Newly Deviced Infra-red Radiometer (ERI Type IR Ground-Scanner) and the Surface Temperature of the Mihara Crater, 0-shima

Abstract

Infra-red radiometer, one of the remote sensing tools, are, in recent years, successfully used to measure the surface temperature of the volcanic and geothemal area. Many handy radiometers have been commercially produced for industrial purposes. Utilization of these radiometers in volcano observations has the following disadvantages; 1) wide field of view, and 2) difficulties of pointing the radiometer to the very points on the photographs. The authors purchased the commerial radiometer (Thermo Ace Model TA-60S) and mounted the optical part (camera) on the base of the baloon theodite. The base of the theodolite is rotated horizontally driven by a DC micro-motor attached to the theoaolite. A telescope was also attached to the camera so as to enable us confirm the observed point even during the scanning. The output of the radiometer can be recorded either with MT data recorder or ink writing recorder. Tis type of radiometer is also useful for continous monitoring the temperature of the vent or fumaroles. The observed temperatures depend on the wave length of the actual spatial temperature distribution, the field of view of the optical system and scanning speed. Detailed examination both on theoretical and experimental on the above points were made and described in the text. Thus, the improved IR radiometer was successfully utilized to observe the surface temperature of the crater bottom of Mihara-yama, 0-shima Volcano, on March 14, 1976. It was found that the temperature of the vent showed remarkable decrease compared with the previous values as well as the average surface temperature of the crater bottom.