Development of infrared imaging devices for the observation of planetary atmosphere

点击翻译按钮获取中文摘要

The motion of the atmosphere of Venus at the altitude of less than 70km has not been studied because it is prevented by the thick cloud layer. But it became possible to observe the motion of lower clouds and surface of Venus after infrared ray turned out to pass through the thick cloud layer. We aimed at the observation of the motion of the atmosphere using Venusian clouds and surface as tracers by the infrared camera in the spacecraft orbiting around Venus. This approach will be the first one in the world.In this study, we developed the imaging device and optical system for infrared camera which can be used in the exploration of Venus and also future exploration of another planet. It is especially important to develop the imaging device and optical system in two bands, near-infrared region (1-3μm) and mid-infrared region (8-12μm). The former corresponds to the emission from the bottom of clouds (at the altitude of 50-70km), which enables us to observe the motion of the atmosphere. On the contrary, the latter corresponds to the thermal radiation from the top of clouds. As a result, it turned out to be best to use PtSi Schottky device in near infrared region and bolometer array in mid-infrared region as radioresistant imaging device. Schottky device needs to be cooled to 60K, and one stage Stirling cooler proved to be able to accomplish it.This research is relatively close to the development of infrared observation spacecraft in astronomical field. In this field, the technology which reduces a thermal noise to the minimum by cooling the infrared device has been improved for the observation of far, dark stars or young planetary system. But, if it is installed to planetary exploration spacecraft, it will be prolonged exposure to the radiation and also the much harsher heat condition than ground-based astronomical observations. In this time, the development of the infrared device suitable for the planetary orbiter was needed, and it was sufficiently achieved.