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Astron. Astrophys. 336, 381-384 (1998)

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Time scales in the JPL and CfA ephemerides

E.M. Standish

Caltech / Jet Propulsion Laboratory JPL 301-150; Pasadena, CA 91109, USA (ems@smyles.jpl.nasa.gov)

Received 24 March 1998 / Accepted 12 May 1998

Abstract

Over the past decades, the IAU has repeatedly attempted to correct its definition of the basic fundamental argument used in the ephemerides. Finally, they have defined a time system which is physically possible, according to the accepted standard theory of gravitation: TCB ("Barycentric Coordinate Time"). Ironically, this time scale is mathematically and physically equivalent to [FORMULA], the time scale that has been used by JPL and by MIT (the group later went to CfA) in their ephemeris creation processes since the 1960's. TCB differs from [FORMULA] by only a constant offset and a constant rate. As such, TCB provides an equivalent alternative to [FORMULA], but it does not allow increased accuracy as others have implied.

Key words: time – ephemerides

Send offprint requests to: E.M. Standish

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© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998
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