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.
The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States. It lies in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, approximately 50 miles (80 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Each of the massive telescopes is mounted on double parallel railroad tracks, so the radius and density of the array can be transformed to adjust the balance between its angular resolution and its surface brightness sensitivity. Astronomers using the VLA have made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission.
Parkes Observatory is a radio astronomy observatory, located 20 kilometres (12 mi) north of the town of Parkes, New South Wales, Australia. It hosts Murriyang, the 64 m CSIRO Parkes Radio Telescope also known as "The Dish", along with two smaller radio telescopes. The 64 m dish was one of several radio antennae used to receive live television images of the Apollo 11 Moon landing. Its scientific contributions over the decades led the ABC to describe it as "the most successful scientific instrument ever built in Australia" after 50 years of operation.
The Cosmic Background Imager was a 13-element interferometer perched at an elevation of 5,080 metres at Llano de Chajnantor Observatory in the Chilean Andes. It started operations in 1999 to study the cosmic microwave background radiation and ran until 2008.
The Caltech Submillimeter Observatory (CSO) was a 10.4-meter (34 ft) diameter submillimeter wavelength telescope situated alongside the 15-meter (49 ft) James Clerk Maxwell Telescope (JCMT) at Mauna Kea Observatories. Beginning in 1986, it was engaged in submillimeter astronomy of the terahertz radiation band. The telescope closed on September 18, 2015.
The Submillimeter Array (SMA) consists of eight 6-meter (20 ft) diameter radio telescopes arranged as an interferometer for submillimeter wavelength observations. It is the first purpose-built submillimeter interferometer, constructed after successful interferometry experiments using the pre-existing 15-meter (49 ft) James Clerk Maxwell Telescope and 10.4-meter (34.1 ft) Caltech Submillimeter Observatory as an interferometer. All three of these observatories are located at Mauna Kea Observatory on Mauna Kea, Hawaii, and have been operated together as a ten element interferometer in the 230 and 345 GHz bands. The baseline lengths presently in use range from 16 to 508 meters. The radio frequencies accessible to this telescope range from 194–408 gigahertz (1.545–0.735 mm) which includes rotational transitions of dozens of molecular species as well as continuum emission from interstellar dust grains. Although the array is capable of operating both day and night, most of the observations take place at nighttime when the atmospheric phase stability is best.
The Low-Frequency Array (LOFAR) is a large radio telescope, with an antenna network located mainly in the Netherlands, and spreading across 7 other European countries as of 2019. Originally designed and built by ASTRON, the Netherlands Institute for Radio Astronomy, it was first opened by Queen Beatrix of The Netherlands in 2010, and has since been operated on behalf of the International LOFAR Telescope (ILT) partnership by ASTRON.
Owens Valley Radio Observatory (OVRO) is a radio astronomy observatory located near Big Pine, California (US) in Owens Valley. It lies east of the Sierra Nevada, approximately 350 kilometers (220 mi) north of Los Angeles and 20 kilometers (12 mi) southeast of Bishop. It was established in 1956, and is owned and operated by the California Institute of Technology (Caltech). The Owens Valley Solar Array portion of the observatory has been operated by New Jersey Institute of Technology (NJIT) since 1997.
The Paul Wild Observatory, also known as the Narrabri Observatory and Culgoora Observatory, is an astronomical research facility located about 24 km west of Narrabri, New South Wales, Australia. It is the home of the Australia Telescope Compact Array, and the Culgoora Solar Observatory.
The Combined Array for Research in Millimeter-wave Astronomy (CARMA) was an astronomical instrument comprising 23 radio telescopes, dedicated in 2006. These telescopes formed an astronomical interferometer where all the signals are combined in a purpose-built computer to produce high-resolution astronomical images. The telescopes ceased operation in April 2015 and were relocated to the Owens Valley Radio Observatory for storage.
Big Bear Solar Observatory (BBSO) is a university-based solar observatory in the United States. It is operated by New Jersey Institute of Technology (NJIT). BBSO has a 1.6-meter (5.2 ft) clear-aperture Goode Solar Telescope (GST), which has no obscuration in the optical train. BBSO is located on the north side of Big Bear Lake in the San Bernardino Mountains of southwestern San Bernardino County, California, approximately 120 kilometers (75 mi) east of downtown Los Angeles. The telescopes and instruments at the observatory are designed and employed specifically for studying the activities and phenomena of the Sun.
Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Region approximately 50 kilometres (31 mi) east of the town of San Pedro de Atacama. The exceptionally arid climate of the area is inhospitable to humans, but creates an excellent location for millimeter, submillimeter, and mid-infrared astronomy. This is because water vapour absorbs and attenuates submillimetre radiation. Llano de Chajnantor is home to the largest and most expensive astronomical telescope project in the world, the Atacama Large Millimeter Array (ALMA). Llano de Chajnantor and the surrounding area has been designated as the Chajnantor Science Reserve by the government of Chile.
The Plateau de Bure Interferometer (PdBI) was a six-antenna interferometer on the Pic de Bure (2550 m) in the French Alps, operated by the Institut de radioastronomie millimétrique. In 2014, it has been replaced by the Northern Extended Millimeter Array. It was specifically designed for millimetre-wave observations and specialises in studies of line emission from molecular gas and radio continuum of cold dust.
Harold "Hal" Zirin was an American solar astronomer also known as Captain Corona to a generation of Caltech Astronomy students.
The OVRO 40 meter Telescope is a radio telescope at the Owens Valley Radio Observatory near Big Pine, California, US. It is owned and operated by Caltech. The telescope is easily visible from the section of US highway 395 just north of Big Pine.
The Large Latin American Millimeter Array (LLAMA) is a single-dish 12 m Nasmyth optics antenna which is under construction in the Puna de Atacama desert in the Province of Salta, Argentina, next to the Qubic experiment. The primary mirror accuracy will allow observation from 40 GHz up to 900 GHz. After installation it will be able to join other similar instruments to perform Very Large Base Line Interferometry or to work in standalone mode. Financial support is provided by the Argentinian and Brazilian governments. The total cost of construction, around US$20 million, and operation as well as the telescope time use will be shared equally by the two countries. Construction planning started in July 2014 after the formal signature of an agreement between the main institutions involved.
The Leighton Radio Telescopes are 10.4 meter parabolic dish antennas designed by Robert B. Leighton in the 1970s, which were fabricated on the Caltech campus during the 1970s and 1980s. The telescope surfaces reached an accuracy of 10 microns RMS, allowing observations throughout the millimeter and submillimeter bands. In all, eight of these telescopes were made. They were used as the six elements of the Owens Valley Radio Observatory (OVRO) millimeter interferometer in California, and as single telescopes at the Caltech Submillimeter Observatory in Hawaii and the Raman Research Institute (RRI) at Bangalore, India. In the spring of 2005, the six Leighton telescopes in Owens Valley were moved to a high mountain site in the White Mountains to form the core of the CARMA array of 25 telescopes. The CARMA array was decommissioned in 2015 at which time the Leighton telescopes were moved back to OVRO, where they are now being repurposed for different projects including the CO Mapping Array Pathfinder (COMAP), the Event Horizon Telescope (EHT), and various transient detection projects.
The Vermilion River Radio Observatory (VRO) was a research facility operated by the University of Illinois from 1959 to 1984, featuring a 400-foot (120 m) linear parabolic radio telescope. The 420-acre (170 ha) site was a pioneering facility in radio astronomy.
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