[P-CG19] Planetary Magnetosphere, Ionosphere, and Atmosphere

[PCG19-P05] Evaluation of the Effect of Dry Heat Sterilization on Antenna for Terahertz Band Spectroscopic Sensor

*Ryoto Yamauchi¹, Yuki Hamaguchi¹, Nozomi Okada², Toshiyuki Nishibori², Atsushi Yamazaki², Hiroyuki Maezawa¹ (1.Osaka Prefecture University, 2.Japan Aerospace Exploration Agency)

Keywords:Terahertz band heterodyne spectroscopy , Terahertz antenna , Mars atmosphere, Planetary Protection, Dry heat sterilization

At present, various Mars missions such as the Mars Ice Mapper project are under consideration on Mars, and we are proceeding the design of the Terahertz Heterodyne Spectroscopy Sensor (THSS) with an eye toward the future development for Mars exploration. The purpose of THSS is to investigate trace molecules and isotopes in the atmosphere for understanding of the material circulation including water, atmospheric photochemistry, meteorology, climate environment, etc. on Mars. Since planetary protection category IV is often applied to Mars missions, evaluation of the durability of components of THSS to dry heat sterilization will be an important issue in the future. In this study, we report the results of a dry heat sterilization test on a terahertz antenna for THSS. The antenna is provided with a coating layer on the surface of the CFRP, an aluminum layer is formed on it by plasma spraying and cold spraying, and the mirror surface is finished with high precision and low roughness by cutting and polishing. As a result, no microporous material remains in the deposited aluminum layer, and a mirror surface roughness of 1 μm or less is achieved by polishing.
For dry-heat sterilization, 125 degrees/ 48 hours, which is one of the conditions recommended by category IV of planetary protection, was adopted in a constant temperature chamber. The performance of the antenna before and after the thermal treatment was compared and evaluated as reflection loss. Since the loss itself is small, it is necessary to use a highly sensitive terahertz sensor. In this experiment, a 649.32 GHz Nb-based SIS mixer detector cooled to 4 K was utilized. The antenna was set in an optical transmission system of the SIS receiver, and the conventional Y-factor measurement was carried out at room temperature to calculate the reflection loss. As a result, the losses before and after heat treatment were 0.77 +/- 0.09% and 0.7 +/- 0.4%, respectively. This suggests that the dry-heat sterilization under the condition of 125 degrees/ 48 hours does not cause statistically significant deterioration on the performance of the antenna.