MERLIN

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For other uses, see Merlin (disambiguation).

The Multi-Element Radio Linked Interferometer Network (MERLIN) is an array of radio telescopes spread across Britain. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of PPARC as a National Facility.

The array consists of up to seven radio telescopes and includes the Lovell Telescope, Mark II, Cambridge, Defford, Knockin, Darnhall and Pickmere (previously known as Tabley). The longest baseline is therefore 217km 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.

1 History
2 The e-MERLIN upgrade
3 Telescope information
4 References
5 External links

[edit] History

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 Lovell Telescope or the Mark II, along with the Mark III at Wardle, the 85ft at Defford and a new telescope at Knockin. The purpose-built telescope is the same as those used in the Very Large Array, which was being constructed at the same time. The construction of the telescope, the installation of microwave communication links and the construction of the correlator were jointly called "Phase 1" of the MERLIN project, which became operational in January 1980.

Two additional telescopes, also of the VLA design, were added in Phase 2 of the project, which was completed in December 1980. 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 and Darnhall. In the first 2 years of operation (1980-1982), the array was used to observe at frequencies of 408MHz (with a resolving power of 1 arcsecond), 1666MHz (0.25 arcsecond) and 5GHz (0.08 arcsecond).

The addition of the Cambridge antenna in 1991 increased both the sensitivity and angular resolution of the array. Since its early days the array has also had a new correlator and new receivers.

[edit] The e-MERLIN upgrade

MERLIN currently uses microwave 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 are being replaced by optical fibre links which will carry a bandwidth of 4 GHz, compared to the current 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.

[edit] Telescope information

The following table lists information about each of the telescopes that make up the network.

Antenna	Diameter	Latitude	Longitude	Aerial photo
Defford	25 m	+52:05:27.61	+02:08:09.62	Location on wikimapia
Cambridge	32 m	+52:10:06.48	-00:02:23.25	Location on wikimapia
Darnhall	25 m	+53:09:21.6	+02:32:03.3	Location on wikimapia
Knockin	25 m	+52:47:23.9	+02:59:44.9	Location on wikimapia
Mark II	25 m	+53:13:51.62	+02:18:34.16	Location on wikimapia
Lovell Telescope	76 m	+53:14:10.50	+02:18:25.74	Location on wikimapia
Pickmere	25 m	+53:17:18.4	+02:26:38.4	Location on wikimapia