Barycentric and heliocentric velocity and position of the Earth. All arguments are double precision.
date double TDB (loosely ET) as a Modified Julian Date (JD-2400000.5) deqx double Julian epoch (e.g. 2000.0) of mean equator and equinox of the vectors returned. If deqx <= 0.0, all vectors are referred to the mean equator and equinox (FK5) of epoch date.
dvb,dpb double barycentric velocity, position dvh,dph double heliocentric velocity, position (Units are AU/s for velocity and AU for position)
The maximum deviations from the JPL DE96 ephemeris are as
barycentric velocity 42 cm/s barycentric position 0.000 046 AU heliocentric velocity 42 cm/s heliocentric position 0.000 011 AU This routine is adapted from the BARVEL and BARCOR Fortran subroutines of P.Stumpff, which are described in Astron. Astrophys. Suppl. Ser. 41, 1-8 (1980). The present routine uses double precision throughout; most of the other changes are essentially cosmetic and do not affect the results. However, some adjustments have been made so as to give results that refer to the new (IAU 1976 "FK5") equinox and precession, although the differences these changes make relative to the results from Stumpff's original "FK4" version are smaller than the inherent accuracy of the algorithm. One minor shortcoming in the original routines that has not been corrected is that better numerical accuracy could be achieved if the various polynomial evaluations were nested. Note also that one of Stumpff's precession constants differs by 0.001 arcsec from the value given in the Explanatory Supplement to the A.E. Defined in slamac.h: D2PI, DS2R P.T.Wallace Starlink 22 December 1993