The Ephemerides: Past, Present and Future

Abstract

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 publi cations, which were based on a multitude of theories, there has developed a continually improving agreement on accurate astronomical constants, planetary, lunar and satellite theo ries and cooperative methods of printing the annual ephemeri des in different languages. This trend is continuing, cur rently, 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 198l, and the expected introduction in 198V of new fundamental planetary and lunar ephemeri des based on the new constants and on the FK5. Currently the differences between the printed ephemerides and observa tions sytematically exceed 2" for Mars at some times and 67 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 print ed accuracy, INTRODUCTIONFrom earl.iest times man has been interested in the Sun, Moon, planets and stars and in determining their positions, Particularly, there has been an interest in being able to predict the positions of the solar system bodies and interest ing phenomena, such as eclipses, planetary groupings and directions, and the times of rising and setting.The results of these interests were numerous mathemati cal, or analog, approaches to the calculations, observations 99 R. L. Buncombe fed.), Dynamics of the Solar System, 99-114.