TheGMValues of Mimas and Tethys and the Libration of Methone

We have determined the GM of the Saturnian satellite Mimas from an analysis of its resonance with Tethys and with the newly discovered satellite Methone ( GM is the product of the Newtonian constant of gravitation G and the satellite's mass M ). Observations of the latter permit a factor of 5 improvement in our knowledge of Mimas's GM ; its value is 2.504 ± 0.002 km 3 s -2 . Tethys's GM was originally found from the Mimas-Tethys resonance. We, however, estimate it using observations of its two Lagrangian satellites, Calypso and Telesto; its value is 41.200 ± 0.007 km 3 s -2 .