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Infrared Space Observatory

infrared spectrum, European Space Agency, heat radiation, infrared radiation, infrared light

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Infrared Space Observatory (ISO), satellite dedicated to the study of astronomical objects through the infrared radiation that the objects emit. Launched by the European Space Agency (ESA) in 1995, the ISO transmitted data about the molecular structure of some of the most far-reaching objects in the universe. The ISO’s mission ended in 1998.

Infrared radiation, like visible light, X rays, and radio waves, is a form of electromagnetic radiation. All objects emit electromagnetic radiation because of their temperature. In cooler objects, the most intense of this heat or thermal electromagnetic radiation falls in the infrared part of the spectrum. Therefore, the amount of infrared radiation that an object emits is a good measure of its temperature.

Infrared radiation is unique from visible light and ultraviolet radiation in that it is not altered as it passes through interstellar matter, the fine gases and dust found between stars. But measuring infrared wavelengths from a ground-based telescope on the earth is difficult. The earth’s atmosphere blocks some infrared wavelengths—water vapor and carbon dioxide in the atmosphere absorb many parts of the infrared region, leaving only a few sections of the infrared spectrum that can be studied from the ground. Furthermore, heat radiation emitted by a ground-based telescope itself tends to mask faint astronomical sources.

The ISO had the advantage of being in orbit above the earth’s atmosphere, where there is nothing to block infrared light. To eliminate its own satellite’s telescope emission of infrared radiation due to heat, the satellite’s telescope was cooled to a very low temperature.


McLean, Ian S., B.Sc., Ph.D.

Professor and Director of Infrared Imaging Detector Laboratory, Department of Physics and Astronomy, University of California at Los Angeles.

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