Evaluation of the haystack antenna and radome

The characteristics of the radome-enclosed Haystack antenna have been evaluated as a radio-astronomical instrument. Important advantages of the radome enclosure are the high pointing precision it permits under all wind conditions, the rms pointing errors being 7" in azimuth and elevation, and the antenna surface tolerance (0.027 in rms) made possible by controlled environment. We searched for but failed to find any detectable radome effects as follows: pointing deviations, gain variations, noise granularity, and polarization effects. The principal electromagnetic effect of the radome is a reduction of aperture efficiency by an amount that varies from about 1 dB at long wavelengths to 2.8 dB at 35 GHz. The noise contribution is about K at 8 GHz and K at 22.2 GHz.