Satellites work by passively sensing energy. A weather satellite senses two forms of energy, visible (reflected sunlight) and infrared (for example, microwave and heat energy), from the earth’s surface, clouds, and atmosphere.

Infrared energy is emitted 24 hours a day and is sensed by satellites continuously. In contrast, visible imagery is available only during daylight hours since sunlight is reflected only during that period. Please note that the animations below are not to scale.