Time evolution of the rotation state of Hyperion in scaled Andoyer actions (top row) and the 3:1 nutation-orbit resonant angle (bottom row) following four spacecraft flybys, each of which occur at t = 0. Solid lines show the result of the full rotation model ℋ, which includes nonaxisymmetry of Hyperion. The solution of the integrable one degree-oſ-ſreedom (i.e., non-chaotic) Hamiltonian ${\mathscr{H}}_3^1$ is shown in dashed lines, integrated from the same initial conditions. The actions L and Λ′ are conserved in ${\mathscr{H}}_3^1$.