Coronal mass ejections observed by heliospheric imagers at 0.2 and 1 au

Context. We study two coronal mass ejections (CMEs) observed between April 1 to 2, 2019 by both the inner Wide-Field Imager for Parker Solar Probe (WISPR-I) onboard (PSP) spacecraft (located about 46 and 38 solar radii during this period) heliospheric imager (HI-1) Terrestrial Relations Observatory Ahead (STEREO-A) spacecraft, orbiting Sun at 0.96 au. This is first of CME observations from viewpoints in similar directions but considerably different distances. Aims. Our objective derive kinematics WISPR-I compare them with results HI-1. allows us understand how PSP affect kinematics, especially due its proximity Sun. Methods. estimated positions, speeds, accelerations, propagation directions, longitudinal deflections using imaging spacecrafts a set analytical expressions that consider as point structure take rapid change position into account. derived each viewpoint independently constraint. Results. found CMEs are slow (<400 km s ?1 ), propagating eastward Sun-Earth line (westward STEREO-A). The second seems accelerate ~0.1 ~0.2 au deflect westward an angular speed consistent rotation speed. some discrepancies distance (up 0.05 au, particularly #1), latitude ~10°), longitude 24°) when comparing fit cases (different or free parameters). Conclusions. Discrepancies likely feature tracked visually, rather than instrumental biases assumptions. For reasons, #1 distance, observations, larger HI-1 result, regardless parameters considered. Error estimates do not show any clear trend associated observing instrument. source region location lack situ counterparts (both near-Earth PSP) support our estimate direction events.