Time variation of the x and y shift parameters computed in the SPICE SPROUTs observations. Upper panel: Shifts for the C III 977 Å line. Lower panel: Same, but for the relatively dim O II 718 Å line in the shortwave detector. The shifts show large changes near perihelia passages and return to a consistent background level (outside of the first ∼2 years) when the spacecraft is more distant from the Sun. The scatter in the shifts is a rough indicator of the level of uncertainty in the observations. The shifts differ between the spectral lines, indicating a wavelength or detector-position dependence in the amount of shift, although some of the difference could be due to lower S/N in the O II line. The vertical green lines show the SolO perihelia times.