Tracking Near-Earth Asteroids’ close approaches: 2023 DZ2, 2018 UY, and 2024 ON by the Southern Hemisphere Asteroid Research Consortium

We present an overview of the capabilities of the Australian collaboration for observing and characterising Near Earth Asteroids, with a focus on its geographic expansion to the West Coast of Australia. The West Coast node, supported by the University of Western Australia, uses the Zadko Observatory, equipped with several optical telescopes dedicated to Space Situational Awareness and Planetary Defence. We report observations of three selected asteroids during close approaches in the past two years: 2023 DZ2, 2018 UY, and 2024 ON. For 2023 DZ2, we demonstrate that despite highly variable photometric conditions, it is possible to extract the asteroid’s rotational signatures. Our analysis yields a rotational period of 6.2770 $\pm$ 0.0450 min. The close approach of 2018 UY provided high-quality photometric data for a body with a previously unknown rotation, which we estimate to be 4.2759 $\pm$ 0.3037 h for half of its full rotation. Our analysis reveals a significant periodic magnitude variation of ($\Delta m\approx 1$), indicating that the asteroid is highly elongated. Assuming a triaxial ellipsoid model, we estimate an upper limit for its elongation to be approximately 2.5 times longer than it is wide. Lastly, 2024 ON, likely a contact binary system, was discovered by NASA’s ATLAS system at Mauna Loa, Hawaii, on July 27, 2024. We present high-quality photometric data, potentially confirming the binary nature of this system with an estimated half-rotation period of 2.9789  $\pm$  0.1363 h.