Lethal Thermal Drones Can Follow Your Footprints Across Fresh Snow
Thermal camouflage is useless when your prints betray you
Fresh snow is more emissive than packed snow. That’s bad news for Russian infantry in Ukraine.
Emissivity is a measure of a material’s efficiency in emitting thermal radiation—in other words, heat. Fresh snow emits heat very efficiently and thus quickly hews close to the temperature of the surrounding environment. Packed snow emits heats less efficiently—and is thus slower to match the environment.
The thermal cameras that are fast becoming the primary sensors of Ukraine’s explosive first-person-view drones will generally read freshly fallen snow as a highly emissive dark expanse more or less matching the air. The same cameras will read the less emissive footprints as warmer and lighter in color.
It’s not that the fresh snow and footprints are actually much different in temperature, Canadian drone expert Roy noted. But for a critical period after someone treads across fresh snow, their footprints will register “an apparent temperature contrast” owing to the difference in emissivity.
