=================================================
     "Evolution of Ephemerides Representation and Diffusion"


                        P. K. Seidelmann
                     U. S. Naval Observatory

Abstract

     There has been, and continues to be, a close interaction between 
celestial mechanics used for the generation of ephemerides, mathematical 
techniques, and computer technology.  As the
computer capabilities of the ephemerides offices and the users of ephemerides 
have improved, the methods of determining and the accuracies of ephemerides 
have changed and the medium and representation of the ephemerides provided 
to the user have evolved.
     Ephemerides have been provided in the form of theories, tables, 
tabulations, polynomials, graphics and subroutines by means of the printed 
page, punched cards, magnetic tape, floppy disks, CD/ROMs and electronic
mail.  As mathematical techniques and computer technology
continue to develop and the requirements for ephemerides evolve,
the methods of representing and diffusing ephemerides will continue to improve.