|Figure 1||Figure 2|
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft captured this pair of images of Iceland's Eyjafyallajökull volcano on April 19, 2010.
The left-hand image (Figure 1) is a color-composite of data from the ASTER visible and near-infrared bands. The eruption plume and drifting veil of ash appear to be homogeneous.
The right-hand image (Figure 2) is a color-composite of data from three of the ASTER thermal infrared bands. These data have been processed to maximize the spectral contrast between the materials found in the eruption plumes. The eruption plume is largely opaque in the thermal infrared image. The opaque eruption plume, as well as the snow, are spectrally "flat" (it exhibits little change in emissivity with wavelength) and appears green in the thermal infrared color composite. The sulfur dioxide plume and drifting ash were not opaque in the thermal infrared image, allowing scientists to exploit distinctive features in the spectra to discriminate these materials. The sulfur dioxide plume appears yellow, and the drifting ash is displayed in hues of red and purple.
With its 14 spectral bands from the visible to the thermal infrared wavelength region and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet. ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.
The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.
The ASTER U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate, Washington, D.C.
More information about ASTER is available at http://asterweb.jpl.nasa.gov/.