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MERLIN (the Multi-Element Radio Linked Interferometer Network)

MERLIN is an array of seven radio telescopes distributed over central England and operated from Jodrell Bank Observatory as a National Facility by the University of Manchester. The outlying telescopes are connected via microwave links to a central correlator situated at Jodrell Bank. This combination of radio antennas forms the equivalent of a single, integrated telescope of huge dimensions and is able to image astronomical objects with high resolution at frequencies from 151 MHz to 24 GHz. MERLIN is the only world-class astronomical facility based entirely within the UK and is one of the few dedicated radio interferometers in the world. The key to MERLIN's success is its ability to see fine detail. With radio telescope separations of up to 217 km, it is the only ground-based facility in the world that routinely matches the resolution of the Hubble Space Telescope (HST) and the new generation of 8-m class optical/IR telescopes such as Gemini and the Very Large Telescope (VLT).

MERLIN often observes simultaneously with the European VLBI Network (EVN), an array of 13 telescopes distributed across Europe and Asia. In fact, joint EVN-MERLIN observations are rapidly becoming the most popular mode of observation at 1.4 and 5 GHz due to the ability of the joint array to provide images of a wide range of radio structures from the arcsecond scale down to the milli-arcsecond scale. The EVN Consortium Board of Directors and its associated Programme Committee and Technical & Operations Group coordinates EVN activities.

Several enhancements to MERLIN are planned during the period covered by this FP6 TNA proposal. Firstly, a £2.2M upgrade of the 76-m diameter Lovell Telescope at Jodrell Bank, the world's third-largest fully-steerable radio telescope, which forms an integral part of MERLIN, is already complete. This upgrade consisted mainly of the replacement of the telescope's 340 surface panels and enables the instrument to be used at higher observing frequencies. The inclusion of the refurbished Lovell telescope in 5-GHz MERLIN observations will result in a sensitivity increase of a factor of ~3.

The other major enhancement to MERLIN will be completed by early 2007 and represents a £6.8M investment that will completely transform the instrument's capabilities. The upgrade is funded by the North West Development Agency (NWDA) and a consortium of three universities - Manchester, UMIST and Cambridge. The project, termed e-MERLIN, will result in the array remaining competitive with, and complementary to, the new generation of expensive telescopes around the world. The new instrument will have significantly greater sensitivity than at present, allowing new areas of science to be opened up, particularly in the fields of extragalactic astronomy and cosmology, star formation across the universe, stellar evolution and studies of the extreme conditions around black holes.

The dramatic increase in sensitivity will be achieved by replacing the current narrow-band microwave link system, used to transmit data from the telescopes to Jodrell Bank, with broad-band fibre-optic cables. Once installed and connected to a new broad-band correlator, each telescope in the e-MERLIN array will transmit data at 30 Gbps back to Jodrell Bank Observatory. At 210 Gbps, the total data rate will be significant since it is greater than the combined Internet traffic of Western Europe. When coupled with the upgrade of the Lovell Telescope and a 30% improvement in receiver efficiency currently under development, the improvement in sensitivity will be a factor of 30-40 at the array's prime observing frequency. e-MERLIN will image in detail objects that can now only be glimpsed in the deepest observations and will detect objects previously unseen at radio wavelengths with unprecedented resolution. The range of science that will be addressed will therefore be transformed.

Even before e-MERLIN comes online, new capabilities will appear at regular intervals during the development and construction period. November 2003 will see the advent of new low-noise 4-8 GHz receivers that will enable observations of CH3OH and excited-state OH masers in conjunction with the Lovell Telescope. In October 2005 the array will be fully frequency flexible and be able to switch between all principal observing bands in under a minute. The implementation of these new capabilities over the period covered by this FP6 Transnational Access proposal is predicted to result in a significant increase in users, especially from European astronomers.

The MERLIN TNA Contact is T. Muxlow (JBO)

More information can be found on the MERLIN Homepage.