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Q. What is infrared light? — Mel A.
A. Infrared is part of the electromagnetic energy spectrum.
Unlike visible light, which also is part of the electromagnetic spectrum, human eyes cannot detect infrared light.

Infrared (IR) is the heat that is emitted by every object whose temperature is above absolute zero, which is about minus 460 degrees Fahrenheit or minus 273 degrees Celsius.

Researchers use infrared sensors for pollution detection, weather prediction and lots of other vital atmospheric and geological applications on Earth. It is used to monitor crop health, tropical rain forest deforestation and industrial pollutants. It also is used for non-invasive detection of breast and skin cancers, and to help firefighters and television news helicopter crews see forest fire hot spots through heavy smoke. Infrared sensors are used in the detection of smog, which contains a range of chemicals that only appear in infrared ranges.

Researchers at NASA's Jet Propulsion Laboratory (JPL) at the California Institute of Technology, Pasadena, California, have developed infrared cameras used as remote sensing instruments aboard space satellites. One recent camera model recorded images of Africa in a study of the environmental impact of burning vegetation.

The infrared detector in that model is part of a major science instrument developed JPL, NASA's Goddard Space Flight Center, Greenbelt, Maryland, and the U.S. Army Research Laboratory, Adelphi, Maryland.

Infrared astronomy dates from the 1960s, when balloons carried telescopes above the obscuring effects of Earth's lower atmosphere. In the early 1970s, small telescopes flown aboard high-flying jets and on sounding rockets discovered a few thousand infrared (IR) sources among the stars. Later, infrared satellites and infrared shuttle payloads were flown in space.

NASA's Great Observatories for Space Astrophysics is a family of four large orbiting satellites carrying telescopes to study the Universe in both visible light and non-visible forms of radiation. The fourth and last of the Great Observatory series is the Space Infrared Telescope Facility (SIRTF) — a 3,000-lb., cryogenically-cooled, one-meter telescope in a satellite as an infrared astronomy observatory.

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