Search

The results of the development and field testing of a compact high-speed deck spectroradiometer for remote sensing reflectance measurements are presented. Validation using data obtained with hydrooptical equipment showed that the new device makes it possible to measure data on remote sensing reflectance with an accuracy sufficient for calculating bio-optical characteristics. Based on the data obtained during field tests of the new device, processed using regional algorithms, the values of the bio-optical characteristics of the Kara and Black seas surface waters were quantitatively assessed. [ABSTRACT FROM AUTHOR]

Frequent fungicide applications are required to manage grapevine powdery mildew (Erysiphe necator). However, this practice is costly and has led to widespread fungicide resistance. A method of monitoring in-field fungicide efficacy could help growers maximize spray-interval length, thereby reducing costs and the rate of fungicide resistance emergence. The goal of this study was to evaluate if hyperspectral sensing in the visible to shortwave infrared range (400 to 2,400 nm) can quantify foliar fungicide efficacy on grape leaves. Commercial formulations of metrafenone, Bacillus mycoides isolate J (BmJ), and sulfur were applied on Chardonnay grapevines in vineyard or greenhouse settings. Foliar reflectance was measured with handheld hyperspectral spectroradiometers at multiple days post-application. Fungicide efficacy was estimated as a proxy for fungicide residue and disease control measured with the Blackbird microscopy imaging robot. Treatments could be differentiated from the untreated control with an accuracy of 73.06% for metrafenone, 67.76% for BmJ, and 94.10% for sulfur. The change in spectral reflectance was moderately correlated with the cube root of the area under the disease progress curve for metrafenone- and sulfur-treated samples (R2 = 0.38 and 0.36, respectively) and with sulfur residue (R2 = 0.42). BmJ treatment impacted foliar physiology by enhancing the leaf mass/area and reducing the nitrogen and total phenolic content as estimated from spectral reflectance. The results suggest that hyperspectral sensing can be used to monitor in-situ fungicide efficacy, and the prediction accuracy depends on the fungicide and the time point measured. The ability to monitor in-situ fungicide efficacy could facilitate more strategic fungicide applications and promote sustainable grapevine protection. [ABSTRACT FROM AUTHOR]

The present study highlights delineation of the distribution of understorey invasive plant species (IPS) in Mudumalai Tiger Reserve (MTR), Western Ghats, India using very high resolution airborne imaging spectroscopy images by evaluating the performance of a Multiple Endmember Spectral Mixture Analysis (MESMA). Lantana camara L. and Chromolaena odorata (L.) R.M.King & H.Rob. have imposed a serious threat to natural ecosystems in MTR by altering the ecosystem processes. The Airborne Visible-Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) based analysis delineated the distribution of understorey IPS, viz., L. camara and C. odorata in MTR, with an overall accuracy of 87 % (k = 0.84) and 84 % (k = 0.8), respectively, with minimal root-mean-square error (RMSE) of MESMA classification (0.001 to 0.0025). In MTR, both the IPS were distributed in large parts and in association with all dominant canopy tree species barring Eucalyptus species. L. camara was majorly found in the southern parts of central MTR with 'high' to 'very high' presence covering 23.09 % and 11.51 % of the total area of central MTR, respectively, in association with Terminalia anogeissiana Gere & Boatwr. and Tectona grandis L.f. Whereas, C. odorata was dominantly found with high (18.11 % area of central MTR) to very high (11.85 % area of central MTR) intensity in the south and southeastern parts within the vicinity of T. anogeissiana and Terminalia elliptica Willd. The study highlights the utilization of high spectral agility in mapping of understorey IPS through spectral differentiation of the patchy distribution of IPS and its intermixing with other local species may be helpful in ecological restoration, conservation of biodiversity, and provisioning long-term management of ecosystem services in highly invaded tropical forests. [ABSTRACT FROM AUTHOR]

To retrieve columnar aerosol properties from sun-photometers both irradiance and radiance calibration factors are needed. For the irradiance the solar calibration constant, V0, that is the instrument counts for a direct normal solar flux extrapolated to the top of the atmosphere, must be determined. The solid view angle, SVA, is the measure of the field of view of the instrument, and it is important for obtaining the Radiance from sky diffuse irradiance measurements. Each of the three sun-photometers networks considered in the present study (SKYNET, AERONET, WMO-GAW) adopts different protocols of calibration and we evaluated the performance of the on-site calibration procedures, applied to SKYNET PREDE-POM instruments, during intercomparison campaigns and laboratory calibrations held in the framework of the Metrology for Aerosol Optical Properties (MAPP) EMPIR project. The on-site calibration, performed as frequently as possible (rather monthly) to monitor change of the machine condition, allow operators to track and evaluate the calibration status on a continuous basis considerably reducing the data gaps incurred by the periodical shipments for performing centralized calibrations. The performance of the on-site calibration procedures for V0 was very good in sites with low turbidity, showing an agreement with a reference calibration between 0.5% and 1.5% depending on wavelengths. In the urban area the agreement decreases between 1.7% and 2.5%. For the SVA the difference varied from a minimum of 0.03 % to a maximum of 3.46%. [ABSTRACT FROM AUTHOR]

The results of the development and field testing of a compact high-speed deck spectroradiometer for remote sensing reflectance measurements are presented. Validation using data obtained with hydrooptical equipment showed that the new device makes it possible to measure data on remote sensing reflectance with an accuracy sufficient for calculating bio-optical characteristics. Based on the data obtained during field tests of the new device, processed using regional algorithms, the values of the bio-optical characteristics of the Kara and Black seas surface waters were quantitatively assessed. [ABSTRACT FROM AUTHOR]

Over the last 15 years, new important developments occurred in the reference method and use of optical sensors dedicated to in-season potato crop nitrogen (N) status (CNS) monitoring. The reference method is based on N nutrition index (NNI) defined as the ratio of critical N concentration (%Nc) and actual plant N concentration (%N) during the growing season, %Nc being deduced from the critical N dilution curve (CNDC) in total crop biomass. New statistical insights on the 11 different existing potato CNDCs worldwide, considered as site- and time-specific because they are built on specific combinations of potato cultivars (G), environment (E) and crop management practices (M), led to the assumption that it could be possible to derive more generic CNDCs providing large sets of data (pairs of biomass and plant N% assessments) from different G×E×M situations. Practical application of the reference method for CNS assessment is labour intensive and time consuming due to plant sampling and laboratory analysis for N content. However, a more generic NNI reference method is valuable to define threshold or critical values of plant N-related biophysical or biochemical variables (BVs) that can be retrieved from optical sensor readings and used as quick indicators for CNS assessment. Optical sensors are classically used to measure leaf or canopy transmittance, reflectance and chlorophyll fluorescence of visible (VIS) and near-infrared (NIR) wavelengths of the electromagnetic spectrum and related to leaf chlorophyll content (LCC) demonstrated as strongly correlated to leaf N content (LNC). Optical sensors applied at the leaf level are mainly handheld devices based on transmittance and chlorophyll fluorescence and have specific advantages and weaknesses that are extensively described to derive BVs and to assess potato CNS. Their main application is dedicated for CNS assessment at small field scale showing low within-field variability. Reflectance-based, remotely sensed optical devices are applied at canopy level from different ground-based, airborne or spaceborne platforms. Ground-based and airborne approaches, combined with different reflectance data analysis and processing mathematical and statistical methods (vegetation indices, chemometrics, machine learning) or physically-based approach such as inversion of radiative transfer models, allowed reliable retrieve of N-related BVs for CNS assessment such as LCC, canopy chlorophyll content (CCC), leaf area index (LAI) or others BVs. Remote sensing from spaceborne platforms, with the recent and forthcoming launches of satellite missions equipped with multispectral and hyperspectral sensors and with enhanced spatial, temporal, spectral and radiometric resolutions in the VIS and NIR regions but also shortwave infrared (SWIR) region allowing to consider plant N related to leaf proteins, have opened new avenues for real-time and reliable CNS monitoring at field and within-field scale over large territories and based on the setup of generic N-related BVs across different growing conditions and multiple G×E×M scenarios. [ABSTRACT FROM AUTHOR]

This review was carried out to understand the retrieval of aerosol optical depth (AOD) datasets for estimating particle concentration and its influence on ambient air and surroundings by various models. Several studies have evaluated particle (PM10 and PM2.5) concentration profiles present in the lowest layers of the atmosphere by using AOD datasets. This study aimed at identifying consistent and precise particle estimation by various datasets retrieved by satellite‐based models for the ground‐level PM concentration. Extremities of satellite sensor data, like specific capabilities, as well as a few drawbacks are presented. Multi‐angle imaging spectroradiometer (MISR), visible infrared imaging radiometer suite (VIIRS) datasets, mixed‐effect model (MEM), and geographically weighted regression (GWR) models outperformed to estimate AOD and PM in comparison with the moderate resolution imaging spectroradiometer (MODIS) and other datasets. The improvised algorithms with higher resolution in the upcoming research would provide an even better estimation for AOD and PM. [ABSTRACT FROM AUTHOR]

The use of tanning devices in Spain is regulated by the Royal Decree 1002/2002, which is based on the European standard EN60335-2-27. The European standard establishes that the total unweighted irradiance between 200 and 280 nm must not exceed 0.003 Wm−2, a requirement that the Spanish regulation modified to 0.03 Wm−2 from 250 to 295 nm. With these differences, the compliance consideration of an artificial tanning device can vary. Spectral irradiance measurements of 41 tanning devices performed with a high-resolution spectroradiometer were analyzed. None of the tanning devices had irradiances higher than 0.003 Wm−2 between 250 (the shortest wavelength measured by the spectroradiometer) and 280 nm, but the limit required by Spanish regulation was exceeded by 11 devices, of which one would have been considered compliant according to the European standard since the effective irradiance was lower than 0.3 Wm−2. Beyond noting the differences that can occur in sunbed inspections according to the established criteria, this work has shown the differences in the spectral and total values of devices in use in Spain, validating the need for periodic inspections. [ABSTRACT FROM AUTHOR]

Shallow and coastal waters are often rich in nutrients (eutrophic), biologically productive, turbid from runoff, and located where the atmosphere above can be more aerosol-laden than over open-ocean waters due to proximity to aerosol sources on land. Although the NASA Earth Observing System's Multi-angle Imaging SpectroRadiometer (MISR) on board the Terra satellite has been monitoring global aerosols for over 23 years, the current operational retrieval algorithm (V23) is not applied over waters less than 50 m in depth or within 5 km of land, designated as "shallow water." This is due to the simplicity of the Dark Water algorithm, applied operationally over deep waters, which assumes the surface is essentially black in the primarily used red and near-infrared spectral bands. In this work, we describe the implementation and validation of a "Shallow Water" aerosol retrieval algorithm for MISR, which takes advantage of all four available spectral bands and includes a Lambertian surface reflectivity term to account for water-leaving radiance. This algorithm compares well to independent, surface-based observations and demonstrates better performance over shallow waters than the operational Dark Water retrieval algorithm. Globally, aerosol retrievals over shallow waters increase the total number of MISR over-water measurements by more than 7 %, including new retrievals made over some of the most biologically productive parts of the ocean. [ABSTRACT FROM AUTHOR]

Spectroradiometric measurements of direct solar irradiance traceable to the SI were performed by three spectroradiometer systems during a 3-week campaign in September 2022 at the Izaña Atmospheric Observatory (IZO) located on the island of Tenerife, Canary Islands, Spain. The spectroradiometers provided direct spectral irradiance measurements in the spectral ranges 300 to 550 nm (QASUME), 550 to 1700 nm (QASUME-IR), 300 to 2150 nm (BiTec Sensor, BTS), and 316 to 1030 nm (Precision Solar Spectroradiometer, PSR), with relative standard uncertainties of 0.7 %, 0.9 %, and 1 % for QASUME/QASUME-IR, the PSR, and the BTS respectively. The calibration of QASUME and QASUME-IR was validated prior to this campaign at Physikalisch-Technische Bundesanstalt (PTB) by measuring the spectral irradiance from two spectral irradiance sources, the high-temperature blackbody BB3200pg as a national primary standard and the tuneable laser facility TULIP. The top-of-atmosphere (ToA) solar irradiance spectra from the spectroradiometers were retrieved from direct solar irradiance measurements using zero-air-mass extrapolation during cloud-free conditions, which were then compared to the TSIS-1 Hybrid Solar Reference Spectrum (HSRS). These ToA solar spectra agreed to within 1 % for spectral ranges longer than 400 nm (for QASUME also at shorter wavelengths) in the spectral regions free of significant trace gas absorption and were well within the combined uncertainties over the full investigated spectral range. Using the results from the comparison with QASUME, the relative standard uncertainty of the TSIS-1 HSRS ToA solar spectrum in the spectral range 308 to 400 nm could be reduced from its nominal 1.3 % to 0.8 %, representing the relative standard uncertainty of the QASUME ToA solar spectrum in this spectral range. The spectral aerosol optical depth (AOD) retrieved from the solar irradiance measurements of these spectroradiometers using the TSIS-1 HSRS as the reference ToA solar spectrum agreed to within 0.01 in optical depth in nearly all common spectral channels of two narrowband filter radiometers belonging to the Global Atmosphere Watch Precision Filter Radiometer (GAW-PFR) network and Aerosol Robotic Network (AERONET). This study shows that it is now possible to retrieve spectral AOD over the extended spectral range from 300 to 1700 nm using solar irradiance measurements traceable to the SI using laboratory-calibrated spectroradiometers with similar quality to that from traditional Langley-based calibrated instruments. The main improvement to previous investigations is the recent availability of the high-spectral-resolution TSIS-1 HSRS with very low uncertainties, which provides the top-of-atmosphere reference for the spectral atmospheric transmission measurements obtained from ground-based solar irradiance measurements. [ABSTRACT FROM AUTHOR]

Remote and proximal sensing platforms at the service of precision olive growing are bringing new development possibilities to the sector. A proximal sensing platform is close to the vegetation, while a remote sensing platform, such as unmanned aerial vehicle (UAV), is more distant but has the advantage of rapidity to investigate plots. The study aims to compare multispectral and hyperspectral data acquired with remote and proximal sensing platforms. The comparison between the two sensors aims at understanding the different responses their use can provide on a crop, such as olive trees having a complex canopy. The multispectral data were acquired with a DJI multispectral camera mounted on the UAV Phantom 4. Hyperspectral acquisitions were carried out with a FieldSpec® HandHeld 2™ Spectroradiometer in the canopy portions exposed to South, East, West, and North. The multispectral images were processed with Geographic Information System software to extrapolate spectral information for each cardinal direction's exposure. The three main Vegetation indices were used: normalized difference vegetation index (NDVI), normalized difference red-edge index (NDRE), and modified soil adjusted vegetation index (MSAVI). Multispectral data could describe the total variability of the whole plot differentiating each single plant status. Hyperspectral data were able to describe vegetation conditions more accurately; they appeared to be related to the cardinal exposure. MSAVI, NDVI, and NDRE showed correlation r =0.63**, 0.69**, and 0.74**, respectively, between multispectral and hyperspectral data. South and West exposures showed the best correlations with both platforms. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effect of cross‐polarization filters on the colors of shade tabs obtained with a digital single‐lens reflex (DSLR) camera, macrolens, and a ring flash. Materials and Methods: Digital images of four shade tables (1M1, 3L2.5, 3R2.5, and 5M3) from the VITA Toothguide 3D‐Master shade guide were taken using a DSLR camera, 100 mm macrolens, and ring flash with two different cross‐polarizing filters (Polar_eyes and Filtropolar), and without (Nonpolarizer; n = 7). The CIE L*a*b* color coordinates of digital images were calculated and remeasured with a spectroradiometer (SR). The color differences (ΔE00) between the SR and digital images were calculated and analyzed with the two‐way analysis of variance (ANOVA) and Tukey HSD test (α = 0.05). Results: ΔE00 values of all test groups were higher than the clinically acceptable threshold (∆E00 > 1.80). While the ∆E00 values of Filtropolar (6.19 ± 0.44) and Polar_eyes (7.82 ± 0.23) groups were significantly higher than the Nonpolarizer (4.69 ± 0.32) for the 1M1 shade tab, ∆E00 value of Polar_eyes (6.23 ± 0.34) was significantly lower than Nonpolarizer (10.71 ± 0.48) group for 5M3 shade tab (p < 0.05). Conclusion: The color‐matching results of tested digital photography techniques with and without cross‐polarization were unacceptable, compared to a spectroradiometer. While digital photography with Polar_eyes cross‐polarizing filter has closer results to the reference device for the low‐in‐value shade table (5M3), for the high‐in‐value shade table (1M1), improved results were obtained without a cross‐polarizing filter. Clinical Significance: The cross‐polarization filters are increasingly used in dentistry for tooth color communication with digital photography techniques. However, the digital photography techniques with‐without cross‐polarization filterers should be improved to obtain clinically acceptable color‐matching results. [ABSTRACT FROM AUTHOR]

The Peak Design Ltd hyperspectral radiometer (HSR1) was tested at the Atmospheric Radiation Measurement User Facility (ARM) Southern Great Plains (SGP) site in Lamont, Oklahoma for two months from May to July 2022. The HSR1 is a prototype instrument that measures total and diffuse spectral irradiance from 360 to 1100 nm with a spectral resolution of 3 nm. The HSR1 spectral irradiance measurements are compared to nearby collocated spectral radiometers including two multifilter rotating shadowband radiometers (MFRSR) and a shortwave array spectroradiometer—hemispheric (SASHe). The total spectral irradiances at 500 nm for the HSR1 compared to the MFRSRs have a mean (relative) difference of 0.01 W m-2 nm-1 (1–2 %). The HSR1 mean diffuse spectral irradiance at 500 nm is smaller than the MFRSRs by 0.03–0.04 (10 %) W m-2 nm-1. The HSR1 clear-sky aerosol optical depth (AOD) is also retrieved by considering Langley regressions and compared to collocated instruments such as the Cimel sunphotometer (CSPHOT), MFRSRs, and SASHe. The mean HSR1 spectral AOD at 500 nm is larger than the CSPHOT by 0.010 (8 %) and larger than the MFRSRs by 0.007–0.017 (6–18 %). In general, good agreement between the HSR1 and other instruments is found in terms of the spectral total irradiance, diffuse irradiance, and AODs at 500 nm. The HSR1 quantities are also compared at other wavelengths to the collocated instruments, where similar agreement is found for the spectral irradiances, although relatively larger disagreement is found at higher wavelengths, especially for spectral AODs. [ABSTRACT FROM AUTHOR]

We report an all-fiber, near-infrared laser heterodyne radiometer (LHR) that uses two distributed feedback (DFB) diode lasers as local oscillators. This scheme allows the retrieval of the column abundances of multiple atmospheric gases of CH4, CO2, and H2O. To improve the detection efficiency, we operated the two DFB diode lasers emitting at 1653 and 1568 nm simultaneously within one scanning cycle. The duration of one scanning cycle was experimentally determined to be 2 s. An atmospheric transmission spectrum of multi-gas was observed within 20 s after averaging ten times. This approach has simplified the sensing system and reduced the probability of being affected by the rapid and random fluctuation of solar radiation due to clouds. We regulated the laser power, and hence, the amplitudes of background heterodyne signals excited by the two local oscillators, to accurately measure the transmission spectrum of each gas species. The results of the sun-tracking observations of this LHR sensor show good agreement with the data taken simultaneously by the GOSAT satellite. [ABSTRACT FROM AUTHOR]

Estimating continuous spatial forest canopy height is difficult in forestry investigations. Using a back propagation (BP) neural network, the ice, cloud, and land elevation satellite (ICESat-2) and its terrain/vegetation products [ ICESat-2/ATLO8 data in growing seasons and moderate resolution imaging spectroradiometer (MODIS) information in 2019-2020] were combined to explore the continuous spatial estimation of forest canopy height in southwest China. The results are as follows: (1) ICESat-2/ATL08 data reliably expressed the natural forest canopy in southwest China and passed the confidence test with R=0.566, P<0.01, compared with remote sensing data for tree height during the same period in 2019. (2) BP neural network fitting of ICESat-2/ATL08 and MODIS data could reliably obtain continuous forest canopy height. Neural network training results showed R²>0.7 and root mean square error of about 2.5 m. The forest canopy height values of 10 randomly selected natural reserves were compared with the homologous remote sensing data from 2005, resulting in R=0.836 (P<0.001). The frequency histogram of continuous forest canopy height showed normal distribution, and the high frequency band was 10-25 m. (3) The mean forest canopy height in southwest China was 16 m, lower than the mean in 2005. However, the forest coverage and forest canopy height increased on the border between southern Chongqing and northern Guizhou, northeastern Guizhou, and Liuzhao Mountain in Yunnan, and it decreased slightly in Dali City in Yunnan. In terms of spatial distribution, values greater than 20 m were distributed in the periphery of Sichuan Basin, the Jinsha River Basin, and Daba Mountain in Chongqing, Wuliang Mountain and Ailao Mountain in Yunnan, and southeastern Guizhou. Rural towns in southwest Sichuan, Daocheng, northeast Chongqing, and the central Yunnan-Guizhou Plateau were all below 10 m. [ABSTRACT FROM AUTHOR]

Retrieval of the cloud thermodynamic phase (CP) is essential for satellite remote sensing and downstream applications. However, there is still a lack of efficient nighttime CP data products. A transfer‐learning‐based deep learning model, transfer‐learning‐ResUnet, is proposed to retrieve the nighttime CP of Himawari‐8 from thermal infrared channels. Cloud products of Himawari‐8 and Moderate‐resolution Imaging Spectroradiometers were selected as labels during training. A benchmark obtained by the Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations confirmed the accuracy of the CP retrieval. During three independent months, the daytime and nighttime retrieval accuracy of the CP was 0.867 and 0.816, respectively, which was superior to that of the Himawari‐8 operational product in the daytime (0.788). Plain Language Summary: Clouds are essential for modulating global weather and climate systems and are routinely monitored by weather satellites such as Himawari‐8, a geostationary Earth‐observing satellite operated by the Japan Meteorological Agency. The cloud thermodynamic phase (CP) product is the main Level 2 product of Himawari‐8 and contains cloud properties. However, Himawari‐8 lacks a nighttime CP product, owing to its retrieval algorithm. Deep learning (DL) has proven to be effective in remote sensing. Among the various deep‐learning model structures, the fusion model of ResNet‐34 and Unet has the most accurate retrieval. Taking this model structure as the basis, the transfer‐learning‐ResUnet was established to improve the retrieval accuracy by integrating the Himawari‐8 and Moderate‐resolution Imaging Spectroradiometers cloud products as labels through a transfer‐learning method. To validate the nighttime CP retrieved by the model, data products obtained by Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations were used. During three independent months, the daytime and nighttime retrieval accuracy of CP retrieval was 0.867 and 0.816, respectively, which were higher than that of Himawari‐8 operational product in the daytime (0.788). Key Points: The cloud thermodynamic phase obtained from Himawari‐8 is essential, but there is no accurate nighttime productA transfer‐learning‐based method provides rapidly obtained and accurate products, with an accuracy higher than that of Himawari‐8 productsIndependent comparisons with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations and Moderate‐resolution Imaging Spectroradiometers show that the retrieval results are reliable for both daytime and nighttime [ABSTRACT FROM AUTHOR]

Spectroradiometric measurements of direct solar irradiance traceable to the SI were performed by three spectroradiometer systems during a three week campaign in September 2022 at the Izaña Atmospheric Observatory (IZO) located on the island of Tenerife, Canary Islands, Spain. The spectroradiometers provided direct spectral irradiance measurements in the spectral range 300 nm to 550 nm (QASUME), 550 nm to 1700 nm (QASUME-IR), 300 nm to 2150 nm (BTS), and 316 nm to 1030 nm (PSR), with relative standard uncertainties of 0.7%, 0.9% and 1% for QASUME/QASUME-IR, PSR, and BTS respectively. The calibration of QASUME and QASUME-IR was validated prior to this campaign at the PTB by measuring the spectral irradiance from two spectral irradiance sources, the high temperature blackbody BB3200pg as national primary standard and the tuneable laser facility TULIP. The Top of Atmosphere (ToA) solar irradiance spectra from the spectroradiometers were retrieved from direct solar irradiance measurements using zero airmass extrapolation during cloudfree conditions which were then compared to the TSIS-1 HSRS solar spectrum. These ToA solar spectra agreed to within 1% for the spectral range longer than 400 nm (for QASUME also at shorter wavelengths) in the spectral regions free of significant trace gas absorption and well within the combined uncertainties over the full investigated spectral range. Using the results from the comparison with QASUME, the relative standard uncertainty of the TSIS-1 HSRS ToA solar spectrum in the spectral range 308 nm to 400 nm could be reduced from its nominal 1.3% to 0.8%, representing the relative standard uncertainty of the QASUME ToA solar spectrum in this spectral range. The spectral Aerosol Optical Depth (AOD) retrieved from the solar irradiance measurements of these spectroradiometers using TSIS-1 HSRS as the reference ToA solar spectrum agreed to within 0.01 in optical depth in nearly all common spectral channels of two narowband filter radiometers belonging to the GAWPFR and AERONET networks. This study shows that it is now possible to retrieve spectral AOD over the extended spectral range from 300 nm to 1700 nm using solar irradiance measurements traceable to the SI using laboratory calibrated spectroradiometers with similar qual20 ity as from traditional Langley-based calibrated instruments. The main improvement to previous investigations is the recent availability of the high spectral resolution TSIS-1 HSRS solar spectrum with very low uncertainties which provides the Top of Atmosphere reference for the spectral atmospheric transmission measurements obtained from ground based solar irradiance measurements. [ABSTRACT FROM AUTHOR]

This study presents a new total column ozone (TCO) retrieval from the Koherent system, developed at the Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center (PMOD/WRC). The instrument is based on a small, cost-effective, robust, low-maintenance and state-of-the-art-technology array spectroradiometer. It consists of a BTS-2048-UV-S-F array spectroradiometer from Gigahertz-Optik GmbH, coupled with an optical fibre to a lens-based telescope mounted on a sun tracker for measuring direct UV irradiance in the ultraviolet wavelength band between 305 to 345 nm. Two different algorithms are developed for retrieving TCO from these spectral measurements: (1) TCO retrieved by a least-squares-fit algorithm (LSF) and (2) a custom-double-ratio (CDR) technique using four specifically selected wavelengths from the spectral measurements. The double-ratio technique is analogous to the retrieval algorithm applied for the Dobson instruments and the Brewer instruments but is adopted here for TCO retrieval with Koherent. The instrument was calibrated in two different ways: (a) absolute calibration of the spectra using the portable reference for ultraviolet radiation QASUME for the LSF retrieval and (b) relative calibration of the extraterrestrial constant (ETC) of the CDR retrieval by minimising the slope between air mass and the relative differences of TCO from QASUME and Koherent. This adjustment of the ETC allows the instrument to be calibrated with standard TCO reference instruments during calibration campaigns, such as a double-monochromator Brewer. A 2-year comparison in Davos, Switzerland, between Koherent and the Brewer 156 (double monochromator) shows that TCO derived from Koherent and the Brewer 156 agree, on average, over the entire period within 0.7 % for all retrievals in terms of offset. The performance in terms of slant path depends on the selected retrieval and the applied corrections. The stray-light-corrected LSF retrieval exhibits a smaller slant path dependency than the CDR retrieval and performs almost as well as a double-monochromator system. The slant path dependency of the CDR is comparable to the slant path dependency of a single Brewer monochromator. The combination of both retrievals leads to performance with an offset close to zero compared to Brewer 156, a seasonal amplitude of the relative difference of 0.08 % and a slant path dependency of maximum 1.64 %, which is similar to other standard TCO instruments such as single Brewer or Dobson. Applying the double-ratio technique by selecting the wavelengths and slit functions from Brewer and Dobson, respectively, allows for the determination of the effective ozone temperature with an uncertainty of 3 K in terms of daily averages. With the improved TCO retrieval, Koherent serves as a new low-maintenance instrument which could also be used to monitor TCO at remote sites. The TCO retrieval presented here may be applied to other array-based spectroradiometers, providing direct spectral measurements in the ultraviolet wavelength band. [ABSTRACT FROM AUTHOR]

A laser correlation study of irradiation damage is carried out on the basis of anodized functional films with the aim of improving the stray light absorptivity in the framework of high-energy laser systems and reducing the contamination of the system after irradiation damage. An experimental study is performed to investigate the effect of different laser characteristics (wavelength, spot diameter, energy and incident angle) on the damage of functional films. On this basis, the damage evolution process was analyzed using ABAQUS secondary development and was in good agreement with the experimental results. In addition, the damage mechanism of the film system is discussed. This study can provide guidance for the optimization of the functional film system, as well as a reference for the design of the main optical path of the high-energy laser system. [ABSTRACT FROM AUTHOR]

Ground-based passive measurements of downwelling atmospheric radiation at ~110.836 GHz allow extracting the spectra of ozone self-radiation (rotational transition J = 61,5–60,6) coming from the low stratosphere–mesosphere and retrieving vertical profiles of ozone concentration at these altitudes. There is a notable (several hundred kHz) ambiguity in the determination of the resonance frequency of this important ozone line. We carried out long-term ground-based measurements of atmospheric microwave radiation in this range using upgraded apparatus with high technical accuracy and spectral resolution (~12 kHz). The obtained brightness temperature spectra allowed us to determine the frequency of this ozone line to be 110,835.909 ± 0.016 MHz. We verified that the Doppler frequency shift by horizontal wind as well as the variations of the tropospheric absorption had little effect on the obtained result. The found value was 131 ± 16 kHz less than that measured in the laboratory and differed from modern model calculations. At the same time, it was close to the results of early semiempirical calculations made more than 40 years ago. The applications where precise knowledge about the resonance frequency of this ozone line can be important were discussed in this paper. [ABSTRACT FROM AUTHOR]

Hyperspectral remote sensing is a useful technique for detecting spatio-temporal changes in crop morphological and physiological health. In order to identify the pestsensitive bands for rice leaf folder (RLF), the groundbased hyperspectral data were recorded at varying damage levels. The first- and second-order derivatives were correlated with correlation coefficient r and per cent leaf damage. The common region identified were recognized as sensitive regions (508-529, 671-680, 721-759, 779-786 and 804-820 nm). The absorption dips were also found using Sensitivity and Continuum Removal Analysis. Combining all, a total of nine spectral bands (518, 549, 661, 674, 678, 731, 789, 816 and 898 nm) were identified as pest-sensitive bands for RLF. The feature-selection method was employed using RELIEFF algorithm to find out the band combinations and bands 518, 661 and 731 nm yielded maximum accuracy of 81.67%. [ABSTRACT FROM AUTHOR]

Array spectroradiometers are increasingly being used to measure natural and artificial optical radiation because of their many advantages compared to traditional instruments. This study aims to thoroughly characterise a commercially available, cost-effective array device (AvaSpec ULS2048-LTEC) and compare its measurements of global solar irradiance in the 290–1100 nm wavelength range with those collected during three short-term field campaigns from more advanced, or specifically designed instruments. Moreover, the AvaSpec observations were compared with the output of a radiative transfer model. The results show that, despite its conceptually simple instrumental design, the AvaSpec can provide measurements of nearly comparable quality to those from reference instruments (e.g., UV index and global horizontal irradiance generally within ±5%) if all corrections are performed. These preliminary observations will be the basis of a long-term series at the Aosta–Saint-Christophe observatory, which can be employed to study solar energy production, biological effects and atmospheric composition changes in the Alpine environment. All procedures, including the encountered issues and proposed solutions, are described in detail. [ABSTRACT FROM AUTHOR]

Monitoring grape nutrient status, from flowering to veraison, is important for viticulturists when implementing vineyard management strategies, in order to produce quality wines. However, traditional methods for measuring nutrient elements incur high labour costs. The aim of this study is to explore the potential of predicting grapevine leaf blade nutrient concentration based on hyperspectral data. Leaf blades were collected at two Pinot Noir commercial vineyards at Martinborough, New Zealand. The leaf blade spectral data were obtained with a handheld spectroradiometer, to evaluate surface reflectance and derivative spectra in the spectrum range between 400 and 2400 nm. Afterwards, leaf blades nutrient concentrations (N, P, K, Ca, and Mg) were measured, and their relationships with the hyperspectral data were modelled by machine learning models; partial least squares regression (PLSR), random forest regression (RFR), and support vector regression (SVR) were used. Pearson correlation and recursive feature elimination, based on cross-validation, were used as feature selection methods for RFR and SVR, to improve the model's performance. The variable importance score of PLSR, and permutation variable importance of RFR and SVR, were used to determine the most sensitive wavelengths, or spectral regions related to each biochemical variable. The results showed that the best predictive performance for leaf blade N concentration was based on PLSR to raw reflectance data (R2 = 0.66; RMSE = 0.15%). The combination of support vector regression with the Pearson correlation selected method and second derivative reflectance provided a high accuracy for K and Ca modelling (R2 = 0.7; RMSE = 0.06%; R2 = 0.62; RMSE = 0.11%, respectively). However, the modelling performance for P and Mg, by different feature groups and variable selection methods, was poor (R2 = 0.15; RMSE = 0.02%; R2 = 0.43; RMSE = 0.43%, respectively). Thus, a larger dataset is needed for improving the prediction of P and Mg. The results indicated that for Pinot Noir leaf blades, raw reflectance data had potential for the prediction of N concentration, while the second-derivative spectra were more suitable to predict K and Ca. This study led to the provision of rapid and non-destructive measurements of grapevine leaf nutrient status. [ABSTRACT FROM AUTHOR]

Grapevine virus-associated disease such as grapevine leafroll disease (GLD) affects grapevine health worldwide. Current diagnostic methods are either highly costly (laboratory-based diagnostics) or can be unreliable (visual assessments). Hyperspectral sensing technology is capable of measuring leaf reflectance spectra that can be used for the non-destructive and rapid detection of plant diseases. The present study used proximal hyperspectral sensing to detect virus infection in Pinot Noir (red-berried winegrape cultivar) and Chardonnay (white-berried winegrape cultivar) grapevines. Spectral data were collected throughout the grape growing season at six timepoints per cultivar. Partial least squares-discriminant analysis (PLS-DA) was used to build a predictive model of the presence or absence of GLD. The temporal change of canopy spectral reflectance showed that the harvest timepoint had the best prediction result. Prediction accuracies of 96% and 76% were achieved for Pinot Noir and Chardonnay, respectively. Our results provide valuable information on the optimal time for GLD detection. This hyperspectral method can also be deployed on mobile platforms including ground-based vehicles and unmanned aerial vehicles (UAV) for large-scale disease surveillance in vineyards. [ABSTRACT FROM AUTHOR]

Optical remote sensing and Earth observation instruments rely on precise radiometric calibrations which are generally provided by the broadband emission from large-aperture integrating spheres. The link between the integrating sphere radiance and an SI-traceable radiance standard is made by spectroradiometer measurements. In this work, the calibration efforts of a Spectra Vista Corporation (SVC) HR-1024i spectroradiometer are presented to study how these enable radiance transfer measurements at the Calibration Home Base (CHB) for imaging spectrometers at the Remote Sensing Technology Institute (IMF) of the German Aerospace Center (DLR). The spectral and radiometric response calibrations of an SVC HR-1024i spectroradiometer are reported, as well as the measurements of non-linearity and its sensitivity to temperature changes and polarized light. This achieves radiance transfer measurements with the calibrated spectroradiometer with relative expanded uncertainties between 1% and 3% ( k = 2 ) over the wavelength range of 380 nm to 2500 nm, which are limited by the uncertainties of the applied radiance standard. [ABSTRACT FROM AUTHOR]

The spiny bollworm (SBW), Earias insulana (Boisd.), is from the most destructive cotton pests in Egypt. Larvae can reduce the yield about 40%. Monitoring and forecasting have become an integral aspect of the crop production system in developed countries to control pests. Recently, remote sensing has gained popularity in agriculture for pest monitoring, yield forecasting and early warning to crop growers for proper time in pest management with the least quantity of ground sampling possible.This work aims to measure the validity of using a new methodology for pest detection in cotton bolls without exposing the plant to any danger., This action could be conducted by making a spectroscopy check using spectroradiometer for every boll in field and compare this reading automatically with the spectral library that was built in earlier by measuring numbers of well-known bolls (healthy and infected measuring of some Vegetation Indices (MCARI, TCARI, NPCI, NDVI, NDWI, WBI) also done from reflectance values that carried out, in order to detect the best indices affected by pest infection. Thermal imaging also was done to differentiate between diseased and non-infected tissue. The results described the reflectance spectra of cotton bolls with known SBW infestations and healthy ones and could identify the certain narrow band that is sensitive to SBW damage, BLUE band has found to be the best for spectrally identifying infested bolls. Normalized Pigment Chlorophyll Index (NPCI) is the best index among vegetation indices used in this research. Complementally, to use remote sensing applications, thermal imaging was used to detect thermal patterns associated with insect infestation. The result of study indicate the validity of using spectral measurement and thermal imaging as a tools of remote sensing in detection of the presence of spiny boll worm without wasting and ruined the bolls in field, this method could be also effective in detection of other pests on other crops. [ABSTRACT FROM AUTHOR]

Objectives: Using moderate-resolution imaging spectroradiometer (MODIS) can detect high spatial resolution but low precision precipitable water vapor (PWV), while global navigation satellite system (GNSS) can retrieve high precision but low spatial resolution PWV, in order to get high spatial resolution and precision PWV, it is necessary to integrate two kinds of data. Methods: Taking Chinese mainland as an example, MODIS PWV was done the correction based on GNSS observation and meteorological data provided by crustal movement observation network of China(CMONOC). Firstly, considering the geographical environment, altitude, climate type and other factors, Chinese mainland was divided into 16 regions, and the correlation analysis of regional MODIS PWV and GNSS PWV was carried out. And then, it was constructed for the correction-model of MODIS PWV by different regions and seasons based on GNSS PWV. After that, the regional model result, the single site model result and the measured GNSS PWV were compared to test the reliability of the model. Finally, MODIS PWV distribution in Chinese mainland can be obtained by MODIS PWV correction and image superposition. Results: The results show that the accuracy of the regional MODIS PWV correction model is similar to that of the single-site model, which can replace the single-site model for MODIS PWV correction. Conclusions: The MODIS PWV correction model of different regions can be used to effectively improve the precision of MODIS PWV. It can be used for providing reference for short-term weather prediction and interferometric synthetic aperture radar atmospheric correction. [ABSTRACT FROM AUTHOR]

Lake Tana, the largest inland water body in Ethiopia, has witnessed significant changes due to ongoing urbanization and socioeconomic activities in recent times. In this study, the two-decade recordings of moderate resolution imaging spectroradiometer (MODIS) were used to derive Forel–Ule index (FUI). The FUI, which ranges from 1 (dark-blue pristine water) to 21 (yellowish-brown polluted water), is important to fully understand the quality and trophic state of the lake in the last two decades. The analysis of FUI over a period of 22 years (2000–2021) indicates that Lake Tana is in a eutrophic state as confirmed by FUI values ranging from 11 to 17. This is in agreement with the trophic state index (TSI) estimated from MERIS diversity-II chlorophyll a (Chl _ a ) measurements for the overlapping 2003-2011 period. The categorical skill scores show that FUI-based lake water trophic state classification relative to MERIS-based TSI has a high performance. FUI has a positive correlation with TSI, (Chl _ a ), turbidity, and total suspended matter (TSM) and negative relations with Chl _ a and TSM (at the lake shoreline) and colored dissolved organic matter. The annual, interannual and seasonal spatial distribution of FUI over the lake show a marked variation. The hydro-meteorological, land-use–land-cover (LULC) related processes are found to modulate the spatiotemporal variability of water quality within the range of lower and upper extremes of the eutrophic state as revealed from the FUI composite analysis. The FUI composites were obtained for the terciles and extreme percentiles of variables representing hydro-meteorological and LULC processes. High FUI composite (poor water quality) is associated with above-normal and extremely high (85 percentile) lake bottom layer temperature, wind speed, precipitation, surface runoff, and hydrometeorological drought as captured by high negative standardized precipitation-evapotranspiration index (SPEI). In contrast, a high FUI composite is observed during below-normal and extremely low (15 percentile) lake skin temperature and evaporation. Conversely good water quality (i.e., low FUI) was observed during times of below-normal and above-normal values of the above two sets of drivers respectively. Moreover, FUI varies in response to seasonal NDVI/EVI variabilities. The relationship between water quality and its drivers is consistent with the expected physical processes under different ranges of the drivers. High wind speed, for instance, displaces algae blooms to the shoreline whereas intense precipitation and increased runoff lead to high sediment loads. Increasing lake skin temperature increases evaporation, thereby decreasing water volume and increasing insoluble nutrients, while the increasing lake bottom layer temperature increases microbial activity, thereby enhancing the phosphorus load. Moreover, during drought events, the low inflow and high temperature allow algal bloom, Chl _ a , and suspended particles to increase, whereas high vegetation leads to an increase in the non-point sources of total phosphorus and nitrogen. [ABSTRACT FROM AUTHOR]

The optical system of an imaging spectrometer working on a geostationary earth orbit (GEO) covering a full optical spectrum of 0.3–12.5 μm is analyzed and designed. It enables a ground coverage of 400 × 400 km by internal scanning and achieves a high spatial resolution of 25 m. The full spectrum is divided into five sub-bands, and each band adopts four spectrometers to splice in the field of view to achieve the ultra-long slit required by the wide swath. The total length of the slit is up to 241.3 mm. This paper focuses on compact spectrometers with long slits that can meet the splicing requirements and points out that low spectral distortions, low stray light, high signal-to-noise ratio, and uniform spectral response are necessary for high-fidelity performance. The Offner and Wynne–Offner high-fidelity spectrometers based on convex blazed gratings are designed, and prototypes of each band are developed as well. The properties of long slits and convex blazed gratings are presented. The maximum length of a single slit is 61.44 mm. The groove density of gratings for five bands ranges from 8.8 lp/mm to 312.1 lp/mm, and the peak efficiency is up to 86.4%. The alignment and test of the spectrometers are introduced. Results show that the developed spectrometers have high fidelity and fulfill all requirements. [ABSTRACT FROM AUTHOR]

Clustering algorithms are commonly used for inspecting the behavior of clouds in both model and satellite data sets. Often overlooked in cluster analysis is the variability that occurs within any clusters generated. This is particularly important in the geophysics where clusters are often generated with a focus on interpretability over mathematical optimization. Two metrics, the Davies‐Bouldin index and the subsom entropy, are used to identify clusters with large internal variability. These metrics are applied to an example set of clusters from prior research that were generated using cloud top pressure‐cloud optical thickness joint histograms from the Moderate Resolution Imaging Spectroradiometer data set. Applying these metrics to the clusters identifies one cluster in particular as a major outlier. Examining the calculations behind these metrics in more detail provides further information about the internal variability of the clusters. The clusters are also examined over several geographic regions showing mostly consistent behavior. There are, however, some large anomalies such as the behavior of the clear sky cluster or the behavior of several different clusters over the Arctic Ocean. To aide our interpretation of these results, two clusters are chosen for a detailed analysis of their subclusters. The geographic distributions and radiative properties of these subclusters are examined and clearly identify that subclusters have physically distinct behavior. This result illustrates that these metrics are capable of determining when a cluster contains physically distinct subclusters. This demonstrates the potential utility of these metrics if they were applied to other geophysical data sets. Key Points: Subclusters are created for an existing set of MODIS cloud clusters to explore the variability within the clustersThe Davies‐Bouldin index and subsom entropy were used as metrics to identify the least representative clustersParticular clusters are then directly analyzed using their subclusters, identifying overlooked behavior within these clusters [ABSTRACT FROM AUTHOR]

Hyperspectral Remote Sensing (HRS) data is vital for crop growth monitoring due to availability of contiguous bands. This research work provides a new novel crop estimator model given the name “Crop Stage estimator” developed using the HRS data on an open-source R platform. The generic model structure provides an easy way to test and modify the importance of crop parameter namely Leaf Area Index to deduce crop growth stages of winter wheat (Triticum aestivum L.) particularly during –heading, tillering and booting. Further, to know the LAI variations at different agriculture sites, the best model was implemented using the AVIRISNG (Airborne Visible Near-Infrared Imaging Spectrometer - Next Generation) hyperspectral datasets. The analysis indicates that during tillering stage the performance was found best during calibration (r = 0.66, RMSE =0.40, and Bias =0.80) and validation (r = 0.98, RMSE =0.20, and Bias =0.12) in comparison to the ground measurements. [ABSTRACT FROM AUTHOR]

This study presents total column ozone (TCO) retrieval from a new system, called Koherent, developed at PMOD/WRC. The instrument is based on a small, cost effective, robust, low-maintenance and state-of-the-art technology array spectroradiometer. It consists of a BTS-2048-UV-S-F array spectroradiometer from Gigahertz-Optik GmbH, coupled with an optical fiber to a lens-based telescope mounted on a sun tracker for measuring direct UV irradiance in the ultraviolet wavelength band between 305 nm to 345 nm. Two different algorithms are developed for retrieving TCO from these spectral measurements: 1) TCO retrieved by a minimal least squares fit algorithm (LSF) and 2) a Custom Double Ratio (CDR) technique using four specifically selected wavelengths from the spectral measurements. The double ratio technique is analogous to the retrieval algorithm applied for the Dobson and the Brewer but adopted and optimized here for TCO retrieval with Koherent. The instrument was calibrated in two different ways: a) absolute calibration of the spectra using the portable reference for ultraviolet radiation QASUME for the LSF retrieval and b) relative calibration of the extraterrestrial constant (ETC) of the CDR retrieval, by minimizing the slope between air mass and the relative differences of TCO from QASUME and Koherent. This adjustment of the ETC allows the instrument to be calibrated with standard TCO reference instruments during calibration campaigns, such as a double monochromator Brewer. A two-year comparison in Davos, Switzerland, between Koherent and the Brewer 156 (double monochromator) shows that TCO derived from Koherent and the Brewer 156 agree in average over the entire period within less than 0.7 % for all retrievals in terms of offset. The performance in terms of slant path depends on the selected retrieval and the applied corrections. The stray light corrected LSF retrieval exhibits a smaller slant path dependency than the CDR retrieval and performs almost as for a double monochromator system. The slant path dependency of the CDR is comparable to the slant path dependency of a single Brewer monochromator. The combination of both retrievals leads to performance with an offset close to zero compared to Brewer 156, a seasonal amplitude of the relative difference of 0.08 % and a slant path dependency of maximum 1.64 %, which is similar as other standard TCO instruments such as single Brewer or Dobson. Applying the double ratio technique by selecting the wavelengths and slit functions from Brewer and Dobson, respectively, allow to determine the effective ozone temperature within 3 K on daily averages. With the improved TCO retrieval, Koherent serves as a new low maintenance instrument to operationally monitor TCO at remote sites. The presented TCO retrieval may be applied to other array based spectroradiometers providing direct spectral measurements in the ultraviolet. [ABSTRACT FROM AUTHOR]

Spectral measurements of UV irradiance are of great importance for protecting human health as well as for supporting scientific research. To perform these measurements, double monochromator scanning spectroradiometers are the preferred devices thanks to their linearity and stray-light reduction. However, because of their high cost and demanding maintenance, CCD-array-based spectroradiometers are increasingly used for monitoring UV irradiance. Nevertheless, CCD-array spectroradiometers have specific limitations, such as a high detection threshold or stray-light contamination. To overcome these challenges, several manufacturers are striving to develop improved instrumentation. In particular, Gigahertz-Optik GmbH has developed the stray-light-reduced BTS2048-UV-S spectroradiometer series (hereafter "BTS"). In this study, the long-term performance of the BTS and its seasonal behavior, regarding global UV irradiance, was assessed. To carry out the analysis, BTS irradiance measurements were compared against measurements from the Brewer MK-III #150 scanning spectrophotometer during three campaigns. A total of 711 simultaneous spectra, measured under cloud-free conditions and covering a wide range of solar zenith angles (SZAs; from 14 to 70 ∘) and UV indexes (from 2.4 to 10.6), were used for the comparison. During the three measurement campaigns, the global UV spectral ratio BTS / Brewer was almost constant (at around 0.93) in the 305–360 nm region for SZAs below 70 ∘. Thus, the BTS calibration was stable during the whole period of study (∼ 1.5 years). Likewise, it showed no significant seasonal or SZA dependence in this wavelength region. Regarding the UV index, a good correlation between the BTS and the Brewer #150 was found, i.e., the dynamic range of the BTS is comparable to that of the Brewer #150. These results confirm the quality of the long-term performance of the BTS array spectroradiometer in measuring global UV irradiance. [ABSTRACT FROM AUTHOR]

The current solar tower plants demand the measurement of high solar irradiance on the receiver. This measurement would facilitate the operation of the plant, the estimation of the receiver efficiency and would contribute to the safety of the receiver. Nowadays, these plants don't have a system to measure the flux because there are some limitations, as the difficulty to add new elements to the design and the structure of the tower. It is necessary to include a flux measurement system in the planning and construction of the commercial plants. This work presents a validation of the new indirect method to measure the flux which only use the surface of the receiver, a radiometer and a digital camera. In the context of an international project, the new method to measure the flux has been tested with a different receiver and with different working conditions. The receiver tested in this project is a volumetric receiver made of silicon carbide. The flux measurements have been done in the solar tower facility of the Plataforma Solar de Almería, the SSPS-CRS. The results obtained with this system have been compared to the results obtained with the reference flux measurement system based on a white lambertian target, obtaining a good level of agreement. This reference method can't be extrapolated to the commercial plants because it has moving parts that can't be added to the design of the towers. The new method avoids these moving elements and simplify the measurement of the flux distribution on the receiver. [ABSTRACT FROM AUTHOR]

Recently, we developed a simple theoretical model for the estimation of the irradiance distribution at the focal plane of commercial off-the-shelf (COTS) camera lenses in case of laser illumination. The purpose of such a model is to predict the incapacitation of imaging sensors when irradiated by laser light. The model is based on closed-form equations that comprise mainly standard parameters of the laser dazzle scenario and those of the main devices involved (laser source, camera lens and imaging sensor). However, the model also includes three non-standard parameters, which describe the scattering of light within the camera lens. In previous work, we have performed measurements to derive these typically unknown scatter parameters for a collection of camera lenses of the Double-Gauss type. In this publication, we compare calculations based on our theoretical model and the measured scatter parameters with the outcome of stray light simulations performed with the optical design software FRED in order to validate the reliability of our theoretical model and of the derived scatter parameters. [ABSTRACT FROM AUTHOR]

Accurate daily snow cover extent is a significant input for hydrological applications in the Qinghai–Tibetan Plateau (QTP). Although several Moderate Resolution Imaging Spectroradiometer (MODIS) daily cloud-free snow cover products over the QTP are openly accessible, the cloud-gap-filled snow cover from these products has not yet been validated. This study assessed the accuracy of cloud-gap-filled snow cover from three open accessible MODIS daily products based on snow maps retrieved from Landsat TM images. The F1-score (FS) from daily cloud-free MODIS snow cover for the combined MOD10A1F and MYD10A1F (SC1) was 64.4%, which was 7.4% points and 5.3% points higher than the other two commonly used products (SC2 and SC3), respectively. The superior accuracies from SC1 were more evident in regions with altitudes lower than 5000 m, with a weighted average FS by the area percentage of the altitude regions of 58.3%, which was 6.9% points and 9.1% points higher than SC2 and SC3. The improved SC1 accuracies also indicated regional clustering characteristics with higher FS values compared to SC2 and SC3. The lower accuracies of cloud-gap-filled snow cover from SC2 and SC3 were mainly due to the limitation in determining snow cover based on the method of the inferred snow line and the overestimation of the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) snow water equivalent (SWE). These results indicate that the temporal filter approach used in SC1 is a good solution to produce daily cloud-gap-filled snow cover data for the QTP because of its higher accuracy and simple computation. The findings can be helpful for the selection of cloud-removal algorithms for determining snow cover dynamics and phenological parameters on the QTP. [ABSTRACT FROM AUTHOR]

Available wearable dosimeters suffer from spectral mismatch during the measurement of broadband UV and visible radiation in environments that receive radiation from multiple sources emitting differing spectra. We observed this type of multi-spectra environment in all five Washington State cannabis farms visited during a field study investigating worker exposure to ultraviolet radiation in 2018. Spectroradiometers do not suffer from spectral mismatch in these environments, however, an extensive literature review conducted at the time of writing did not identify any spectroradiometers that were directly deployable as wearable dosimetry devices. To close this research gap, we developed a microcontroller system and platform that allows for researchers to mount and deploy the Ocean Insight Flame-S Spectroradiometer as a wearable device for measurement of UV and visible wavelengths (300 to 700 nm). The platform validation consisted of comparing measurements taken under platform control with measurements taken with the spectrometer controlled by a personal computer running the software provided by the spectroradiometer manufacturer. Three Mann–Whitney U-Tests (two-tailed, 95% CI), one for each intensity condition, compared the central tendency between the total spectral power (TSP), the integral of a spectrum measurement, measured under both control schemas. An additional analysis of per pixel agreement and overall platform stability was performed. The three Mann–Whitney tests returned no significant difference between the set of TSPs for each filter condition. These results suggest that the spectroradiometer takes measurements of equivalent accuracy under both control schemas, and can be deployed as a wearable device for the measurement of wavelength resolved UV and visible radiation. [ABSTRACT FROM AUTHOR]

The results of spectrometry with an ASD FieldSpec 3 FR spectroradiometer at wavelengths ranging from 350 to 2500 nm for hydrogenated amorphous and crystalline titanium and zirconium diborides are presented. The results were used to determine changes in the spectral characteristics of hydrogen in bulk and film TiB2 and ZrB2. The spectrometry was performed with the contact method using a Unit Contact Probe. The bulk test samples and spraying targets were prepared by the powder metallurgy method. X-ray diffraction identified that the samples had crystalline structure. Thin films of titanium and zirconium diborides were produced by magnetron sputtering of TiB2 and ZrB2 targets in an argon atmosphere. The structure of the films was studied using an EMP-100 electron diffractometer employing the transmission method at a residual pressure of ~7 ∙ 10–3 Pa. The electron diffraction patterns showed a strong 'halo' at the center, being indicative of amorphous structure of the films, promoting hydrogen transfer process. The samples were hydrogenated from the gas phase at a hydrogen pressure of 0.1 MPa and a temperature of 870 K. A critical analysis of published methods for the quantitative determination of hydrogen in high-temperature borides was provided. The spectrometry method is advantageous in that it is fast, precise, nondestructive, and surface-sensitive, and the entire spectrum is displayed in real time. The intensities of the Brackett Bβ and Balmer Hβ hydrogen lines for crystalline and amorphous TiB2 were compared, and the absorption of hydrogen by the crystalline sample was found to be 4.1 times higher than that by the amorphous one. In polycrystalline TiB2, lines with a halfwidth of 200–300 nm were observed at 500 and 750 nm, which was explained by the subbarrier tunneling of hydrogen atoms between neighboring interstitials, ranging, in particular, for many lattice parameters. The absorbed hydrogen amount in the amorphous film was 1.4 times higher than on the starting film. Magnetron sputtering of ceramic targets was known to lead to the introduction of impurities several tens of nanometers in size (short-range crystalline ordering) into the film, to which the hydrogen penetration process was sensitive. The presence of hydrogen atoms resulted in spectral bell-like curves, partially overlapping each other. By analogy with metal amorphous alloys, the shape of these curves could be explained by quasi-interstices. In the amorphous titanium diboride, a bell-like Balmer Hβ curve was observed, confirming short-range crystalline ordering. Correlation between the hydrogen absorption and the lattice energy and bonding energy of Me–B atoms was established. When hydrogen was absorbed by crystalline titanium and zirconium diborides, TiB2 was found to absorb higher amounts of hydrogen because of lower lattice energy and Ti–B atomic bond energy. As the spectroradiometer method is prompt and informative, we can recommended it for the identification of hydrogenated amorphous and crystalline ceramic materials. [ABSTRACT FROM AUTHOR]

Sea ice roughness can serve as a proxy for other sea ice characteristics such as ice thickness and ice age. Arctic-wide maps that represent spatial patterns of sea ice roughness can be used to better characterize spatial patterns of ice convergence and divergence processes. Sea ice surface roughness can also control and quantify turbulent exchange between sea ice surface and atmosphere and therefore influence surface energy balance at the basin scale. We have developed a data processing system that produces georeferenced sea ice roughness rasters that can be mosaicked to produce Arctic-wide maps of sea ice roughness. This approach starts with Top-of-Atmosphere radiance data from the Multi-angle Imaging SpectroRadiometer (MISR). We used red-band angular data from three MISR cameras (Ca, Cf, An). We created a training data set in which MISR pixels were matched with co-located and concurrent lidar-derived roughness measurements from the Airborne Topographic Mapper (ATM). We used a K-nearest neighbor algorithm with the training data to calibrate the multi-angle data to values of surface roughness and then applied the algorithm to Arctic-wide MISR data for two 16-day periods in April (spring) and July (summer). After georeferencing the roughness rasters, we then mosaicked each 16-day roughness dataset to produce Arctic-wide maps of sea ice roughness for spring and summer. Assessment of the results shows good agreement with independent ATM roughness data, not used in model development. A preliminary exploration of spatial and seasonal changes in sea ice roughness for two locations shows the ability to characterize the roughness of different ice types and the results align with previous studies. This processing system and its data products can help the sea ice research community to gain insights into the seasonal and interannual changes in sea ice roughness over the Arctic. [ABSTRACT FROM AUTHOR]

The melting curve of osmium (Os) has been determined up to 35 GPa and 5800 K using a laser heated diamond anvil cell facility. Al2O3 was used as the thermal insulator and pressure transmitting medium. Melting was detected by the laser speckle method, and spectroradiometric technique was employed for determination of melting temperature. The measured melting curve has been compared with available theoretical melting curves. The Simon-Glatzel fit to the experimental data agrees reasonably well with the recently reported theoretical melting curve using Z-method. The melting slope of the measured melting curve is 58.0 K/GPa at P = 0.1 MPa. The melting line of Os is seen to cross that of W around 6 GPa, making it the most refractory metal. The density dependence of Grüneisen parameter [γ(ρ)] has also been determined analytically, using the experimentally obtained melting slope. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to analyze the color infiltration in monolithic zirconia after grinding, which plays an essential role in the color stability of restorations after occlusal adjustment. Methods: One hundred and eight white zirconia plates (36 Dentsply Sirona—Cercon high translucency [C], 36 Zirkonzahn—Prettau [P], 36 Zirkonzahn—Prettau anterior [Pa]) were stained by infiltration with target colors Vita A2, A3.5, and A4. In a standardized experimental setup, all plates were grinded in nine successive steps (from baseline to 500 μm), and color was measured with a spectroradiometer at each grinding step. Color differences ΔE00 between initial color and after each grinding step were calculated. The data was analyzed using regression, Kruskal‐Wallis test, inverse prediction, and simultaneous 95%‐confidence intervals. Results: Grinding had a significant effect on color stability across all zirconia types and target colors (p < 0.001). At each cut level and target color, ΔE00 means for groups C, P, and Pa were statistically different (p < 0.05). Among the three zirconia types, Pa had the lowest ΔE00 mean score for cut levels 20–100 μm for A2 and between 50 and 300 μm for A3.5 and A4. For all other cut levels, differences between Pa and P were not significant (α = 0.05). C had the largest mean ΔE00 except for A4 until 100 μm, where it was second best. Conclusion: Zirconia type had a significant effect on the color infiltration depth across all target colors. Pa showed the best color stability until 150 μm material reduction, whereas C presented significantly less color stability than the other two zirconia materials. Clinical significance: Color stability is important for minimizing the risk of restoration failure due to unacceptable color changes after grinding. Pa is less susceptible to color change and has an additional buffer of 60 μm until exceeding the color acceptability threshold. When higher flexural strength is needed, P is to be preferred. [ABSTRACT FROM AUTHOR]

In plants, it is one of the important factors to provide ecological factors for productivity. Plants perceive the effects of environmental factors outside as stress and create appropriate physiological responses in their metabolism. Water stress is a type of abiotic stress and is one of the important factors affecting the growth and development of plants. Irrigation water management is very important for sustainable use of water resources. Therefore, support tools are becoming increasingly important in deciding irrigation. With the developments the technology, computerized support applications are usually used in agricultural areas. In the study, it is aimed to determine the effects of irrigation applications performed in different periods on yield quality and spectral reflections of safflower plant and to create applicable irrigation programs in safflower cultivation. From the reflections detained from safflower leaves by using spectroradiometer device, the determination of safflower plant according to water ratio different situations is done. Reflections are taken as three groups where the plants are grown at wavelengths of 325 nm to 1075 nm. Water due diligence related with safflower is consist of two stages. The first stage is the provision of the feature vector, the second stage is the classification of the feature vector related to data. As classification methods, support vector machine, k-nearest neighbor and decision tree are used. In comparison of three groups, the average value of the performance is high. As a result, considering the fallowed method and the procedure used, it is evaluated that such studies can be used in agriculture and cultivation. [ABSTRACT FROM AUTHOR]

Due to advantages such as the high efficiency of light utilization, small volume, and vibration resistance, digital micro-mirror device (DMD)-based spectrometers are widely used in ocean investigations, mountain surveys, and other field science research. In order to eliminate the stray light caused by DMDs, the stray light in DMD-based spectrometers was first measured and analyzed. Then, the stray light was classified into wavelength-related components and wavelength-unrelated components. Moreover, the noise caused by the stray light was analyzed from the perspective of encoding equation, and the de-noising decoding equation was deduced. The results showed that the accuracy range of absorbance was enhanced from [0, 1.9] to [0, 3.1] in single-stripe mode and the accuracy range of absorbance was enhanced from [0, 3.8] to [0, 6.3] in Hadamard transform (HT) multiple-stripe mode. A conclusion can be drawn that the de-noising strategy is feasible and effective for enhancing the SNR in DMD-based spectrometers. [ABSTRACT FROM AUTHOR]

The variations in vegetation coverage (defined as the area with Normalised Difference Vegetation Index (NDVI) > 0.2) and atmospheric patterns occurring during various vegetation seasons in the Kabul River Basin (KRB) in Afghanistan during 2001–2019 were analyzed. The analysis was done based on the NDVI, land surface temperature (LST), precipitation images from the remote sensing data, and geopotential height and temperature at 500 hPa from the retrospective datasets. The results revealed that the vegetation dynamics in KRB are impacted by both precipitation and LST. In the winter season, the LST has a more substantial role in shaping the vegetation dynamics than precipitation, while it is on contrary during the summer season. Cluster analysis showed that the four atmospheric patterns (e.g., Sub-Tropical High Pressure (STHP), Western European ridge-the Eastern Mediterranean and the Black Sea trough, Caspian Sea ridge (CSR), and the Mediterranean Sea trough-Central to Eastern Iran trough) can be identified and connected with the periods with the highest and the lowest vegetation coverage (VC) anomalies in the study area. The CSR and the Mediterranean Sea trough-the Central to Eastern Iran trough are the patterns responsible for the most positive VC anomalies. At the same time, the STHP and Western Europe ridge-the Eastern Mediterranean and the Black Sea trough are responsible for the most negative VC anomalies. As the atmospheric patterns have a significant role in shaping the vegetation status, a quick alert system to prevent agricultural areas from water or temperature stresses can be developed based on observations of them. [ABSTRACT FROM AUTHOR]

Determining coastal boundaries on land is essential to understanding the process of soil salinization. Once, It can be observed, and the coastal boundaries may help explain these areas' damage levels. This study aimed to observe the change in soil salinity and saltwater intrusion and use both values to determine the coastal boundaries in Subang, Indramayu, and Cirebon regencies. This study employed a multi-temporal data of Landsat 5 TM and Landsat 8 OLI-TIRS satellite imageries (2009–2015), the water spectral reflectance collected from the field survey, and the elevation data to gain the elevation information. The corrected Landsat and water reflectance data were combined and processed to obtain the saltwater intrusion using soil salinity index (SSI), salinity index (SI), brightness index (BI), normalized difference salinity index (NDSI), soil salinity index (SSI), and water salinity index (WSI). Besides that, five linear and multiple regression equations as a semi-empirical model, namely saltwater intrusion index (SWII), are also used. Only BI, SSI, and two SWII models show reasonable saltwater intrusion with 44%, 24%, and 52% accuracy. These models with below 0.2 (dS/m) represented the non-saline, while others used the saline regime to determine the boundaries. The spatial distribution of saltwater intrusion may become unreliable since its accuracy does not always relate to the land cover. Since the acceptable models mostly elucidate that the entire region in Indramayu regency has been experiencing saltwater intrusion since 2015, the boundaries are far from the coastline. [ABSTRACT FROM AUTHOR]

In situ hyperspectral remote-sensing reflectance ( R r s (λ) ) is used to derive water quality products and perform autonomous monitoring of aquatic ecosystems. Conventionally, above-water R r s (λ) is estimated from three spectroradiometers which measure downwelling planar irradiance ( E d (λ) ), sky radiance ( L s (λ) ), and total upwelling radiance ( L t (λ) ), with a scaling of L s (λ) / E d (λ) used to correct for surface-reflected radiance. Here, we incorporate direct and diffuse irradiance, ( E d d (λ) ) and E d s (λ) ), from a hyperspectral pyranometer (HSP) in an R r s (λ) processing algorithm from a solar-tracking radiometry platform (So-Rad). HSP measurements of sun and sky glint (scaled E d d (λ) / E d (λ) and E d s (λ) / E d (λ) ) replace model-optimized terms in the 3C (three-glint component) R r s (λ) algorithm, which estimates R r s (λ) via spectral optimization of modelled atmospheric and water properties with respect to measured radiometric quantities. We refer to the HSP-enabled method as DD (direct-diffuse) and compare differences in R r s (λ) and R r s (λ) variability (assessed over 20 min measurement cycles) between 3C and DD as a function of atmospheric optical state using data from three ports in the Western Channel. The greatest divergence between the algorithms occurs in the blue part of the spectrum where DD has significantly lower R r s (λ) variability than 3C in clearer sky conditions. We also consider R r s (λ ) processing from a hypothetical two-sensor configuration (using only the L t (λ) spectroradiometer and the HSP and referred to as DD2) as a potential lower-cost measurement solution, which is shown to have comparable R r s (λ ) and R r s (λ ) variability to DD in clearer sky conditions. Our results support that the HSP sensor can fulfil a dual role in aquatic ecosystem monitoring by improving precision in R r s (λ) alongside its primary function to characterize aerosols. [ABSTRACT FROM AUTHOR]