THE ASTEROID EPHEMERIDES PROGRAM AT THE US NAVAL OBSERVATORY

The U.S. Naval Observatory has begun a program of ephemeris improvemen t and reference frame determination from the main belt asteroids. The program is, currently, starting out with a limited set of observations of the larger asteroids to determine the equator and equinox correcti ons for the USNO W1J00 transit circle observations catalog, and, if po ssible, improve the orbits of these asteroids based on this limited se t of observations. For this project, transit circle observations of th e Sun and the planets Mercury through Jupiter, are also being used to determine the equator, equinox, and ephemeris corrections. the next go al is to improve the orbits of the larger asteroids in the optical ref erence frame using observation series that cover a much longer period of time. This will allow the exploration of the differences between th e dynamical reference frame based on radar observations of main belt a steroids and its relation with the optical reference frame. Other goal s include the exploration of the mass distribution in the main asteroi d belt from high precision observations, and the effect of this mass o n the ephemerides of the major planets.