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|JEphem Ephemeris trail VSOP87|
VSOP87 is a planetary theory built by P. Bretagnon and G. Francou in the Bureau des Longitudes. With this theory, they produced data files, which have been used in JEphem to compute the coordinates of the planets, from Mercury to Neptune.
This work is presented in Astronomy and Astrophysics, n°202, pp309-315 (1988).
The original files can be found at ftp://ftp.bdl.fr/pub/ephem/planets/vsop87.
The VSOP87 files contain the VSOP87 analytical solutions of the motion of the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Earth-Moon Barycenter. There are six different versions of the theory VSOP87 which may be recognized by the type of coordinates and the reference frame. The main version VSOP87 consists of the series in elliptic elements as in the case of previous solution VSOP82 and the other versions VSOP87 are built in rectangular variables (versions A,C,E) or spherical variables (versions B,D). (...) TIME SCALE ========== The time used in VSOP87 theory is dynamical time. We can considered this time equal to Terrestrial Time (TT) which is measured by international atomic time TAI. So, the time argument in VSOP87 theory is equal to TAI + 32.184 s. REFERENCE SYSTEM ================ The coordinates of the main version VSOP87 and of the versions A, B, and E are given in the inertial frame defined by the dynamical equinox and ecliptic J2000 (JD2451545.0). The coordinates of the versions C and D are given in the frame defined by the mean equinox and ecliptic of the date. This frame is deduced from the previous one by precessional moving between J2000 and the epoch of the date.
PRECISION ========= The main version of VSOP87 is similar to the previous theory VSOP82. In the both cases the constants of integration have been determined by fitting to the numerical integration DE200 of the Jet Propulsion Laboratory.More detailed informations can be found in the A&A article ; in p. 311 of this document, they give the time spans for which a precision of 1" is ensured :
|Precision (arc second)||0.001||0.006||0.005||0.023||0.020||0.100||0.016||0.030|
getPrecision(int whichBody, double jd)of class