Trajectory Determination for Coronal Ejecta Observed by WISPR/ Parker Solar Probe

The Wide-field Imager for Solar Probe (WISPR) onboard the Parker Solar Probe (PSP), observing in white light, has a fixed angular field of view, extending from 13.5∘ to 108∘ from the Sun and approximately 50∘ in the transverse direction. Because of the highly elliptical orbit of PSP, the physical extent of the imaged coronal region varies directly as the distance from the Sun, requiring new techniques for analysis of the motions of observed density features. Here, we present a technique for determining the 3D trajectory of CMEs and other coronal ejecta moving radially at a constant velocity by first tracking the motion in a sequence of images and then applying a curve-fitting procedure to determine the trajectory parameters (distance vs. time, velocity, longitude, and latitude). To validate the technique, we have determined the trajectory of two CMEs observed by WISPR that were also observed by another white-light imager, either the Solar and Heliophysics Observatory (SOHO) / Large Angle and Spectrometric COronagraph (LASCO)-C3 or the Solar Terrestrial Relations Observatory (STEREO)-A/HI1. The second viewpoint was used to verify the trajectory results from this new technique and help determine its uncertainty.