Spy Satellites

Use of space satellites to spy on other nations and provide intelligence that might be crucial to a nation's security and other interests. Military strategists have always sought higher ground to look down on enemies, and spy satellites afford just such a unique position.

There are two basic types of spy satellites—those that eavesdrop on communications for signals intelligence, or SIGINT, and those that generate high-quality image intelligence, or IMINT. SIGINT satellites detect and intercept radio, mobile telephone, and data transmissions for the National Security Agency (NSA). Signals intelligence satellites cannot intercept communications carried over landlines, however. The United States operates signals intelligence satellites in geo-stationary, elliptical, and low Earth orbits.

IMINT satellites return images to the National Imagery and Mapping Agency (NIMA) and fall into three general categories—radar imaging, optical imaging, and a combination of the two. Radar imaging satellites use radio (microwave) signals to scan the earth, while optical satellites use mirrors to gather light for photography. Radar imaging satellites generate a microwave beam, bounce it off an object, receive the echo, and then reconstitute the information into a picture. A relatively new technology is synthetic aperture radar (SAR) satellites, which are unhindered by darkness or bad weather. Optical imaging suffers from the inability to see through clouds, a shortcoming overcome by space-based imaging radar.

All imaging satellites suffer from relatively short windows of opportunity in which to take images. However, due to various technological advances, spy satellites can now remain over an area for about 10 minutes. With enhancements in optical and radar technology, satellite developers hope to place satellites at higher orbits so they can take pictures for longer durations. Imaging quality has also been greatly enhanced. Early optical imaging satellites produced photographs that ranged in resolution down to about two meters. The current generation of U.S. spy satellites is reportedly able to identify objects on the ground as small as 10 centimeters.

The National Reconnaissance Office (NRO) operates satellites for the U.S. military and the intelligence community, while U.S. reconnaissance satellites are launched by the Air Force. The NRO designs, builds, and operates the nation's reconnaissance satellites, and supplies data to the Central Intelligence Agency (CIA) and the Department of Defense (DoD). The first spy satellite program in the United States was named Corona. Corona was designed to take photographs over the Soviet Union and China, replacing the dangerous U2 flights over the territory of those two nations. U2 flights had been ongoing since 1956, but Soviet radar systems had soon proven better able to track the planes than originally thought.

With the fallout from the U2 spy plane incident of 1960, in which Air Force pilot Gary Powers and his plane were shot down over the Soviet Union, a better way of seeing Soviet installations had to be found. Satellite photography proved to be the way. After taking the photographs, the satellite would jettison the developed film back to Earth.

After several rocket failures, Corona made its first successful flight and film return in August 1960. Bringing back the first images of Earth from outer space was no small achievement. Of the first 30 Corona missions, only 12 were considered successes. Camera systems such as those employed in Corona continued in use until the 1980s, after which image data began being beamed directly to Earth.

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