Minimisation of r.m.s. phase error in large reflector antennas

A method of minimising the r.m.s. phase error in a large, paraboloidal reflector antenna is presented. The problem involves the search for the axis, the focus and the focal length of the paraboloid which best fit the actual reflector, in the least-square sense. Although standard techniques may be successfully employed, the method presented in this paper is simple, and results can be quickly obtained with the aid of a digital computer. By using an appropriate programming method, no excessive storage is required. As an illustration of the technique, the required parameters of the best-fit paraboloid are computed for the 210ft Parkes radiotelescope, when the dish is tilted at an angle of 40° from the zenith.