Location and width of every first-order secular spin–orbit resonance reachable by Saturn over the migration of Titan, with amplitudes down to 10⁻⁸. Each resonant angle is of the form σ_j = ψ + ϕ_j where ϕ_j has frequency ν_j labelled on the graph according to its index in the orbital series (see Table 2). For a given value of Titan’s semi-major axis, the interval of obliquity enclosed by the separatrix is shown in pink. The centre of the resonance (i.e. Cassini state 2) with ϕ₃ is shown by a red line and the upper and lower separatrices are highlighted in blue. The ridge line a = r_F dividing the close-in and far-away satellite regimes is represented by a dashed blue line. The region E₁ where the satellite’s Laplace state P₁ is unstable isshown in black. The singular point S₁ is shown by a red dot.