Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Abstract Only
Publication Acceptance Date: July 5, 2001
Publication Date: N/A
Technical Abstract: With the successful launch of NASA's Terra satellite in December 1999 a new tool for observing land surface properties becomes available, i.e. multispectral thermal infrared data from the Advanced Spaceborne Thermal Emission Reflectance Radiometer (ASTER) instrument. ASTER has 5 channels in the 8 to 12 micrometer wave band with 90 meter resolution. These data can be used to assess the spectral variations of surface emissivity. Knowledge of the surface emissivity is important for determining the radiation balance at the land surface. For arid lands with sparse vegetation the problem is difficult because the emissivity of the exposed soils and rocks is highly variable. We will present some early ASTER data acquired over the Jornada Experimental Range and White Sand National monument in New Mexico on May 09, 2000 and May 12, 2001. The Jornada site is typical of a desert grassland where the main vegetation components are grass and shrubs. The Temperature Emissivity Separation (TES) algorithm is used to extract the temperature and 5 emissivities from the 5 channels of ASTER data. TES makes use of an empirical relation between the range of observed emissivities and their minimum value. Good quantitative agreement with laboratory measurements was found for the emissivities extracted for the gypsum sands of the White Sands. This target is the only one that was relatively uniform over the ASTER footprint. For the site within the Jornada the results were quantitatively consistent with ground measurements.