(a) 68 projected and co-added images of Neptune’s equatorial plane, revealing material along the arcs Fraternité and Égalité, as well as the satellites Proteus (P) and Galatea (G). The frame is 7.1 × 10.7 arcsec² wide. (b) Equivalent width of the arcs (Fraternité and Égalité) vs. longitude extracted from Fig. 3b, at an angular resolution of 2°. The X-axis origin is the longitude L_Fr of the centre of the Fraternité arc measured from the J2000.0 ascending node, where L_Fr = 217.43 deg, at the reference epoch (see Table 1).