KPL/PCK

Asteroid Vesta P_constants (PcK) SPICE kernel file
===========================================================================
 
     By: Boris Semenov (NAIF)    06-OCT-2003
 
 
Organization
--------------------------------------------------------
 
     The sections of this file are as follows.
 
     Introductory Information:
 
         --   Version description
 
         --   Disclaimer
 
         --   Sources
 
     Pck Data:
 
         --   Orientation constants for asteroid Vesta
 
         --   Radii for asteroid Vesta

     Frames data:

         --   VESTA_FIXED frame definition
 
 
Version description
--------------------------------------------------------
 
     This file was created on October 6, 2003. 
     
     This is a preliminary PCK containing draft values for the pole
     direction, prime meridian location, rotation period and shape
     (from [1].)
     
 
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) Thomas, Peter C. et al. ``Vesta: Spin Pole, Size, and Shape
           from HST Images.'' ICARUS 128, 1997. Article NO. IS975736. 
           pp. 93-94.


Orientation constants for asteroid Vesta
--------------------------------------------------------
 
     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 Vesta is 2000004. See the NAIF_IDs
     required reading for further information on NAIF integer codes.
 
     The pole direction, prime meridian location, and rotation period
     are set to the following values from [1]:

       "New data from the 1996 Hubble HST observations of Vesta allow a 
        refinement of the pole solution to: RA = 301 deg, Dec = 41 deg,
        +/- 5 deg. The prime meridian is now given by W = 292 deg +
        1617.332776 deg * d; see Section 3a and Eq. 1. The new data,
        and a scaling correction, change the fit radii to 289, 280,
        229, +/- 5 km."

 
     \begindata
 
        BODY2000004_POLE_RA    = ( 301.0    0.0              0.0 )
        BODY2000004_POLE_DEC   = (  41.0    0.0              0.0 )
        BODY2000004_PM         = ( 292.0 1617.332776         0.0 )
 
     \begintext


Radii for asteroid Vesta
--------------------------------------------------------
     
     The radii provided in the keyword below are also from [1]. 

     \begindata
 
        BODY2000004_RADII      = ( 289.0  280.0  229.0  )
 
     \begintext


VESTA_FIXED Frame Definition
--------------------------------------------------------

     The Vesta fixed frame is defined in the same as any other PCK
     frame:
 
        *  +Z along the North pole;
      
        *  +X toward the prime meridian;
      
        *  +Y completes the right hand frame;
      
        *  the origin of this frame is at the center of the body.
      
     The orientation of this frame is computed by evaluating
     corresponding rotation constants provided in this PCK file.

     \begindata

        FRAME_VESTA_FIXED      =  2000004
        FRAME_2000004_NAME     = 'VESTA_FIXED'
        FRAME_2000004_CLASS    =  2
        FRAME_2000004_CLASS_ID =  2000004
        FRAME_2000004_CENTER   =  2000004

        OBJECT_2000004_FRAME   = 'VESTA_FIXED'

     \begintext