; de403_2000-2020.bsp LOG FILE ; ; Created 2004-10-05/08:59:52.00. ; ; BEGIN NIOSPK COMMANDS SPK_FILE = de403_2000-2020.bsp SOURCE_NIO_FILE = de403_2000-2020.nio BEGIN_TIME = CAL-ET 1999 DEC 24 00:00:00.000 END_TIME = CAL-ET 2021 JAN 02 00:00:00.000 ; END NIOSPK COMMANDS This de403.bsp file was made from a subset of the multi-century source de403, provided by Myles Standish in order to fill a Cassini long-term Earth avoidance study to be conducted by John Smith and Robert Maddock of JPL's Navigation and Flight Mechanics Section. DE403 is documented in JPL IOM 314.10-124 by Myles Standish, dated May 8, 1995. Accuracy ------- The JPL "DE" series of planetary ephemerides have been widely used throughout the astronomical community for over 20 years. They have been put to many different uses. A short list of the applications of these ephemerides includes: the construction of the tables in the "Astronomical Almanac" (for that matter all almanac producers world wide), planning of solar system observations with the Hubble Space Telescope, navigation of interplanetary missions, lunar laser ranging, solar system radar ranging, and solar system observations via VLBI. One method of describing the accuracy of the positions provided in DE403 is to consider the angles between various ephemeris objects as viewed from Earth. If the two objects observed are taken from the list (Sun, Mercury, Venus, Mars, Moon) the angles computed from the ephemeris positions are accurate to one or two milli-arcsecond.(This assumes all appropriate corrections are applied for light time, stellar aberration, and relativistic effects to the ephemeris derived positions.) If you add the barycenter of Jupiter to this list, uncertainty in ephemeris derived angles may grow to a few hundredths of an arcsecond. Adding Saturn, Uranus and Neptune will raise the uncertainty level to approximately 0.1 arcseconds. Finally, adding Pluto to the list raises the observable errors to 0.3 arcseconds for the present and increasing into the future. Radial distances to the centers of objects follow a similar trend. The radial distances between the inner objects of the solar system as computed via the ephemeris are accurate to 1 to 2 km. The distance between the Earth and the Jupiter Barycenter is accurate to better than 10 km. The uncertainty in the distances to Saturn, Uranus and Neptune are approximately 1000, 2000 and 4000 km respectively. For Pluto, the radial distance from earth may be in error up to 10000 km for the present and growing into the future. The above statements refer to the internal consistency of the ephemeris. These statements of accuracy also hold when comparing positions with the J2000 radio source reference frame adopted by the IAU and IERS. When comparing the position of a planet (other than Pluto) as seen from earth with catalogue positions of stars, the DE403 positions of the planets are very likely to be more accurate than knowledge of the positions of the stars in the catalog (with the possible exception of the Hipparchos catalog). In the case of Pluto, the error in the DE403 position of Pluto is likely to be close to the error in the catalogue positions of stars.