The advanced spaceborne thermal emission and reflection radiometer (ASTER) is a research facility instrument to be launched on NASA's Earth Observing System AM1 (EOS AM-1) platform in 1998. ASTER has three spectral bands in the VNIR, six bands in the SWIR, and five bands in the TIR regions with 15, 30, and 90 m ground resolution respectively. The VNIR subsystem has one backward-viewing band for stereoscopic observation in the along-track direction. Because the data will have wide spectral coverage and relatively high spatial resolution, we will be able to discriminate a variety of surface materials and reduce problems resulting from mixed pixels. ASTER will provide the highest spatial resolution surface temperature and emissivity data of all the EOS AM-1 instruments. The primary science objective of the ASTER mission is to improve understanding of the local- and regional-scale processes occurring on or near the Earth's surface and lower atmosphere, including surface-atmosphere interactions. Specific areas of the science investigation can be listed as: (1) vegetation and ecosystem dynamics, (2) land surface climatology, (3) volcano monitoring, (4) aerosols and clouds, (5) carbon cycling and in the marine ecosystem, (6) hydrology, and (7) geology and soil. There are four categories of data; global data sets, regional data sets, and local data sets to be obtained by data acquisition requests (DAR) from scientists. Prioritization of data acquisition requests will be done using the factors such as observation category, user category, and science discipline.