=========================== ============================ IMCCE - Observatoire de Paris EARTH POSITION AND VELOCITY January 1998 =========================== ============================ Description: The routine EPV allows to compute the rectangular coordinates of the Earth, position and velocity, with respect to the Sun and to the barycenter of the solar system and referred to the J2000 mean equator and equinox. We use a simplified solution from planetary theory VSOP87 (P. Bretagnon and G. Francou, 1988, A&A, 202, 309). The fortran code is an adaptation made by P.T. Wallace (Rutherford Appleton Laboratory, UK) for the SOFA project. This routine can be used for the calculation of the apparent places of the stars, over the time span 1900-2100, with an accuracy always better than 420 km for the heliocentric positions and 0.05 m/s for the heliocentric velocities. In case of the barycentric coordinates, the comparisons with VSOP87 give difference always smaller than 420 km for the positions and 0.05 m/s for the velovities over the same time span 1900-2100. The comparisons with the JPL ephemerides DE200, DE403 and DE405 give more important differences, owing to the different planetary masses system used in these solutions. Positions 1900-2100 Velocities 1900-2100 EPV-DE200 < 878 km EPV-DE200 < 0.046 m/s EPV-DE403 < 1569 km EPV-DE200 < 0.046 m/s EPV-DE405 < 1572 km EPV-DE200 < 0.045 m/s Authors' Address: P. Bretagnon, G. Francou IMCCE - Observatoire de Paris 77, Avenue Denfert-Rochereau 75014, Paris, France Tel : (33) 1 40 51 22 69 (33) 1 40 51 22 60 Fax : (33) 1 46 33 28 34 E-mail : pierre@imcce.fr francou@imcce.fr Contents: With the Fortran 77 routine EPV (file epv.f), we give example programs which allows to compute the positions and velocities of the Earth with respect to the Sun and to the barycenter of the solar system. The program EPVEQ gives the coordinates referred to the mean equator and equinox J2000 (files epveq.f and epveq.r). The program EPVEC gives the coordinates referred to the dynamical ecliptic and equinox J2000 of VSOP87 theory (files epveq.f and epveq.r) with the obliquity 23d 26' 21.409". File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- README 80 . This file epv.f 80 916 Fortran77 routine EPV. Earth position and velocity. Heliocentric and barycentric coordinates. Mean equator and equinox J2000. epveq.f 80 987 Fortran77 program example of use of EPV for the equatorial coordinates J2000. epveq.r 80 168 Results of the program EPVEQ. epvec.f 80 1034 Fortran77 program example of use of EPV for the ecliptic coordinates J2000. epvec.r 80 168 Results of the program EPVEC. -------------------------------------------------------------------------------- ================================================================================ User feed-back is encouraged. Unless otherwise specified, send comments and bug reports to: E-mail : comments@imcce.fr Fax : (33) 1 46 33 28 34 Postal mail: IMCCE - Observatoire de Paris 77 avenue Denfert Rochereau F-75014 PARIS ================================================================================