PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

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


General information about SPICE C-kernels
=========================================

   In the SPICE system, pointing data for an instrument platform, or
   for a specific instrument, are stored as C-kernels (CK).  The
   pointing of a platform or an instrument is often expressed in terms
   of a transformation matrix from some standard base reference frame
   to a instrument-fixed frame. In the past, the instrument was often a
   camera, and the transformation was thus dubbed the ``C-matrix'';
   hence the choice of C as the name for the pointing kernel.
 
   The data contained in C-kernel files can be accessed and manipulated
   by a collection of 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.
 
   To use C-kernels, a Spacecraft Clock Kernel (SCLK) is required.
   Also, for C-Kernels containing orientation of project-defined
   frames, a Frame Kernel file is required.
 
   Refer to the CK Required Reading (ck.req) document provided with the
   Toolkit or available from the NAIF Node of the PDS, to get more
   information on how to access C-kernel data.
 

Deep Impact C-kernels Contained on This Volume
==============================================

   This directory contains the SPICE C-kernel files for the Deep Impact
   mission. All files are in IEEE big endian binary format and suitable
   for use on UNIX workstations and MACs.
 
   The following CK files are provided in this directory (only the
   leading portion of the file name is shown; the extension of all CK
   file names is ".bc"):

      dif_sc_050112_050809       Deep Impact Flyby (DIF) spacecraft
                                 orientation CK file based on the low
                                 rate real-time attitude telemetry and
                                 covering the whole primary mission.

      dif_sc_050225_highrate     DIF spacecraft orientation CKs based 
      dif_sc_050704_highrate     on the high-rate recorded attitude 
                                 telemetry covering two short windows 
                                 when such telemetry was produced -- 
                                 first at the beginning of the mission
                                 and second for about one hour around 
                                 the closest encounter.

      dif_hga_050117_050801_vch  DIF High Gain Antenna (HGA) orientation
      dif_hga_050118_050801_bch  CK files produced from channelized 
                                 telemetry, each covering the whole 
                                 primary mission. The "vch" file is 
                                 based on the "measured" gimbal angles
                                 while the "bch" file is based on the 
                                 commanded channels.

      dii_sc_050112_050703       Deep Impact Impactor (DII) spacecraft
      dii_sc_050703_050704       orientation CK files. The first of the
                                 two files provides coverage for the
                                 whole period when DII was attached to
                                 DIF; attitude is this file is provided
                                 as a fixed offset of DII frame
                                 relative to the DIF frame derived from
                                 the in-flight calibration data. The
                                 second file provides DII orientation
                                 from separation until the impact; this
                                 orientation is based on DII attitude
                                 telemetry data.

   These CK files should be loaded into a user application in the
   following order to guarantee that, when available, the most accurate
   attitude data is returned to calling application ahead of the less 
   accurate data:

      dif_hga_050118_050801_bch.bc
      dif_hga_050117_050801_vch.bc

      dif_sc_050112_050809.bc
      dif_sc_050225_highrate.bc
      dif_sc_050704_highrate.bc

      dii_sc_050112_050703.bc
      dii_sc_050703_050704.bc


Deep Impact CK File Naming Scheme
=================================

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

      sc_struct_YYMMDD[_yymmdd][_ident][_vX]

   where:

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

      struct    is the name of the spacecraft structure: "sc" for 
                spacecraft itself; "hga" for the High Gain Antenna;

      YYMMDD    is the file coverage start date;

      yymmdd    is the file coverage stop date (optional; provided only
                if the file covers more than one day);

      ident     is a token further identifying the data in the file
                (optional). Examples: "highrate" for high-rate
                data, "bch" for "B"-channel based attitude, etc.

      vX        is the file version number (optional; if omitted,
                the file version is "0").

   The file with the highest version number supersedes all files with
   the same name but earlier version numbers.


Kernel File Details 
===================

   The most detailed description of the data in a binary CK file is
   provided in metadata included inside the comment area of the file.
   This information can be viewed using the utility programs COMMNT and
   SPACIT included in the NAIF Toolkit. The Toolkit is available from
   the NAIF website.

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

   Regarding Deep Impact project specific information provided in this
   data set and for general information about the 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 

