Resurfacing the Jodrell Bank mk II radio telescope

Abstract

The MkII radio telescope at Jodrell Bank was built in 1964 and has been used for radio astronomy in the intervening years. It has an elliptical reflecting surface of major axis 38. 1m and minor axis 25. 4m, with the focus of the paraboloid at 12. 2m above the vertex. The reflecting surface is made from continuously welded 12 s. w. g. steel sheet supported with a strong backing structure. The original specification called for a surface accuracy of plus or minus 13 mm peak and therefore the performance of the antenna degraded at wavelengths shorter than about 10 cm. A method of construction of new panels to be mounted for convenience on the old surface was sought. The surface accuracy was to be better than 1 mm r. m. s. overall, with a focal length of 12. 45m. Fabricated aluminium panels were found to offer the least expensive solution, with adjustment from the front surface. Panel adjustment after installation on the telescope was made initially by theodolite and tape, followed by a set of holographic measurements using radio interferometers observing celestial radio sources