VEX PCK Files                                                               
  =============                                                               
                                                                              
  This "aareadme.txt" file describes the contents of the kernels/pck directory
  of the VEX SPICE data server. It also provides the file naming conventions  
  used for the VEX PCK kernels, and it provides identification of the most    
  current version of each kind of PCK file.                                   
                                                                              
  PCK files in this directory are either binary or text files. Text files are 
  created manually with the information from mainly the 2000 IAU Report.      
  Binary files are created from the information contained in the EOP files    
  provided by IERS.                                                           
                                                                              
  The most detailed description of the data in a text PCK file is provided in 
  metadata included inside the description area of the file. This information 
  can be viewed using any text editor program.                                
                                                                              
  For a binary PCK kernel, this information can be viewed using utility       
  programs COMMNT and SPACIT included into the NAIF Toolkit.                  
                                                                              
  At least a basic knowledge of the SPICE system is needed in order to use    
  these kernels. The SPICE toolkit provides versions in Fortran (SPICELIB), C 
  (CSPICE), IDL (icy) and Matlab (mice), and the user can choose any one that 
  suits him/her.                                                              
                                                                              
  The SPICELIB routine FURNSH, CSPICE function furnsh_c, and icy and mice     
  routine cspice_furnsh load a kernel file into the kernel pool as shown      
  below.                                                                      
                                                                              
      CALL FURNSH ( 'kernel_name' )                                           
      furnsh_c    ( "kernel_name" );                                          
      cspice_furnsh, 'kernel_name'                                            
      cspice_furnsh( 'kernel_name' )                                          
                                                                              
  In the case when two or more files contain data overlapping in time for a   
  given object, for binary kernels, the file loaded last takes precedence.    
                                                                              
  If two (or more) text kernels assign value(s) using the '=' operator to     
  identical keywords, the data value(s) associated with the last loaded       
  occurrence of the keyword are used -all earlier values have been replaced   
  with the last loaded value(s).                                              
                                                                              
  All binary PCK files (*.BPC) contained in this directory are unix binary    
  files. These may be used as is (without format conversion) in a non-unix    
  environment by using any recent version of the SPICE Toolkit (Version N0052 
  or later).                                                                  
                                                                              
  All text PCK files (*.TPC) contained in this directory are unix text files. 
  These may be used in a non-compatible text environment by using the ASCII   
  mode of FTP to port the files.                                              
                                                                              
  Contact                                                                     
                                                                              
	ESA SPICE Service       esa_spice@sciops.esa.int
                                                                              
  , or                                                                        
                                                                              
    Jose Luis Vazquez    jlvazquez@sciops.esa.int                             
                                                                              
  if you have any questions.                                                  
                                                                              
                                                                              
                                                                              
  References                                                                  
  ==========                                                                  
                                                                              
  1. PCK Reading (NAIF Document).                                             
                                                                              
  2. NAIF IDs Required Reading (NAIF Document).                               
                                                                              
  All the NAIF Documents are available at the NAIF web:                       
                                                                              
      http://naif.jpl.nasa.gov                                                
                                                                              
                                                                              
                                                                              
                                                                              
  Venus Express PCK Directory Structure                                       
  ====================================                                        
                                                                              
                                                                              
  aareadme.txt                    This file.                                  
                                                                              
  former_versions                 Subdirectory that contains obsolete versions
                                  of the PCK files that have been updated in  
                                  the Current PCK Kernel Set.                 
                                                                              
  EARTH_[sdat]_[edat]_[pdat].BPC  SPICE kernel containing the reconstructed
                                  orientation of the Earth as a function of
                                  time for the interval from [sdat] until
                                  [edat]. From [pdat] the information
                                  contained in the file corresponds to
                                  predicted data. The rotational effects
                                  included are precession, nutation, rotation
                                  through true siderial time, polar motion
                                  and nutation corrections.
                                                                              
  DE403_MASSES.TPC                SPICE kernel containing the masses for the sun
                                  and planetary barycenters. These masses are 
                                  given as ratios to of Solar GM to barycenter
                                  GM.                                         
                                                                              
  PCKvvvvv.TPC                    SPICE kernel containing size, shape and
                                  orientation data for planets, satellites
                                  and asteroids in the solar system.
                                                                              
                                                                              
                                                                              
                                                                              
-------------------                                                           
                                                                              
        This file was last modified on March 17th, 2009. (J. Vazquez)