Accurate measurements of snow areas and surface albedo are crucial to advancing our understanding of the global climate system. This is because of the highly reflective nature of snow combined with its large surface coverage （snow can cover up to 40% of the Earth’s land surface during the Northern Hemisphere winter）. The reflectance of snow varies 　with both solar incidence angle and the viewing angle. Visible sensors with different spatial resolutions have been used to infer the snow parameters. Currently

only nadir-viewing directional reflectance data are available from satellite observations. Observations at multiple angles are needed to infer the hemispheric reflectance albedo of snow fields.We propose to study the directional reflectance of snow fields using POLDER data

which contains information from different viewing angles and polarizations. POLDER was successfully launched on the ADEOS-1 satellite in August

1996

however

because POLDER data are not yet available

data from ASAS

a pointable

airborne spectroradiometer

were used in this study. Data collected over Glacier National Park of Montana show strong angular dependence. Preliminary results confirm the anisotropic nature of the snow reflectance. Knowledge of the bi-directional reflectance function（BDRF） of snow-covered surfaces is the key to developing a true albedo model in the future.