On the previous post, we ended with the concept of the electromagnetic spectrum. There is an extremely important phenomenon that relates the temperature of a body to the infrared radiation that is part of that spectrum. It turns out that everybody emits infrared radiation depending on its temperature. It would only stop if it reached the 273 negative degrees, turns out absolute 0, temperature in which would cease all molecular movement and with that the emission of that radiation.
So, if you capture the infrared radiation emitted by a body – which we cannot see – you can know its temperature, but is there and know where it is located.
A man or an animal could escape from sight by hiding behind something or with a good camouflage, but could not cool, at least not much, and avoid the emission of infrared rays.
And the satellites travel above all these regions.
Therefore they can photograph areas of the surface that are far from the reach of an observer (Rangers, lookouts). But they are not ordinary photographs like the ones we see every day, but infrared photographs that capture this radiation that is related to temperature.
The focus of a forest fire, the position of a ship in trouble, the atmospheric alteration that precedes a storm can be photographed by a camera installed on board a satellite.
The image, digitized, can be sent to a ground station and converted back into a visible image.
The same technology, can detect areas suitable for crops, location of transport terrestrial or aquatic, groups of animals, differentiating them between the hot or cold blooded. It could be used if necessary to detect the presence of human groups in restricted areas.
As an interesting fact; infrared radiation can travel through smoke, fog and polluted air masses.