cmglee Cambridge MRAO One Mile Half Mile 4C

The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO),

Cambridge, UK Cambridge ( ) is a College town, university city and the county town in Cambridgeshire, England. It is located on the River Cam approximately north of London. As of the 2021 United Kingdom census, the population of Cambridge was 145,700. Cam ...

is an array of

radio telescopes 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 p ...

(two fixed and one moveable, fully steerable 60-ft-diameter

parabolic reflector A parabolic (or paraboloid or paraboloidal) reflector (or dish or mirror) is a reflective surface used to collect or project energy such as light, sound, or radio waves. Its shape is part of a circular paraboloid, that is, the surface genera ...

s operating simultaneously at 1407 MHz and 408 MHz)The operation of the Cambridge one-mile telescope

Monthly Notices of the Royal Astronomical Society ''Monthly Notices of the Royal Astronomical Society'' (MNRAS) is a peer-reviewed scientific journal covering research in astronomy and astrophysics. It has been in continuous existence since 1827 and publishes letters and papers reporting orig ...

, Vol. 134, p.87 designed to perform

aperture synthesis 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 ...

interferometry Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...

History

The One Mile Telescope was completed by the Radio Astronomy Group of

Cambridge University , mottoeng = Literal: From here, light and sacred draughts. Non literal: From this place, we gain enlightenment and precious knowledge. , established = , other_name = The Chancellor, Masters and Schola ...

in 1964. The telescope was used to produce the 5C catalogue of radio sources. Observations with larger incremental spacings were used to observe individual radio sources with unprecedented sensitivity, angular resolution, and image quality. These surveys required intensive use of inverse

Fourier transform A Fourier transform (FT) is a mathematical transform that decomposes functions into frequency components, which are represented by the output of the transform as a function of frequency. Most commonly functions of time or space are transformed ...

s, and were made possible by development of a new generation of computers such as the

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

. In 1971, Sir

Martin Ryle Sir Martin Ryle (27 September 1918 – 14 October 1984) was an English radio astronomer who developed revolutionary radio telescope systems (see e.g. aperture synthesis) and used them for accurate location and imaging of weak radio sourc ...

described why, in the late 1950s, radio astronomers at MRAO decided on the construction of the new One Mile telescope: "Our object was twofold. First we wanted to extend the range of our observations far back in time to the earliest days of the Universe, and this required a large increase in both sensitivity and resolution. With greater resolution we hoped that we might be able to draw radio maps of individual radio sources with sufficient detail to give some indication of the physical processes which brought them into being." One of the One Mile Telescope dishes was temporarily used to improve the resolution of

MERLIN Merlin ( cy, Myrddin, kw, Marzhin, br, Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a mage, with several other main roles. His usual depiction, based on an amalgamation of historic and leg ...

(then MTRLI) from 1987 until Autumn 1990.

Technical innovations

The One-Mile Telescope, was the first to use Earth-rotation

(described by Ryle as "super-synthesis"The New Cambridge Radio Telescope
Nature, Vol. 194, pp. 517) and the first to give radio maps with a resolution better than that of the human eye. The telescope was made up of three 120 ton dishes, each of which is 18 m in diameter. Two of the dishes are fixed, while the third can be moved along an 800 m long (half mile) rail track, at speeds of up to 6.4 km/h. There were 60 different stations along the track, which is straight to within 0.9 cm, and whose far end was raised by 5 cm to allow for the curvature of the Earth over its length. The observing frequencies were usually 408 MHz (75 cm; the resolution was 80 arcsec) and 1.4 GHz (21 cm; the resolution was 20 arcsec, three times better than that of the unaided eye).

Notable achievements

Over a 20-year career, the telescope was used to map individual objects, and to do several deep field surveys. Though still occasionally used, it is now essentially retired (one of the dishes is occasionally used for undergraduate projects or b
amateur radio astronomers
. The construction of this telescope and development of the Earth-rotation

used when operating it contributed to

and

Antony Hewish Antony Hewish (11 May 1924 – 13 September 2021) was a British radio astronomer who won the Nobel Prize for Physics in 1974 (together with fellow radio-astronomer Martin Ryle) for his role in the discovery of pulsars. He was also awarded th ...

receiving the

Nobel Prize for Physics ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then " ...

in 1974.

References

External links

*
Two antennae of the One-Mile Telescope on Google Maps
{{radio-astronomy Radio telescopes Cavendish Laboratory Interferometric telescopes