Adjustable light source for low light level with nearly constant correlated color temperature

Low light level (LLL) calibration becomes more and more important since the rapid growth of remote sensing. The spectral radiance at normal higher light levels can be calibrated with good accuracy, while LLL spectral radiance cannot. If an adjustable light source can be designed at nearly constant correlated color temperature (CCT) covering several orders of magnitude, low light level spectral radiance can be obtained with the help of a photodetector. Whether or not the spectral distribution of an integrating sphere based light source is nearly constant is investigated. By adjusting the diameter of the variable aperture between the integrating sphere and tungsten lamp, the spectral radiance can be varied over 6 orders of magnitude. However, the relative spectrum in the red region increases notably when the spectral radiance is decreased to 1/100000. If the spectral radiance is decreased further, the spectral difference can be more than 300% and CCT decreases more than 250 K. By using baffles and another integrating sphere, low light level radiation source at nearly constant spectral distribution is obtained. The variation of CCT is less than 50 K over 6 orders of magnitude.

Spectral radiance characteristics and vegetative indices of crops -A ground based remote sensing technique

The spectral radiance characteristics and vegetation indices like simple difference, ratio vegetation, normalised vegetation perpendicular vegetation transformed vegetation and tasseled cap transformation of mung been sunflower and groundnut crops at different growth stages have been studied. The experiment was conducted in post rainy season during 1990-91 in the farm of Agricultural College. Pune using hand held multi-spectral radiometer. The significance of spectral variation of radiance and vegetative indices with respect to the phenological stages are discussed.

Novel LED-based radiation source and its application in diffuse reflectometry and polarization measurements

An LED sphere radiator (LED-SR) was constructed to improve the accuracy in spectral radiance factor measurements performed with the robot-based gonioreflectometer at PTB. Its properties with respect to the spectral range and coverage, the temporal stability, and the homogeneity of the radiation field are presented. Two types of matte ceramic reflection standards were used for spectral radiance factor validation measurements comparing the standardly used halogen sphere radiator (Halogen-SR) and the LED-SR. Due to its designed spectral range at the border between the visible and the UV-A spectral range, the LED-SR is well suited for many applications in diffuse reflectometry. Its use for absolute radiance factor measurements and investigations of the fluorescence properties of diffuse reflecting samples is shown. Reliable polarization-resolved measurements at wavelengths below 430 nm could be carried out with PTB’s gonioreflectometer for the first time due to the beneficial signal-to-noise ratio of the LED-SR.

Why PV Modules should preferably not be oriented to the South and why we need new measurements of spectral radiance for the energy meteorology

<p>PV modules tilted and oriented toward east and west directions gain gradually more importance as an alternative to the presently-preferred south (north in the Southern Hemisphere) orientation and it is shown to become economically superior even under the reimbursement of feed-in tariff (FIT). This is a consequence of the increasing spread between the decreasing costs of self-consumed solar power and the costs for power from the grid. One-minute values of irradiance were measured by silicon sensors at different orientations and tilt angles in Hannover (Germany) over three years. We show that south-oriented collectors give the highest electrical power during the day, whereas combinations of east and west orientations (E-W) result in the highest self-consumption rate (SC), and combinations of southeast and southwest (SE-SW) orientations result in the highest degree of autarky (AD), although they reduce the yearly PV Power by 5–6%. Moreover, the economic analysis of PV systems without FIT shows that the SE-SW and E-W combinations have the lowest electricity cost and they are more beneficial in terms of internal rate of return(IRR),compared to the S orientation at the same tilt. For PV systems with FIT, the S orientation presently provides the highest transfer of money from the supplier. However, as a consequence of the continuing decline of FIT, the economic advantage of S orientation is decreasing. E-W and SE-SW orientations are more beneficial for the owner as soon as FIT decreases to 7 Ct/kWh. East and west orientations of PV modules do not only have benefits for the individual owner but avoid high costs for storing energy—regardless who would own the storage facilities—and by avoiding high noon peaks of solar energy production during sunny periods,which would become an increasing problem for the grid if more solarpower is installed. Furthermore, two types of commonly used PV software (PVSOL and PVsyst) were used to simulate the system performance. The comparison with measurements showed that both PV software underestimate SC and AD for all studied orientations, leading to the conclusion that improvements are necessary in modelling. Such improvements, however, also require a better knowledge of the angular dependence of the spectral radiance under all sky conditions. Since the spectral radiance is complex and usually changes within seconds, we developed a new instrument capable of measuring the spectra of sky radiance in more than 100 directions within one second. First measurements with this novel instrument are shown. </p>

Cautionary Analysis of Spectral Radiance from Io’s Active Volcanoes Derived from Galileo Near-Infrared Mapping Spectrometer Data

Between 1996 and 2001, the Galileo Near-Infrared Mapping Spectrometer (NIMS) obtained 190 observations of the volcanic Jovian moon Io. Rathbun et al. (2018) [Astron. J., 156, 207] published a list of 287 measurements of 3.5 μm spectral radiance from some of Io’s active volcanoes, derived from a subset of the NIMS data. However, the spectral radiances reported by Rathbun et al. are lower, in some cases by multiple orders of magnitude, than other analyses of the same observations and spectral radiances derived from contemporaneous ground-based data. In many cases, the Rathbun et al. hot-spot radiances are underreported by a factor of π, likely due to a mistake in unit conversion. For a small number of powerful hot spots, additional discrepancies appear to be the result of poor fits to data limited in wavelength range by NIMS detector saturation and a methodology that discards short-wavelength NIMS data that otherwise would have provided more robust temperature model fits.

Quantification of CH₄ coal mining emissions in Upper Silesia by passive airborne remote sensing observations with the Methane Airborne MAPper (MAMAP) instrument during the CO₂ and Methane (CoMet) campaign

Methane (CH4) is the second most important anthropogenic greenhouse gas, whose atmospheric concentration is modulated by human-induced activities, and it has a larger global warming potential than carbon dioxide (CO2). Because of its short atmospheric lifetime relative to that of CO2, the reduction of the atmospheric abundance of CH4 is an attractive target for short-term climate mitigation strategies. However, reducing the atmospheric CH4 concentration requires a reduction of its emissions and, therefore, knowledge of its sources. For this reason, the CO2 and Methane (CoMet) campaign in May and June 2018 assessed emissions of one of the largest CH4 emission hot spots in Europe, the Upper Silesian Coal Basin (USCB) in southern Poland, using top-down approaches and inventory data. In this study, we will focus on CH4 column anomalies retrieved from spectral radiance observations, which were acquired by the 1D nadir-looking passive remote sensing Methane Airborne MAPper (MAMAP) instrument, using the weighting-function-modified differential optical absorption spectroscopy (WFM-DOAS) method. The column anomalies, combined with wind lidar measurements, are inverted to cross-sectional fluxes using a mass balance approach. With the help of these fluxes, reported emissions of small clusters of coal mine ventilation shafts are then assessed. The MAMAP CH4 column observations enable an accurate assignment of observed fluxes to small clusters of ventilation shafts. CH4 fluxes are estimated for four clusters with a total of 23 ventilation shafts, which are responsible for about 40 % of the total CH4 mining emissions in the target area. The observations were made during several overflights on different days. The final average CH4 fluxes for the single clusters (or sub-clusters) range from about 1 to 9 t CH4 h−1 at the time of the campaign. The fluxes observed at one cluster during different overflights vary by as much as 50 % of the average value. Associated errors (1σ) are usually between 15 % and 59 % of the average flux, depending mainly on the prevailing wind conditions, the number of flight tracks, and the magnitude of the flux itself. Comparison to known hourly emissions, where available, shows good agreement within the uncertainties. If only emissions reported annually are available for comparison with the observations, caution is advised due to possible fluctuations in emissions during a year or even within hours. To measure emissions even more precisely and to break them down further for allocation to individual shafts in a complex source region such as the USCB, imaging remote sensing instruments are recommended.

VELOX – A new thermal infrared imager for airborne remote sensing of cloud and surface properties

The new airborne thermal infrared (TIR) imager VELOX (Video airbornE Longwave Observations within siX channels) is introduced. The commercial camera system of VELOX covers six spectral bands with center wavelengths between 7.7 µm and 12 µm. VELOX is currently applied on board the German High Altitude and Long Range Research Aircraft (HALO). It observes two-dimensional fields of upward terrestrial spectral radiance with a horizontal spatial resolution of approximately 10 m by 10 m at a target distance of 10 km. Atmospheric temperature values are rather low compared to the original application of the TIR imager system and range close to the detection limit of the sensor. This challenge requires additional calibration efforts to reduce the measurement uncertainties of VELOX. These calibration and correction procedures, including radiometric calibrations, non-uniform corrections, bad-pixel replacements, and window corrections for data collected by VELOX, are presented. First measurements acquired by VELOX during the EUREC4A (ElUcidating the RolE of Cloud-Circulation Coupling in ClimAte) campaign are presented, including an analyses of the cloud top brightness temperature, cloud mask/fraction, and cloud top altitude data. They reveal that the cloud top temperature can be resolved with a resolution of better than 0.1 K, which translates into a resolution of approximately 40 m with respect to cloud top altitude.

Reproducibility of Pansharpening Methods and Quality Indexes versus Data Formats

In this work, we investigate whether the performance of pansharpening methods depends on their input data format; in the case of spectral radiance, either in its original floating-point format or in an integer-packed fixed-point format. It is theoretically proven and experimentally demonstrated that methods based on multiresolution analysis are unaffected by the data format. Conversely, the format is crucial for methods based on component substitution, unless the intensity component is calculated by means of a multivariate linear regression between the upsampled bands and the lowpass-filtered Pan. Another concern related to data formats is whether quality measurements, carried out by means of normalized indexes depend on the format of the data on which they are calculated. We will focus on some of the most widely used with-reference indexes to provide a novel insight into their behaviors. Both theoretical analyses and computer simulations, carried out on GeoEye-1 and WorldView-2 datasets with the products of nine pansharpening methods, show that their performance does not depend on the data format for purely radiometric indexes, while it significantly depends on the data format, either floating-point or fixed-point, for a purely spectral index, like the spectral angle mapper. The dependence on the data format is weak for indexes that balance the spectral and radiometric similarity, like the family of indexes, Q2n, based on hypercomplex algebra.

Pengukuran Suhu Permukaan Menggunakan Pancaran Spektral dari Citra Satelit: Studi Kasus di Banda Aceh

Abstrak. Tingginya tingkat urbanisasi menyebabkan meluasnya wilayah perkotaan dan menciptakan daerah keras yang mengakibatkan suhu tinggi di wilayah perkotaan, termasuk Banda Aceh. Permasalahan ini tentu menimbulkan ketidaknyamanan bagi masyarakat Banda Aceh. Beberapa penelitian melaporkan bahwa suhu udara yang terlalu tinggi dapat menyebabkan masalah kesehatan yang serius di masyarakat. Suhu permukaan Banda Aceh diukur menggunakan Spectral Radiance dari Satellite Imager, kemudian dibandingkan dengan data yang diukur langsung di lokasi penelitian. Hasil menunjukkan suhu udara di Banda Aceh berkisar antara 22,32°C hingga 34,86°C. Selain itu, terjadi korelasi antara penggunaan ruang dengan tingkat suhu udara Banda Aceh berdasarkan parameter hard area dan vegetasi. Namun, hanya variabel jarak dengan badan air yang memiliki korelasi signifikan terhadap perubahan tingkat suhu.Surface Temperature Distribution Using Spectral Radiance from Satellite Imagery: A Case Study in Banda AcehAbstract. The high rate of urbanization will have an effect on land change. The increasing number of buildings and lack of green open space will hinder the direction of wind speed, cause inconvenience to the public. The purpose of this study was to determine the distribution of surface temperature in the city of Banda Aceh based on the spectral emission of Landsat images from vegetation density, distance from the river, and built-up area. The air temperature data were obtained using the classification method from the digital number value of the Landsat image to the spectral radiance and then converted into air temperature. The density of the built-up area was analyzed from the Normalized Difference Vegetation Index (NDBI) and the density of the vegetation was analyzed from the Normalized Difference Vegetation Index (NDVI). The air temperature distribution map from the image is divided into 3 zones that are densely populated (built-up area), vegetation and distance to water bodies to be measured directly in the field. The air temperature from the lansat 8 images ranged from 22.32°C to 34.86°C. The zone with a distance of 3,457 km from a water body, with less vegetation density (0) and a built-up area of 0.16-0.23 has a temperature of 31.96oC -32.45oC, while the zone with a water body distance of 1,255 km with a built-up area below zero and vegetation has a temperature of 25.82oC-27.09oC. Based on the parameters of space use (vegetation and built-up area) and the distance between the zone and the water body, it has an influence on the distribution of air temperature in the city of Banda Aceh.

Spatial modelling of urban heat islands and its planning implications in Obio/Akpor local government area

Urban Heat Island (UHI) has become a global recurring phenomenon in most urban centres. Obio/Akpor Local Government Area has had a fair share of this phenomenon owing to its thriving trend in both planned and unplanned urbanisations. The study looks at the impact of UHI in selected communities in Obio/Akpor Local Government in five epochs of 2000, 2005, 2010, 2015 and 2020. Parts of the objectives include identifying the UHI in these communities in the Local Government Area, modelling of UHI in selected communities in Obio/Akpor Local Government Area and determining the trend in UHI using Epoch data of Urban Surface Temperature from LANDSAT thermal imageries Figure 1. The study adopted Thermal Infrared Remote (TIR) Sensing and Geospatial Information System (GIS) Techniques using LANDSAT TM, LANDSAT ETM and LANDSAT OLI sensors to acquire Urban Surface temperature data emitted by objects in the study area and store the information as a digital number (DN) thermal band (B6, B61 and B10) as well as secondary data acquired from the Nigerian Meteorological Agency (NIMET). Urban Surface Temperature was obtained through the following processes: Acquisition of Urban Surface Temperature value of the study area in form of DN, the conversion of DN to Spectral radiance using the Spectral radiance equation. The data were processed, analysed, and modelled using ESRI’s ArcGIS 10.1. The results revealed that in 2000, the Average Urban Temperature of the study area was 23.480°C, the value increase to 27.647°C in 2005 with a difference of 4.167°C. The temperature of 2005 increased to 31.598°C in 2010 with a difference in temperature of 3.951°C. Accordingly, the temperature of 2010 increased to 33.054°C in 2015 with a temperature difference of 1.456°C and temperature of 2015 increased to 33.070°C with a difference of 0.016°C. The analysis shows an increasing trend of 40% in the Urban Surface Temperature in the study area in the various years under investigation. The study recommends that development should be extended to other Local Government Areas in the state to reduce rural-urban migration to Obio/Akpor Local Government. Tree planting should be encouraged as a way of mitigating the effect of air pollution, heatwaves and harmful gases emitted into the environment by combust engines and gas flaring, the use of combustion engines be replaced by electric cars to reduce the level of carbon dioxide (CO2) emitted ti environment. Policymakers to restrict unplanned urban growth and to increase tree planting in the built-up areas.