Orbit Determination of Binary Asteroids

International audienceIn addition to the detection of an asteroid moon or a binary asteroid, the knowledge of the satellite's true orbit is of high importance to derive fundamental physical parameters of the binary system such as its mass and to shed light on its possible formation history and dynamical evolution (prograde/retrograde orbit, large/small eccentricity or inclination, etc.). A new methodology for preliminary orbit determination of binary asteroids and visual binaries in general is proposed. It is based on Thiele Innes method combined with a `trial and error' Monte-Carlo technique. This method provides the full set of solutions (bundle of orbits, with the 7 orbital elements) even for a reduced number of observations. The mass is a direct by-product of this orbit determination, from which one can next infer the bulk-density and porosity. In addition to the bundle of orbits, the method provides the marginal probability densities of the foreseen parameters. Such error analysis since it avoids linear approximation can be of importance for the prediction of the satellite's position in the plane-of-sky during future stellar occultations or subsequent observations, but also for the analysis of the orbit's secular evolution. After briefly describing the method, we present the algorithm and its application to some practical cases, with particular emphasis on asteroids binaries and applications on orbital evolution