KPL/PCK

P_constants (PcK) SPICE kernel file
===========================================================================
 
        By: Boris Semenov (NAIF)    13-AUG-2004
 
 
Organization
--------------------------------------------------------
 
     The sections of this file are as follows.
 
     Introductory Information:
 
         --   Version description
 
         --   Disclaimer
 
         --   Sources
 
     Pck Data:
 
         --   Orientation constants for Comet Comet 67P/Churyumov-Gerasimenko
 
         --   Radii for Comet Comet 67P/Churyumov-Gerasimenko
 
 
Version description
--------------------------------------------------------
 
     This file was created on August 13, 2004. 
     
     This is a preliminary PCK containing draft values for the rotation
     period and shape (obtained from [1]) and placeholder values for
     pole direction and prime meridian location (set to line up with
     the ecliptic north pole in J2000 coordinates.)
     
 
Disclaimer
--------------------------------------------------------
 
     This constants file may not contain the parameter values that you
     prefer. Note that this file may be readily modified by you or
     anyone else. NAIF suggests that you inspect this file visually
     before proceeding with any critical or extended data processing.
 
     NAIF requests that you update the `by line' and date if you modify 
     the file.
 
 
Sources
--------------------------------------------------------
 
     The sources for the constants listed in this file are:
 
        1) ESA Science and Technology Server, Rosetta area,
           http://sci.esa.int/science-e/www/object/index.cfm?
           fobjectid=14615


Orientation constants for Comet Comet 67P/Churyumov-Gerasimenko
--------------------------------------------------------
 
     The inertial reference frame for these constants is J2000; this is
     the default reference frame for PCK orientation data.
 
     The epoch of the constants is J2000; this is Julian ephemeris date
     (JED) 2451545.0.
 
     The NAIF integer code for Comet 67P/Churyumov-Gerasimenko
     (67P/C-G) is 1000012. See the NAIF_IDs required reading for
     further information on NAIF integer codes.
 
     Since the comet pole direction is not known, it has been
     arbitrarily chosen to point toward ecliptic north at the J2000
     epoch. The RA and DEC below are those of the ecliptic north pole
     in J2000 coordinates. The prime meridian W0 term has also been
     arbitrarily chosen to be zero.

     The W1 term was set to correspond to the period of 12.0 hours
     ([1]).
 
     \begindata
 
        BODY1000012_POLE_RA    = ( 270.0        0.0    0.0 )
        BODY1000012_POLE_DEC   = (  66.560709   0.0    0.0 )
        BODY1000012_PM         = (   0.0      720.0    0.0 )
 
     \begintext


Radii for Comet 67P/Churyumov-Gerasimenko
--------------------------------------------------------
     
     The radii provided in the keyword below are 

          a/b/c = 2.5km/1.5km/1.5km

     which correspond to the ellipsoidal, rugby ball shape and
     approximate size of 5 x 3 km ([1]).
 
     \begindata
 
        BODY1000012_RADII     =   (  2.5   1.5   1.5  )
 
     \begintext