Thermal remote sensing of volcanoes by means of DLR's FireBIRD mission - a case study of the 2015 Villarrica Volcano eruption, Chile

Abstract

The experimental small satellite Technology Experiment Carrier-1 (TET-1) is one of two satellites of the German Aerospace Center (DLR) FireBIRD mission. Its repetition rate is approximately five days at the equator. TET-1 operates two infrared cameras, one in the mid wave infrared and one in the long wave infrared, as well as a three-channel camera in the visible (red and green) and near infrared. Due to the higher spatial resolution and higher sensitivity with regard to thermal anomalies, with data from TET-1, a more detailed analysis of volcanic activity is possible than with data from other satellite missions such as the Moderate Resolution Imaging Spectroradiometer (MODIS). Here, we present an atmospheric correction of the TET-1 data, based on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Emissivity Database (GDEM) and MODIS water vapor data with the shortest temporal baseline to the TET-1 acquisitions. Next, area coverage, the temperature, and radiant power of the detected thermal hotspots were derived at subpixel level and compared with observations derived from Visible Infrared Imaging Radiometer Suite (VIIRS) and MODIS data. As a case study, a time series of nine TET-1 acquisitions before and after the 3 March 2015 eruption of the Villarrica Volcano was analyzed. This Chilean volcano is one of the most active volcanoes in the South Andes Volcanic Zone. First thermal anomalies were detected nine days before the eruption. After the first eruption on 3 March 2015, a decrease of the radiant power was observed. This was followed by a stronger increase of the radiant power on 25 April 2015. In addition to the analysis of the thermal signals due to volcanic activity, we also studied the eruption-related ash coverage at the eastern flank of the ice-capped Villarrica Volcano. TET-1 images acquired before and after the 3 March 2015 eruption were compared to map this ash coverage. Higher resolution optical data from Landsat-8 were used to validate the results obtained from TET-1 imagery.