Ionosphere of comet 67P during the Rosetta mission. From top to bottom panels: ionospheric TEC derived from RPC-MIP, observed electron density (N_e) along the Rosetta spacecraft trajectory, and heliocentric distance (r_h) of comet 67P (blue, scale on the left), and cometocentric distance (r_c) of Rosetta from 67P (red, scale on the right), respectively. Top two panels: the blue points show 320 s average data and red shows the corresponding daily averages (see Sect. 2).