Abstract:
Since its launch in December 1999, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument has been observing over 1300 of the world's volcanoes during the day and night and at different times of the year. At the onset of an eruption, the temporal frequency of these regularly scheduled observations can be increased to as little as 1–3 days at higher latitudes. However, even this repeat time is not sufficient for near real-time monitoring, which is on the order of minutes to hours using poorer spatial resolution (>1 km/pixel) instruments. The eruption of Bezymianny Volcano (Kamchatkan Peninsula, Russia) in March 2000 was detected by the Alaska Volcano Observatory (AVO) and also initiated an increased observation frequency for ASTER. A complete framework of the eruptive cycle from April 2000 to January 2001 was established, with the Advanced Very High Resolution Radiometer (AVHRR) data used to monitor the large eruptions and produce the average yearly background state for the volcano. Twenty, nearly cloud-free ASTER scenes (2 days and 18 nights) show large thermal anomalies covering tens to hundreds of pixels and reveal both the actively erupting and restive (background) state of the volcano. ASTER short-wave infrared (SWIR) and thermal infrared (TIR) data were also used to validate the recovered kinetic temperatures from the larger AVHRR pixels, as well as map the volcanic products and monitor the thermal features on the summit dome and surrounding small pyroclastic flows. These anomalies increase to greater than 90 °C prior to a larger eruption sequence in October 2000. In addition, ASTER has the first multispectral spaceborne TIR capability, which allowed for the modeling of micrometer-scale surface roughness (vesicularity) on the active lava dome. Where coupled with ongoing operational monitoring programs like those at AVO, ASTER data become extremely useful in discrimination of small surface targets in addition to providing enhanced volcanic mapping capabilities.