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

摘要

Large deployable antennas with a mesh surface woven by fine metal wires arean important technology for communications satellites and space radiotelescopes. However, it is difficult to make metal mesh surfaces withsufficient radio-frequency (RF) performance for frequencies higher thanmillimeter waves. In this paper, we present the RF performance of metal meshsurfaces at 43 GHz. For this purpose, we developed an apparatus to measure thereflection coefficient, transmission coefficient, and radiative coefficient ofthe mesh surface. The reflection coefficient increases as a function of metalmesh surface tension, whereas the radiative coefficient decreases. Theanisotropic aspects of the reflection coefficient and the radiative coefficientare also clearly seen. They depend on the front and back sides of the metalmesh surface and the rotation angle. The transmission coefficient was measuredto be almost constant. The measured radiative coefficients and transmissioncoefficients would cause significant degradation of the system noisetemperature. In addition, we carried out an astronomical observation of awell-known SiO maser source, R Cas, by using a metal mesh mirror on the NRO45-m radio telescope Coude system. The metal mesh mirror considerably increasesthe system noise temperature and slightly decreases the peak antennatemperature. These results are consistent with laboratory measurements.