Examples of early remote sensing

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History of remote sensing

Photography is generally dated from 1839, with the introduction of the photographic process known as the daguerreotype. Remote sensing is generally dated from 1858, when Gaspard Felix Tournachon (who was known by his pseudonym Nadar) photographed from a balloon the village of Petit Becetre, near Paris.

Remote sensing is the collection of data about something by means of an instrument not in contact with it. Most typically this refers to Earth-directed sensors riding on aircraft and satellites.

During the American Civil War, balloons were used to observe enemy positions and reportedly to take photographs of them. This was the first of many times that war spurred advancements in remote sensing. From the Civil War until the First World War, people experimented with other platforms such as rockets, kites, and pigeons, but the great step forward was the invention of the airplane, a much more stable and reliable platform.

World War I was fought with only crude aerial reconnaissance, but by World War II the technology had become highly sophisticated. Between the wars, military research and development in remote sensing was minor, but the experiences of World War I encouraged work in civilian uses of remote sensing, such as forestry, agriculture, and geology.

World War II pushed remote sensing beyond visible-spectrum photography into infrared detection and radar systems. Radar is not only invisible (microwave), but also active, as distinguished from the previous passive aerial cameras. It detects energy sent out by itself, like a person with a flashlight. Because the resolution of a radar system is related to wavelength and antenna length, aircraft-mounted radar systems with their short antennas originally required high-powered, short-wavelength emitters, but the development of synthetic-aperture radar (SAR) permitted high resolution with longer wavelengths by "synthesizing" a longer antenna.

One century after the origin of remote sensing, and only months after the first man-made satellite (Sputnik 1, 4 October 1957), remote sensing moved to outer space. The United States' Explorer 6 transmitted the first space photograph of the Earth in August 1959. The first systematic satellite observation came with the launch of the United States' TIROS 1 in 1960. This was a meteorological satellite, designed to track weather clouds. Landsat 1 (originally called the Earth Resources Technology Satellite or ERTS) was the first satellite to collect data specifically on the Earth's surface and natural resources. It was launched on 23 July 1972.

(See the next help article for more on the Landsat program.)

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