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Encyclopedia > Radio telescope
The 64 meter radio telescope at Parkes Observatory
The 64 meter radio telescope at Parkes Observatory

A radio telescope is a form of directional radio antenna used in radio astronomy and in tracking and collecting data from satellites and space probes. In their astronomical role they differ from optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on radio sources. Radio telescopes are typically large parabolic ("dish") antenna used singularly or in an array. Radio observatories are located far from major centers of population in order to avoid electromagnetic interference (EMI) from radio, TV, radar, and other EMI emitting devices. This is similar to the locating of optical telescopes to avoid light pollution, with the difference being that radio observatories will be placed in valleys to further shield them from EMI as opposed to clear air mountain tops for optical observatories. They can also pick up where a black hole is in the universe. The Parkes radio telescope. ... The Parkes radio telescope. ... The big dish The Parkes Observatory is a radio telescope observatory, 20 kilometres north of the town of Parkes, New South Wales, Australia. ... Log-periodic dipole array A directional antenna is an antenna which transmits or receives maximum power in a particular direction. ... A Yagi-Uda beam antenna Short Wave Curtain Antenna (Moosbrunn, Austria) A building rooftop supporting numerous dish and sectored mobile telecommunications antennas (Doncaster, Victoria, Australia) An antenna is a transducer designed to transmit or receive radio waves which are a class of electromagnetic waves. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... For other uses, see Satellite (disambiguation). ... Technicians work on the Ulysses space probe. ... For other uses, see Astronomy (disambiguation). ... Eight Inch refracting telescope. ... It has been suggested that this article or section be merged with Radio waves. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... Radio sources are objects in outer space that emit strong radio waves. ... A parabola A graph showing the reflective property, the directrix (light blue), and the lines connecting the focus and directrix to the parabola (blue) In mathematics, the parabola (from the Greek: παραβολή) (IPA pronunciation: ) is a conic section generated by the intersection of a right circular conical surface and a plane... This article is about scientific observatories. ... Radio Frequency Interference (RFI) is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. ... See TV (disambiguation) for other uses and Television (band) for the rock band European networks National In much of Europe television broadcasting has historically been state dominated, rather than commercially organised, although commercial stations have grown in number recently. ... For other uses, see Radar (disambiguation). ... An optical telescope is a telescope which is used to gather, and focus, light, for directly viewing a magnified image, making a photograph, etc. ... This time exposure photo of New York City shows sky glow, one form of light pollution. ... Fljótsdalur in East Iceland, a rather flat valley In geology, a valley is a depression with predominant extent in one direction. ...

Contents

Early radio telescopes

Reber's first "dish" radio telescope - Wheaton, IL 1937

The first radio antenna used to identify an astronomical radio source was one built by Karl Guthe Jansky, an engineer with Bell Telephone Laboratories, in 1931. Jansky was assigned the job of identifying sources of static that might interfere with radio telephone service. Jansky's antenna was designed to receive short wave radio signals at a frequency of 20.5 MHz (wavelength about 14.6 m). It was mounted on a turntable that allowed it to rotate in any direction, earning it the name "Jansky's merry-go-round". It had a diameter of approximately 100 ft (30 m). and stood 20 ft (6 m). tall. By rotating the antenna on a set of four Ford Model-T tires, the direction of the received interfering radio source (static) could be pinpointed. A small shed to the side of the antenna housed an analog pen-and-paper recording system. After recording signals from all directions for several months, Jansky eventually categorized them into three types of static: nearby thunderstorms, distant thunderstorms, and a faint steady hiss of unknown origin. Jansky finally determined that the "faint hiss" repeated on a cycle of 23 hours and 56 minutes. This four-minute lag is a typical an astronomical sidereal day, the time it takes any "fixed" object located on the celestial sphere to pass overhead twice. By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the Milky Way and was strongest in the direction of the center of the galaxy, in the constellation of Sagittarius. Image File history File links Download high-resolution version (813x1024, 317 KB) Grote Webers original Radio Antenna - 1937 Wheaton, IL Photo - NRAO archives http://www. ... Image File history File links Download high-resolution version (813x1024, 317 KB) Grote Webers original Radio Antenna - 1937 Wheaton, IL Photo - NRAO archives http://www. ... Karl Guthe Jansky (October 22, 1905 – February 14, 1950), was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. ... Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) was the main research and development arm of the United States Bell System. ... Static is unwanted background radio noise or jumbled waves that interfere with the detection of the desired waves. ... A radiotelephone is a communications device that allows two or more people to talk using radio. ... Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly in use at that time. ... For other uses, see Frequency (disambiguation). ... MegaHertz (MHz) is the name given to one million (106) Hertz, a measure of frequency. ... 1908 Ford Model T advertisement The Model T (colloquially known as the Tin Lizzie and the Flivver) was an automobile produced by Henry Fords Ford Motor Company from 1908 through 1928. ... An analog or analogue signal is any time continuous signal where some time varying feature of the signal is a representation of some other time varying quantity. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... The celestial sphere is divided by the celestial equator. ... For other uses, see Milky Way (disambiguation). ... This article is about the star grouping. ... For other uses, see Sagittarius. ...


Grote Reber was one of the pioneers of what became known as radio astronomy when he built the first parabolic "dish" radio telescope (9 m in diameter) in 1937. He was instrumental in repeating Karl Guthe Jansky's pioneering but somewhat simple work, and went on to conduct the first sky survey in the radio frequencies. After World War II, substantial improvements in radio astronomy technology were made by astronomers in Europe, Australia and the United States, and the field of radio astronomy began to blossom. Grote Reber (December 22, 1911 – December 20, 2002) was one of the pioneers of radio astronomy. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000...


Radio telescope types

A cylindrical paraboloid antenna.
A cylindrical paraboloid antenna.

The range of frequencies in the electromagnetic spectrum that makes up the radio spectrum is very large. This means the variety and types of antennas that are used as radio telescopes vary in design, size, and configuration. At wavelengths of 30 meters to 3 meters (10 MHz - 100 MHz), they are generally directional antenna arrays similar to "TV antennas" or large stationary reflectors with moveable focal points. Since the wave length being observed with these types of antennas are so long, the "reflector" surfaces can be constructed from coarse wire mesh. At shorter wavelengths “dish” style radio telescopes predominate. The angular resolution of a dish style antenna is a function of the diameter of the dish in proportion to the wavelength of the electromagnetic radiation being observed. This dictates the size of the dish a radio telescope needs to have a useful resolution. Radio telescopes operating at wavelengths of 3 meters to 30 cm (100 MHz to 1 GHz) are usually well over 100 meters in diameter. Telescopes working at wavelengths above 30 cm (1 GHz) range in size from 3 to 90 meters in diameter. Image File history File links Download high resolution version (533x800, 105 KB)Molonglo Observatory Synthesis Telescope operated by the University of Sydney. ... Image File history File links Download high resolution version (533x800, 105 KB)Molonglo Observatory Synthesis Telescope operated by the University of Sydney. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High... It has been suggested that this article or section be merged with Radio waves. ... Log-periodic dipole array A directional antenna is an antenna which transmits or receives maximum power in a particular direction. ... Angular resolution describes the resolving power of any optical device such as a telescope, a microscope, a camera, or an eye. ...


Big dishes

The 76.0 m Lovell radio telescope at Jodrell Bank Observatory which, at the time of its construction, was the largest stearable dish radio telescope in the world.

In the late 1950s and early 1960s saw the development of large single-dish radio telescopes. The largest individual radio telescope is the RATAN-600 (built in 1977 in the USSR, belongs to Russia since 1991) with 576 meter diameter of circular antenna (RATAN-600 description). Other two individual radio telescopes at Pushchino Radio Astronomy Observatory, Russia, designed specially for the low frequency observations, are between the largest in their class. LPA (LPA description (in Russian)) is 187 x 384 m size phased array meridional radio telescope, and DKR-1000 is 1000 x 1000 m cross radio telescope (DKR-1000 description (in Russian) ). The largest radio telescope in Europe is the 100 meter diameter antenna in Effelsberg, Germany, which also was the largest fully steerable telecope for 30 years until the Green Bank Telescope was opened in 2000. The largest radio telescope in the United States until 1998 was Ohio State University's The Big Ear. Download high resolution version (800x890, 173 KB) The 76. ... Download high resolution version (800x890, 173 KB) The 76. ... The 76m Lovell Telescope at Jodrell Bank Observatory. ... Zelenchukskaya (Russian: Зеленчукская) is the Caucasus Mountains site of the Special Astrophysical Observatory (Специальная Астрофизическая Обсерватория) of the Russian Academy of Sciences, St Petersburg. ... The metre, or meter (symbol: m) is the SI base unit of length. ... Since its inauguration in 1972, the Effelsberg 100-m radio telescope is one of the worlds largest fully steerable telescopes. ... The Robert C. Byrd Green Bank Telescope (GBT) is the worlds largest fully steerable radio telescope. ... The Ohio State University (OSU) is a coeducational public research university in the state of Ohio. ... The Big Ear was a radio telescope located on the grounds of the Ohio Wesleyan Universitys The Perkins Observatory from the 1960s to 1998 when it was disassembled. ...


Other well known disk radio telescopes include the Arecibo radio telescope located in Arecibo, Puerto Rico, which is steerable within about 20° of the zenith and is the largest single-aperture telescope (cf. multiple aperture telescope) ever to be constructed, and the fully steerable Lovell telescope at Jodrell Bank in the United Kingdom. A typical size of the single antenna of a radio telescope is 25 metre, dozens of radio telescopes with comparable sizes are operated in radio observatories all over the world. The Arecibo Observatory is located in Arecibo, Puerto Rico on the north coast of the island. ... Flag Seal Nickname: Gentilic: Arecibeños Location Location of Arecibo, Puerto Rico within Puerto Rico Government Founded 1616 Mayor Lemuel Soto Political party NPP Senatorial district 3 - Arecibo Representative district 13, 14 Geographical characteristics Area Total 443. ... Sir Alfred Charles Bernard Lovell OBE PhD FRS (born 31 August 1913, Oldland Common, Bristol) is a British physicist and radio astronomer. ... The 76m Lovell Telescope at Jodrell Bank Observatory. ... This article is about scientific observatories. ...


Radio interferometry

The Very Large Array, an interferometric array formed from many smaller telescopes, like many larger radio telescopes.
The Very Large Array, an interferometric array formed from many smaller telescopes, like many larger radio telescopes.

One of the most notable developments came in 1946 with the introduction of the technique called astronomical interferometry. Astronomical radio interferometers usually consist either of arrays of parabolic dishes (e.g. the One-Mile Telescope), arrays of one-dimensional antennas (e.g. the Molonglo Observatory Synthesis Telescope) or two-dimensional arrays of omni-directional dipoles (e.g. Tony Hewish's Pulsar Array). All of the telescopes in the aray are widely separated and are connected together using coaxial cable, waveguide, optical fiber, or other type of transmission line. This not only increases the total signal collected, it can also be used in a process called Aperture synthesis to vastly increase resolution. This technique works by superposing (interfering) the signal waves from the different telescopes on the principle that waves that coincide with the same phase will add to each other while two waves that have opposite phases will cancel each other out. This creates a combed telescope that is the size of the antennas furthest apart in the array. In order to produce a high quality image, a large number of different separations between different telescopes are required (the projected separation between any two telescopes as seen from the radio source is called a baseline) - as many different baselines as possible are required in order to get a good quality image (For example the Very Large Array (VLA) in Socorro, New Mexico has 27 telescopes giving 351 independent baselines at once to achieve resolution of 0.2 arc seconds at 3 cm wavelengths[1]). Martin Ryle's group in Cambridge obtained a Nobel Prize for interferometry and aperture synthesis[2]. The Lloyd's mirror interferometer was also developed independently in 1946 by Joseph Pawsey's group at the University of Sydney[3]. In the early 1950s the Cambridge Interferometer mapped the radio sky to produce the famous 2C and 3C surveys of radio sources. The largest existing radio telescope array is the Giant Metrewave Radio Telescope, located in Pune, India. A larger array, LOFAR (the 'LOw Frequency ARray') is currently being constructed in western Europe, consisting of 25 000 small antennas over an area several hundreds of kilometres in diameter. Very Large Array at Socorro, New Mexico, USA. Photo taken by Hajor, 08. ... Very Large Array at Socorro, New Mexico, USA. Photo taken by Hajor, 08. ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ... Interferometry is the applied science of combining two or more input points of a particular data type, such as optical measurements, to form a greater picture based on the combination of the two sources. ... Diagram showing a possible layout for an astronomical interferometer, with the mirrors laid out in a parabolic arrangement (similar to the shape of a conventional telescope mirror). ... One antenna from the One-Mile Telescope The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO) was completed by the Radio Astronomy Group of Cambridge University in 1964. ... Molonglo Observatory Synthesis Telescope The Molonglo Observatory Synthesis Telescope (MOST) is a radio telescope operating at 843 MHz. ... A simple half-wave dipole antenna that a shortwave listener might build. ... Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for Physics in 1974 (together with fellow radio-astronomer Martin Ryle) for his work on the development of radio aperture synthesis and its role in the discovery of pulsars. ... The Interplanetary Scintillation Array (IPS Array or Pulsar Array) was built at the Mullard Radio Astronomy Observatory in 1967 and originally covered four acres (16,000 m²). It was extended in 1978 to nine, and re-furbished in 1989. ... Coaxial Cable For the weapon, see coaxial weapon. ... Look up waveguide in Wiktionary, the free dictionary. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length. ... A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy, such as electromagnetic waves or acoustic waves, as well as electric power transmission. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... For other uses, see Interference (disambiguation). ... Surface waves in water This article is about waves in the most general scientific sense. ... Surface waves in water This article is about waves in the most general scientific sense. ... This article is about a portion of a periodic process. ... The Very Large Array (VLA) is a radio astronomy observatory located on the Plains of San Augustin, between the towns of Magdalena and Datil, some fifty miles (80 km) west of Socorro, New Mexico, USA. U.S. Route 60 passes through the complex. ... Socorro is a city located in Socorro County, New Mexico in the Rio Grande Valley, at an elevation of 4579 feet. ... This article or section does not cite its references or sources. ... Sir Martin Ryle (September 27, 1918 – October 14, 1984) was a British radio astronomer who developed revolutionary radio telescope systems (see e. ... The Cavendish Astrophysics Group (formerly the Radio Astronomy Group) is based at the Cavendish Laboratory at Cambridge University. ... The Nobel Prizes (Swedish: ), as designated in Alfred Nobels will in 1895, are awarded for physics, chemistry, physiology or medicine, literature, and peace. ... Lloyds mirror is a classic optics experiment and was first described in 1834. ... Joseph Lade Pawsey (May 14, 1908–November 30, 1962) was an Australian-born engineer, radiophysicist, and radio astronomer. ... The University of Sydney, established in Sydney in 1850, is the oldest university in Australia. ... The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge (between the Grange Road football ground and the current Cavendish Laboratory). ... The Second Cambridge Catalogue of Radio Sources (2C) was published in 1955 by John R Shakeshaft and colleagues. ... The Third Cambridge Catalogue of Radio Sources (3C) is an astronomical catalogue of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz. ... Giant Metrewave Radio Telescope (GMRT), located near Pune in India, is the worlds largest radio telescope at metre wavelengths. ... , Pune (IPA: , Marathi: पुणे) is a city located in the western Indian state of Maharashtra. ... LOFAR is the LOw Frequency ARray for radio astronomy. ...


Astronomical observations

Main article: Radio astronomy

Many astronomical objects are not only observable in visible light but also emit radiation at radio wavelegths. Besides observing energetic objects such as pulsars and quasars, radio telescopes are able to "image" most astronomical objects such as, galaxies, nebulae, and even radio emissions from planets. The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... “Visible light” redirects here. ... Radiation as used in physics, is energy in the form of waves or moving subatomic particles. ... It has been suggested that this article or section be merged with Radio waves. ... It has been suggested that Radio pulsar be merged into this article or section. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... For other uses, see Galaxy (disambiguation). ... The Triangulum Emission Nebula NGC 604 The Pillars of Creation from the Eagle Nebula For other uses, see Nebula (disambiguation). ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ...


See also

See also List of observatories Radio telescopes A more complete list of radio telescopes can be found by looking at the radio telescopes category External links AstroSurf. ... Aperture synthesis is a type of interferometry that mixes signals from a collection instruments to produce measurements having the same angular resolution as an instrument the size of the entire collection. ... William Herschel knew as early as 1779 (Herschel 1805) that stars appeared much larger in telescopes than they really were but he did not know why. ... The Very Large Array, a radio interferometer in New Mexico, USA Radio astronomy is a subfield of astronomy that studies celestial objects in the radio frequency portion of the electromagnetic spectrum. ... This article is about the search for extra-terrestrial intelligence. ... This article does not cite any references or sources. ...

Category

  • Complete list of radio telescopes

Notes

  1. ^ gps.caltech.edu - Microwave Probing of the Invisible by Duane O. Muhleman
  2. ^ Nature 158 pp 339 1946
  3. ^ Nature 157 pp 158 1946

Nature is a prominent scientific journal, first published on 4 November 1869. ... Nature is a prominent scientific journal, first published on 4 November 1869. ...

References

  • astronomytoday.com - "Radio Astronomy" by Sancar J Fredsti
  • Rohlfs, K., & Wilson, T. L. (2004). Tools of radio astronomy. Astronomy and astrophysics library. Berlin: Springer.
  • Asimov, I. (1979). Isaac Asimov's Book of facts; Sky Watchers. New York: Grosset & Dunlap. Page 390 - 399. ISBN 0803893477

  Results from FactBites:
 
Radio telescope - Wikipedia, the free encyclopedia (729 words)
The largest radio telescope in Europe is the 100 meter diameter antenna in Effelsberg, Germany, which also was the largest fully steerable telecope for 30 years until the Green Bank Telescope was opened in 2000.
The largest radio telescope in the United States until 1998 was Ohio State University's The Big Ear.
Grote Reber (December 22, 1911 – December 20, 2002) was one of the pioneers of radio astronomy.
  More results at FactBites »

 
 

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