Solar zenith angles larger than 70 degrees

[rese_support]

I recently have some RapidEye images obtained in winter and the solar zenith angles are larger than 70 degrees. I tried to set the solar zenith angle to 70, but channel blue, red and green show very high percentages of pixels with reflectance less/equal zero (more than 20%). Is it possible to keep the original solar zenith angles from RapidEye images for processing (ATCOR 2 without DEM)? 

I'm sorry, but there is no way to get meaningful results out of imagery with such large solar zenith angles using ATCOR. BRDF effects and self shadowing will lead to large errors in the results. That's why we decided to set the limit to the zenith angle at 70 degrees. You would need to go with an empirical correction approach (empirical line normalization) for this kind of data then.