Families of QS and HS orbits in the 2D-CRTBP presented on the (x_d, e_d) plane, where x_d is the position of the periodic orbit (dust particle) in the rotating frame of reference for µ = 2.1186 × 10⁻¹¹. Families denoted by I correspond to family ƒ, which consists of QS orbits, namely stable (blue) symmetric periodic orbits with ∆ϖ = 180°, and II denotes the family of HS orbits, i.e. unstable (red) symmetric periodic orbits with ∆ϖ = 0°. Primed (or unprimed) symbols indicate the direction (positive or negative crossing) of the orbit on the Poincaré surface of section at y_d = 0 and ${\dot{y}}_{\text{d}}>0$ (or ${\dot{y}}_{\text{d}}<0$), since the two branches of each family are equivalent (see also Table 1). The magenta and green dots correspond to the vcos, and the solid (dashed) lines demonstrate the vertical stability (instability).