NASA's EOS satellite, to be launched in 1998, will carry a high-resolution (≥15m) scanner (ASTER) as well as a moderate-resolution (≥250 m), wide-angle scanner (MODIS). The images produced by these instruments are complementary for measuring and mapping forests at scales from local to global. High-resolution ASTER images permit the accurate identification of distinctive forest units down to tens of meters in size, measurement of the area of forest lands in given categories, and characterization of spectral endmembers necessary for spectral mixture analysis. Wide-angle MODIS images are necessary for regional and global monitoring of forest resources. Used together with MODIS data, ASTER permits more meaningful image classification through distinction between acute anthropogenic effects such as small-scale clear-cutting, and widespread low-level changes in green foliage due to natural causes.