Illustration of the Doppler velocity lobes caused by SPICE PSF artifacts during a co-observing campaign between IRIS and SPICE. The SPICE data show a characteristic redshift and blueshift pattern (examples circled) around bright intensity features – compare the top left panel (IRIS) with the top right panel (SPICE), both observing the same location. This pattern similarly appears in IRIS (not shown) when the PSF from Figure 1 is applied to IRIS (not shown) and (largely) disappears when the PSF regularization method described in Plowman et al. (2023) is applied. This is strong evidence that the Doppler velocity lobes are caused by the PSF tilt out of λ and into y.