Optimal surface adjustment of Haystack antenna

The primary reflector panels of the 37-m (120-ft) diameter Haystack antenna are prestressed to form an integrated parabolic shell of revolution. The adjustment mechanisms of the reflector surface are highly interacting, and the region of influence of each adjustment mechanism is large and intersects in a major way the influence regions of other adjustment mechanisms. The influence surface for each adjustment is computed using a detailed finite-element model of the antenna and the reflector structures. The optimal adjustments, i.e. the adjustments that minimize surface RMS, are obtained using the computed influence surfaces by solving a quadratic programming problem. The resolution of holography introduces errors in the holography map, but the resulting error in the computed adjustments are eliminated by using, in lieu of the actual influence surfaces, the transformed influence surfaces obtained by the convolution of the actual influence surfaces with the holography resolution function. The procedure, which was used to reduce surface RMS of the Haystack from 639 micron (25.1 mil) to 194 micron (7.6 mil), is applicable to other antennas.<
>