EPSC Abstracts Vol. 15, EPSC2021-227, 2021 https://doi.org/10.5194/epsc2021-227 Europlanet Science Congress 2021 © Author(s) 2022. This work is distributed under the Creative Commons Attribution 4.0 License. Dynamical characterisation of small asteroid family members by an occultation astrometry survey Luana Liberato 1,2 , Paolo Tanga 1 , Rodrigo Leiva 1,3 , and Federica Spoto 4 1 Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France 2 Grupo de Dinâmica Orbital e Planetologia, UNESP – São Paulo State University, CEP 12516-410, Guaratinguetá, SP, Brazil 3 Departamento de Astronomía, Universidad de Chile, Camino del Observatorio 1515, Las Condes, Santiago, Chile 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 15, Cambridge, MA 02138, USA Up to now, we know that there are more than 100 asteroid families in the main asteroid belt with over 130000 objects as members[1]. These families are created from impact(s)on a (parent) asteroid, which generates countless fragments with approximately the same initial orbit. The study of the asteroid families can provide information on the events that originated the family, the dynamical evolution of their members, and the evolution of other bodies in the main asteroid belt. The classification and age estimation of these families is a massive work that requires the knowledge of many physical properties of their members, such as the albedo, diameter, mass, and the determining parameter, the Yarkovsky drift[2]. The Yarkovsky effect is an important parameter that can be used as a clock to the family age estimation, and also to derive asteroid density. The lack of data, mainly the Yarkovsky drift, makes it hard to obtain unbiased estimates of the ages of the families, especially for those with a small number of members[3]. As the ground-based direct imaging astrometry accuracy deteriorates considerably with the asteroid’s distance. Hence, the Yarkovsky drift used to calibrate the ages of asteroid families in the main belt comes from measurements on Near-Earth Asteroids[4]. These are better obtained since the NEAs usually have accurate orbits, which is crucial for Yarkovsky drift measurements. Therefore, to obtain the drift rate we need very precise astrometric measurements from the asteroids, currently provided in the Gaia DR2 catalogue for about 14000 asteroids [5]. But to increase the sample, we take advantage of the stellar occultation technique, which consists of observing the exact time of the event where an object passes in front of a star and block its light for a brief moment. That is a powerful observation technique that can provide high accuracy astrometric measurements, reaching uncertainties on the order of a few milliarcseconds, without the need for significantly large telescopes and special equipment. That level of precision is only possible thanks to the Gaia mission because having a precise position of the stars decreases the uncertainty in the astrometry for other bodies. GaiaDR3, planned for next spring (See Paolo Tanga’s presentation), will considerably improve the amount of epoch astrometry of asteroids already available in Gaia DR2, by a factor of10. Using Gaia data and stellar occultation technique, we can obtain direct high accuracy astrometry and measure the size, position, shape and even the presence of a companion or a ring around the occulting body. If the uncertainty in the astrometry is small enough, we can measure the Yarkovsky drift on the asteroid.