Assessing light pollution in Mongolia: current status and future trends using remote sensing and citizen science data

<jats:p>The inappropriate or excessive use of artificial light, known as light pollution, can have serious environmental consequences for humans, wildlife, and our climate (DarkSky.org). Light pollution is a relatively new and less investigated topic in Mongolia. Previously, there was little awareness about its significant negative impacts. To understand the extent of light pollution in Ulaanbaatar, the capital city of Mongolia, we compared it with a city less affected by light pollution. Ulaanbaatar and Tucson, Arizona, USA, were selected for this investigation. Both cities have populations of around one million. We used NASA's VIIRS/NPP Lunar BRDF-Adjusted Nighttime Lights Yearly SQM data to analyze light pollution from 2012 to 2023. ArcGIS applications were employed to map light pollution in the selected cities. The National Observatory Khurel Togoot in Ulaanbaatar is much more affected by light pollution than Kitt Peak National Observatory in Tucson. Ulaanbaatar and its observatory suffer from significant light pollution due to urbanization and uncontrolled lighting conditions. In the Gobi region of Mongolia, cities are expanding rapidly due to mining and urbanization, resulting in uncontrolled lighting. This light pollution poses a significant threat to the visibility of stars and celestial phenomena, making it difficult for astronomers, researchers, and enthusiasts to study and appreciate the cosmos. Monitoring and implementing dark sky protection  using satellite data are crucial for preserving the conditions needed for observing the night sky in the Mongolian Gobi desert.</jats:p>