Radial speed profiles in the solar equatorial plane for each model (polytropic, thermodynamic, and WTD) for each perihelion encounter 1-4. Superimposed are the corotating trajectories of the spacecraft during each encounter, expanded by 10 days on either side of the nominal encounter dates. The approximate location of the spacecraft at the time of PSP’s point of perihelion pass is indicated by the location of each spacecraft label.