PDS_VERSION_ID      = PDS3                                                    
RECORD_TYPE         = STREAM                                                  
                                                                              
OBJECT     = TEXT                                                             
  PUBLICATION_DATE = 2009-04-15                                               
  NOTE             = "Description of the GEOMETRY directory                   
                      contents for MESSENGER archive volumes"                 
END_OBJECT = TEXT                                                             
                                                                              
END                                                                           
                                                                              
All MESSENGER geometry data are contained in a separate data set. This        
data set will be incrementally and cumulatively delivered in conjunction      
with each archive delivery as described in the MESSENGER DMSAP. This          
data sets contain geometry data in the form of SPICE kernels.  Each           
incremental delivery covers one or more MESSENGER mission phases as           
follows:                                                                      
                                                                              
    Phase             PDS Volumes                                             
    -----------       ---------------------------                             
                                                                              
    LAUNCH            No Increment                                            
    ---------------------------------------------                             
                                                                              
    EARTH CRUISE                                                              
    EARTH FLYBY                                                               
    VENUS 1 CRUISE                                                            
    VENUS 1 FLYBY                                                             
    VENUS 2 CRUISE                                                            
    VENUS 2 FLYBY     Incremental Delivery 1                                  
    -----------------------------------------------                           
                                                                              
    MERCURY 1 CRUISE                                                          
    MERCURY 1 FLYBY   Incremental Delivery 2                                  
    -----------------------------------------------                           
                                                                              
    MECURY 2 CRUISE                                                           
    MECURY 2 FLYBY    Incremental Delivery 3                                  
    -----------------------------------------------                           
                                                                              
    MECURY 3 CRUISE                                                           
    MERCURY 3 FLYBY   Incremental Delivery 4                                  
    -----------------------------------------------                           
                                                                              
    MECURY 4 CRUISE                                                           
    MERCURY ORBIT     Incremental Delivery 5 - 7                              
    -----------------------------------------------                           
                                                                              
The data sets contain:                                                        
----------------------                                                        
                                                                              
.ti  (ik)   -- SPICE system for providing instrument field of view            
               definitions and other ancillary data.                          
                                                                              
.bc  (ck)   -- SPICE system for providing attitude information for            
               spacecraft and instrument platforms.                           
                                                                              
.tpc (pck)  -- Planetary constants kernels. Models used for rotations of      
               solar system bodies and shapes (constants and matrices of      
               planets and satellites). Includes mission specific             
               overlay for Mercury shape.                                     
                                                                              
.tf  (fk)   -- MESSENGER reference frame file. Also known as the Frames       
               Kernel. Contains the MESSENGER spacecraft, science             
               instrument, and communications antennae frame                  
               definitions.                                                   
                                                                              
.tls (lsk)  -- Leapsecond kernel for providing information to convert         
               between UTC times and any other time system.                   
                                                                              
.bsp (spk)  -- MESSENGER spacecraft ephemeris file. Also known as the         
               Planteary Spacecraft Ephemeris Kernel (SPK) file.              
                                                                              
.tsc (sclk) -- MESSENGER spacecraft clock coefficients file. Also known       
               as the Spacecraft clock kernel (SCLK) file. Models the         
               spacecraft clock against the Terrestrial Dynamical Time        
               (TDT) time system.