2.8-minute beamwidth, millimeter-wave antenna--Measurement and evaluation

The measurement and evaluation of the principal electrical and mechanical features of a 15-ft diameter precision millimeter-wave antenna are described. Contour measurements show that the surface accuracy of the paraboloid is not degraded by partial solar illumination and wind. The pattern functions of an off-axis feed Cassegrainian system are derived to determine the feasibility of achieving two nearly identical patterns desired for radiometric observations. The antenna characteristics have been measured by two methods: (1) the use of a transmitting facility located in the far field of the antenna and (2)drifting the antenna beam across the solar limbs. These measurements show that a high-resolution antenna can be significantly degraded by atmospheric turbulence.