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Sánchez de Miguel, A., Kyba, C. C. M., Aubé, M., Zamorano, J., Cardiel, N., Tapia, C., et al. (2019). Colour remote sensing of the impact of artificial light at night (I): The potential of the International Space Station and other DSLR-based platforms. Remote Sensing of Environment, 224, 92–103.
Abstract: Sensors on remote sensing satellites have provided useful tools for evaluation of the environmental impacts of nighttime artificial light pollution. However, due to their panchromatic nature, the data available from these sensors (VIIRS/DNB and DMSP/OLS) has a limited capacity accurately to assess this impact. Moreover, in some cases, recorded variations can be misleading. Until new satellite platforms and sensors are available, only nighttime images taken with DSLR cameras from the International Space Station (ISS), airplanes, balloons or other such platforms can provide the required information. Here we describe a theoretical approach using colour-colour diagrams to analyse images taken by astronauts on the ISS to estimate spatial and temporal variation in the spectrum of artificial lighting emissions. We then evaluate how this information can be used to determine effects on some key environmental indices: photopic vision, the Melatonin Suppression Index, the Star Light Index, the Induced Photosynthesis Index, production of NO2-NO radicals, energy efficiency and CO2 emissions, and Correlated Colour Temperature. Finally, we use the city of Milan as a worked example of the approach.
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Kolláth, K., & Kolláth, Z. (2020). On the feasibility of using ceilometer backscatter profile as input data for skyglow simulation. Journal of Quantitative Spectroscopy and Radiative Transfer, in press, in press.
Abstract: Atmospheric conditions can significantly affect the sky brightness originating from artificial lights. Previous works studied the cloudiness, cloud base height, optical depth of cloud, aerosol optical depth and aerosol scale height as atmospheric parameters affecting night sky brightness. Instead of using these parameters as a simplification of the real cloud and aerosol profile, we processed the raw backscatter data of a laser ceilometer instrument. Sky brightness was obtained from camera images available at the same meteorological observation site. Case studies are shown in selected cases, where we analyzed the correspondences with the backscatter data and the camera images. We performed Monte Carlo simulations with the dominant light sources to verify the numerical predictions of sky radiances. Although the limitations of the ceilometer device to obtain optical properties of the atmosphere, ceilometers provide valuable source of data for evaluation of the light pollution measurements.
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Kolláth, Z., Cool, A., Jechow, A., Kolláth, K., Száz, D., & Tong, K. P. (2020). Introducing the Dark Sky Unit for multi-spectral measurement of the night sky quality with commercial digital cameras. Journal of Quantitative Spectroscopy and Radiative Transfer, 253, 107162.
Abstract: Multi-spectral imaging radiometry of the night sky provides essential information on light pollution (skyglow) and sky quality. However, due to the different spectral sensitivity of the devices used for light pollution measurement, the comparison of different surveys is not always trivial. In addition to the differences between measurement approaches, there is a strong variation in natural sky radiance due to the changes of airglow. Thus, especially at dark locations, the classical measurement methods (such as Sky Quality Meters) fail to provide consistent results. In this paper, we show how to make better use of the multi-spectral capabilities of commercial digital cameras and show their application for airglow analysis. We further recommend a novel sky quality metric the ”Dark Sky Unit”, based on an easily usable and SI traceable unit. This unit is a natural choice for consistent, digital camera-based measurements. We also present our camera system calibration methodology for use with the introduced metrics.
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Min, M., Zheng, J., Zhang, P., Hu, X., Chen, L., Li, X., et al. (2020). A low-light radiative transfer model for satellite observations of moonlight and earth surface light at night. Journal of Quantitative Spectroscopy and Radiative Transfer, in press, 106954.
Abstract: Lunar sun-reflected light can be effectively measured through a low-light band or a day/night band (DNB) implemented on space-based optical sensors. Based on moonlight, nocturnal observations for artificial light sources at night can be achieved. However, to date, an open-sourced and mature Low-Light Radiative Transfer Model (LLRTM) for the further understanding of the radiative transfer problem at night is still unavailable. Therefore, this study develops a new LLRTM at night with the correction of the lunar and active surface light sources. First, the radiative transfer equations with an active surface light source are derived for the calculation based on the lunar spectral irradiance (LSI) model. The simulation from this new LLRTM shows a minimal bias when compared with the discrete ordinates radiative transfer (DISORT) model. The simulated results of radiance and reflectance at the top of the atmosphere (TOA) also show that the surface light source has a remarkable impact on the radiative transfer process. In contrast, the change in the lunar phase angle has minimal influence. Also, comparing with space-based DNB radiance observations, LLRTM shows the potential to simulate space-based low-light imager observations under an effective surface light source condition during the night.
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Bouroussis, C. A., & Topalis, F. V. (2020). Assessment of outdoor lighting installations and their impact on light pollution using unmanned aircraft systems – The concept of the drone-gonio-photometer. Journal of Quantitative Spectroscopy and Radiative Transfer, 253, 107155.
Abstract: This paper presents the ongoing work of the lighting laboratory to develop a standardized method for the measurement of several types of lighting installations using unmanned aircraft systems. The technology of unmanned aircraft systems can incorporate multiple types of sensors and can be programmed to fly in predefined areas and routes in order to perform complex measurements with limited human intervention. This technology provides the freedom of measurements from several angular positions and altitudes in a fast, easy, accurate and repeatable way. The overall aim of this work is to assess the lighting installations, not only against the applicable lighting standards but also to investigate and reveal issues related to light pollution and obtrusive lighting. The latter are issues that in most cases are neglected due to the lack of standardized methods of calculation and measurement. Current assessment methods require illuminance or luminance measurements of horizontal and vertical surfaces generally from the ground. The proposed approach provides a holistic three-dimensional evaluation of the lighting installations beyond the common methods and geometries and opens the discussion for future update of the relevant standards on outdoor lighting. In the scope of this paper, several proof-of-concept cases are presented.
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