Measurements of Antenna Surface for a Millimeter-Wave Space Radio Telescope II; Metal Mesh Surface for Large Deployable Reflector

TL;DR

This study evaluates the RF performance of metal mesh surfaces for large deployable space radio telescope antennas at 43 GHz, revealing how surface tension and orientation affect reflection and radiative coefficients, impacting system noise.

Contribution

The paper provides the first detailed RF performance measurements of metal mesh surfaces at 43 GHz, including effects of tension and anisotropy, and demonstrates their impact through astronomical observations.

Findings

Reflection coefficient increases with surface tension.

Radiative coefficient decreases with surface tension.

Metal mesh surfaces degrade system noise temperature in practice.

Abstract

Large deployable antennas with a mesh surface woven by fine metal wires are an important technology for communications satellites and space radio telescopes. However, it is difficult to make metal mesh surfaces with sufficient radio-frequency (RF) performance for frequencies higher than millimeter waves. In this paper, we present the RF performance of metal mesh surfaces at 43 GHz. For this purpose, we developed an apparatus to measure the reflection coefficient, transmission coefficient, and radiative coefficient of the mesh surface. The reflection coefficient increases as a function of metal mesh surface tension, whereas the radiative coefficient decreases. The anisotropic aspects of the reflection coefficient and the radiative coefficient are also clearly seen. They depend on the front and back sides of the metal mesh surface and the rotation angle. The transmission coefficient was measured to be almost constant. The measured radiative coefficients and transmission coefficients would cause significant degradation of the system noise temperature. In addition, we carried out an astronomical observation of a well-known SiO maser source, R Cas, by using a metal mesh mirror on the NRO 45-m radio telescope Coude system. The metal mesh mirror considerably increases the system noise temperature and slightly decreases the peak antenna temperature. These results are consistent with laboratory measurements.