Left: time evolution of estimated TEVs from the two water transitions; the blue points indicate HO and the red points indicate HO; each point represents a daily mean and the error bars indicate the corresponding standard deviation. The solid red and blue lines denote 30 d running averages. The spacecraft cometo-centric distance is shown in the same panel as the magenta line. Right: daily averaged difference and its standard deviation shown as vertical lines for collocated data points as a function of time. The point clouds of different colors correspond to a different month (August 13, 2015 was the perihelion passage). There is a definite TEV dependence on the heliocentric distance, where the velocities obtained from HO transitions tend to be larger starting from around May 2015, peaking in August–September 2015, and decreasing again afterward. The maximum differences are on the order of 0.15–0.2 km s⁻¹. See Sect. 4.5 for discussion.