Radial distance from the Sun centre of the CME front, obtained by the 3D reconstruction, as a function of time. The different symbols indicate the instruments that were used, as shown in the legend. The average speed for the whole period is obtained by a linear fit, which is indicated by the dashed line. The CME front acceleration is obtained by a quadratic fit, which is indicated by the dotted line (details are given in the main text). The error bar, corresponding to ±1 R_⊙ for all points, is shown only for the first data point to allow a better visual inspection of the fitting.