Mark V/Mark VA Telescope

Scope and Content

The series provides an extremely detailed record of the project, and includes correspondence files (the major correspondents being Observatory staff, the University of Manchester officials, the Science Research Council, the UK Atomic Energy Authority which acted as the SRC's agent for the project and H C Husband the designer). The files provide a particularly good overview of the politics of the project, including its funding, the design of the telescope, and the issues relating to the siting of the telescope in mid-Wales, which attracted considerable controversy.

Administrative / Biographical History

The Mark V (later Mark VA) was a major project of the late 1960s and 1970s to build a massive steerable radio-telescope. This telescope would have been the world's largest and would have been much bigger than the Mark Ia. Lovell had been considering a much larger telescope from the late 1950s, originally been in the form of the 1000-ft Mark IV telescope which would have been built at Jodrell Bank, close to the existing telescopes. The Mark IV was cancelled at an early stage, but the very large telescope idea was backed by the Fleck Committee, which reported on the future development of British radio-astronomy in 1965 .

The Mark V was initially considered for Jodrell Bank and Husband and Co. were again appointed as consulting engineers. Like the Mark II, it had an elliptical bowl, and the size of the dish was larger than proposed by the Fleck report. In 1965, the first feasibility study was produced, although by this stage the idea of an elliptical bowl had been dropped. Instead there would be a 400ft circular aperture, with the telescope mounted on railway lines. Siting the telescope at Jodrell Bank was dropped as impractical and an alternative site was sought within 100 miles of the Observatory. In contrast to the Mark I, the Mark V would be owned by the Science Research Council (which replaced the DSIR in 1965), and administered by the University, rather than owned by the University outright. It was initially hoped the telescope could be built for around £5m, but there was a continuing inflation in costs. In this project the UK Atomic Energy Authority acted as agent to the SRC in its dealings over the design and the contracts (it was hoped this would avoid some of the problems encountered in the mark I project).

In 1967, a design study was agreed, and this was completed by H C Husband in 1969, setting out a scheme for a 400ft telescope. There were numerous design issues; apart from the very size of the structure, there was a growing realisation that to take advantage of very high frequency radio amplifiers, the reflecting dish needed to maintain its paraboloid shape at all angles of elevation with only very small deviations. These proved difficult to resolve. Alternative design approaches such as used by the Effelsberg radio-telescope in Germany had maintained the true paraboloid at all elevations despite having gravitational deflections. Comparisons between the German concept and the 1969 Mark V design study indicated the inferiority of the latter, and some Jodrell Bank staff spoke in favour of the German model. Lovell sought to overcome the issue by adding a complex jacking system to the bowl's design to assure the integrity of the paraboloid. This added significantly to costs, which were already rising in an inflationary environment.

In early 1970s the SRC Council approved the design. however, a change of government in mid-1970 and ensuing reductions in planned government expenditure put the project i jeopardy. This lead to a major revision in the design, with the telescope being renamed the Mark VA. The revised design involved greater use of reinforced concrete in preference to expensive steelwork.

In June 1971, the Treasury authorised the new Mark VA design, a 375 ft telescope. The project moved slowly over the next few years, with projected costs continuing to rise. In June 1974, the SRC finally confirmed that it would not support the project any longer and it was cancelled. This was the last attempt by the Observatory to build a major radio-telescope larger than the Mark IA; thereafter the focus was on developing its network of smaller telescopes as a large-scale interferometer (which ultimately became the MERLIN network).

Apart from design, the site of the Mark V also created numerous problems. Sites were examined at various locations in the English-Welsh border area and a site at Meifod, Montgomery shire was selected. Although the project was supported by Montgomery shire County Council there was sustained opposition from local residents and from the Council for the Protection of Rural Wales.