Atmospheric effect on spatial resolution of surface imagery

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Abstract
Atmospheric scattering and absorption tend to reduce appreciably the spatial resolution of satellite images of the earth’s surface. Photons that were reflected by the surface out of the field of view are scattered by the atmosphere into the field of view (adjacency effect). As a result the apparent field of view is increased. The atmospheric effect on the spatial resolution is calculated and compared with the sensor resolution. It is found that the 30-m resolution of the Landsat Thematic Mapper (TM) is reduce to 100 m by a hazy atmosphere. Consequently, simple empirical expressions are developed for the upward radiance at nadir for a given nonuniform surface reflectivity and for the atmospheric modulation transfer function (MTF). These expressions relate the radiance above a field with a background of different reflectivity (nonuniform surface) to the radiance above the same field if the surface is uniform. These expressions are used to deduce the noise equivalent surface reflectance (NEΔρ) and the SNR due to the atmospheric path radiance fluctuations caused by the adjacency effect. It is shown that in the near IR the NEΔρ due to the radiance fluctuations is ~0.01.