The figure and dynamical parameters of Io inferred from internal structuremodels

The recent Galileo spacecraft explored Jupiter and its satellite system and provided us with new geodetic data. In order to discuss the dynamical para meters and secular tidal effect of Io, the theory of synchronous satellite is described in detail. Using the new geodetic data of Io, two sets of Io's internal structure models are constructed based on the asthenosphere assum ption. The liberation parameters alpha, beta, gamma and dynamical flattenin g H are calculated for the models of Io. A comparison of Io with the Moon i ndicates that they are quite different in many characteristics in spite of the fact that they axe approximately equal in mass and size and that they b oth orbit synchronously.