Technical Abstract: Validation of new satellite sensors and algorithms is an integral part of the Earth Observing System (EOS). Questions concerning the quality of the sensor technology and the algorithms used to process the data must be answered to provide estimates of errors that may be propagated through applications of the imagery. Ground measurements were used to calibrate and dvalidate Landsat ETM+ imagery at 30 m spatial resolution which were then aggregated to MODIS imagery at 250 m spatial resolution. This was done to determine the accuracy of individual measures of directional reflectance of land surfaces from atmospheric corrections, the full distribution of directional reflectance, albedos, and traditional nadir reflectance. The preliminary results showed that the products available from the EOS system are reasonably accurate. The study also showed the value of scaling from surface measurements to fairly high spatial resolution satellite imagery and then using the calibrated/validated high resolution satellite imagery to validate the low spatial resolution satellite imagery.