MERLIN
Encyclopedia
The Multi-Element Radio Linked Interferometer Network (MERLIN) is an interferometer array of radio telescope
s 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 telescope
s and includes the Lovell Telescope
, Mark II
, Cambridge, Defford, Knockin
, Darnhall and Pickmere
(previously known as Tabley). The longest baseline is therefore 217 km and MERLIN can operate at frequencies
between 151 MHz
and 24 GHz
. At a wavelength
of 6 cm (5 GHz frequency), MERLIN has a resolution of 40 milliarcseconds which is comparable to that of the HST
at optical wavelengths.
Some of the telescopes are occasionally used for EVN
and VLBI
observations in order to create an interferometer with even larger baselines, providing images with much greater angular resolution
.
In 1973, Henry Proctor Palmer made the suggestion of extending the interferometer links already in place at Jodrell Bank at the time, which started the planning of the telescope array.Lovell, Astronomer by Chance, p. 312 Construction started in 1975. The system was originally officially called MTRLI (Multi-Telescope Radio Linked Interferometer), but was commonly referred to by the simpler name of MERLIN. It originally consisted of either the 76m Lovell Telescope
or the 25m Mark II
, along with the 25m Mark III
at Wardle, the 85 ft at Defford and a new telescope at Knockin. This
new telescope was made by E-Systems and was constructed based on the designed for the telescopes in the Very Large Array
, which was being constructed at the same time also by E-Systems.
The construction of the new telescope, the installation of microwave communication links and the construction of the correlator were jointly called "Phase 1" of the MERLIN project, the funding for which was approved on 30 May 1975. The construction of the new telescope started on 9 July 1976, and was completed by 8 October 1976. The telescope was first controlled remotely from Jodrell in January 1977. The microwave links were installed in May 1978. The first observations using the system - measurements of 30 distant radio sources - were taken in January and February 1980. The final cost of phase 1 of the system was £2,179,000 (1976).
Two additional telescopes were added in Phase 2 of the project, along with their radio links to Jodrell Bank. While it was originally proposed that one of the telescopes would be sited at Jodrell Bank and the other at Darnhall, the pair were finally sited at Pickmere (also known as Tabley) and Darnhall. The two telescopes were the same as that at Knockin. Construction on both telescopes started on 9 April 1979, and was completed by 31 October 1979. The Pickmere telescope was connected into MTRLI for the first time on 20 July 1980, followed by the Darnhall telescope on 16 December 1980. The second phase was formally completed on the 31 December 1981, and had cost £3,142,210.
The longest baseline of MTRLI was 134 km, between Pickmere and Defford. The first map produced by the array was published on 6 November 1980. In the first 2 years of operation (1980–1982), the array was used to observe at frequencies of 408 MHz (with a resolving power of 1 arcsecond), 1666 MHz (0.25 arcsecond) and 5 GHz (0.08 arcsecond).
When the Mark II
's surface was replaced in 1987, it could be used along with the three E-systems telescopes on the 22 GHz frequency, expanding MTRLI at that frequency.
One of the 18 m dishes of the One-Mile Telescope
was temporarily used in MTRLI from 1987 until Autumn 1990, which greatly improved its resolution.
MTRLI was renamed to MERLIN in the early 1990s, and shortly afterwards the addition of the purpose-built 32 m Cambridge antenna in 1991 increased both the sensitivity and angular resolution
of the array. The array also had a new correlator and new, cooled receivers, and some of the microwave links between the telescopes were improved so that the array could observe both hands of polarization.
Since 1996, carousels for the different receivers on each of the E-systems telescopes and the Mark II
telescope were installed (the Cambridge telescope already had such a system installed), providing frequency agility. In 1997 and 1998, dual-frequency (5 and 22 GHz) observations were made with the array for the first time.
There are plans to construct a telescope in Ireland
that would be added to the array.
links to send astronomical data back from the remote stations. These links have a limited bandwidth so much of the data is thrown away. In order to increase the sensitivity of the telescope the current links have been replaced by optical fibre links which will carry a bandwidth of 4 GHz, compared to the original limit of 30 MHz, increasing the sensitivity of the array by a factor of around 30. This vast increase in data means that the old correlator will no longer be able to cope, so a new correlator is under construction which will be capable of processing over 200 Gbit/s.
Another major development which is part of the upgrade is frequency flexibility — the ability to alter the observing band of the entire array in a matter of minutes using rotating carousels of receivers. Some telescopes in the array already have this capability, while the rest require the visit of an engineer to change the receiver. When e-MERLIN becomes operational the telescope will be able to switch rapidly between 1.4, 5, 6 and 22 GHz. This is required in order to take advantage of optimum conditions for high frequency observations where atmospheric conditions can severely affect results.
Work started on the e-MERLIN upgrade in May 2004 and it was completed in 2009 .
) announced that the (e-MERLIN/JIVE
) project was at risk because of a £80m shortfall in its budget. This was due to the initial recommendations of the Particle Physics, Astronomy and Nuclear Physics Science Committee (PPAN), that had listed the project as a "lower priority". Following concerns that PPAN's recommendations did not adequately represent the UK's astronomical priorities, STFC
established a wider consultation review involving various advisory panels to re-priorities the STFC
program. The Ground-Based Astronomy Consultation Panel then recommended e-MERLIN should be changed from the lowest band ("lower priority"), to the second highest, adding that "e-Merlin could be a world-leading facility well into the next decade" and "e-Merlin offered dramatic potential to both traditional UK radio astronomy users and importantly to a broader community".
On 8 July 2008 STFC
presented their final version of the programmatic review at a Town
Meeting at the Royal Society stating:
'Given the strategic importance of e-MERLIN to the future of UK radio astronomy and to the highly ranked SKA project, we are working with the University of Manchester and other stakeholders to find a viable way in which e-MERLIN operations can be supported in the medium term on a shared cost basis. We have made provision for STFC
support of operations to be made available to facilitate such a solution.'
The telescope can also be used for highly precise astrometry
.
In 1998, MERLIN in conjunction with the Hubble Space Telescope
discovered the first Einstein ring
.
The telescope has also been used in combination with the VLA to carry out a weak lensing analysis.
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...
s spread across 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...
. The array is run from Jodrell Bank Observatory in 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...
by the University of Manchester
University of Manchester
The University of Manchester is a public research university located in Manchester, United Kingdom. It is a "red brick" university and a member of the Russell Group of research-intensive British universities and the N8 Group...
on behalf of STFC
STFC
STFC can stand for:* Science and Technology Facilities Council, a UK research council created by the merger of the Council for the Central Laboratory of the Research Councils and the Particle Physics and Astronomy Research Council on 1 April 2007* Star Trek: First Contact, a 1996 filmSTFC may...
as a National Facility.
The array consists of up to seven radio telescope
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...
s and includes 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...
, 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...
, Cambridge, Defford, Knockin
Knockin
-History:Knockin is a village and civil parish located on the B4396 in Shropshire, England. It comprises mainly historic detached buildings in a rural setting. Much of Knockin was owned by the Earl of Bradford until it was sold off in lots to meet other financial demands. The Earl still owns the...
, Darnhall and Pickmere
Pickmere
Pickmere is a village and civil parish near Northwich in the Borough of Cheshire East. It has a population of 541. Landmarks in and around the village include a lake, Pick Mere, at ....
(previously known as Tabley). The longest baseline is therefore 217 km and MERLIN can operate at frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
between 151 MHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
and 24 GHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
. At a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of 6 cm (5 GHz frequency), MERLIN has a resolution of 40 milliarcseconds which is comparable to that of the HST
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
at optical wavelengths.
Some of the telescopes are occasionally used for EVN
European VLBI Network
The European VLBI Network was formed in 1980 by a consortium of five of the major radio astronomy institutes in Europe . Since 1980, the EVN and the Consortium has grown to include 9 institutes with 12 radio telescopes in 8 western European countries as well as associated institutes with...
and VLBI
Very Long Baseline Interferometry
Very Long Baseline Interferometry is a type of astronomical interferometry used in radio astronomy. It allows observations of an object that are made simultaneously by many telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.Data...
observations in order to create an interferometer with even larger baselines, providing images with much greater angular resolution
Angular resolution
Angular resolution, or spatial resolution, describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object...
.
MTLRI
| Original MTRLI telescopes | |
|---|---|
| Name | Coordinates Geographic coordinate system A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers. The coordinates are often chosen such that one of the numbers represent vertical position, and two or three of the numbers represent horizontal position... (links to map & photo sources) |
| 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... |
53°14′10.50"N 02°18′25.74"W |
| 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... |
53°13′51.62"N 02°18′34.16"W |
| Mark III Mark III (radio telescope) The Mark III was a portable and fully steerable radio telescope located at Wardle, near Nantwich, Cheshire in the north-west of England . Constructed in 1966, it was remotely controlled from Jodrell Bank Observatory, and was mainly used as part of the MERLIN radio telescope network... |
53°06′09.16"N 02°31′15.63"W |
| Defford | 52°05′27.61"N 02°08′09.62"W |
| Knockin | 52°47′23.9"N 02°59′44.9"W |
| Pickmere | 53°17′18.4"N 02°26′38.4"W |
| Darnhall | 53°09′21.6"N 02°32′03.3"W |
In 1973, Henry Proctor Palmer made the suggestion of extending the interferometer links already in place at Jodrell Bank at the time, which started the planning of the telescope array.Lovell, Astronomer by Chance, p. 312 Construction started in 1975. The system was originally officially called MTRLI (Multi-Telescope Radio Linked Interferometer), but was commonly referred to by the simpler name of MERLIN. It originally consisted of either the 76m 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...
or the 25m 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...
, along with the 25m Mark III
Mark III (radio telescope)
The Mark III was a portable and fully steerable radio telescope located at Wardle, near Nantwich, Cheshire in the north-west of England . Constructed in 1966, it was remotely controlled from Jodrell Bank Observatory, and was mainly used as part of the MERLIN radio telescope network...
at Wardle, the 85 ft at Defford and a new telescope at Knockin. This
new telescope was made by E-Systems and was constructed based on the designed for the telescopes in the Very Large Array
Very Large Array
The Very Large Array is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles west of Socorro, New Mexico, USA...
, which was being constructed at the same time also by E-Systems.
The construction of the new telescope, the installation of microwave communication links and the construction of the correlator were jointly called "Phase 1" of the MERLIN project, the funding for which was approved on 30 May 1975. The construction of the new telescope started on 9 July 1976, and was completed by 8 October 1976. The telescope was first controlled remotely from Jodrell in January 1977. The microwave links were installed in May 1978. The first observations using the system - measurements of 30 distant radio sources - were taken in January and February 1980. The final cost of phase 1 of the system was £2,179,000 (1976).
Two additional telescopes were added in Phase 2 of the project, along with their radio links to Jodrell Bank. While it was originally proposed that one of the telescopes would be sited at Jodrell Bank and the other at Darnhall, the pair were finally sited at Pickmere (also known as Tabley) and Darnhall. The two telescopes were the same as that at Knockin. Construction on both telescopes started on 9 April 1979, and was completed by 31 October 1979. The Pickmere telescope was connected into MTRLI for the first time on 20 July 1980, followed by the Darnhall telescope on 16 December 1980. The second phase was formally completed on the 31 December 1981, and had cost £3,142,210.
The longest baseline of MTRLI was 134 km, between Pickmere and Defford. The first map produced by the array was published on 6 November 1980. In the first 2 years of operation (1980–1982), the array was used to observe at frequencies of 408 MHz (with a resolving power of 1 arcsecond), 1666 MHz (0.25 arcsecond) and 5 GHz (0.08 arcsecond).
When 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...
's surface was replaced in 1987, it could be used along with the three E-systems telescopes on the 22 GHz frequency, expanding MTRLI at that frequency.
One of the 18 m dishes of the One-Mile Telescope
One-Mile Telescope
The One-Mile Telescope at the Mullard Radio Astronomy Observatory is an array of radio telescopes designed to perform aperture synthesis interferometry.- History :The One Mile Telescope was completed by the Radio Astronomy Group of Cambridge...
was temporarily used in MTRLI from 1987 until Autumn 1990, which greatly improved its resolution.
MERLIN
| Current MERLIN telescopes | |
|---|---|
| Name | Coordinates Geographic coordinate system A geographic coordinate system is a coordinate system that enables every location on the Earth to be specified by a set of numbers. The coordinates are often chosen such that one of the numbers represent vertical position, and two or three of the numbers represent horizontal position... (links to map & photo sources) |
| 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... |
53°14′10.50"N 02°18′25.74"W |
| 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... |
53°13′51.62"N 02°18′34.16"W |
| Defford | 52°05′27.61"N 02°08′09.62"W |
| Knockin | 52°47′23.9"N 02°59′44.9"W |
| Pickmere | 53°17′18.4"N 02°26′38.4"W |
| Darnhall | 53°09′21.6"N 02°32′03.3"W |
| Cambridge | 52°10′1.2"N 0°2′13.4"E |
MTRLI was renamed to MERLIN in the early 1990s, and shortly afterwards the addition of the purpose-built 32 m Cambridge antenna in 1991 increased both the sensitivity and angular resolution
Angular resolution
Angular resolution, or spatial resolution, describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object...
of the array. The array also had a new correlator and new, cooled receivers, and some of the microwave links between the telescopes were improved so that the array could observe both hands of polarization.
Since 1996, carousels for the different receivers on each of the E-systems telescopes and 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...
telescope were installed (the Cambridge telescope already had such a system installed), providing frequency agility. In 1997 and 1998, dual-frequency (5 and 22 GHz) observations were made with the array for the first time.
There are plans to construct a telescope in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
that would be added to the array.
e-MERLIN
MERLIN currently uses microwaveMicrowave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
links to send astronomical data back from the remote stations. These links have a limited bandwidth so much of the data is thrown away. In order to increase the sensitivity of the telescope the current links have been replaced by optical fibre links which will carry a bandwidth of 4 GHz, compared to the original limit of 30 MHz, increasing the sensitivity of the array by a factor of around 30. This vast increase in data means that the old correlator will no longer be able to cope, so a new correlator is under construction which will be capable of processing over 200 Gbit/s.
Another major development which is part of the upgrade is frequency flexibility — the ability to alter the observing band of the entire array in a matter of minutes using rotating carousels of receivers. Some telescopes in the array already have this capability, while the rest require the visit of an engineer to change the receiver. When e-MERLIN becomes operational the telescope will be able to switch rapidly between 1.4, 5, 6 and 22 GHz. This is required in order to take advantage of optimum conditions for high frequency observations where atmospheric conditions can severely affect results.
Work started on the e-MERLIN upgrade in May 2004 and it was completed in 2009 .
STFC's Programmatic Review 2007-8
On 6 March 2008 the Science and Technology Facilities Council (STFCScience and Technology Facilities Council
The Science and Technology Facilities Council is a UK government body that carries out civil research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy .-History:It was formed in April 2007 as a merger of the Particle...
) announced that the (e-MERLIN/JIVE
JIVE
The Joint Institute for VLBI in Europe was formed in 1993 by the European Consortium for VLBI and is a member of the European VLBI Network . Very Long Baseline Interferometry is a type of astronomical interferometry used in radio astronomy...
) project was at risk because of a £80m shortfall in its budget. This was due to the initial recommendations of the Particle Physics, Astronomy and Nuclear Physics Science Committee (PPAN), that had listed the project as a "lower priority". Following concerns that PPAN's recommendations did not adequately represent the UK's astronomical priorities, STFC
Science and Technology Facilities Council
The Science and Technology Facilities Council is a UK government body that carries out civil research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy .-History:It was formed in April 2007 as a merger of the Particle...
established a wider consultation review involving various advisory panels to re-priorities the STFC
Science and Technology Facilities Council
The Science and Technology Facilities Council is a UK government body that carries out civil research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy .-History:It was formed in April 2007 as a merger of the Particle...
program. The Ground-Based Astronomy Consultation Panel then recommended e-MERLIN should be changed from the lowest band ("lower priority"), to the second highest, adding that "e-Merlin could be a world-leading facility well into the next decade" and "e-Merlin offered dramatic potential to both traditional UK radio astronomy users and importantly to a broader community".
On 8 July 2008 STFC
Science and Technology Facilities Council
The Science and Technology Facilities Council is a UK government body that carries out civil research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy .-History:It was formed in April 2007 as a merger of the Particle...
presented their final version of the programmatic review at a Town
Meeting at the Royal Society stating:
'Given the strategic importance of e-MERLIN to the future of UK radio astronomy and to the highly ranked SKA project, we are working with the University of Manchester and other stakeholders to find a viable way in which e-MERLIN operations can be supported in the medium term on a shared cost basis. We have made provision for STFC
Science and Technology Facilities Council
The Science and Technology Facilities Council is a UK government body that carries out civil research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astronomy .-History:It was formed in April 2007 as a merger of the Particle...
support of operations to be made available to facilitate such a solution.'
Scientific results
Among many other things, MERLIN has been used to observe:- Radio-loud galaxies, for example Messier 87Messier 87Messier 87 is a supergiant elliptical galaxy. It was discovered in 1781 by the French astronomer Charles Messier, who cataloged it as a nebulous feature. The second brightest galaxy within the northern Virgo Cluster, it is located about 16.4 million parsecs from Earth...
. - Quasars, for example 3C 418.
- Spectral line observations of HydroxylHydroxylA hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
(OH) in interstellar gas clouds.
The telescope can also be used for highly precise astrometry
Astrometry
Astrometry is the branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies. The information obtained by astrometric measurements provides information on the kinematics and physical origin of our Solar System and our Galaxy, the Milky...
.
In 1998, MERLIN in conjunction with the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
discovered the first Einstein ring
Einstein ring
In observational astronomy an Einstein ring is the deformation of the light from a source into a ring through gravitational lensing of the source's light by an object with an extremely large mass . This occurs when the source, lens and observer are all aligned...
.
The telescope has also been used in combination with the VLA to carry out a weak lensing analysis.