Design, construction, and performance of the Leighton 10.4-m-diameter radio telescopes

The design, construction, and measurement of 10-m-class radio telescopes operating at millimeter and submillimeter wavelengths present many challenges. The radio telescopes developed by Robert Leighton provide a solution to these problems. These 10.4-m-diameter telescopes have diffraction-limited beams at wavelengths as short as 300 μm. The paper describes the techniques Robert Leighton developed to solve many of the problems in building precision telescopes. The areas covered include the design of the homologous reflector support structure, the computer program used to accurately predict the deformation of the surface, the construction techniques used to minimize the stress and bending moments in the structure, and the methods developed for producing and measuring a 10.4-m-diameter reflector surface to the required accuracy. The reflectors for the Leighton telescopes consist of honeycomb Al panels supported on a steel spaceframe backing structure. The spaceframe utilizes precision machined members and pin joints. The 84 panels form a hexagonal tiling pattern in the aperture plane and are figured using a custom-built machine. The Al reflecting surface is then applied to the front of each panel. The telescopes are routinely fabricated and installed with an rms surface accuracy of less than 35 μm without any adjustments/corrections. Computer calculations of the homologous deformation of the telescopes as they move in elevation have been verified by holography. A Leighton telescope installed at the Caltech Submillimeter Observatory on Mauna Kea, HI, has achieved an accuracy of <20 μm