Fig 2.3.2.1: Plane parallel, no refraction, with extinctions at various altitudes

Image: AT2-ELS

The intensity measured at the top of the atmosphere consists of

• light reflected from the surface;
• light scattered in the atmosphere from different altitudes.

For each altitude we have to consider

• the extinction on the downward path from the top of atmosphere;
• the scattering probability;
• ths extinction on the way back to the top of atmosphere.