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Fundamental Arguments of the Current Nutation Theory: Dynamical Reference Frame

Published online by Cambridge University Press:  14 August 2015

E.M. Standish
E.M. Standish*
Affiliation:
Caltech/JPL JPL 301-150; Pasadena, CA 91109 USA [email protected]

Extract

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The latest JPL planetary and lunar ephemerides, DE405, are now referenced to the ICRF with an accuracy of about 1 mas. This has been accomplished mainly by fitting the ephemerides to 18 VLBI observations of the Magellan Spacecraft in orbit around Venus, 1990-1994, and to 2 VLBI observations of the Phobos Spacecraft in its approach to Mars, 1989. The orientation of DE405 is discussed in more detail elsewhere in this volume (Standish, 1997). Since all of the parameters of the inner solar system are now determined to 1 mas or better, one should be able to extract numerically the fundamental arguments of the nutation theories to the level of 1 mas.

There are two ways of extracting the ecliptic, for example, from a numerical ephemeris: 1) one computes the node and obliquity of the instantaneous ecliptic at multiple points in time and then fits these with analytic functions, or 2) one fits an analytical planetary theory to the ephemerides and then computes the node and obliquity from the theory’s parameters. This paper relates a short example using method #1 and concludes that method #2 is probably more preferable.

Type
II. Joint Discussions
Information
Highlights of Astronomy , Volume 11 , Issue 1: Highlights of Astronomy. As presented at the XXIIIrd General Assembly of the IAU (Part A), 1997 , 1998 , pp. 168
Copyright
Copyright © Kluwer 1998

References

Standish, E.M. (1981) Two Differing Definitions of the Dynamical Equinox and the Mean Obliquity. Astron Astrophys., 101, L17–18.Google Scholar
Standish, E.M. (1982) Orientation of the JPL Ephemerides, DE200/LE200, to the Dynamical Equinox of J2000. Astron. Astrophys., 114, pp. 297–302.Google Scholar
Standish, E.M. (1997) Linking the dynamical reference frame to the ICRF. elsewhere in this volume.Google Scholar