Mark III (radio telescope)
Encyclopedia
The Mark III was a portable and fully steerable radio telescope
located at Wardle
, near Nantwich
, Cheshire
in the north-west of England
(at 53°06′09.16"N 02°31′15.63"W). Constructed in 1966, it was remotely controlled from Jodrell Bank Observatory, and was mainly used as part of the MERLIN
radio telescope network. It was designed by Charles Husband
at the instigation of Bernard Lovell
.
Similar to the Mark II
, it had an elliptical dish with a major axis of 125ft/38.1m and a minor axis of 83 ft 4 in/25.4m. Unlike the Mark II, however, the dish is constructed of a wire mesh, with the wires 1 inches (25.4 mm) apart set to an accuracy of 0.5 inches (12.7 mm). When pointed to the horizon, the telescope was 81% efficient at wavelengths of 21cm (the hydrogen line
), dropping to 45% at 11 cm. When the bowl was pointed to the horizon, the structure deformed slightly under gravity, meaning that the telescope becomes 14% efficient at 11 cm.
The focus cabin was an ~8 foot cube, also similar to the Mark II, supported by four steel girders. It could be accessed via a ladder up one of the girders, which could be climbed when the bowl of the telescope was directed towards the horizon.
The telescope was steered in azimuth and elevation
by hydraulic drive systems. Two of the six bogies on which the telescope sat were driven, and motion in elevation was done using two 16 feet (4.9 m) long hydraulic piston
s. Both were driven by a 5 horse power electric motor, at up to 5 degrees per minute. The drive system was protected using over-pressure alarms, cut-outs and relief valves, as well as two alarms (one at the telescope, one at Jodrell).
The main aim for the telescope when constructed was to use it in conjunction with the Lovell Telescope
as a fully steerable interferometer to determine the sizes of radio sources. It was not known what size the radio sources would be, and so the optimal telescope separation was not known (the separation is inversely proportional to the resolution of the interferometer). As a result, the telescope was built such that it could be completely disassembled and reassembled on a new site within 6 months.
The baseline between the telescope and the Lovell Telescope
was 24km, giving a resolution ranging between 0.2 and 17 arcseconds depending on the frequency that was being observed at.
In 1996, it was decommissioned due to its age and lack of sensitivity compared with modern telescopes. It was subsequently dismantled and sold for scrap.
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
located at Wardle
Wardle, Cheshire
Wardle is a village and civil parish in the unitary authority of Cheshire East and the ceremonial county of Cheshire, England. The village lies 4 miles to the north west of Nantwich. Nearby villages include Barbridge, Calveley and Haughton. The Shropshire Union Canal and the A51 run side by side...
, near Nantwich
Nantwich
Nantwich is a market town and civil parish in the Borough of Cheshire East and the ceremonial county of Cheshire, England. The town gives its name to the parliamentary constituency of Crewe and Nantwich...
, Cheshire
Cheshire
Cheshire is a ceremonial county in North West England. Cheshire's county town is the city of Chester, although its largest town is Warrington. Other major towns include Widnes, Congleton, Crewe, Ellesmere Port, Runcorn, Macclesfield, Winsford, Northwich, and Wilmslow...
in the north-west of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
(at 53°06′09.16"N 02°31′15.63"W). Constructed in 1966, it was remotely controlled from Jodrell Bank Observatory, and was mainly used as part of the 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...
radio telescope network. It was designed by Charles Husband
Charles Husband
Sir Henry Charles Husband was a leading architect and consulting engineer in Great Britain. His offices were based in Sheffield, England. He designed bridges and major civil engineering works and had a role in designing the Jodrell Bank radio telescope.- Biography :Husband was educated at King...
at the instigation of Bernard Lovell
Bernard Lovell
Sir Alfred Charles Bernard Lovell OBE, FRS is an English physicist and radio astronomer. He was the first Director of Jodrell Bank Observatory, from 1945 to 1980.-Early Life:...
.
Technical specifications
Funding for the telescope was obtained in 1963 from the DSIR. The telescope was designed by Husband and Co. consulting engineers, and was constructed by Fairey Engineering. It started observations in July 1967. The telescope could be controlled either locally, or by remote control over UHF and microwave links from Jodrell Bank Observatory (normally the latter).Similar to the Mark II
Mark II (radio telescope)
The Mark II is a radio telescope located at Jodrell Bank Observatory, near Goostrey, Cheshire, in the north-west of England. It was built on the site of the 218 ft Transit Telescope. Construction was completed in 1964...
, it had an elliptical dish with a major axis of 125ft/38.1m and a minor axis of 83 ft 4 in/25.4m. Unlike the Mark II, however, the dish is constructed of a wire mesh, with the wires 1 inches (25.4 mm) apart set to an accuracy of 0.5 inches (12.7 mm). When pointed to the horizon, the telescope was 81% efficient at wavelengths of 21cm (the hydrogen line
Hydrogen line
The hydrogen line, 21 centimeter line or HI line refers to the electromagnetic radiation spectral line that is created by a change in the energy state of neutral hydrogen atoms. This electromagnetic radiation is at the precise frequency of 1420.40575177 MHz, which is equivalent to the vacuum...
), dropping to 45% at 11 cm. When the bowl was pointed to the horizon, the structure deformed slightly under gravity, meaning that the telescope becomes 14% efficient at 11 cm.
The focus cabin was an ~8 foot cube, also similar to the Mark II, supported by four steel girders. It could be accessed via a ladder up one of the girders, which could be climbed when the bowl of the telescope was directed towards the horizon.
The telescope was steered in azimuth and elevation
Elevation
The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....
by hydraulic drive systems. Two of the six bogies on which the telescope sat were driven, and motion in elevation was done using two 16 feet (4.9 m) long hydraulic piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s. Both were driven by a 5 horse power electric motor, at up to 5 degrees per minute. The drive system was protected using over-pressure alarms, cut-outs and relief valves, as well as two alarms (one at the telescope, one at Jodrell).
The main aim for the telescope when constructed was to use it in conjunction with the Lovell Telescope
Lovell Telescope
The Lovell Telescope is a radio telescope at Jodrell Bank Observatory, near Goostrey, Cheshire in the north-west of England. When it was constructed in 1955, the telescope was the largest steerable dish radio telescope in the world at 76.2 m in diameter;it is now the third largest, after the...
as a fully steerable interferometer to determine the sizes of radio sources. It was not known what size the radio sources would be, and so the optimal telescope separation was not known (the separation is inversely proportional to the resolution of the interferometer). As a result, the telescope was built such that it could be completely disassembled and reassembled on a new site within 6 months.
The baseline between the telescope and the Lovell Telescope
Lovell Telescope
The Lovell Telescope is a radio telescope at Jodrell Bank Observatory, near Goostrey, Cheshire in the north-west of England. When it was constructed in 1955, the telescope was the largest steerable dish radio telescope in the world at 76.2 m in diameter;it is now the third largest, after the...
was 24km, giving a resolution ranging between 0.2 and 17 arcseconds depending on the frequency that was being observed at.
In 1996, it was decommissioned due to its age and lack of sensitivity compared with modern telescopes. It was subsequently dismantled and sold for scrap.