Density maps of the VIR visible data set used in the study. Panel A: CSR mission phase; panel B: CTS; panel C: CSS; panel D: CSH; and panel E: regroups every four. For details about the mission phases, see Table 1 and Sect. 2.2. Each map is built with TOPCAT with a Plate Carée projection (see Sect. 2.4), and observations are represented as points. The scale corresponds to the square root of the observation density.