Measurement of the noise improvement of a 34-meter Cassegrain antenna retrofitted with a low-backscattering strut

Large axially-symmetric ground-based dual-reflector antennas are used in a variety of applications simultaneously requiring very high gain and very low noise (e.g., satellite communications, radio astronomy, deep-space communications, and radar). In these systems, reducing the noise by 10% is equivalent to increasing the antenna gain by roughly 0.5 dB. Since the early days of radio astronomy this fact has continuously driven efforts to reduce the noise of front-end low-noise amplifiers-a major noise contributor. As the performance of the front-end amplifiers improved, the relative importance of the noise generated by the surrounding warm ground increased, causing the antenna noise to become a major factor in the overall system sensitivity. The results of Moreira, Prata and Thorburn (see IEEE Trans. Antennas Propagat., vol.44, no.4, p.492-9, 1996) are used to implement a low back-scattering cross section on a single strut of the Jet Propulsion Laboratory Deep Space Station 13 (DSS-13) antenna-a research and development 34-meter diameter deep-space communication beam-waveguide shaped Cassegrain antenna, located in Goldstone, California. The antenna and associated noise measurements are discussed, and the improvement on the system noise temperature is presented.