PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2007-01-02
   NOTE                 = "SP-Kernel Information"
END_OBJECT              = TEXT
                                                                     
END 

General information about SPICE SP-kernels
==========================================
 
   The purpose of the SP-kernel (SPK), which stands for S(pacecraft)
   and P(lanet) Kernel, is to allow ephemerides for any collection of
   solar system bodies, spacecraft or any other objects in 3D space to
   be combined under a common file format, and accessed by a common set
   of subroutines. SP Kernels provide the state of a target relative to
   its center of motion, where ``state'' implies Cartesian position and
   velocity at a requested epoch.
 
   The SPK format is supported 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 SP-kernels, a Leapseconds Kernel (LSK) is required. Also, to
   use SP-Kernels containing states defined relative to non-inertial or
   project-defined frames, a Frames Kernel (FK) and/or Planetary
   Constants Kernel (PcK) are required.
 
   Refer to the SPK Required Reading (spk.req) document provided with
   the Toolkit or available from the NAIF Node of the PDS, to get more
   information on how to access SP-kernel data.
 

Deep Impact SP-kernels Provided in This Directory 
=================================================
 
   This directory contains the SPICE SP-Kernel files for the Deep
   Impact Flyby (DIF) and Impactor (DII) spacecraft, Deep Impact
   mission targets comets Tempel 1 and Boethin, and solar system
   bodies. All files are in IEEE big endian binary format and suitable
   for use on UNIX workstations and MACs. The following files are
   present in this directory. (Only the leading portions of the file
   names are shown; the file name extensions of the binary SPK files
   are always ".bsp"):

      dif_preenc174_nav_v1   SPK file providing DIF spacecraft
                             trajectory as well as ephemerides of the
                             comets Tempel 1 and Boethin and solar
                             system bodies for the whole duration of
                             the mission, based on the last predict
                             pre-encounter trajectory solution 174.

      dii_preenc174_nav_v1   SPK file providing DII spacecraft
                             trajectory as well as ephemerides of the
                             comets Tempel 1 and solar system bodies
                             for the whole duration of the mission,
                             based on the last predict pre-encounter
                             trajectory solution 174.

      di_finalenc_nav_v1     SPK file providing an earlier version of 
                             the DIF, DII, and Tempel 1 trajectories
                             for the two days period around encounter,
                             reconstructed by DI NAV team from DIF and
                             DII optical navigation data. DIF and DII
                             spacecraft trajectories provided in this
                             SPK use impact site as the center of
                             motion.

      di_finalenc_nav_v3     SPK file providing the latest version of
                             the DIF, DII, and Tempel 1 trajectories
                             for the two days period around encounter,
                             reconstructed by DI NAV team from DIF and
                             DII optical navigation data. DIF and DII
                             spacecraft trajectories provided in this
                             SPK use impact site as the center of
                             motion.

      di_finalenc_nav_v3_to06048   SPK file providing the latest
                             version of the DIF, DII, and Tempel 1
                             trajectories for the two days period
                             around encounter, reconstructed by DI NAV
                             team from DIF and DII optical navigation
                             data and then adjusted by Science Data
                             Center, Cornell University to shift DIF
                             and DII spacecraft trajectories to be with
                             respect to the comet center rather than to
                             the impact site.
 
      di_tempel1_ssd_v1.bsp  SPK providing Tempel 1 ephemeris spanning
                             from 2000 through 2050, produced at the
                             end of the mission by the Solar System
                             Dynamics Group at JPL. Comet ephemeris
                             data provided in the file is the same as
                             the data provided in di_finalenc_nav_v1,
                             di_finalenc_nav_v3, and 
                             di_finalenc_nav_v3_to06048 SPK files.


   NOTE 1: the best solution for processing the impact data is provided
   in the file di_finalenc_nav_v3_to06048.bsp.

   NOTE 2: of the two NAV solutions providing spacecraft trajectories
   with respect to the impact site, the best one is in the file
   di_finalenc_nav_v3.bsp. di_finalenc_nav_v1.bsp SPK is included in
   the archive only because it was used to compute derived geometry
   items in the set of DI science products generated in
   November/December 2005.

   NOTE 3: the "preenc174" SPK files do not provide adequate accuracy
   for processing of the encounter image data. The encounter (for
   Impactor) and closest approach times (for Flyby) computed using
   spacecraft and comet trajectory provided in these SPKs are different
   from the actual times by over ten seconds. On the other hand these
   files provided trajectory spanning the whole mission and, therefore,
   cover every DIF and DII science observation that took place during
   cruise and far approach.

   NOTE 4: The following four of these SPKs should be loaded in
   this order to make sure that the best trajectory solutions are
   available to the calling application at any given time:

      dii_preenc174_nav_v1.bsp
      dif_preenc174_nav_v1.bsp
      di_tempel1_ssd_v1.bsp
      di_finalenc_nav_v3_to06048.bsp


Deep Impact SPK File Naming Scheme
==================================

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

      sc_ident_prod_vX[_modif].bsp

   where:

      sc        is the name of the spacecraft: "dif" or "dii" or 
                "di" (contains trajectory data for both spacecraft,
                Flyby and Impactor.) The exception to this is the file
                for Tempel 1 that provides data only for the comet but
                still has "di" as the first token indicating that the
                comet trajectory solution was derived primarily from
                Deep Impact mission observations.
 
      ident     is a token identifying the type and coverage of
                trajectory data provided in the file. Examples:
                "preenc174" -- complete mission trajectory based on
                pre-encounter predicted trajectory OD solution 174;
                "finalenc" -- final reconstructed encounter trajectory,
                etc.

      prod      is a token identifying the data producer. Examples: 
                "nav" -- DI Navigation team, etc.

      vX        is the file version number.

      modif     is an optional modifier indicating additional
                processing done to create the file. Example:
                "to06048" -- "t"empel "o"ffset, solution generated on
                2006 DOY 048.

   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 each SPK 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.


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 

