7527 20250204105339.0 CTALK-2025-0064 Ivantsov, Anatoliy Astrometric bias due to overlapping image profiles in the focal plane and its removal in the positions of near-Earth asteroids 2022 2022-08-04 Both astrometric and photometric data of high accuracy provided by the Gaia catalog, its completeness to 21 mag allow evaluating the closeness of past astrometric positions of asteroids to the stars in the focal plane. In case the corresponding image profiles are overlapping, there is a photocenter bias shifting the positions measured towards each other. By correlating astrometric measurements of near-Earth asteroids collected at the IAU Minor Planet Center with the Gaia EDR3 catalog we identified 460,149 asteroid positions as of November 15, 2021, that had been measured within 9'' to stellar images, and thus, are likely affected by the photocenter bias to a varying degree. Assuming image FWHM constant for each observatory all year round, we have fitted the differences (O−C) in astrometric measurements of near-Earth asteroids. After doing that we recalculated the bias values and demonstrate the corresponding statistics. The identified measurements can be further rejected or down-weighted in the orbital fitting process for improving the overall orbital propagation. We emphasize the need of supplying the image FWHM each time the astronomers are submitting their astrometric measurements to the IAU Minor Plane Center. NO near-Earth asteroids asteroids photocenter bias ephemerides orbital fitting Eggl, Siegfried Hestroffer, Daniel XXXI IAU General Assembly Focus Meeting 10 Synergy of Small Telescopes, and Large Surveys for Solar System & Exoplanetary Bodies Research, Busan, Republic of Korea anatoliy.ivantsov@ksb-orb.be https://www.iauga2022.org 2848959 http://publi2-as.oma.be/record/7527/files/iaufm10_ivantsov_slides.pdf 10358 http://publi2-as.oma.be/record/7527/files/iaufm10_ivantsov_slides.gif?subformat=icon icon 13739 http://publi2-as.oma.be/record/7527/files/iaufm10_ivantsov_slides.jpg?subformat=icon-180 icon-180 Contributed CTALKCONT