Hi everyone,

I have been using libRadtran (an open-source radiative transfer model) and there is something I don't quite understand in the geometry specifications of the radiative calculations.

The user can specify the solar zenith angle (sza) and the cosine of the satellite viewing angle (umu). So far, so good.

The question I have is why are the two not symmetric when calculating radiance or transmittance? Meaning, if the sun zenith is 0° and satellite viewing angle 60°, why are the results different from when the sun zenith is 60° and the satellite viewing angle 0°? What am I missing here?

Thanks in advance!