How did the early warning satellite find the missile?

Missile early warning satellites were developed days after the launch of artificial satellites. The United States launched its first early warning satellite in the early 1960s. This kind of satellite runs in the universe and keeps an eye on the ever-changing earth. Infrared detectors on satellites are particularly sensitive to missile plumes. It can "watch" the missile launch thousands of miles away and send the dangerous information of nuclear attack back to the ground air defense center in time, which can win valuable half-hour early warning time.

In fact, the principle of early warning satellite finding missiles is similar to that of ground-to-air missiles and air-to-air missiles using infrared rays to automatically chase enemy planes.

The infrared detector on the satellite can detect the flame emitted by the missile, because in nature, as long as the temperature of all objects is higher than absolute zero (-273℃), it will radiate infrared rays invisible to the naked eye. When the engine of intercontinental missile burns, the flame formed by high-temperature gas will produce powerful infrared radiation, and the infrared detector on the satellite can give an alarm to the ground station within tens of seconds after the missile is launched. However, the early warning satellite mistook the sunlight reflected from the high-altitude clouds for the infrared radiation of the missile tail flame and for a large-scale nuclear attack. This happened in the United States, which frightened the United States at that time.

In order to avoid false alarm, the TV camera with high-resolution telephoto lens is installed on the early warning satellite. When the infrared detector detects the missile flame, it immediately controls the TV camera to automatically shoot the image of the target area, so the TV screen of the ground station displays the moving image of the missile flame at the speed of 1-2 frames per second. According to the different shapes of the jet flame at different heights, it can be judged whether there is a missile attack, and the flight trajectory of the active phase of the missile can be roughly measured.

The infrared wavelength of missile plume radiation is mainly about 2.7 microns, so the infrared detectors on satellites mostly use lead sulfide detector arrays. It consists of about 2000 unit devices, and the most sensitive wavelength is 2.7 microns. When the satellite runs in geosynchronous orbit at an altitude of 36,000 kilometers, the reconstructed infrared detector array can "see" 40% of the earth's surface.

Since 197 1, four geosynchronous early warning satellites deployed by the United States over the Atlantic Ocean have detected more than 1000 missile launches around the world, including SS- 18, SS- 19 intercontinental missiles and SS-N-8 submarine missiles of the former Soviet Union. Spaceborne infrared detector can detect the missile within 90 seconds after the missile is launched and track it until the missile engine is turned off. The information obtained is forwarded by the relay communication satellite and can be transmitted to the ground within 3 minutes.