Radiometric Method Research Articles

Differential Radiometric Methods for Measurements of the Vertical Profile of Water Vapor in the Troposphere and Stratosphere of the Earth

Differential methods for determining the height profile of one of the most important greenhouse gases in the Earth’s atmosphere—water vapor—based on ground and satellite radio thermal microwave measurements in the absorption band of 22 GHz, are considered. The substantiation of a fundamentally new difference-differential method is carried out using the difference of differential signals on different slopes of the absorption line of the measured gas. This method makes it possible to increase the spatial selectivity of measurements and reduce the influence of clouds, precipitation, and third-party gases, as well as carry out measurements above the water surface. The results of the calculation of the kernels of integral equations are given for measurements in the absorption band of water vapor of 22 GHz. The selectivity of the kernels makes it possible to restore the water-vapor profile both in the lower troposphere layer to heights of 8 km and in the stratospheric–mesospheric layer of 30–80 km. The advantage of the proposed methods is the differential nature of the measurements, which does not require the absolute calibration of sources and long-term stability of the equipment.

Impacts of different radiometric calibration methods on the retrievals of sun-induced chlorophyll fluorescence and its relation to productivity for continuous field measurements

Sun-induced chlorophyll fluorescence (SIF), now observed from space on a global scale, has been shown to be a powerful proxy for photosynthetic activity. Long-term in situ field canopy SIF measurements are improving, enabling better understanding of SIF signal and support to satellite missions. Since SIF retrievals rely on the absolute irradiance radiance measurements, accurate outdoor radiometric calibration is necessary to provide accurate radiance data, especially for long-term continuous measurements on forest stands. However, standard laboratory calibration methods are not practical to be performed for outdoor long-term measurements, and several in-field alternative methods are generally used, which may result in some uncertainties. Here we evaluate the effects of different radiometric calibration methods on SIF retrievals and its relation with gross primary productivity (GPP) at the canopy level. Three widely used methods are used, i.e., well-established laboratory methods with integrating sphere, laboratory-calibrated reference spectrometer (ASD FieldSpec Pro), and a light calibration source with a white reference panel. Our results indicate that different radiometric calibrations have marginal effects on vegetation indices but have significant effects on the SIF absolute value, and have slight effects on diurnal and seasonal patterns of SIF. Moreover, the relationships between GPP and SIF retrieved using different calibration coefficients are similar at both diurnal and seasonal scales, but with different regression slopes. Therefore, we recommend that a standard laboratory radiometric calibration is conducted using an integrating sphere before installation in the field and a regular in-field calibration with a well-calibrated spectrometer and white reference, especially for long-term observation above a forest canopy. Our findings have strong implications for the ongoing and future ground canopy SIF measurements and suggest the need for a consistent radiometric calibration method, especially for cross-site comparison studies.

ESTIMATION OF THE EFFICIENCY OF THE DRY METHOD OF DECONTAMINATION OF SURFACE CONTAMINATION OF ALPHA-EMITTING-RADIONUCLIDES

The article describes the evaluation of the efficiency of using the technology of dry method of decontamination of α-radionuclides from working surfaces of premises for different materials, equipment and building structures. Materials and methods. Instruments for measuring of ambient dose equivalent rate (ADER) with a lower limit of 0.03 μSv/h. Specific activity of α-radionuclides in the samples was determined by radiometric, radiochemical and spectrometric methods using standard methods in the accredited laboratory. The measurements in situ were also carried out using the ISOCS «CANBERRA» mobile gamma-ray spectrometry system with high purity germanium detector and a collimator. Technological equipment included industrial vacuum cleaner with nozzles; high-pressure device; packing sets for RAW collection; HEPA filters; personal protective equipment. Results. Maps of spatial distribution of surface α-contamination in the building was constructed. We performed cluster analysis of data for zoning of contaminated surfaces. The decontamination factor for porous (brick, concrete), smooth (wood, brown tiles, laminate) and sticky (bitumen, mastic) surfaces was determined. Conclusion. The cluster analysis made it possible to identify 4 levels of surface α- and β- contamination, particles/cm2 ∙ min: zone I - for α- above 50, for β- above 10,000; zone II - for α- 5-50, for β- 2,000-10,000; zone III - for α- no more than 5, for β- 2000; zone IV - corresponds to the background values of the workspace surfaces. The dry decontamination method revealed a high content of fine dust aerosol fraction deposited in the lungs. To increase the efficiency of dust suppression, water aerosol with droplet size of 100 - 400 microns and quartz sand with particle size of 100-200 microns were sprayed at the rate of 200-400 g per 1 m2. The decontamination coefficient depends on the coating material and the level of surface contamination: concrete - 91 to 97.8%; brick - 85-86%, wood - 38.8-53%; brownstone tiles - up to 29%; mastic - 22-28%; bitumen - 15.9-20%. To protect the personnel, radiation-hygienic rationing of PM10 and PM2,5 content is necessary.

Multilayer Perceptron-Based Phenological and Radiometric Normalization for High-Resolution Satellite Imagery

Radiometric normalization is an essential preprocessing step that must be performed to detect changes in multi-temporal satellite images and, in general, relative radiometric normalization is utilized. However, most relative radiometric normalization methods assume a linear relationship and they cannot take into account nonlinear properties, such as the distribution of the earth’s surface or phenological differences that are caused by the growth of vegetation. Thus, this paper proposes a novel method that assumes a nonlinear relationship and it uses a representative nonlinear regression model—multilayer perceptron (MLP). The proposed method performs radiometric resolution compression while considering both the complexity and time cost, and radiometric control set samples are extracted based on a no-change set method. Subsequently, the spectral index is selected for each band to compensate for the phenological properties, phenological normalization is performed based on MLP, and the global radiometric properties are adjusted through postprocessing. Finally, a performance evaluation is conducted by comparing the results herein with those from conventional relative radiometric normalization algorithms. The experimental results show that the proposed method outperforms conventional methods in terms of both visual inspection and quantitative evaluation. In other words, the applicability of the proposed method to the normalization of multi-temporal images with nonlinear properties is confirmed.

Radiometric and Atmospheric Corrections of Multispectral μMCA Camera for UAV Spectroscopy

This study presents a complex empirical image-based radiometric calibration method for a Tetracam μMCA multispectral frame camera. The workflow is based on a laboratory investigation of the camera’s radiometric properties combined with vicarious atmospheric correction using an empirical line. The effect of the correction is demonstrated on out-of-laboratory field campaign data. The dark signal noise behaviour was investigated based on the exposure time and ambient temperature. The vignette effect coupled with nonuniform quantum efficiency was studied with respect to changing exposure times and illuminations to simulate field campaign conditions. The efficiency of the proposed correction workflow was validated by comparing the reflectance values that were extracted from a fully corrected image and the raw data of the reference spectroscopy measurement using three control targets. The Normalized Root Mean Square Errors (NRMSE) of all separate bands ranged from 0.24 to 2.10%, resulting in a significant improvement of the NRMSE compared to the raw data. The results of a field experiment demonstrated that the proposed correction workflow significantly improves the quality of multispectral imagery. The workflow was designed to be applicable to the out-of-laboratory conditions of UAV imaging campaigns in variable natural conditions and other types of multiarray imaging systems.

Calibration algorithm for cooled mid-infrared systems considering the influences of ambient temperature and integration time.

Midwave infrared systems with cooled detectors are generally used for high-precision or quantitative measurement, such as radiometry and thermometry. As a basis of these applications, radiometric calibration aims to obtain the relationship between the infrared images and the incident radiant flux generated by the scene or targets. Conventional radiometric calibration algorithms do not take the influences of integration and ambient temperature into consideration. As a consequence, the accuracy of calibration deteriorates whenever the temperature or the integration time varies. To solve this problem, we analyzed the effects of integration time and ambient temperature on coefficients of the radiometric calibration formula by theoretical and experimental analysis. Then, a radiometric calibration method is deduced to remove the variation of integration time and ambient temperature on the accuracy of calibration and radiometry. Several radiometric calibration experiments were conducted using a midwave infrared camera inside a chamber with controllable temperature. The results indicate that the proposed calibration algorithm is more effective and accurate, compared with conventional calibration methods, in complicated working conditions with variable integration times and ambient temperatures.

Optical Method of Detection of Oil Contamination on Water Surface in UV Spectral Range

Efficiency analysis of optical (photo and radiometric) method of oil contamination detection based on differences between reflective characteristics of clean and oil-contaminated water surfaces was conducted with sounding wave selection in UV, visible, near-infrared and medium-infrared regions of the spectrum. It is shown that, in terms of eye safety, width of thickness interval of detected oil films and atmospheric attenuation, the most promising type of sounding for monitoring of oil contamination is UV sounding at a wavelength of 0.355 µm, which allowing to detect oil films with thickness of at least 2 µm reliably with probability of correct detection exceeding 0.9 and probability of false alarms of 0.002 with relative measurement noise not exceeding 5 %.

Elaboration of an environmentally appropriate technology of siderite ores concentration

Decrease of iron content in siderite ores, mined in mines stipulated a necessity to elaborate technologies of their concentration, which allow increasing iron content at least 35%. As a result of analysis of existing technologies of minerals concentration it was determined, that X-ray radiometric method is the most promising one for siderite ores concentration. Its essence is in a controlled supply of lump material of definite size, distribution of lump flows by streams and by the piece supply of ore lumps into analysis-division zone, in which the X-ray fluorescent analysis of main chemical elements takes place. Special microprocessor means of the measuring-control system make comparison of measuring results with the set threshold of separation and make decisions to direct the particular piece to one of the grading product. As the result, the particular piece comes to a chute either with rich product or by free fall comes to the chute of poor product. Tests of the technology of lump siderite ore separation accomplished by using industrial X-ray radiometric separators. Influence of ore size on the concentration process indices studied. It was determined, that at implementation the X-ray radiometric method of separation it is reasonable to limit by machine classes of 250– 100 mm and 100–30 mm. A technological flowchart proposed to provide the concentrate obtaining with the size of 30–10 mm and iron content of 35%. The concentrate can be used for reducing roasting of it in shaft furnaces. The formed screenings after concentration in the high intensity fields were proposed to subject to metallization in the rotating furnaces or rotating hearth furnaces. The metallized product can be smelted in an ore-thermal furnace to obtain steel semi-product used in large-scale EAF.

A New Pseudoinvariant Near-Infrared Threshold Method for Relative Radiometric Correction of Aerial Imagery

The utilization of high-resolution aerial imagery such as the National Agriculture Imagery Program (NAIP) data is often hampered by a lack of methods for retrieving surface reflectance from digital numbers. This study developed a new relative radiometric correction method to retrieve 1 m surface reflectance from NAIP imagery. The advantage of this method lies in the adaptive identification of pseudoinvariant (PIV) pixels from a time series of Landsat images that can fully characterize the temporally spectral variations of land surface. The identified PIV pixels allow for an effective conversion of digital numbers to surface reflectance, as demonstrated through the validation at 150 sites across the contiguous United States. The results show substantial improvement in the agreement of NAIP-derived normalized difference vegetation index (NDVI) values with Landsat-derived NDVI reference. Across the sites, root mean square error and mean absolute error were reduced from 0.37 ± 0.14 to 0.08 ± 0.07 and from 0.91 ± 0.64 to 0.18 ± 0.52, respectively. Over 70% PIV pixels on average were derived from vegetated areas, while water and developed areas together contributed 27% of the PIV pixels. As the NAIP program is continuing to generate new images across the country, the advantages of its high spatial resolution, national coverage, long time series, and regular revisits will make it an increasingly crucial data source for a variety of research and management applications. The proposed method could benefit many agricultural, hydrological, and urban studies that rely on NAIP imagery to quantify land surface patterns and dynamics. It could also be applied to improve the preprocessing of high-resolution aerial imagery in other countries.

Multispectral UAS Data Accuracy for Different Radiometric Calibration Methods

Unmanned aircraft systems (UAS) allow us to collect aerial data at high spatial and temporal resolution. Raw images are taken along a predetermined flight path and processed into a single raster file covering the entire study area. Radiometric calibration using empirical or manufacturer methods is required to convert raw digital numbers into reflectance and to ensure data accuracy. The performance of five radiometric calibration methods commonly used was investigated in this study. Multispectral imagery was collected using a Parrot Sequoia camera. No method maximized data accuracy in all bands. Data accuracy was higher when the empirical calibration was applied to the processed raster rather than the raw images. Data accuracy achieved with the manufacturer-recommended method was comparable to the one achieved with the best empirical method. Radiometric error in each band varied linearly with pixel radiometric values. Smallest radiometric errors were obtained in the red-edge and near-infrared (NIR) bands. Accuracy of the composite indices was higher for the pixels representing a dense vegetative cover in comparison to a lighter cover or bare soil. Results provided a better understanding of the advantages and limitations of existing radiometric calibration methods as well as the impact of the radiometric error on data quality. The authors recommend that researchers evaluate the performance of their radiometric calibration before analyzing UAS imagery and interpreting the results.

Application of Remote Sensing Data in Lithological Discrimination of Kerdous Inlier in the Anti Atlas Belt of Morocco

Remote sensing data reveals a great importance for lithological mapping due to their spatial, spectral and radiometric characteristics. Lithological mapping using spatial data is a preliminary and important step to mineral mapping. In this work, several spectral and radiometric transformations methods were applied on Landsat 8 OLI data to enhance lithological units in the study area situated in the Anti Atlas belt. The methods of Optimum Index Factor (OIF), Decorrelation Stretching (DS), Principal Components Analysis (PCA) and Band Ratioing (BR) showed good results for lithological mapping in comparison with the existing geological and field investigation. An RGB color composite of OLI bands 651 was developed for mapping lithological units of the study area by fusing optimum index factor (OIF) and decorrelation stretching methods. furthermore, Band ratios derived from image spectra were applied in two RGB color composites (7+4/2, PC1, PC2)Â and (PC1, 7/6, 3/7) providing good discrimination of the lithological units. The Landsat-8 OLI data significantly provided satisfied results for lithological mapping.

Investigations on chemical composition and natural radioactivity levels from salt water and peloid used in pelotherapy from the Techirghiol Lake, Romania

The work presents the historical evolution, objectives, goals, concepts, chemical and radiometric methods, results and conclusions for salt waters and natural peloids used in pelotherapy. This study assesses chemical composition, natural radioactivity concentrations and the radiological hazard in peloid and salt water samples, from ten places in the Techirghiol Lake from Romania. Pelotherapy is a very important procedure, and thus, the materials used for this purpose must be well characterized to guaranty safety use. Concentrations of elements such as Sr, Ba, Mn, Fe, Sb, Zn, Cu, Pb, Ti, Ni, Cr, As have been measured using ICP-OES analytical technique. The natural radionuclides such as 238U, 226Ra, 232Th and 40K have been determined by gamma-ray spectrometry. The average activity concentrations were of 0.48 ± 0.10Bq/kg for 238U, 0.60 ± 0.10Bq/kg for 226Ra, 0.30 ± 0.08Bq/kg for 232Th and 17.5 ± 1.3Bq/kg for 40K for salt water samples. Also, the mean activity concentrations for peloids were: 5.70 ± 1.00 Bq/kg for 238U, 6.85 ± 1.60Bq/kg for 232Th, 15.3 ± 3.7Bq/kg for 226Ra and 95.8 ± 5.5Bq/kg for 40K. The results from this study contribute to the identification of possible contaminants in the salt water and peloid, and their association with the potential ecological and human health risk. In this context, of using salt water and peloid in a relatively long treatment period, several radiological indices have been calculated, to determine if the radionuclide's content can be also harmful to human health. The assessment indicates that humans are not exposed to concentrations of metal contaminants higher than the international recommended values.

Radiometric calibration methods for day/night whole sky imagers and extinction imagers.

This paper discusses the new radiometric calibration methods and results that we have developed to apply to day/night whole sky imager data and extinction imager data. Day/night whole sky imagers detect the presence and location of clouds and categorize them by opacity. The new day and night cloud algorithms for these instruments are documented elsewhere, and these algorithms depend on the use of the new calibrations we have developed. In this paper, we document our calibration methods for determining the absolute radiance of the whole sky imager scene at each pixel in the images as well as the results of the calibrations. The extinction imagers are new systems we developed that determine beam transmittance and path extinction for horizontal paths through the atmosphere. These instruments and their algorithms are documented elsewhere, and they also depend on the new calibration results. The extinction imager algorithms only require relative radiances, as opposed to absolute radiances. The calibration steps for the two instruments are quite similar, and they include dark correction; linearity calibration, which corrects for nonlinearities in the signal versus flux relationship; absolute calibration (for the whole sky imager); and uniformity calibration, which corrects for pixel-to-pixel nonuniformities. These developments include methods for handling uniformity calibrations in a system using a fisheye lens and the calibration of both visible and short-wave IR systems. This paper presents both the new methods and results in support of the papers documenting the algorithms.

Analysis of the Results of Astroclimate Research at the Kara-Dag Radioastronomical Station in Crimea and the Possibilities for Reducing the Influence of the Atmosphere on Millimeter-Band Radioastronomical Observations

The results of astroclimate research at the Kara-Dag radioastronomical station (Crimea) from July 22 to September 21, 2017, are presented. The algorithms for processing the data obtained by the atmospheric profile method are analyzed. The broad bands of the MIAP-2 receivers are shown to lead to a non-cosecant dependence of the antenna temperatures on viewing angle. The absorption calculation from three zenith angles by the least-squares method and a reference region with a brightness temperature close to the air temperature is optimal. The patterns of change in atmospheric transparency parameters and their connection with the climatic peculiarities of the observing site are considered. The existing atmospheric circulation is shown to create favorable conditions for nighttime astronomical observations in the millimeter wavelength range on the territory of the Kara-Dag station. Alternative and cheaper approaches to reducing the influence of atmospheric moisture on the measurements in this range than the existing trends are proposed. The first approach consists in choosing a location in a zone with a suitable wind rose and a relief leading to the replacement of moist warm air by dry cold one, for example, in the zones of such local winds as a bora. The second approach suggests the introduction of atmospheric parameter measurements by radiometric methods and allowance for their influence in a real time scale. Since the results obtained are based on limited statistics, they are preliminary ones and stimulate further systematic measurements at Kara-Dag.

Apidima Cave fossils provide earliest evidence of Homo sapiens in Eurasia.

Two fossilized human crania (Apidima1 and Apidima2) from Apidima Cave, southern Greece, were discovered inthe late 1970s but have remained enigmatic owing to their incomplete nature, taphonomic distortion and lack of archaeological context and chronology. Here we virtually reconstruct both crania, provide detailed comparative descriptions and analyses, and date them using U-series radiometric methods. Apidima2 dates to more than 170thousand years ago and has a Neanderthal-like morphological pattern. By contrast, Apidima1 dates to more than 210thousand years ago and presents a mixture of modern human and primitive features. These results suggest that two late Middle Pleistocene human groups were present at this site-an early Homo sapiens population, followed by a Neanderthal population. Our findings support multiple dispersals of early modern humans out of Africa, and highlight the complex demographic processes that characterized Pleistocene human evolution and modern human presencein southeast Europe.

Rapid Quantification of Radioactive Strontium-90 in Fresh Foods via Online Solid-Phase Extraction-Inductively Coupled Plasma-Dynamic Reaction Cell-Mass Spectrometry and Its Comparative Evaluation with Conventional Radiometry.

This paper describes a rapid quantification method for radioactive strontium (90Sr) in fresh foods (perishable foods) and has been comparatively evaluated with the common classical radiometric quantification method. Inductively coupled plasma–dynamic reaction cell-mass spectrometry with online solid-phase extraction (cascade-ICP–MS) rapidly determines 90Sr in a pure water-based sample. Despite its advantages, its application to fresh foods (perishable foods) has not yet been reported; however, the analytical potential of this method for fresh foods must be evaluated. In this study, 90Sr was determined in 12 fresh foods via improved cascade-ICP–MS (Icas-ICP–MS). Addition and recovery tests were demonstrated using real samples of grape, apple, peach, Japanese pear, rice, buckwheat, soybean, spinach, shiitake mushroom, grass, sea squirt, and flounder. With a decomposed solution of Japanese pear, the measurement value coincided with the amount of spiked 90Sr. The reproducibility of the measurements was represented by relative standard deviations of 14.2 and 5.0% for spiked amounts of 20 and 200 Bq/kg, respectively (n = 10), and the recovery rates were 93.7 ± 7.1%. In this case, the limit of detection (LOD) was 2.2 Bq/kg (=0.43 pg/kg). These results were compared with the data obtained using a common classical radiometric quantification method (nitrate precipitation-low background gas flow counter (LBC) method) in the same samples. Both the methods showed equivalent performances with regard to reproducibility, precision, and LODs but different analysis times. Icas-ICP–MS required ∼22 min for analysis, whereas the nitrate precipitation-LBC method required 20 days, confirming that Icas-ICP–MS is the suitable method for analyzing 90Sr in fresh foods.

Isolation and quantification of a 93Mo isotope solution from proton irradiated niobium

93Mo (4000 y half-life) formed through the 93Nb(p,n)93Mo reaction was isolated from a niobium target foil previously used in a low energy medical cyclotron. 93Mo has identical characteristic x-ray emission and mass as the isomer 93mNb and stable Nb present in the target foil at much higher concentrations. This makes distinction between 93Mo, 93mNb and stable Nb difficult using radiometric or mass spectrometric methods. An anion exchange method in combination with x-ray spectrometry and ICP-MS/OES enabled quantitative isolation of about 0.4 μg 93Mo (14 kBq) from 93mNb with a separation factor >104 on a single column. An extraction chromatography column (TEVA) was used to reach a93mNb/93Mo activity ratio of <10−6 and an atom ratio 93Nb/93Mo <1% making the 93Mo suitable for both radiometric and mass spectrometric testing. 93Mo is the only radioisotope of molybdenum with a long enough half-life suitable for this purpose. Calibration of the 93Mo isotope solution was done through x-ray spectrometry using a characterized BEGe-detector in combination with a99mTc solution. This is the first reported isolation of a93Mo solution in the literature and the first time a LSC-spectrum of 93Mo is shown.

A Radiometric Method for Measuring the 14С Activity in Irradiated Graphite

A Radiometric Method for Measuring the 14С Activity in Irradiated Graphite

Comparison of Electric and Radiometric Methods for Liquid Dielectric Diagnostic

Comparison of Electric and Radiometric Methods for Liquid Dielectric Diagnostic

Management of Spent Nuclear Fuel from Research Reactors at the Kurchatov Institute

The problems of managing spent nuclear fuel stored in at-reactor repositories at the NRC Kurchatov Institute and current methods of inventorying the nuclear content of the repositories are discussed. Methods of identifying FA and leak-tight bottles with fuel rods by means of radiometric methods of measuring the radiation parameters of АF are discussed. The use of remote-controlled machines makes it possible to reduce the effect of high radiation fields on the workers and protect them in their work. The main problems arising during long-term storage of spent fuel are degradation of the protective barriers of the fuel rods and the lack of information on the radioactive content and the produced high-level wastes. Regular inventorying of the repositories ensures that the missing data are replaced, and in preparation for shipment attention is focused on restoring the outer casings of the packages for shipment to reprocessing facilities.