Lovell Radio Telescope Dish Improvements, United Kingdom

The University of Manchester has been awarded a grant from the Joint Infrastructure Fund (JIF) to fund a £2 million upgrade of its Lovell Telescope at the Jodrell Bank Observatory in the UK.

DISH REPLACEMENT

Over the summers of 2001 and 2002 it is planned that the surface of the 76m Lovell Radio Telescope dish will be replaced as the present surface is not in good condition.

The original steel surface of each of the several hundred panels that make up the surface will be replaced with a new surface made from galvanised steel. This must be used, rather than aluminium, in order that the part of the telescope that rotates in elevation (the bowl structure) remains balanced.

TELESCOPE IMPROVEMENTS

The expectation is that this will provide a substantial increase in the highest operating frequency of the telescope and, in particular, make it fully efficient at 5GHz. The improved performance would come from three improvements:

• The individual panel surfaces would be smoother than the present panels
• The shape of some of the panel formers which define the surface shape of each panel can be improved helping to ensure that each panel shape corresponds to the appropriate section of the parabolic surface
• By the use of a holographic technique using observations made simultaneously by the Lovell and MkII telescopes, it is possible to measure the offset of each panel from the desired parabolic surface. Each individual panel can then be adjusted to bring the whole surface to the desired parabolic shape. The surface is set at an appropriate elevation so that the performance is maximised over the greatest possible range of elevations

EXPANSION IN CAPABILITY

An expansion of the useable frequency range by a factor of four and an increase in the sensitivity at the key operational frequency of 5GHz by a factor of five will allow a wide range of new science to be carried out.

NEW REFLECTING SURFACE

The present surface panels will be replaced by new galvanised steelplates. Attachment will be with self tapping screws to avoid thermal distortions of the type induced in the present surface by spot welding.

SURFACE ADJUSTMENT

Using modern holographic profiling techniques, the new surface will be set to optimise the efficiency of the telescope for operation at frequencies above 5GHz.

NEW POINTING CONTROL SYSTEM

The present drive and control system will be replaced so to increase the precision of the positional control. This will involve independent control of individual drive motors.

REFURBISHMENT OF THE TRACK AND FOUNDATIONS

Remedial work on the surface layer of the foundations has been carried out to prevent water ingress. The outer azimuthal track has been re-laid to the current British standard.

Whereas the present telescope can operate efficiently at wavelengths down to 18cm (a frequency of 1.8GHz) the performance, on the present surface accuracy, drops off dramatically at shorter wavelengths. The new surface will, in contrast, be almost fully efficient at a wavelength of 5cm (6GHz) which is a major operating frequency of the Merlin (Multi Element Radio Linked Interferometer Network) array.

CONTRACTORS

A team from SHAL Engineering of Sheffield will install the new panels. The upgrade package has four main elements, with the work planned to be carried out over the summers in 2001 to 2002 at a fraction of the cost (at least £30 million) of building a new telescope of the same size and comparable performance.