MEX CK SPICE Kernels                                                        
  ====================                                                        
                                                                              
                                                                              
  This "aareadme.txt" file describes the contents of the kernels/ck directory 
  of the MEX SPICE data server. It also provides the file naming conventions  
  used for the MEX CK files.                                                  
                                                                              
  The CK in this subdirectory provide information on:                         
                                                                              
    - predicted and reconstructed spacecraft orientation CKs,                 
                                                                              
    - "planning" spacecraft CKs,                                              
                                                                              
    - orientation CKs for instruments with moving parts.                      
                                                                              
    - orientation for the Solar Arrays.                                       
                                                                              
  Each kernel file provides information of only one of the types above.       
                                                                              
  * Predicted spacecraft orientation CK files are produced by an automated    
    system located at ESAC, operated by the ESA SPICE Team.                   
                                                                              
  * "Planning" CK files are also produced using ADCS. These files contain the 
    spacecraft orientation requested by the MEX Project Science Team through  
    the Pointing Timeline Request (PTR) files. Each of these files is produced
    at the end of a medium term planning cycle. They should only be used in   
    support of the planning activity and NEVER for data analysis since the    
    pointing may change before being implemented on the spacecraft during the 
    short term planning activities.                                           
                                                                              
  * The third kind of spacecraft orientation CK files contain RECONSTRUCTED   
    data. There should be only one kernel of this type, with the orientation  
    of the spacecraft for all the time periods for which the predicted        
    attitude was not accurate enough; for these periods, a recostruction of   
    the attitude was requested to ESOC, and stored in this kernel.            
                                                                              
  * The instrument CKs are generated by the instrument teams, and contain     
    orientation of the moving parts for each instrument.                      
                                                                              
  * The CKs for the Solar Arrays contain information about their orientation, 
    with respect to the spacecraft reference frame.                           
                                                                              
                                                                              
  The contents and time span covered by any CK file may be easily determined  
  using the "ckbrief" utility program available in all copies of the          
  SPICE Toolkit. Examples of usage:                                           
                                                                              
    %ckbrief  <ck_file_name> <sclk_file_name> <lsk_file_name>                 
                                                                              
                                                                              
  This utility requires a SPICE sclk file and an lsk file in addition to the  
  CK file; use the latest versions of these files.                            
                                                                              
  Descriptive information about how/why/when an CK file was created is usually
  available in the "comment area" of the file. This may be viewed using the   
  "commnt" utility program available in all copies of the SPICE Toolkit. Use  
  the "-r" option to read the comments. Example:                              
                                                                              
    %commnt -r <ck_file_name>                                                 
                                                                              
                                                                              
  All binary CK files (*.BC) contained in this directory are unix binary      
  files. These may be used as is (without format conversion) in a non-unix    
  environment when using any recent version of the SPICE Toolkit (Version     
  N0052 or later).                                                            
                                                                              
  For information on the content of this folder or information in general on  
  SPICE for MEX, contact                                                      
                                                                              
        ESA SPICE Team,           esa_spice@sciops.esa.int                    
                                                                              
  , or                                                                        
                                                                              
        Jose Luis VAzquez,        jlvazquez@sciops.esa.int                    
                                                                              
                                                                              
                                                                              
  References                                                                  
  ==========                                                                  
                                                                              
    1. Data Delivery Interface Document (DDID), Appendix H - FD  products     
       Issue 3.0 (MEX-ESC-IF-5003)                                            
                                                                              
    2. CK Required Reading (NAIF Document).                                   
                                                                              
    3. NAIF IDs Required Reading (NAIF Document).                             
                                                                              
    4. Mars Express Frames Definition Kernel (FK), latest version.            
                                                                              
                                                                              
  All the NAIF Documents are available at the NAIF web:                       
                                                                              
    http://naif.jpl.nasa.gov                                                  
                                                                              
                                                                              
                                                                              
  Mars Express CK Directory Structure                                         
  ===================================                                         
                                                                              
    aareadme.txt                  This file.                                  
                                                                              
    former_versions               Subdirectory that contains obsolete         
                                  versions of the CK files that have been     
                                  updated in the Current CK Kernels Set.      
                                                                              
    ATNM_PYYMMDDhhmmss_xxxxx.BC   Contains Mars Express predicted attitude    
                                  information covering the time span          
                                  starting at the date YYMMDDhhmmss. This     
                                  attitude information corresponds to the     
                                  ESOC attitude file named:                   
                                                                              
                                  ATNM_FDLMMA_DAPYYMMDDhhmmss_xxxxx.MEX       
                                                                              
                                  where xxxxx designates the version number.  
                                                                              
    ATNM_PTRvvvvv_YYMMDD_xxx.BC   Contains Mars Express predicted attitude    
                                  information covering the time span          
                                  starting at the date YYMMDD. This attitude  
                                  information corresponds to the PTR file     
                                  version vvvvv delivered from POS to ESOC    
                                  and it is intended for the Teams to check   
                                  the pointings. The final attitude file is   
                                  fixed after iterating the PTR and it may    
                                  differ from this "planning C-Kernel".       
                                                                              
    ATNM_RECONSTITUTED_xxxxx.BC   Contains Mars Express RECONSTITUTED attitude
                                  information. This attitude information      
                                  corresponds to all reconstituted attitude   
                                  files delivered from ESOC to PST. This file 
                                  is updated every time new reconstituted data
                                  are available. The file contains gaps       
                                  between data segments. Extensive            
                                  documentation specifying valid interpolation
                                  intervals (periods with no data gaps) is    
                                  provided in the comment area. Please refer  
                                  to text above for information about using   
                                  the COMMNT utility.                         
                                                                              
    MEX_ASPERA_SAF_yymmdd_xx.BC   Contains the Mars Express ASPERA-3 Sensor   
                                  Assembly Frame (SAF) orientation data       
                                  relative to the ASPERA-3 Unit Reference     
                                  Frame. These data describe the rotation of  
                                  the ASPERA-3 scanner. The file covers the   
                                  time span starting at the date yymmdd. For  
                                  further information about the definition of 
                                  these frames, please refer to [5].          
                                                                              
    MEX_SA_YYYYVvvvv.BC           Contains orientation for the Solar Arrays,  
                                  for the year YYYY. vvvv is the version      
                                  number, and it is increased when new data is
                                  added to the file.                          
                                                                              
                                                                              
-------------------                                                           
                                                                              
        This file was last modified on March 4th, 2009. (J. Vazquez)