Infrared satellite data provide information regarding the thermal state and nature of activity at active volcanoes. Such radiometry has been hampered, however, by the tendency of many currently operational sensors to saturate over high-radiance targets. Here the simulated response of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) to high-temperature volcanic features is presented and compared to that of the Landsat Thematic Mapper (TM), which has provided the bulk of useful data since the mid 1980's. We find that ASTER's improved spectral resolution and increased dynamic range will markedly reduce the problem of sensor saturation common in TM-based studies, thus providing valuable data previously unavailable. Saturation will still occur however, when the fractional area of high-temperature (~1000 ¿C) material approaches ~1% (~9 m2) of ASTER's 30-m short-wave infrared pixels. ¿ 1999 American Geophysical Union