Space-borne Submillimeter Wave Calibration Load with Specular Absorbers

Abstract

A calibration load with specular-reflection absorbers for a submillimeter-wave radiometer is proposed, and the results of fabrication and performance tests are described. The load consists of a pair of flat-surface specular absorbers set at their Brewster angle giving polarization-independent performance. By the use of absorbers with specular surfaces, the electrical and thermal design for a hig-power reflection loss calibration load becomes easy. The obtained effective brightness temperature and coherent power reflection coefficient are 300 K and less than -60 dB, respectively, at frequencies between 624 and 650 GHz. The load has been used for the absolute calibration of the SMILES (Superconducting Submillimeter-wave Limb-Emission Sounder on the International Space Station/Japanese Experiment Module).