Objects In This Ephemeris
--------------------------------------------------------
 
     Osculating conic elements of most comets available in the DASTCOM database
     are present in this file.

     Not included: comets with orbital periods longer than 1000 years.

 
Production/History of this Ephemeris
--------------------------------------------------------
 
     This file was produced by Jeff Bytof of the Navigation Ancillary
     Information Facility (NAIF) at the Jet Propulsion Laboratory. 

     The JPL Solar System Dynamics group maintains the DASTCOM database, 
     which can be accessed at http://ssd.jpl.nasa.gov/et_form.html.

     The DASTCOM data was changed with the UNIX utility 'awk' 
     into a format suitable for input to the SPICE utility program 'mkspk5',
     which created the SP-kernel file.

     Periodic comets were selected with orbital periods of less than 1000 years.
     Multiple apparitions of the same comet are stored as separate
     segments with different provisional NAIF IDs.   Subtract one million
     from the provisional NAIF ID to get the original DASTCOM record number. 

     Times in the range 1809 NOV 14 01:20:00.000 to 2190 FEB 17 22:40:00.000 (ET)
     may be input to SP-kernel reading software to obtain comet position and 
     velocity.  Accuracy of comet positions and velocities obtained is degraded 
     if you are not near the calculation epoch of an element set.  

     A list of the file's comet NAIF IDs is stored in the SPICE text kernel pcomets_v1.txt. 

     The source DASTCOM file is pcomets_dastcom_v1.txt, and field descriptions
     are in file pcomets_dastcom_desc_v1.txt.
      
 
Usage
--------------------------------------------------------
 
     To determine the state of a comet with respect to the sun and planets, 
     the use of planetary ephemeris DE405 is recommended. 
 
     DE405 is available via anonymous ftp on NAIF's ftp server: naif
     (ip address 128.149.126.23) in the directory
     pub/naif/generic_kernels/spk. Both binary and transfer format
     ephemerides are available. They are in the files.
 
        de405s.bsp ( binary format )
        de405s.xsp ( transfer format )
 
 
Accuracy
--------------------------------------------------------
 
     These are low accuracy elements, not to be used in 
     precison work, but may be useful for preliminary searches. 
     
 
Inquiries
--------------------------------------------------------
 
     If you have any questions regarding this file contact
 
        Jeff Bytof 
        jbytof@spice.jpl.nasa.gov
        Phone (818) 354-2504
        FAX   (818) 393-6388
 
        JPL
        MS 301/125L
        4800 Oak Grove Drive
        Pasadena, CA 91109