A great many of the satellites sent into space by the USA and Russia are used for military activities. These range from eaves-dropping on important telephone calls to detecting the x-rays and electromagnetic pulses given off by nuclear explosions. Early military satellites were used to take close-up pictures of enemy territory but had to return home to have their film developed. Modern satellites use digital technology to take photographs, so they never run out of film. Amazingly, they can photograph things as small as the headlines on a newspaper.
The military space program is a significant but largely unseen aspect of space operations. Nearly a dozen countries have some kind of military space program, but the U.S. program dwarfs the efforts of all these other countries combined.
Military space operations are divided into five main areas: reconnaissance and surveillance, signals intelligence, communications, navigation, and meteorology. Only the United State and Russia operate spacecraft in all five areas. Several other countries have long used communications satellites for military purposes. In the 1990s, several countries in addition to Russia and the United State began developing reconnaissance satellites.
Reconnaissance and surveillance involve the observation of Earth for various purposes. Dedicated reconnaissance satellites, like the United States’ Improved CRYSTAL and the Russian Terilen, take photographs of targets on the ground and relay them to receiving stations in nearly real time. These satellites, however, cannot take continuous images like a television camera. Instead, they take a black-and-white photograph of a target every few seconds. Because they are in low orbits and are constantly moving, they can photograph a target for only a little over a minute before they move out of range. The best American satellites, which are similar in appearance to the Hubble Space Telescope, can see objects about the size of a softball from hundreds of miles up but they cannot read license plates. The Russians also occasionally use a system that takes photographs on film and then returns the film to Earth for processing. This provides them with higher-quality photos. The United States abandoned this technology in the 1980s after developing superior electronic imaging technology.
Other surveillance satellites, such as the American DSP and Space-Based Infrared System (SBIRS, pronounced “sibirs”) and the Russian Oko (or “eye”), are equipped with infrared telescopes and scan the ground for the heat produced by a missile’s exhaust. They can be used to warn of missile attack and can predict the targets of missiles fired hundreds or thousands of miles away. There are also satellites that look at the ground in different wavelengths to peer through camouflage, try to determine what objects are made of, and analyze smokestack emissions.
Signals intelligence satellites can operate either in low Earth orbit or in extremely high, geosynchronous orbit, where they appear to stay in one spot in the sky. These satellites listen for communications from cellular telephones, walkie-talkies, microwave transmissions, radios, and radar. They relay this information to the ground, where it is processed for various purposes. Contrary to popular myth, these satellites do not collect every conversation around the world. There is far more information being transmitted every day over the Internet than can be collected by evens the best spy agency.