Mount Pleasant observations of the Vela pulsar between 1981 and 2005. (a) The evolution of the spin frequency ν. (b) Frequency residuals relative to a linear model for the 700 d of data before the second glitch (MJD 46257). (c) The evolution of the spin-down rate . Both ν and were obtained from fits of a simple slow-down model to TOAs in a moving window covering 20 days, and moving by 5 d each stride. (d) Daily DM measurements. The solid line is the DM model we use for the data obtained in the 1980s. The segmented line is an extrapolation backward from a DM model adjusted to data after MJD 54 000.