- All celestial objects with a temperature above absolute zero emit some form of electromagnetic radiation. In order to study the universe, scientists use several different types of telescopes to detect these different types of emitted radiation in the electromagnetic spectrum. Some of these are gamma ray, x-ray, ultra-violet, regular visible light (optical), as well as infrared telescopes.
Leading discoveries 
There were several key developments that led to the invention of the infrared telescope:
- In 1800, William Herschel discovered infrared radiation.
- In 1878, Samuel Pierpoint Langley created the first bolometer. This was a very sensitive instrument that could electrically detect incredibly small changes in temperature in the infrared spectrum.
- In the 1950s, scientists used lead-sulfide detectors to detect the infrared radiation from space. These detectors were cooled with liquid nitrogen.
- Between 1959 and 1961, Harold Johnson created near-infrared photometers which allowed scientists to measure thousands of stars.
- In 1961, Frank Low invented the first germanium bolometer. This invention, cooled by liquid helium, led the way for current infrared telescope development.
The three different types of infrared telescopes are ground-based telescopes, air-borne telescopes, and space telescopes. All three types of telescopes contain an infrared camera that must be cooled to hundreds of degrees below zero as well as a special solid-state infrared detector.
Ground-based telescopes were the first type of infrared telescopes to be used to observe outer space. Their popularity increased in the mid-1960s. Ground-based telescopes have limitations because water vapor in the Earth's atmosphere absorbs infrared radiation. Ground-based infrared telescopes tend to be placed on high mountains and in very dry climates to improve visibility.
In the 1960s, scientists used balloons to lift infrared telescopes to higher altitudes. With balloons, they were able to reach about 25 miles up. In 1967, infrared telescopes were placed on rockets. These were the first air-borne infrared telescopes. A more recent air-borne infrared telescope to reach the stratosphere was NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) in May 2010. Together, United States scientists and the German Aerospace Center scientists placed a 17 ton infrared telescope on a Boeing 747 jet airplane.
Placing infrared telescopes in space completely eliminates the interference from the Earth's atmosphere. One of the most significant infrared telescope projects was the Infrared Astronomical Satellite (IRAS) that launched in 1983. It revealed information about other galaxies, as well as information about the center of our galaxy the Milky Way. NASA presently has solar-powered spacecraft in space with an infrared telescope called the Wide-field Infrared Survey Explorer (WISE). It was launched on December 14 in 2009.
Selective comparison 
|Selected infrared space telescopes|
Existing infrared telescopes 
- Infrared Telescope Facility, 1979–
- Gornergrat Infrared Telescope, 1979–2005
- Infrared Optical Telescope Array, 1988–2006
- United Kingdom Infrared Telescope, 1979–
- Spitzer Space Telescope, 2003
See also 
|Wikimedia Commons has media related to: Infrared telescopes|
- Hamilton, J. (2010, July 2) NASA's flying telescope sees early success. National Public Radio. Retrieved from http://www.npr.org/templates/story/story.php?storyId=128015118
- Griggs, B. (2009, December 14) NASA launches infrared telescope to scan entire sky. Cable News Network. Retrieved from http://www.cnn.com/2009/TECH/space/12/14/wise.spacecraft.launch/index.html
- JPL: Herschel Space Observatory: Related Missions