VDA based on onset times of Solar Orbiter EPT and HET electron channels. The horizontal axis shows the inverse of the average unit-less speed of electrons as observed in each channel. The vertical axis presents the determined onset time for each energy channel. Onset times observed by EPT (HET) are marked in blue (red). Horizontal error bars represent the width of the energy channels, and vertical error bars represent the time resolution used to determine the onsets (30 s). The orange and green lines are linear fits to the lowest 10 and 18 energy channels of EPT, respectively. The grey lines represent the slope corresponding to a path length matching the nominal Parker spiral length at Solar Orbiter’s radial distance.