The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a joint Japan/U.S. space activity, operating on NASA's Terra spacecraft since March 2000. ASTER is scheduled to acquire 600 images per day in 14 spectral bands in the visible, shortwave infrared, and thermal infrared wavelength regions, with a spatial resolution of 15 to 90 m per pixel. An additional off-nadir visible stereo band allows creation of digital elevation models. ASTER data have been extensively used to monitor natural hazards and disasters, and the ASTER project has responded to data acquisition requests through the International Charter. Systematic, institutional activities involve working with organizations to monitor and assess volcanoes, forest fires, tsunamis, glacier lake outbursts, hurricane damage and earthquakes. Less regular observations include tornadoes, industrial fires, oil spills, and deforestation. Examples of large-scale assignment of ASTER resources occurred after: Hurricane Katrina in the southern U.S.; and the Indian Ocean tsunami following the Banda-Aceh earthquake. Adding to the high spatial resolution and multispectral aspects of the data is the ability to schedule nighttime acquisitions, particularly valuable for monitoring thermal phenomena like volcanic eruptions and forest fires.