet optical reflectivity and resonant soft X-ray scattering with medium energy resolution over a broad energy range, achieved by using a self-focusing monochromator consisting of a plane mirror and three variable line spacing gratings. The unique character of the diffractometer comprises 4-circles in the vertical plane and 2-circles in the horizontal plane. Thirteen motions are available inside the UHV chamber with a base pressure of 1 × 10?9 mbar. Two sample holders working independently over a temperature range of 37 K–400 K are controlled by a closed-cycle cryostat, while the bottom holder inside a high field compact pulsed magnet is available for measurements requiring a magnetic field.
关键词： ultraviolet-vacuum ultraviolet reflectance,soft x-ray-ultraviolet beamline,resonant elastic scattering,diffractometer,Singapore synchrotron light source
更新于2025-09-10 09:29:36
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Seasonal Variation in Spectral Response of Submerged Aquatic Macrophytes: A Case Study at Lake Starnberg (Germany)
摘要： Submerged macrophytes are important structural components of freshwater ecosystems that are widely used as long-term bioindicators for the trophic state of freshwater lakes. Climate change and related rising water temperatures are suspected to affect macrophyte growth and species composition as well as the length of the growing season. Alternative to the traditional ground-based monitoring methods, remote sensing is expected to provide fast and effective tools to map submerged macrophytes at short intervals and over large areas. This study analyses interrelations between spectral signature, plant phenology and the length of growing season as influenced by the variable water temperature. During the growing seasons of 2011 and 2015, remote sensing reflectance spectra of macrophytes and sediment were collected systematically in-situ with hyperspectral underwater spectroradiometer at Lake Starnberg, Germany. The established spectral libraries were used to develop reflectance models. The combination of spectral information and phenologic characteristics allows the development of a phenologic fingerprint for each macrophyte species. By inversion, the reflectance models deliver day and daytime specific spectral signatures of the macrophyte populations. The subsequent classification processing chain allowed distinguishing species-specific macrophyte growth at different phenologic stages. The analysis of spectral signatures within the phenologic development indicates that the invasive species Elodea nuttallii is less affected by water temperature oscillations than the native species Chara spp. and Potamogeton perfoliatus.
关键词： spectral library,bioindication,remote sensing reflectance modeling,submerged aquatic vegetation,phenologic variations
更新于2025-09-10 09:29:36
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Infrared reflectance, transmittance, and emittance spectra of MgO from first principles
摘要： By using density functional theory calculations we determined the influence of anharmonic effects on the infrared reflectance, transmittance, and emittance of MgO. The goal is to determine the limit of validity of a perturbative (multiphonon) approach. MgO is chosen as a test material because of the availability of different kinds of radiative properties measured experimentally. Nonanalytic terms of the three-phonon scattering coefficients are explicitly calculated and do not provide measurable effects. The agreement is overall very good to such an extent that, already at room temperature, one can clearly identify regions in which four-phonon scattering processes are dominant with respect to the three-phonon ones. The influence of isotopic disorder at cryogenic temperatures is also settled.
关键词： emittance,transmittance,density functional theory,MgO,infrared reflectance,anharmonic effects,phonon-phonon interactions
更新于2025-09-10 09:29:36