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Manuscript Title: The ephemeris program GLE2000.
Authors: J. Schastok, H. Gleixner, M. Soffel, H. Ruder, M. Schneider
Program title: GLE2000
Catalogue identifier: ABHM_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 54(1989)167
Programming language: Fortran.
Keywords: Ephemerides, Post-newtonian Equations of motion, Gravitational Interaction of Extended bodies, Numerical integration Of second order Differential equations, Seventh order Runge-kutta-nystrom Method, Astrophysics, Gravitational systems.
Classification: 1.5.

Nature of problem:
Within the framework of General Relativity (post - Newtonian approximation) the equations of motion for the pointmasses of the Planets, Earth, Moon and Sun are solved numerically. Considering Earth and Moon as extended bodies we add Newtonian accelerations due to figure effects. Initial conditions and constants are taken from the ephemerides DE118 created by the Jet Propulsion Laboratory (JPL).

Solution method:
To solve the coupled second order differential equations for translational and rotational motion we use a seventh order Runge - Kutta - Nystrom method developed by Fehlberg. This method has proved to be rather efficient to integrate velocity dependent accelerations.

Running time:
Given a requested relative accuracy for the planetary positions of 10**-18 after one step of integration (one day) about 6 seconds per step are needed on a BASF 7/88. Changing the requested accuracy by one order of magnitude typically changes the running time by a factor of two.