Abstract

Long-term astronomical survey programmes conducted from space (Gaia) and from the ground (KMTnet) provide invaluable data for the study of Small Solar System Bodies. These surveys deliver extensive observational datasets for hundreds of thousands of objects, enabling detailed modelling of their physical and dynamical properties, as well as comprehensive statistical analyses. Such studies are essential for understanding the formation and subsequent evolution of the Solar System.

The project focuses on specific categories of objects, notably binary asteroids and tumblers. The combination of photometric and astrometric data collected over periods of up to ten years allows robust constraints to be placed on asteroid shapes, spin states and orbital parameters. Our established French–Korean collaboration benefits from the synergy between space-based Gaia observations and ground-based KMTnet data, as well as from complementary expertise in photometry and astrometry. Initiated in 2020, the collaboration now aims to be strengthened through the involvement of PhDs, and the development of a broader international research network with experts colleagues on light-curve inversion. The workshop also lays the groundwork for the exploitation of forthcoming LSST data.

Scientific justification

Long-term astronomical survey programmes from space (Gaia) and from ground (KMTnet), provide valuable harvest for the science of Small Solar System Bodies (SSSBs). Indeed, they yield large data sets of observations for several 400,000 bodies, enabling to perform detailed modelling of physical and dynamical parameters, and a comprehensive statistical analysis. These are needed to understand our Solar System’s formation, and its subsequent evolution.

The goal of our project is to investigate very specific categories of objects, such as binaries (an asteroid with a moon) and tumblers (non-principal axis rotator). Of particular interest to us, the combination of the large amount of photometric and astrometric data acquired over up to 10years, helps modelling the asteroids shape/spin state and orbits, yielding important physical and dynamical parameters. As we have seen from preliminary analysis, our collaborative French+Korean project benefits from the synergy between Gaia (space-based) and KMTnet (ground-based) sparse and dense observations, and the complementarity of our respective expertise on photometry and astrometry, and will also be a basis for the future LSST data to come (yielding again 10 years long-term survey astrometric and photometric observations of a huge numbers of small bodies).

The team members are strongly involved in the Gaia European space mission (France), and in the KMTnet Korean network (Korea), and PIs within LSST/SSSC (both Korea and France). The collaboration initiated in 2020, which suffered from the COVID pandemia, has shown the potential of our data set and our analysis approach ; it has been presented to the IAU-GA (Lee, H-J et al. 2024, contrib. to Focus Meeting « FM3 Follow-up observations of small bodies in the Solar System in the era of large discovery surveys »). Moreover, our previous collaboration helped to better define the targets of interest, and getting prepared for Gaia DR4 and LSST data to come in 2026. We want to strengthen the collaboration by including PhDs, and preparing for a research network. Both teams have additional collaboration with colleagues in PL and CZ, experts in physical modelling (spin, shape, size) of small bodies from light-curves and sparse photometric data.

The French team at Paris observatory has been involved in ESA’s Gaia space mission since 2000, mostly in direct observations with the space telescope aiming at studies of Solar System Objects (SSOs), especially for asteroids and small bodies. They have directly contributed to the Gaia data validation and releases. Moreover, the team has international expertise in dynamical modeling and orbit computation with astrometric data. They have developed the DynAstVO database for NEOs, available at Paris observatory Data Centre and Europlanet server in open data.

The Korean team at KASI has been operating the Korea Microlensing Telescope Network (KMTNet network) of three ground-based telescopes with 1.6m aperture , all located in the Southern hemisphere (Australia, South Africa, South America). There is no equivalent facility with such observing programme available in PSL or in Europe. Indeed, the ideal location in longitude and size of the telescopes, with garanteed time, ensure long-term observations of high quality of our SSO targets. KASI team has conducted observational studies of small solar system bodies, including Near-Earth asteroids (within Space Situational Awareness program). They have expertise in lightcurve analysis and three-dimensional shape modeling of asteroids, and dynamical studies of airless bodies.

Preliminary program

Sessions
1. Gaia mission, observations, content and data releases
2. KMTnet survey and observations of Solar System Objects
3. Photometric observations campaigns
4. Modeling of asteroids from photometric and astrometric data
5. Tumbling asteroids from long-term surveys
6. VRT/LSST and future observing programmes/surveys
7. General discussions