Fast Fourier-transform calculation of artificial night sky brightness maps

Abstract

Light pollution poses a growing threat to optical astronomy, in addition to its detrimental impacts on the natural environment, the intangible heritage of humankind related to the contemplation of the starry sky and, potentially, on human health. The computation of maps showing the spatial distribution of several light pollution related functions (e.g. the anthropogenic zenithal night sky brightness, or the average brightness of the celestial hemisphere) is a key tool for light pollution monitoring and control, providing the scientific rationale for the adoption of informed decisions on public lighting and astronomical site preservation. The calculation of such maps from satellite radiance data for wide regions of the planet with sub-kilometric spatial resolution often implies a huge amount of basic pixel operations, requiring in many cases extremely large computation times. In this paper we show that, using adequate geographical projections, a wide set of light pollution map calculations can be reframed in terms of two-dimensional convolutions that can be easily evaluated using conventional fast Fourier-transform (FFT) algorithms, with typical computation times smaller than 10^-6 s per output pixel.

arXiv commentAuthor formatted text of the accepted version of the paper published in Journal of Quantitative Spectroscopy & Radiative Transfer 240 (2020) 106658

References in corpus (9)

• The new world atlas of artificial night sky brightness
• The first world atlas of the artificial night sky brightness
• Limiting the impact of light pollution on human health, environment and stellar visibility
• Representations of celestial coordinates in FITS
• The propagation of light pollution in the atmosphere
• Naked eye star visibility and limiting magnitude mapped from DMSP-OLS satellite data
• Night sky brightness at sites from DMSP-OLS satellite measurements
• Characterizing the zenithal night sky brightness in large territories: How many samples per square kilometer are needed?
• On lamps, walls, and eyes: the spectral radiance field and the evaluation of light pollution indoors

Cited by in corpus (5)

• Protecting the night sky darkness in astronomical observatories: a linear systems approach
• PSFs for mapping artificial night sky luminance over large territories
• Modelling the artificial night sky brightness at short distances from streetlights
• Estimating linear radiance indicators from the zenith night sky brightness: on the Posch ratio for natural and light polluted skies
• On the Posch ratio for irradiance in coastal waters and the high seas