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Levin, N., & Phinn, S. (2016). Illuminating the capabilities of Landsat 8 for mapping night lights. Remote Sensing of Environment, 182, 27–38.
Abstract: Remote sensing of night-lights has been enhanced in recent years with the availability of the new VIIRS Day and Night band, the commercial EROS-B satellite and astronaut photographs from the International Space Station. However, dedicated space-borne multispectral sensors offering radiance calibrated night lights imagery are yet to be launched. Here we examined the capabilities of Landsat 8 to acquire night time light images of the Earth. Examining seven night-time Landsat 8 scenes, we found that brightly lit areas in both urban (Berlin, Las Vegas, Nagoya and Tel-Aviv) and gas flares (Basra, Kuwait) areas were detected in all eight bands of Landsat 8. The threshold for detection of lit areas was approximately 0.4 W/m2/μm/sr in bands 1–5 and 8 of Landsat 8. This threshold level was higher than Landsat dark noise levels, and slightly lower than post launch Landsat 8 OLI band dependent noise equivalent radiance difference levels. Drawing on this, we call on the USGS to plan an annual night-time acquisition of urban and gas flares areas globally, and to enable the performance of the future Landsat 10 to be established in a way that it will be sensitive enough to image the Earth at night, thus performing as Nightsat during the night.
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Zamorano, J., Sánchez de Miguel, A., Ocaña, F., Pila-Diez, B., Gómez Castaño, J., Pascual, S., et al. (2016). Testing sky brightness models against radial dependency: a dense two dimensional survey around the city of Madrid, Spain. JQSRT, 181, 52–66.
Abstract: We present a study of the night sky brightness around the extended metropolitan area of Madrid using Sky Quality Meter (SQM) photometers. The map is the first to cover the spatial distribution of the sky brightness in the center of the Iberian peninsula. These surveys are neccessary to test the light pollution models that predict night sky brightness as a function of the location and brightness of the sources of light pollution and the scattering of light in the atmosphere. We describe the data-retrieval methodology, which includes an automated procedure to measure from a moving vehicle in order to speed up the data collection, providing a denser and wider survey than previous works with similar time frames. We compare the night sky brightness map to the nocturnal radiance measured from space by the DMSP satellite. We find that i) a single source model is not enough to explain the radial evolution of the night sky brightness, despite the predominance of Madrid in size and population, and ii) that the orography of the region should be taken into account when deriving geo-specific models from general first-principles models. We show the tight relationship between these two luminance measures. This finding sets up an alternative roadmap to extended studies over the globe that will not require the local deployment of photometers or trained personnel.
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Aubé, M., Kocifaj, M., Zamorano, J., Solano Lamphar, H. A., & Sanchez de Miguel, A. (2016). The spectral amplification effect of clouds to the night sky radiance in Madrid. Journal of Quantitative Spectroscopy and Radiative Transfer, 181, 11–23.
Abstract: Artificial Light at Night (ALAN) may have various environmental impacts ranging from compromising the visibility of astronomical objects to the perturbation of circadian cycles in animals and humans. In the past much research has been carried out to study the impact of ALAN on the radiance of the night sky during clear sky conditions. This was mainly justified by the need for a better understanding of the behavior of ALAN propagation into the environment in order to protect world-class astronomical facilities. More recently, alongside to the threat to the natural starry sky, many issues have emerged from the biological science community. It has been shown that, nearby or inside cities, the presence of cloud cover generally acts as an amplifier for artificial sky radiance while clouds behave as attenuators for remote observers. In this paper we show the spectral behavior of the zenith sky radiance amplification factor exerted by clouds inside a city. We compare in-situ measurements made with the spectrometer SAND-4 with a numerical model applied to the specific geographical context of the Universidad Complutense de Madrid in Spain.
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Jechow, A., Hölker, F., Kolláth, Z., Gessner, M. O., & Kyba, C. C. M. (2016). Evaluating the summer night sky brightness at a research field site on Lake Stechlin in northeastern Germany. Journal of Quantitative Spectroscopy and Radiative Transfer, 181, 24–32.
Abstract: We report on luminance measurements of the summer night sky at a field site on a freshwater lake in northeastern Germany (Lake Stechlin) to evaluate the amount of artificial skyglow from nearby and distant towns in the context of a planned study on light pollution. The site is located about 70 km north of Berlin in a rural area possibly belonging to one of the darkest regions in Germany. Continuous monitoring of the zenith sky luminance between June and September 2015 was conducted utilizing a Sky Quality Meter. With this device, typical values for clear nights in the range of 21.5–21.7 magSQM/arcsec2 were measured, which is on the order of the natural sky brightness during starry nights. On overcast nights, values down to 22.84 magSQM/arcsec2 were obtained, which is about one third as bright as on clear nights. The luminance measured on clear nights as well as the darkening with the presence of clouds indicate that there is very little influence of artificial skyglow on the zenith sky brightness at this location. Furthermore, fish-eye lens sky imaging luminance photometry was performed with a digital single-lens reflex camera on a clear night in the absence of moonlight. The photographs unravel several distant towns as possible sources of light pollution on the horizon. However, the low level of artificial skyglow makes the field site at Lake Stechlin an excellent location to study the effects of skyglow on a lake ecosystem in a controlled fashion.
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Kolláth, Z., Dömény, A., Kolláth, K., & Nagy, B. (2016). Qualifying lighting remodelling in a Hungarian city based on light pollution effects. Journal of Quantitative Spectroscopy and Radiative Transfer, 181, 46–51.
Abstract: The public lighting system has been remodelled in several Hungarian cities. In some cases the majority of the old luminaries were fitted with high pressure sodium lamps and they were replaced with white LED lighting with a typical correlated colour temperature of about 4500 K. Therefore, these remodelling works provide a testbed for methods in measurements and modelling. We measured the luminance of the light domes of selected cities by DSLR photometry before and after the remodelling.
Thanks to the full cut off design of the new lighting fixtures we obtained a slight decrease even in the blue part of the sky dome spectra of a tested city. However, we have to note that this positive change is the result of the bad geometry (large ULR) of the previous lighting system. Based on Monte Carlo radiative transfer calculations we provide a comparison of different indicators that can be used to qualify the remodelling, and to predict the possible changes in light pollution.
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