VEX FK SPICE Kernels                                                        
  ====================                                                        
                                                                              
                                                                              
  This "aareadme.txt" file describes the contents of the kernels/fk directory 
  of the VEX SPICE data server. It also provides the file naming conventions  
  used for the VEX CK files.                                                  
                                                                              
  All these FK files are produced manually with the information supplied by   
  Venus Express teams describing the frames for the spacecraft and its science
  instruments. Some of these FK files (for tracking stations) are provide     
  specifically for the Radio Science investigation.                           
                                                                              
  The most detailed description of the data in an FK file is provided in      
  metadata included inside the description area of the file. This information 
  can be viewed using any text editor program.                                
                                                                              
  At least a basic knowledge of the SPICE system is needed in order to use    
  this 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 matlab   
  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 FK files (*.TF) contained in this directory are UNIX text files. These  
  may be downloaded to a different system (Mac OS, Windows) by using the ASCII
  mode of FTP.                                                                
                                                                              
  Contact                                                                     
                                                                              
	ESA SPICE Service       esa_spice@sciops.esa.int
                                                                              
  , or                                                                        
                                                                              
    Marc Costa Sitja   mcosta@sciops.esa.int                             
                                                                              
  if you have any questions.                                                  
                                                                              
                                                                              
  References                                                                  
  ==========                                                                  
                                                                              
    1. Frames Required 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 FK Directory Structure                                        
  ====================================
                                                                              
    aareadme.txt          This file.                                          
                                                                              
    former_versions       Subdirectory that contains obsolete versions of the 
                          FK files that have been updated in the Current FK   
                          Kernel Set.                                         
                                                                              
    EARTH_TOPO_YYMMDD.TF  FK kernel for the topocentric reference
                          frames for the Deep Space Network (DSN)
                          stations. This kernel was released on the
                          date indicated in the filename YY-MM-DD.

                                                                              
    EARTHFIXEDIAU.TF      SPICE kernel that associates the IAU_EARTH
                          with the EARTH_FIXED reference frame alias.
                                                                              
    EARTHFIXEDITRF93.TF   This kernel makes the ITRF93 frame coincide
                          with the EARTH_FIXED reference frame.
                                                                              
    VEX_Vxx.TF            FK containing the complete set of frame
                          definitions for the Venus Express Spacecraft
                          (VEX), including definitions for the VEX
                          fixed and VEX science instrument frames.
                          This kernel also contains NAIF ID/name
                          mapping for the VEX instruments.

    VEX_DSK_SURFACES_Vvv.TF

                          FK containing surface name-ID mappings for
                          the Venus Express structures DSKs surfaces.

    ESTRACK_Vxx.tf        This kernel defines a topocentric reference
                          frame for each of the ESA ESTRACK ground
                          stations.
                                                                              
    RSSDvvvv.TF           This frame kernel defines a number of mission
                          independent frames that could be used by any
                          of the users of any of the ESA planetary
                          missions, and that are not 'built' in the
                          SPICE toolkit.
                                                                              
                                                                              
-------------------                                                           
                                                                              
        This file was last modified on March 12th, 2016. (M. Costa)