Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope

TL;DR

This study evaluates the reflection performance and durability of two antenna surface materials, copper foil CFRP and aluminum-coated CFRP, under thermal cycling for use in a millimeter-wave space radio telescope, revealing material suitability for space conditions.

Contribution

It provides empirical data on the thermal cycle durability and reflection loss of candidate antenna materials for space radio telescopes, aiding material selection.

Findings

Copper foil CFRP met ASTRO-G requirements after thermal cycling.

Aluminum-coated CFRP exceeded reflection loss limits before cycle end.

Cracks increased with thermal cycles, affecting reflection performance.

Abstract

In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41-45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number density of the cracks. Nevertheless, the loss of the copper foil surface met the requirements of ASTRO-G at the end of the equivalent life, whereas that of the aluminum-coated surface exceeded the maximal value in the requirement even before the end of the cycle.