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The Cavendish Astrophysics Group (formerly the Radio Astronomy Group) is based at the Cavendish Laboratory at the University of Cambridge. The group operates all of the telescopes at the Mullard Radio Astronomy Observatory except for the 32m MERLIN telescope, which is operated by Jodrell Bank.
The group is the second largest of three astronomy departments in the University of Cambridge.
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A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. The discovery of the cosmic microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy.
Antony Hewish was a British radio astronomer who won the Nobel Prize for Physics in 1974 for his role in the discovery of pulsars. He was also awarded the Eddington Medal of the Royal Astronomical Society in 1969.
Sir Martin Ryle was an English radio astronomer who developed revolutionary radio telescope systems and used them for accurate location and imaging of weak radio sources. In 1946 Ryle and Derek Vonberg were the first people to publish interferometric astronomical measurements at radio wavelengths. With improved equipment, Ryle observed the most distant known galaxies in the universe at that time. He was the first Professor of Radio Astronomy in the University of Cambridge and founding director of the Mullard Radio Astronomy Observatory. He was the twelfth Astronomer Royal from 1972 to 1982. Ryle and Antony Hewish shared the Nobel Prize for Physics in 1974, the first Nobel prize awarded in recognition of astronomical research. In the 1970s, Ryle turned the greater part of his attention from astronomy to social and political issues which he considered to be more urgent.
Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and orientation, the lobe-pattern of the interferometer produces an output which is one component of the Fourier transform of the spatial distribution of the brightness of the observed object. The image of the source is produced from these measurements. Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations. For example, the Event Horizon Telescope project derived the first image of a black hole using aperture synthesis.
COAST, the Cambridge Optical Aperture Synthesis Telescope, is a multi-element optical astronomical interferometer with baselines of up to 100 metres, which uses aperture synthesis to observe stars with angular resolution as high as one thousandth of one arcsecond. The principal limitation is that COAST can only image bright stars.
The Mullard Radio Astronomy Observatory (MRAO) is located near Cambridge, UK and is home to a number of the largest and most advanced aperture synthesis radio telescopes in the world, including the One-Mile Telescope, 5-km Ryle Telescope, and the Arcminute Microkelvin Imager. It was founded by the University of Cambridge and is part of the Cambridge University, Cavendish Laboratories, Astrophysics Department.
The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO), Cambridge, UK is an array of radio telescopes designed to perform aperture synthesis interferometry.
The Westerbork Synthesis Radio Telescope (WSRT) is an aperture synthesis interferometer built on the site of the former World War II Nazi detention and transit camp Westerbork, north of the village of Westerbork, Midden-Drenthe, in the northeastern Netherlands.
The Interplanetary Scintillation Array is a radio telescope that was built in 1967 at the Mullard Radio Astronomy Observatory, in Cambridge, United Kingdom, and was operated by the Cavendish Astrophysics Group. The instrument originally covered 4 acres. It was enlarged to 9 acres in 1978, and was refurbished in 1989.
The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge. The interferometer consisted of an array of 4 fixed elements to survey the sky. It produced the two Cambridge catalogues of radio sources, discovering some of the most interesting astronomical objects known. The telescope was operated by the Radio Astronomy Group of Cambridge University.
The National Centre for Radio Astrophysics is a research institution in India in the field of radio astronomy is located in the Pune University Campus, is part of the Tata Institute of Fundamental Research, Mumbai, India. NCRA has an active research program in many areas of Astronomy and Astrophysics, which includes studies of the Sun, Interplanetary scintillations, pulsars, the Interstellar medium, Active galaxies and cosmology and particularly in the specialized field of Radio Astronomy and Radio instrumentation. NCRA also provides exciting opportunities and challenges in engineering fields such as analog and digital electronics, signal processing, antenna design, telecommunication and software development.
An astronomical interferometer or telescope array is a set of separate telescopes, mirror segments, or radio telescope antennas that work together as a single telescope to provide higher resolution images of astronomical objects such as stars, nebulas and galaxies by means of interferometry. The advantage of this technique is that it can theoretically produce images with the angular resolution of a huge telescope with an aperture equal to the separation, called baseline, between the component telescopes. The main drawback is that it does not collect as much light as the complete instrument's mirror. Thus it is mainly useful for fine resolution of more luminous astronomical objects, such as close binary stars. Another drawback is that the maximum angular size of a detectable emission source is limited by the minimum gap between detectors in the collector array.
The Dominion Radio Astrophysical Observatory is a research facility founded in 1960 and located at Kaleden, British Columbia, Canada. The site houses four radio telescopes: an interferometric radio telescope, a 26-m single-dish antenna, a solar flux monitor, and the Canadian Hydrogen Intensity Mapping Experiment (CHIME) — as well as support engineering laboratories. The DRAO is operated by the Herzberg Institute of Astrophysics of the National Research Council of the Government of Canada. The observatory was named an IEEE Milestone for first radio astronomical observations using VLBI.
The Institute of Astronomy of Nicolaus Copernicus University in Toruń, known prior to 1 October 2019 in scientific publications as the Toruń Centre for Astronomy, is an optical and radio observatory located at in Piwnice, about 15 km north of Toruń, Poland. It houses two single-dish antenna telescopes, 32 metres and 15 metres in diameter, as well as the largest Polish optical telescope – 90 cm Schmidt-Cassegrain camera. The facility is operated by the Nicolaus Copernicus University. Also, photometry using 60 cm Cassegrain telescope is made and radio measurements of the Sun at 127 MHz frequency have been recorded on a daily basis since 1958 using a 23 m interferometer.
The Ooty Radio Telescope (ORT) is located in Muthorai near Ooty, in South Indian state of Tamil Nadu. It is part of the National Centre for Radio Astrophysics (NCRA) of the Tata Institute of Fundamental Research (TIFR), which is funded by the Government of India through the Department of Atomic Energy. The radio telescope is a 530-metre (1,740 ft) long and 30-metre (98 ft) tall cylindrical parabolic antenna. It operates at a frequency of 326.5 MHz with a maximum bandwidth of 15 MHz at the front end.
In optical astronomy, interferometry is used to combine signals from two or more telescopes to obtain measurements with higher resolution than could be obtained with either telescopes individually. This technique is the basis for astronomical interferometer arrays, which can make measurements of very small astronomical objects if the telescopes are spread out over a wide area. If a large number of telescopes are used a picture can be produced which has resolution similar to a single telescope with the diameter of the combined spread of telescopes. These include radio telescope arrays such as VLA, VLBI, SMA, astronomical optical interferometer arrays such as COAST, NPOI and IOTA, resulting in the highest resolution optical images ever achieved in astronomy. The VLT Interferometer is expected to produce its first images using aperture synthesis soon, followed by other interferometers such as the CHARA array and the Magdalena Ridge Observatory Interferometer which may consist of up to 10 optical telescopes. If outrigger telescopes are built at the Keck Interferometer, it will also become capable of interferometric imaging.
The Green Bank Interferometer (GBI) is a former radio astronomy telescope located at Green Bank, West Virginia (US) and operated by the National Radio Astronomy Observatory (NRAO). It included three on-site radio telescopes of 85-foot (26m) diameter, designated 85-1, 85-3, and 85-2 and a portable telescope.
Govind Swarup was a pioneer in radio astronomy. In addition to research contributions in multiple areas of astronomy and astrophysics, he was a driving force behind the building of "ingenious, innovative and powerful observational facilities for front-line research in radio astronomy".
Pushchino Radio Astronomy Observatory is a Russian radio astronomy observatory. It was developed by Lebedev Physical Institute (LPI), Russian Academy of Sciences within a span of twenty years. It was founded on April 11, 1956, and currently occupies 70 000 square meters.