One of the main difference between atmospheric effect on nadir and off-nadir observations is the adjacency effect. For nadir remote sensing

the adjacency effect is azimuthally isotropic

but in off-nadir remote sensing

the effect is azimuthally dependent and the contribution of the background in the direction of the observer is greater than others. In this paper

we consider the space composed by the sensor

the target pixel

and environmental pixel and use geometric relations to describe the single scattering of diffuse reflection from the environmental one toward the sensor

in order to get a first-order aproximation of the atmospheric PSF for off-nadir observation. Our approximation is compared with Monte Carlo simulation results. Then we design a Wiener filter to remove the adjacency effect on ASAS images. The correction results are evaluated by visual evaluation of image quality and the analysis of spatial correlation between pixels in the original

corrected offnadir and nadir images.