High-precision Astrometric Positioning of Near-Earth Asteroids—via the Close Approach Method

Abstract High-precision astrometry of near-Earth asteroids (NEAs) is critical for orbit determination and impact risk assessment, yet it remains challenging due to their rapid apparent motion and short-range systematic errors. In this work, we apply the close approach astrometric technique to eight events involving NEAs Camillo and 2017 VR12, observed using the 1 m telescope at Yunnan Observatory. By modeling the squared relative angular distance between the NEA and Gaia-catalog reference stars, we derive the epoch of minimum separation and the impact parameter. Our results show that the close approach method significantly mitigates common-mode atmospheric turbulence and instrumental distortions. For Camillo, we achieve a post-fit residual precision of approximately 4–7 mas, indicating a substantially smaller internal scatter than conventional astrometry obtained under similar observing conditions. These results demonstrate that the close approach technique can provide milliarcsecond-level relative astrometry for NEAs under favorable observing conditions, while also highlighting the limitations imposed by extreme apparent motion and image trailing in very fast-moving targets.