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.
- Thomas Edison used an alternative technology, his tasimeter, to measure heat in the Sun's corona during the solar eclipse of July 29, 1878.
- 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. [2]
Infrared telescopes may be ground-based, air-borne, or space telescopes. They contain an infrared camera with a special solid-state infrared detector which must be cooled to cryogenic temperatures. [3]
Ground-based telescopes were the first to be used to observe outer space in infrared. 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 (40 kilometres) up. In 1967, infrared telescopes were placed on rockets. [2] These were the first air-borne infrared telescopes. Since then, aircraft like the Kuiper Airborne Observatory (KAO) have been adapted to carry 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. [4]
Placing infrared telescopes in space 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. [2] 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, 2009. [5]
Infrared is electromagnetic radiation (EMR) in the spectral band between microwaves and visible light. It is invisible to the human eye. IR is generally understood to encompass wavelengths from around 750 nm to 1000 μm.
Infrared astronomy is a sub-discipline of astronomy which specializes in the observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers, and falls in between visible radiation, which ranges from 380 to 750 nanometers, and submillimeter waves.
An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Historically, observatories were as simple as containing an astronomical sextant or Stonehenge.
A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley.
Far-infrared astronomy is the branch of astronomy and astrophysics that deals with objects visible in far-infrared radiation.
The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), is an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, following IRAS (1983) and ISO (1995–1998). It was the first spacecraft to use an Earth-trailing orbit, later used by the Kepler planet-finder.
The Gerard P. Kuiper Airborne Observatory (KAO) was a national facility operated by NASA to support research in infrared astronomy. The observation platform was a highly modified Lockheed C-141A Starlifter jet transport aircraft with a range of 6,000 nautical miles (11,000 km), capable of conducting research operations at altitudes of up to 48,000 feet (14 km).
NASA's series of Great Observatories satellites are four large, powerful space-based astronomical telescopes launched between 1990 and 2003. They were built with different technology to examine specific wavelength/energy regions of the electromagnetic spectrum: gamma rays, X-rays, visible and ultraviolet light, and infrared light.
The Stratospheric Observatory For Infrared Astronomy (SOFIA) was an 80/20 joint project of NASA and the German Aerospace Center (DLR) to construct and maintain an airborne observatory. NASA awarded the contract for the development of the aircraft, operation of the observatory and management of the American part of the project to the Universities Space Research Association (USRA) in 1996. The DSI managed the German parts of the project which were primarily science- and telescope-related. SOFIA's telescope saw first light on May 26, 2010. SOFIA was the successor to the Kuiper Airborne Observatory. During 10-hour, overnight flights, it observed celestial magnetic fields, star-forming regions, comets, nebulae, and the Galactic Center.
The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telescope in 2021. Herschel carries a 3.5-metre (11.5 ft) mirror and instruments sensitive to the far infrared and submillimetre wavebands (55–672 µm). Herschel was the fourth and final cornerstone mission in the Horizon 2000 programme, following SOHO/Cluster II, XMM-Newton and Rosetta.
Planck was a space observatory operated by the European Space Agency (ESA) from 2009 to 2013. It was an ambitious project that aimed to map the anisotropies of the cosmic microwave background (CMB) at microwave and infrared frequencies, with high sensitivity and small angular resolution. The mission was highly successful and substantially improved upon observations made by the NASA Wilkinson Microwave Anisotropy Probe (WMAP).
A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally it was an optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects – an optical telescope. Nowadays, the word "telescope" is defined as wide range of instruments capable of detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
Frank James Low was a solid state physicist who became a leader in the new field of infrared astronomy, after inventing the gallium doped germanium bolometer in 1961. This detector extended the range of the observable spectrum to much longer wavelengths.
An airborne observatory is an airplane, airship, or balloon with an astronomical telescope. By carrying the telescope to a sufficiently high altitude, the telescope can avoid cloud cover, pollution, and carry out observations in the infrared spectrum, above water vapor in the atmosphere which absorbs infrared radiation. Some drawbacks to this approach are the instability of the lifting platform, the weight restrictions on the instrument, the need to safely recover the gear afterward, and the cost compared to a comparable ground-based observatory.
Gamma-ray astronomy is the astronomical observation of gamma rays, the most energetic form of electromagnetic radiation, with photon energies above 100 keV. Radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy.
SAFIR is a proposed NASA space observatory for far-infrared light. The plan calls for a single large mirror 5–10 meters (16–33 ft) in diameter, cryogenically cooled to 5 kelvins. This would feed detector arrays sensitive from 5 to 1000 µm. The possibility of servicing such a telescope in space has been evaluated.
Origins Space Telescope (Origins) is a concept study for a far-infrared survey space telescope mission. A preliminary concept in pre-formulation, it was presented to the United States Decadal Survey in 2019 for a possible selection to NASA's large strategic science missions. Origins would provide an array of new tools for studying star formation and the energetics and physical state of the interstellar medium within the Milky Way using infrared radiation and new spectroscopic capabilities.
The GUSTO mission is a high-altitude balloon mission that carry an infrared telescope to measure fine-structure line emission from the interstellar medium. The mission was developed by NASA's Explorers Program, and was launched in December 2023 from Antarctica.
