Titan's forced rotation : a 3-degree of freedom theory

We present a 3-degree of freedom theory of Titan's forced rotation, as a rigid body. Such a study is possible thanks to the Cassini data of the gravitational potential of Titan. We use a semi-analytical model based on the recent analytical works of Henrard & Schwanen (2004), on a numerical integration and on an identification of the arguments as an integer combination of the fundamental ones. Titan's orbital motion is modelized with TASS theory (Vienne and Duriez, 1995). We find that the equilibrium obliquity is nearly zero, and that the fundamental periods of the free librations around the equilibrium are respectively 2.1, 167 and 306 years. Moreover, we enlight the influence of a 703-years period present in Titan's inclination, on its obliquity.