PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2007-12-21 
   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.

   Three types of Cassini C-kernel files are present on this volume:
   Imaging Science Subsystem (ISS) image navigation data C-kernels, Attitude
   and Articulation Control Subsystem (AACS) reconstructed and predicted
   orientation data.

   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.

   It is not unusual for CK files to be revised. The user is urged
   to be sure that CK data have not been superseded by searching
   the latest data releases for appropriate coverage.


Cassini C-kernels contained on this volume
==========================================

   This directory contains the SPICE C-kernel files for the Cassini
   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 volume (only the leading
   portion of the file name is shown; the extension of all CK file names
   is ".bc"):

-- Cassini Spacecraft Orientation CK Files, produced by the Attitude
   and Articulation Control Subsystem:

           [StartDate]_[EndDate][Type][V][_xxxxxxxx]
 
   where:
 
           [StartDate]    File coverage start date (YYDOY);
 
           [EndDate]      File coverage stop date (YYDOY);
 
           [Type]         Type of the data stored in the file: ``r'' =
                          reconstruction (called "ACTUAL" in the PDS
                          label), ``p'' = predict;

           [V]            File version. The first file generated for a
                          specific time frame is version ``a''. Subsequent
                          files containing revised information for the
                          same time period are given the next higher
                          version letter -- ``b'', ``c'', etc;

           [_xxxxxxxxx]   Optional freeform text that can be included
                          to provide the user additional clues about
                          the contents of the file.


   For example the file:

           03215_03220ra.bc

   is a binary C-kernel containing reconstructed data that covers a time
   period in 2003 from day of the year 215 to 220. It is the first version
   of the reconstruction file.


-- Cassini ISS C-Smithed C-kernel files, produced by the ISS team:

           [StartDate]_[EndDate]c[Version]_ISS
 
   where:
 
           [StartDate]    File coverage start date (YYDOY);
 
           [EndDate]      File coverage stop date (YYDOY);

           [Version]      File version (beginning with the letter 'a'
                          and incrementing from there).

   For example, the file:

           99213_99243ca_ISS.bc

   is a binary C-smithed C-kernel that covers the time period from 1999,
   day 213 to day 243 and it is the first version of this file.

   Note that complete time coverage for C-kernels is not guaranteed to
   be available for each release of data due to the processing schedule
   of AACS.


-- Cassini CDA Instrument orientation C-kernel files, produced by the
   NAIF team using the instrument position data provided by the CDA
   team:

           cas_cda_[CreationDate]
 
   where:
 
           [CreationDate]   File creation date (YYYYMMDD);
 

   For example, the file:

           cas_cda_20061027.bc

   is a binary CDA orientation C-kernel created on 2006-10-27.

   The CDA CK file with the latest creation date supersedes all
   previous CDA CK files.


-- Cassini MIMI/LEMMS Instrument orientation C-kernel files, produced
   by the MIMI/LEMMS team at APL using the instrument position data
   from telemetry:

           cas_lemms_[YYDOY]_[yydoy]_v[N]
 
   where:
 
           [YYDOY]    File coverage begin date
 
           [yydoy]    File coverage end date

           [N]        File version

   For example, the file:

           cas_lemms_05109_20001_v1.bc

   is a binary MIMI/LEMMS orientation C-kernel covering from 2005-04-19
   to 2020-01-01, version 1.


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.

   Comparisons between some AACS predicted and reconstructed C-kernels
   can be found in the ``extras/ckxtra/cknav/'' directory. Additional
   information about ISS C-kernels can be found in the 
   ``extras/ckxtra/ckiss'' directory.

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

   Regarding Cassini 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

      Adrian W Tinio 
      (818)-354-7511
      Adrian.W.Tinio@jpl.nasa.gov
      
   address:
   
      Navigation and Ancillary Information Facility (NAIF)
      Jet Propulsion Laboratory
      MS 301-125L
      4800 Oak Grove Drive
      Pasadena CA 91109 USA 

