Article

UNCERTAINTIES IN THE JPL PLANETARY EPHEMERIS

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Abstract

The numerically integrated planetary ephemerides by JPL, IMCCE, and IPA are largely based on the same observation set and dynamical models. The differences between ephemerides are expected to be consistent within uncertainties. Uncertainties in the orbits of the major planets and the dwarf planet Pluto based on recent analysis at JPL are described.

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... Without new observations, DE421 accuracy rapidly decreases. According to Folkner (2010), Mars ephemeris uncertainty declines to about 10 km by the end of 2015, and ephemeris uncertainties of other planets (except the Earth) are even larger by then. ...
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Poster
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Chapter
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The planetary ephemeris is an essential tool for interplanetary spacecraft navigation, studies of solar system dynamics (including, for example, barycenter corrections for pulsar timing ephemeredes), the prediction of occultations, and tests of general relativity. We are carrying out a series of astrometric VLBI observations of the Cassini spacecraft currently in orbit around Saturn, using the Very Long Baseline Array (VLBA). These observations provide positions for the center of mass of Saturn in the International Celestial Reference Frame (ICRF) with accuracies ~0.3 milli-arcsecond (1.5 nrad), or about 2 km at the average distance of Saturn. This paper reports results from eight observing epochs between 2006 October and 2009 April. These data are combined with two VLBA observations by other investigators in 2004 and a Cassini-based gravitational deflection measurement by Fomalont et al. in 2009 to constrain a new ephemeris (DE 422). The DE 422 post-fit residuals for Saturn with respect to the VLBA data are generally 0.2 mas, but additional observations are needed to improve the positions of all of our phase reference sources to this level. Over time we expect to be able to improve the accuracy of all three coordinates in the Saturn ephemeris (latitude, longitude, and range) by a factor of at least three. This will represent a significant improvement not just in the Saturn ephemeris but also in the link between the inner and outer solar system ephemeredes and in the link to the inertial ICRF. Comment: Accepted for publication in the Astronomical Journal
California Institute of Technology. 1.0 0.0
  • P R Peabody
  • J F Scott
  • E G Orozco
Peabody, P. R., Scott, J. F., and Orozco, E. G., 1964, "JPL Ephemeris Tapes E9510, E9511, and E9512", Technical Memorandum 33-167, Jet Propulsion Laboratory, California Institute of Technology. 1.0 0.0 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050 0 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050 1960 1970 1980 1990 2000 2020 2040 1950 2010 2030 2050