Then they are cooled off. An animal or a hotplate is heated from the inside. But all objects radiate heat regardless of how they have been heated. The thermo binoculars measure the infrared radiation from the objects. High clouds are cold at the top.
Low clouds are warmer.
That is why the satellite can tell the difference between high and low clouds. A healthy forest has a different temperature from a sick forest. Towns are warmer than the countryside. In this way, the satellite may pick up much information. The glow lamp is smaller than the area in which the thermo binoculars are measuring.