The instrument is “a single-channel, near-infrared optical transient detector that can detect the momentary changes in an optical scene, indicating the presence of lightning,” NOAA explains. In other words, it’s like a camera that is programmed to take a picture every time the near-infrared “scene” changes.
The mapper has obvious benefits to the National Weather Service and the meteorological community at large. Sudden increases in lightning activity within thunderstorms — which the lightning mapper will detect — often signal that they are becoming severe and violent. Local Weather Service meteorologists can monitor the data from the GLM to determine in real time if a storm is becoming severe and issue warnings sooner than they would have otherwise been able to.