One-Mile Telescope
Encyclopedia
The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO)
is an array of radio telescopes (2 fixed and 1 moveable, fully steerable 60-ft-diameter parabolic reflector
s operating simultaneously at 1407 MHz and 408 MHz) designed to perform aperture synthesis
interferometry.
of Cambridge University
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
s, and were made possible by development of a new generation of computers such as the Titan
.
In 1971, Sir Martin Ryle
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
(then MTRLI) from 1987 until Autumn 1990.
(described by Ryle as "super-synthesis") 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).
The construction of this telescope and development of the Earth-rotation aperture synthesis
used when operating it contributed to Martin Ryle
and Antony Hewish
receiving the Nobel Prize for Physics in 1974.
Mullard Radio Astronomy Observatory
Mullard Radio Astronomy Observatory is home to a number of large aperture synthesis radio telescopes, including the One-Mile Telescope, 5-km Ryle Telescope, and the Arcminute Microkelvin Imager...
is an array of radio telescopes (2 fixed and 1 moveable, fully steerable 60-ft-diameter parabolic reflector
Parabolic reflector
A parabolic reflector is a reflective device used to collect or project energy such as light, sound, or radio waves. Its shape is that of a circular paraboloid, that is, the surface generated by a parabola revolving around its axis...
s operating simultaneously at 1407 MHz and 408 MHz) designed to perform aperture synthesis
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...
interferometry.
History
The One Mile Telescope was completed by the Radio Astronomy GroupCavendish Astrophysics Group
The Cavendish Astrophysics 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...
of Cambridge University
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
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
Fourier transform
In mathematics, Fourier analysis is a subject area which grew from the study of Fourier series. The subject began with the study of the way general functions may be represented by sums of simpler trigonometric functions...
s, and were made possible by development of a new generation of computers such as the Titan
Titan (computer)
Titan was the prototype of the Atlas 2 computer developed by Ferranti and the University of Cambridge Mathematical Laboratory in Cambridge, England...
.
In 1971, Sir Martin Ryle
Martin Ryle
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...
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
The Multi-Element Radio Linked Interferometer Network is an interferometer array of radio telescopes spread across England. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of STFC as a National Facility.The array consists of up to seven radio...
(then MTRLI) from 1987 until Autumn 1990.
Technical innovations
The One-Mile Telescope, was the first to use Earth-rotation aperture synthesisAperture 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...
(described by Ryle as "super-synthesis") 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 by amateur radio astronomers).The construction of this telescope and development of the Earth-rotation aperture synthesis
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...
used when operating it contributed to Martin Ryle
Martin Ryle
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...
and Antony Hewish
Antony Hewish
Antony Hewish FRS is a British radio astronomer who won the Nobel Prize for Physics in 1974 for his work on the development of radio aperture synthesis and its role in the discovery of pulsars...
receiving the Nobel Prize for Physics in 1974.