Program: GN-2005B-Q-34

We propose to use the high angular resolution provided by NIRI/ALTAIR to follow-up the orbits of binary main-belt systems already discovered (22 Kalliope, 45 Eugenia, 87 Sylvia, 90 Antiope, 103 Camilla, 283 Emma) and better constrain their orbital elements. Determination of the precise orbital elements of the secondary can be done by multiple observations spanning large periods of time (on several years). Our group developed a new method to separate the geometrical orbit determination from the dynamical one including secular variations of the orbital plane and the pericenter. Without any assumptions, this method led to the determination of the main orbital elements (a, P, e, i) of these binary systems (see Marchis et al., 2003, 2004, 2005). Additional observations will allow to detect unambiguously the precession of their orbit and constrain the distribution of mass in their interior (density, mass, porosity) giving direct insights on their formation processes.