  Starting from several monthly data sets of Rosetta's COmetary Pressure Sensor
we reconstruct the gas density in the coma around comet
67P/Churyumov-Gerasimenko. The underlying inverse gas model is constructed by
fitting ten thousands of measurements to thousands of potential gas sources
distributed across the entire nucleus surface. The ensuing self-consistent
solution for the entire coma density and surface activity reproduces the
temporal and spatial variations seen in the data for monthly periods with
Pearson correlation coefficients of 0.93 and higher. For different seasonal
illumination conditions before and after perihelion we observe a systematic
shift of gas sources on the nucleus.
