Sunlight beams off a partly cloudy Atlantic Ocean just after sunrise as the International Space Station orbited 263 miles above on March 5, 2025. This is an example of sunglint, an optical phenomenon that occurs when sunlight reflects off the surface of water at the same angle that a satellite sensor views it. The result is a mirror-like specular reflection of sunlight off the water and back at the satellite sensor or astronaut.
While sunglint often produces visually stunning images, the phenomenon can create problems for remote sensing scientists because it obscures features that are usually visible. This is particularly true for oceanographers who use satellites to study phytoplankton and ocean color. As a result, researchers have developed several methods to screen sunglint-contaminated imagery out of data archives.
Despite the challenges posed by sunglint, the phenomenon does offer some unique scientific opportunities. It makes it easier, for instance, to detect oil on the water surface, whether it is from natural oil seeps or human-caused oil spills. This is because a layer of oil smooths water surfaces.
Text credit: Adam Voiland
Image credit: NASA
