A linear systems approach to protect the night sky: implications for current and future regulations

Abstract

The persistent increase of artificial light emissions is causing a progressive brightening of the night sky in most regions of the world. This process is a threat for the long-term sustainability of the scientific and educational activity of ground-based astronomical observatories operating in the optical range. Huge investments in building, scientific and technical workforce, equipment and maintenance can be at risk if the increasing light pollution levels hinder the capability of carrying out the top-level scientific observations for which these key scientific infrastructures were built. Light pollution has other negative consequences, as e.g. biodiversity endangering and the loss of the starry sky for recreational, touristic and preservation of cultural heritage. The traditional light pollution mitigation approach is based on imposing conditions on the photometry of individual sources, but the aggregated effects of all sources in the territory surrounding the observatories are seldom addressed in the regulations. We propose that this approach shall be complemented with a top-down, ambient artificial skyglow immission limits strategy, whereby clear limits are established to the admissible deterioration of the night sky above the observatories. We describe the general form of the indicators that can be employed to this end, and develop linear models relating their values to the artificial emissions across the territory. This approach can be easily applied to other protection needs, like e.g. to protect nocturnal ecosystems, and it is expected to be useful for making informed decisions on public lighting, in the context of wider spatial planning projects.

Keeping light pollution at bay: a red-lines, target values, top-down approach

“…This naturally leads to the need of adopting tight light emission caps, whose territorial allocation is a science-informed but essentially social and political issue. The logical link between limiting the effects and limiting the overall emissions is a necessary consequence of the physics of the propagation of light in the atmosphere (Aubé, 2015;Aubé et al, 2020;Bará and Lima, 2018;Bará et al, 2019c;Cinzano and Falchi, 2012;Falchi and Bará, 2020;Garstang, 1986Garstang, , 1989Garstang, , 1991Kocifaj, 2016).…”

“…There is however a particular field where the effects to be addressed can be confidently defined with little or no ambiguity: the artificial brightness of the night sky. Some first-class optical observatories have already undergone major losses on the night sky over them, others are currently losing it and others may still find jeopardized their ability to carry out the scientific observations for which they were built and equipped if the artificial brightness surpasses some definite instrument-dependent limits (Walker, 1970;Falchi and Bará, 2020). The effect to keep under control is then clear: the artificial radiance entering the photometric bands of their observing instruments, including, when appropriate, the naked human eye.…”

“…The calculation of the contribution of every pixel of the surrounding territory can be made using available models (Aubé et al, 2020;Bará and Lima, 2018;Falchi and Bará, 2020). This usually requires standardizing the atmospheric conditions under which will be carried out the assessment.…”

“…These detrimental effects are not limited to a specific field, but transversally affect the environment, the nocturnal landscape, the starry sky as a scientific and cultural global commons, and arguably, public health, among others (Aubé et al, 2020;Alamús et al, 2017;AMA 2012AMA , 2016Bará, 2016;Bennie at al, 2015;Bonmati-Carrion et al, 2014;Cho et al, 2015;Cinzano et al, 2001;Czeisler, 2013;Davies et al, 2015Davies et al, , 2015Davies et al, , 2016Davies et al, , 2020Dobler et al, 2015Dobler et al, , 2016Falchi et al, 2016;Garcia-Saenz et al, 2018;Gaston et al, 2013Gaston et al, , 2014van Grunsven et al, 2020;Haim and Portnov, 2013;Hölker et al, , 2010bKyba et al, 2017;Longcore and Rich, 2004;Marin and Jafari, 2008;Rich and Longcore, 2006;Portnov, 2016, 2018;Sanders et al, 2020). Being artificial light at night (ALAN) a pollutant, addressing its negative effects is becoming part of the public agenda in many countries of the world (Bará et al, 2019;Falchi et al, 2011;Falchi and Bará, 2020;Longcore et al, 2015;Schroer et al, 2020;Zielińska-Dąbkowska et al 2020).…”

A New Approach to Identify on-Ground Lamp Types From Night-Time Iss Images

“…Besides, NTL also embarrasses professional astronomical observations (Kyba, 2018;Riegel, 1973;Zhang et al, 2017). With respect to the above-mentioned challenges, the necessity to regulate light pollution becomes further more recognized (Cho et al, 2011;Falchi and Bará, 2020;Morgan-Taylor, 2015).…”