As Voyager 1 made its swing-by of Io, it passed through and behind the satellite's plamsa torus. The phase paths of the coherent 13 cm and 3.6-cm wavelength signals transmitted from the spacecraft were shortened differentially by the plasma, resulting in the observation of a dispersive Doppler signature in the signals received at the NASA/Jet Propulsion Laboratory (JPL) deep space network (DSN) stations. Ray path integration through three different models of the electron distribution of the torus of Io (Warwick et al. 1979; Birmingham et al., this issue; Bagental et al., this issue) have performed. The results of the integrations are compared with the dispersive doppler data.