Objects In This Ephemeris
--------------------------------------------------------
 
        Name                  Id-code
        -------------         -------
        Comet Encke           1000025
 
 
Approximate Time Coverage
 
        From: 2001 NOV 02 00:00:00 (TDB)
        To  : 2007 FEB 14 00:00:00 (TDB)
 
 
Status
--------------------------------------------------------
 
     This is the current best estimate for the position of Comet Encke as
     of January 22, 1997. Currently, no formal updates to this ephemeris
     are planned. However, if you need a more recent ephemeris and have
     reason to believe that observations following the creation date of
     this ephemeris may significantly improve the positional knowledge for
     comet Encke, we recommend that you contact NAIF and to the extent that
     resources are available we will attempt to provide an update to this
     ephemeris.
 
     This ephemeris is intended only for use in early planning of
     observations of comet Encke.
 
 
Production/History of this Ephemeris
--------------------------------------------------------
 
     This ephemeris was produced by Bill Taber of the Navigation Ancillary
     Information Facility (NAIF) at the Jet Propulsion Laboratory on 22 Jan
     1997 for use by the SIRTF project. It was transformed to SPK format
     from a numerical integration performed by Don Yeomans of the Solar
     Systems Dynamics group of the Astrodynamics and Navigation section
     (section 312) of the Jet Propulsion Laboratory. The source file of
     integrated states from which this ephemeris was created are from
     "Yeomans' solution 27" for the Encke trajectory.
 
     The ephemeris is based on 178 observations over the interval of years
     from 1984 to 1996.
 
     The ephemeris was integrated using the JPL developmental ephemeris
     DE-403 to provide a gravitational force model.
 
 
Usage
--------------------------------------------------------
 
     To determine the state of Encke with respect to any object other than
     the sun, you need at a minimum a planetary ephemeris. Since the
     planetary ephemeris used for the dynamical force model in the
     integration of the comet ephemeris was DE-403, it is recommended that
     you use DE403 when computing states of Encke with respect to anything
     other than the sun.
 
     DE403 is available via anonymous ftp on NAIF's ftp server: naif-sun
     (ip address 128.149.126.11) in the directory
     pub/naif/generic_kernels/spk. Both binary and transfer format
     ephemerides are available. They are in the files.
 
        de403s.bsp ( binary format )
        de403s.xsp ( transfer format )
        de403s.cmt ( comments about de403s )
 
 
Accuracy
--------------------------------------------------------
 
     The extent to which the position of comet Encke as observed agrees
     with the position predicted by this ephemeris changes over time. As
     Encke makes its closest approach to earth, (2003 NOV 17) the position
     of Encke may disagree with the position predicted by this ephemeris by
     up to 2 arcminutes. When Encke is far from earth, one can expect
     better agreement.
 
     The accuracy relative to SIRTF cannot be assessed at this time.
 
     If you plan to observe Encke near the epoch of its closest approach to
     earth, you should contact NAIF late in the year 2002 or early 2003 and
     request an new ephemeris for Encke. It is anticipated that an
     ephemeris accurate to better than 5 arcseconds (as seen from earth)
     should be available at that time.
 
 
Inquiries
 
     If you have any questions regarding this ephemeris contact
 
        Bill Taber
        btaber@spice.jpl.nasa.gov
        Phone (818) 354-4279
        FAX   (818) 393-6388
 
        JPL
        MS 301/125L
        4800 Oak Grove Drive
        Pasadena, CA 91109