Modern missiles can be guided to a target, often by their own systems. The most common kind of homing technology detects and locks on to infrared (IR) radiation, such as the heat from a jet exhaust. Modern systems detect two wavelengths: 3-5 micrometres and 8-13 micrometres. The second wavelength isn’t absorbed by the atmosphere, so it’s much easier to track. This also makes flares – the intense infrared countermeasures that are ejected by a target in order to lure the missile off course – less effective. Missiles are essentially rockets fitted with an explosive warhead and an infrared detection sensor connected to a flight computer. These sensors are often made of mercury cadmium telluride to pick up the specific infrared wavelengths emitted by the enemy target.
