3:30 PM - 5:00 PM
[SVC35-P02] Imaging of sulfur dioxide gas concentration distribution in the plume of Aso Volcano using a multiband infrared cameras
Keywords:uncooled infrared camera, SO2 gas, volcano observations, infrared remote sensing
Measuring the amount of SO2 gas emitted from volcanoes is effective for predicting short-term volcanic activity. We are developing an imaging system for remote sensing of SO2 gas under the “Promotion Project for Next Generation Volcano Research B2” with the aim of developing an optical multispectral remote sensing system for analyzing volcanic surfaces phenomena. In this project, we plan to develop a multiband infrared camera system called the Surface Phenomena Imaging Camera with Uncooled Infrared Camera (SPIC-UC). Our goal is to make SPIC-UC a hand-held imaging system that can be used for both ground-based and airborne observations. In this report, we present an overview of one of the SPIC prototypes, a multiband uncooled infrared camera; SPIC-Uncooled /4VGA (SPIC-UC/4VGA), which observes temperature distribution and SO2 gas concentration distribution, and test observation results of volcanic plumes of Aso Volcano using this camera.
SPIC-UC/4VGA consists of four uncooled infrared cameras (Cameras 1, 2, 3 and 4) with built-in optical filters. All of these cameras employ a focal plane array (FPA) type amorphous silicon microbolometer element. Camera 1 measures the 7500-14000 nm region, Camera 2 measures the 9000-14000 nm region, Camera 3 measures the 7950-9300 nm region that corresponds to the SO2 absorption band, and Camera 4 measures the region from 11785 to 12785 nm, where there is no SO2 absorption. These four cameras can acquire frame synchronous data at 30 fps. SPIC-UC/4VGA is designed to be environmentally resistant for outdoor use. The results of the basic performance evaluation tests completed to date indicate that all cameras can achieve absolute temperature accuracy within ±2K. In addition, camera 3 for SO2 detection was able to achieve a NETD of approximately 0.39 K.
To demonstrate the functionality of the device, a volcano experimental observation (Mt. Aso Nakadake volcanic plume observation) using the SPIC-UC/4VGA was conducted on November 27, 2021. Observations were made from the Kusasenri observatory located 3.15 km west of the crater of Mt. Aso Nakadake. To evaluate acquired images, we conducted radiative transfer simulations with the radiative transfer analysis code MODTRAN4.0 for each camera considering the observation geometry, atmospheric conditions, and SO2 concentration (0 to 50 ppmv).
We could evaluate the observed brightness-temperature distributions are the result of capturing the emission of SO2 gas, whose concentration was estimated to be between 0 and 15 ppmv. Estimated daily amount of emitted SO2 gas were between 2000 and 3000 tons per day. These values were in good agreement with by the Japan Meteorological Agency's SO2 observations (using mini-DOAS: remote sensing of SO2 gas using UV) (1800-3000tons/day) for the same period.
From these results, it can be said that SPIC-UC/4VGA can be used as a measurement device for SO2 gas concentration in volcanic plumes. In the future, we plan to increase the number of observations and improve the accuracy by improving the on-site calibration method.
SPIC-UC/4VGA consists of four uncooled infrared cameras (Cameras 1, 2, 3 and 4) with built-in optical filters. All of these cameras employ a focal plane array (FPA) type amorphous silicon microbolometer element. Camera 1 measures the 7500-14000 nm region, Camera 2 measures the 9000-14000 nm region, Camera 3 measures the 7950-9300 nm region that corresponds to the SO2 absorption band, and Camera 4 measures the region from 11785 to 12785 nm, where there is no SO2 absorption. These four cameras can acquire frame synchronous data at 30 fps. SPIC-UC/4VGA is designed to be environmentally resistant for outdoor use. The results of the basic performance evaluation tests completed to date indicate that all cameras can achieve absolute temperature accuracy within ±2K. In addition, camera 3 for SO2 detection was able to achieve a NETD of approximately 0.39 K.
To demonstrate the functionality of the device, a volcano experimental observation (Mt. Aso Nakadake volcanic plume observation) using the SPIC-UC/4VGA was conducted on November 27, 2021. Observations were made from the Kusasenri observatory located 3.15 km west of the crater of Mt. Aso Nakadake. To evaluate acquired images, we conducted radiative transfer simulations with the radiative transfer analysis code MODTRAN4.0 for each camera considering the observation geometry, atmospheric conditions, and SO2 concentration (0 to 50 ppmv).
We could evaluate the observed brightness-temperature distributions are the result of capturing the emission of SO2 gas, whose concentration was estimated to be between 0 and 15 ppmv. Estimated daily amount of emitted SO2 gas were between 2000 and 3000 tons per day. These values were in good agreement with by the Japan Meteorological Agency's SO2 observations (using mini-DOAS: remote sensing of SO2 gas using UV) (1800-3000tons/day) for the same period.
From these results, it can be said that SPIC-UC/4VGA can be used as a measurement device for SO2 gas concentration in volcanic plumes. In the future, we plan to increase the number of observations and improve the accuracy by improving the on-site calibration method.