KPL/PCK

Asteroid Vesta P_constants (PcK) SPICE kernel file
===========================================================================
 
     By: Boris Semenov (NAIF)    25-FEB-2011
 
 
Organization
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     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


Version description
--------------------------------------------------------
 
     This file was updated on February 25, 2011.

     Vesta pole orientation (Ra, Dec) was changed to (305.8, 41.4)
     degrees per MCR-111475 and "Dawn Planetary Constants and Models
     Document" Revision 2.0, Feb 16, 2011

     This file was updated on October 12, 2004.

     VESTA_FIXED frame definition was removed. It is now in the DAWN Frames
     Kernel file.

     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 and the earlier
     versions of 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.

        2) "Dawn Planetary Constants and Models Document" Revision 2.0, 
           Feb 16, 2011


Orientation constants for asteroid Vesta
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     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, rotation period and
     radii in the previous versions of this PCK (version 0.0 and 0.1)
     were 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."

     The pole direction, prime meridian location, rotation period and
     radii in this version are set to the following values from [2]:

       "5.3 Vesta Pole and Prime Meridian

        The Vesta pole and prime meridian values are shown below.

        RA  Vesta = 305.8 +/- 3.1 deg      Right Ascension in EME2000 [25]
        DEC Vesta = 41.4 +/- 1.5 deg       Declination in EME2000 [25]
        W   Vesta = 292 + w * D deg        Prime Meridian
        w   Vesta = 1617.332776 deg/day    Rotation rate


        5.4 Vesta Shape Parameters

        The Vesta shape is described as a triaxial ellipsoid with 
        values 289, 280, 229 km [15] or as a sphere with a radius 
        of 265 km [16]. ... 


        9 References

        ...
        15. "Vesta: Spin Pole, Size, and Shape from HST Images", P. 
            Thomas, et al., Icarus, v128, p88~94 (1997)."
        16. "Impact Excavation on Asteroid 4 Vesta: Hubble Space 
            Telescope Result", P. C. Thomas, et al, Science, 227, 
            1492-1494, 1997.
        ...
        25. "Improved Measurement of Asteroid (4) Vesta's Rotational 
            Axis Orientation", Jian-Yang Le, et al., Submitted to 
            Icarus: MS# ICARUS-11539, 2010."

     The Vesta orientation constants are provided in the keywords below.
 
     \begindata
 
        BODY2000004_POLE_RA    = ( 305.8    0.0              0.0 )
        BODY2000004_POLE_DEC   = (  41.4    0.0              0.0 )
        BODY2000004_PM         = ( 292.0 1617.332776         0.0 )
 
     \begintext


Radii for asteroid Vesta
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     The Vesta radii from [2] are provided in the keyword below.

     \begindata
 
        BODY2000004_RADII      = ( 289.0  280.0  229.0  )
 
     \begintext

End of PCK file.