PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2006-03-01
   NOTE                 = "SCL-Kernel Information"
END_OBJECT              = TEXT
                                                                     
END 


General information about SPICE SCL-kernels
===========================================

   In the SPICE system, the Spacecraft Clock Kernel (SCLK) contains
   information required to perform a mapping between Ephemeris time
   (ET) and spacecraft on-board time (SCLK).

   The spacecraft clock coefficient information contained in a SCLK
   file can be manipulated by a collection subroutines that are part of
   the SPICELIB library, the major component of the NAIF Toolkit. These
   subroutines can be integrated into user application programs.
   Information about obtaining the SPICE Toolkit is located in the
   "software" subdirectory of the main directory of this dataset.

   Refer to the SCLK Required Reading (sclk.req) document provided with
   the Toolkit or available from the NAIF Node of the PDS, to get more
   information on how to convert between ET and spacecraft clock times.


Deep Impact SCL-kernels Contained in This Directory 
===================================================

   This volume contains the following Deep Impact Flyby (DIF) and Deep
   Impact Impactor (DII) SCLK files (only the leading portion of the
   file name is shown; the extension of all file names is ".tsc"):

      dif_sclkscet_00015          "official" DIF SCLK kernel file. This
                                  SCLK kernel provides data for the
                                  primary (SCU A) DIF on-board clock
                                  based on the final correlation
                                  released at the end of the primary
                                  mission. This is the official SCLK
                                  file used by the ground system during
                                  mission operations.
                                  
      dif_sclkscet_00015_science  "improved" DIF SCLK kernel file. This
                                  SCLK kernel provides data for the
                                  primary (SCU A) DIF on-board clock
                                  based on the final correlation. This
                                  SCLK provides an improved correlation
                                  (as compared to the official SCLK)
                                  and is recommended to be used for
                                  post encounter data processing.

      dif_sclkscet_00010_scu_b    "SCU B" DIF SCLK kernel file. This
                                  SCLK kernel provides data for the
                                  secondary (SCU B) DIF on-board clock
                                  based on the final correlation
                                  released at the end of the primary
                                  mission. This SCLK must be used ONLY
                                  to process data that were stored on
                                  the SCU B side of the spacecraft.

      dii_sclkscet_00008          DII SCLK kernel file. This SCLK
                                  kernel provides data for the DII
                                  on-board clock based on the final
                                  correlation released prior to the
                                  encounter.

      dii_sclkscet_00008_science  DII SCLK kernel file. This SCLK
                                  provides modified correlation (as
                                  compared to the official SCLK)
                                  consistent with the final encounter
                                  trajectory solution by DI NAV and is
                                  recommended to be used for post
                                  encounter data processing.

   Note that only one of the three DIF SCLK files must be loaded into a
   user application at any given time because all three DIF SCLK
   kernels provide for the same clock ID, -140. The same applies to DII
   SCLK files -- only one of the two SCLK should be loaded at any given
   time.


Deep Impact SCLK File Naming Scheme
===================================

   The Deep Impact SCLKs provided on this volume are named according to
   the following scheme:

      sc_sclkscet_VVVVV[_ident].tsc

   where:

      sc        is the name of the spacecraft: "dif" or "dii";

      sclkscet  is the literal script carried over from the source 
                SCLKvSCET file name;

      VVVVV     is the file version number;

      ident     is a token further identifying the data in the file
                (optional). Examples: "scu_b" for SCU B clock, etc.


Kernel File Details
===================
 
   The most detailed description of the data in an SCLK file is
   provided in metadata included inside the descriptive text areas
   within the file. This information can be viewed using any text
   editor.


Contact Information
===================

   Regarding Deep Impact project specific information provided in this
   data set and for general information about SPICE system:
   
      Boris Semenov
      (818)-354-8136
      Boris.Semenov@jpl.nasa.gov
      
   or

      Chuck Acton
      (818)-354-3869 
      Chuck.Acton@jpl.nasa.gov

   address:
   
      Navigation and Ancillary Information Facility (NAIF)
      Jet Propulsion Laboratory
      MS 301-125L
      4800 Oak Grove Drive
      Pasadena CA 91109 USA