The Ephemerides: Past, Present and Future

Over the years there has been a continuing trend toward unification of both the annually printed volumes of ephemerides and the fundamental bases for the ephemerides. Thus, from many completely independent national and private publications, which were based on a multitude of theories, there has developed a continually improving agreement on accurate astronomical constants, planetary, lunar and satellite theories and cooperative methods of printing the annual ephemerides in different languages. This trend is continuing, currently, with the adoption of a new system of astronomical constants in 1976, consideration of revisions of nutation, the planned revision of the A.E. (American Ephemeris and Astronomical Ephemeris) for 1981, and the expected introduction in 1984 of new fundamental planetary and lunar ephemerides based on the new constants and on the FK5. Currently the differences between the printed ephemerides and observations sytematically exceed 2″ for Mars at some times and 6″. for Neptune at all times. It is anticipated that a new set of fundamental theories will be introduced which will be based on a consistent set of astronomical constants and in agreement with the available observational data to the printed accuracy.