MONITORING, ASSESSMENT AND MITIGATION OF VOLCANIC HAZARDS USING THE SPACEBORNE ASTER INSTRUMENT

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is proving extremely valuable for the study of many earth processes such as glacial monitoring, heat balance determinations, and volcanic observations. The latter includes eruption monitoring of >1500 active volcanoes. ASTER has an increased spectral and spatial resolution two and four times greater than Landsat ETM images. In addition, its greater dynamic range provides unsaturated data from high temperature volcanic targets. ASTER has a nominal repeat time of 16 days, reduced to as little as 5 days through the instrument's unique ability to point off nadir. With these features plus the ability to generate digital elevation models (DEMs), ASTER should be the premiere instrument for volcanic hazard monitoring. However, the data flow from sensor to scientist is convoluted and limits the near real-time availability. These issues are currently being investigated through integration with high temporal, low spatial resolution instruments.

Two volcanic eruptions have been examined in detail in the two years that ASTER has been operational: Bezymianny, Russia (June-December 2000) and Mt. Etna, Italy (July-August 2001). At Bezymianny, ASTER data have been compared to AVHRR near-real time data, with ASTER revealing much more detail on the dome's surface. Thermal anomalies covering hundreds of pixels were present for a much longer period than AVHRR observed. The data highlight the non-eruptive thermal state of the volcano and show a thermal concentration along a fissure prior to the larger eruption in late October. This was detected by AVHRR and resulted in the formation of a hot flow deposit only seen in the ASTER data. The multispectral thermal data have also allowed the dome's compositional and textural changes to be mapped. During the Etna activity, pre-, syn-, and post-eruption ASTER images were acquired and permitted the mapping of lava flow areal extent and estimates of thermal flux. Typical ASTER-derived pixel integrated temperatures were ~250°C-350°C for active flows. In addition, ASTER-derived DEMs allow for quantitative documentation of the summit crater topography and estimates of lava flow volumes. ASTER also provided detailed multispectral observations of the airborne ash and SO2 plumes.