Quantitative evaluation of outdoor artificial light emissions using low Earth orbit radiometers

TL;DR

This study uses low Earth orbit radiometers and ground data to quantitatively assess outdoor light emission changes at the municipality level, demonstrating a significant reduction in public lighting and its impact on overall light pollution.

Contribution

It introduces a simple model combining satellite measurements and ground-truth data to evaluate outdoor lighting changes at the municipality level.

Findings

Municipality reduced outdoor lighting from 93.2 to 28.7 Mlm.

Lumen emission density decreased from 0.768 to 0.208 Mlm/km2.

Public streetlight emissions dropped from 74.86% to 44.68% of total light emissions.

Abstract

Low Earth orbit radiometers allow monitoring nighttime anthropogenic light emissions in wide areas of the planet. In this work we describe a simple model for assessing significant outdoor lighting changes at the municipality level using on-orbit measurements complemented with ground-truth information. We apply it to evaluate the transformation effected in the municipality of Ribeira (42{\deg} 33 23 N, 8{\deg} 59 32 W) in Galicia, which in 2015 reduced the amount of installed lumen in its publicly-owned outdoor lighting system from 93.2 to 28.7 Mlm. This significant cutback, with the help of additional controls, allowed to reduce from 0.768 to 0.208 Mlm/km2 the lumen emission density averaged across the territory. In combination with the VIIRS-DNB annual composite readings these data allow to estimate that the relative weight of the emissions of the public streetlight system with respect to the total emissions of light in the municipality changed from an initial value of 74.86% to 44.68% after the transformation. The effects of the sources spectral shift and the photon calibration factor on the radiance reported by the VIIRS-DNB are also evaluated.