ROSINA COPS neutral density measurements for August 23 2014 are shown in black for two cometary rotations together with associated illumination conditions on the nucleus. Color coded on the nucleus is the cosine of the solar zenith angle θ for different time instances as seen from the s/c. For cases with a large total illuminated area and visible surface area of the nucleus the COPS data peaks, which lead to the fundamental assumption of the correlation between insolation and gas production rate. Narrow shaped features and gaps in the data are not of cometary origin and discussed in Sect. 2.4.