Because snow is one of the few features on the earth's surface bright enough to reflect low light levels, night-time visible imagery can be used to observe snow provided the moon is sufficiently bright. The DMSP satellites, which orbit the earth at noon and midnight local time, have demonstrated that snow can be easily detected when the moon is above the horizon, at the time of the satellite overpass, and between the first quarter and last quarter phase. By utilizing night-time as well as day-time visible imagery, snow-cover conditions can be better monitored.