Free Astronomy Magazine March-April 2026

5 ASTRO PUBLISHING Today, however, satellite observa- tions reveal a far more complex re- ality. The global transition to LED technology has fundamentally al- tered light pollution’s spectral com- position, spatial distribution, and atmospheric behaviour. The true nature of light pollution itself has changed, with consequences for as- tronomical observations, including those conducted by large ground- based observatories. Modern satellites are providing an unprecedented global view of artifi- cial light emissions, revealing a com- plex and concerning evolution of night-time illumination. Most global assessments of light-pollution trends rely primarily on data from the VIIRS (Visible Infrared Imaging Radiome- ter Suite), carried by meteorological and Earth-observation satellites such as the Suomi NPP and NOAA-20. Nevertheless, while VIIRS is extraor- dinarily sensitive to faint night-time radiance, it operates with a critical blind spot: it is essentially colour- blind to blue light. VIIRS is a panchro- matic night-imaging sensor opti- mised for wavelengths within the MARCH-APRIL 2026 A rtist’s impression of artificial sky- glow spreading from urban areas toward nearby mountain observato- ries, illustrating how distant city light- ing can degrade night-sky quality even at high-altitude sites. [A. Anfuso]