Bureau des Longitudes, Paris, France
jchapron@bdl.fr
A new method of approximation for time series over a long range has been developped and applied to ephemerides of the solar system. Using as a source the result of a numerical integration, a frequency analysis is made and a fit with Poisson series is realized to approximate the source over a long time interval (several tens of periods of the body concerned). The method has been applied in two cases: planetary and natural satellite ephemerides. For planetary motions we have chosen as a source JPL ephemerides. Under a compact form, heliocentric rectangular coordinates are represented. An easy handable software is then elaborated upon the basis of this approximation. A program (PLANEPH) computes planetary ephemerides between 1900 and 2099 in different coordinate systems and provides most of the data existing in published ephemerides. The method has been applied also to the faint satellites of Jupiter. A numerical integration of the satellite motions has been performed and the ephemeris fitted to observations. A compact approximation has been built by frequency analysis. A complete software provides astrometric coordinates of J6, J7, J8 and J9. Collected observations and softwares are available via ftp.