High-Resolution Satellite and Airborne Thermal Infrared Imaging of the 2006 Eruption of Augustine Volcano

Thermal infrared (TIR) images provided a timely preand syn-eruption record of summit changes, lava flow emplacement, and pyroclastic-flow-deposit distribution during the Alaska Volcano Observatory’s (AVO) response to the 2006 eruption of Augustine Volcano. A series of images from both handheld and helicopter mounted forward looking infrared radiometers (FLIR) captured detailed views during a series of 13 overflights from December 2005 through August 2006. In conjunction with these images, data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) provided frequent multispectral synoptic views of the eruption’s emissions and deposits. The ASTER Urgent Request Protocol system also facilitated more frequent scheduling and faster data availability during the eruption. Airborne and satellite imaging provided 20 different days of TIR coverage over the 5-month eruptive period, with 4 of those days covered by both FLIR and ASTER. The high-resolution TIR images documented gradual pre-eruption heating of the summit, emplacement of pyroclastic-flow deposits, rapid temperature increase as the lava dome and flows formed, and slow cooling of the volcanic deposits that followed. The high-resolution data uniquely documented segmentation of the lava flows into hot areas of increased flow deformation and cooler, more stable crust on the active flows. In contrast, the satellite TIR data provided synoptic views of the areal distribution of volcanic products at Augustine including the extent and composition of the plumes. 1 Alaska Volcano Observatory, U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508. 2 Alaska Volcano Observatory, Geophysical Institute, University of Alaska Fairbanks, P.O. Box 755905, Fairbanks, AK 99775. 3 Department of Geology and Planetary Science, University of Pittsburg, Pittsburg, PA 15260. 528 The 2006 Eruption of Augustine Volcano, Alaska After more than 10 months of increasing seismicity, deformation, gas emission, and heat flow, Augustine Volcano, Alaska (fig. 1), explosively erupted on January 11, 2006. The volcano produced a total of 13 explosions during the last 3 weeks of January 2006. A new summit lava dome and two short, blocky lava flows were emplaced from February to March. A series of 13 forward looking infrared radiometer (FLIR) over-flights and 7 daytime and 15 nighttime Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scenes were acquired in response to this activity. The FLIR and ASTER data provided several significant observations as part of a much larger suite of real-time or near-real-time data from other satellite (AVHRR, MODIS), airborne (visual, gas), and ground-based (seismometers, global positioning system [GPS], radiometers) sensors used at AVO (see Bailey and others, this volume; Cervelli and others, this volume, Coombs and others, this volume; McGee and others, this volume; Power and Lalla, this volume). In this chapter, we summarize airborne FLIR observations acquired between December 2005 and August 2006 and the longer record of spaceborne ASTER observations acquired between December 2000 and May 2006. The high-resolution FLIR data document the gradual pre-eruption heating of the summit, the formation of pyroclastic-flow deposits, the rapid increase in temperature as the lava dome and flows formed, and the slow cooling of volcanic deposits after the eruption. In addition to these observations of the eruption, the ASTER data provide a baseline from which to examine temperature trends over several years leading up to and during the most recent volcanic unrest. Instrumentation and Methodology FLIR Surveys and Data Processing The primary airborne imaging system used in this study consists of a FLIR Systems ThermaCAM PM595 infrared camera and a Sony EVI-370 NTSC video camera housed in a helicopter-mounted four-axis gyrostabilized gimbal (see Schneider and others, 2008, for system details). A handheld version of the PM595 camera was used for repeat ground-based time-lapse imaging. The infrared camera utilizes a 320×240 microbolometer detector array, which is sensitive from 7.5 – 13 μm, converting TIR emitted radiance into brightness temperature. The gimbal-mounted system has an integrated 12o lens with a horizontal field of view of 210 m and a pixel resolution of 65 cm at a distance of 1 km; the handheld system has an integrated 24o lens with a horizontal field of view of 420 m and a pixel resolution of 1.3 m at a distance of 1 km. The observation distance of each survey ranged from 0.5 to 5 km, averaging about 1.2 km. The measured FLIR brightness temperature is captured by using one of three ranges, −40 to 120oC, 80 to 500oC, and 350 to 1,500oC. In the low Figure 1. Nighttime 8.3-μm thermal infrared (TIR) images of Augustine Volcano acquired at 2245 AKST March 13, 2006, from the Terra spacecraft, oriented with north up. A, Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). B, Moderate Resolution Imaging Spectroradiometer (MODIS). Both MODIS and the Advanced Very High Resolution Radiometer (AVHRR) have ~1-km spatial resolution, which provides high-temporal-resolution views of North Pacific volcanic activity; however, these datasets lack sufficient spatial detail to capture persistent, low-level thermal features, smaller-scale activity, and eruptive deposits, are captured by ASTER TIR (90 m) and shortwave infrared (SWIR) (30 m) images.