MERLIN is an array of seven radio telescopes across the UK, connected to a central correlator at Jodrell Bank Observatory (JBO) and operated as a dedicated radio interferometer to produce high resolution images. With a maximum baseline length of 220 km, MERLIN provides a unique capability for radio imaging at 0.01 – 0.15-arcsec resolution at frequencies of 1.5, 5 and 22 GHz (L, C and K bands). The e-MERLIN project is a major upgrade to the instrument involving the installation of new receivers, analogue and digital electronics, optical-fibre links to each telescope and a new correlator at JBO. This will increase the useable bandwidth by more than two orders of magnitude, and hence the continuum sensitivity by more than 10x. In addition, the increase in bandwidth will dramatically improve aperture coverage for continuum observations resulting in enhanced image fidelity together with simultaneous spectral-index imaging. The e-MERLIN upgrade is now well underway: new receivers are in service, the optical fibre network has been installed and the digital transmission equipment has been tested.

The locations of the radio telescopes participating in the MERLIN project are as follows:

Telescope name	Latitude	Longitude
Cambridge	52° 10’ 00” N	00° 02’ 15” E
Darnhall	53° 09’ 22” N	02° 32’ 07” W
Defford	52° 06’ 01” N	02° 08’ 39” W
Knockin	52° 47’ 24” N	02° 59’ 49” W
Jodrell Bank (Lovell + MKII)	53° 14’ 10” N	02° 18’ 26” W
Pickmere	53° 17’ 18” N	02° 26’ 44” W

Frequencies used currently:

Frequency band	Observing mode
1300 – 1700 MHz	Spectral lines, continuum
4000 – 8000 MHz	Spectral lines, continuum
22.00 – 24.00 GHz	Spectral lines, continuum

Research programmes: Solar wind studies, stellar studies, extra-galactic physics, galaxy and star formation, gravitational lenses and dark matter, astrometry and reference frames.