PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2010-03-15
   NOTE                 = "SCL-Kernel Information"
END_OBJECT              = TEXT

END


General Information About SPICE SCL-Kernels
===========================================

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

   The spacecraft clock coefficient information contained in SCLK file
   can be manipulated using the SPICE Toolkit APIs, calls to which can
   be integrated into user application programs. The information
   regarding how to obtain the SPICE system toolkit for a number of
   languages and computer platforms is located in the ``/software''
   subdirectory of the main directory of this data set.

   Refer to the ``sclk.req'' document provided with the toolkit to get
   more information about conversion between ET and spacecraft clock
   times.


MESSENGER SCL-kernels Contained in This Data Set
================================================

   This data set contains the following MESSENGER SCLK files (only name
   portion of the file name is shown on the right; the extension of all
   file names is ``.tsc''):

      messenger_[VER]   MESSENGER Spacecraft clock coefficients Kernel
                        (SCLK) files containing actual MESSENGER
                        on-board clock to ET mapping coefficients
                        computed using time calibration packets from
                        the spacecraft engineering telemetry.

   If this data set contains multiple SCLK files, the one with the
   latest version ([VER]) supersedes all previous versions.


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

   The most detailed description of the data in an SCLK file is
   provided in metadata included inside the description area of the
   file. This information can be viewed using any text editor program.

   Note that the SCLK kernels provided in this data set have been
   determined to be in a relativistic solar system barycentric frame of
   reference. This has been verified through confirmation that the
   ephemerides used to compute the SCLK kernel correlations are in a
   solar barycentric frame. It is critically important that the users
   of these kernels for time applications be aware of this and that
   they properly interpret the time correlations in the SCLK kernels.
   The file ``sea_2007_010.pdf'' in the ``document'' directory should
   be consulted for information on how to do this. In addition, the
   file ``sea_2003_024.pdf'' in the ``document'' directory gives
   further information on the format and design of these kernels.


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

   Regarding MESSENGER project specific information provided in this
   data set:

      Mike Reid
      (240)-228-4537
      Mike.Reid@jhuapl.edu

   address:

      The Johns Hopkins University Applied Physics Laboratory
      11100 Johns Hopkins Road
      Laurel, MD 20723

   For general information about SPICE system:

      Charles H. Acton, Jr,
      (818)-354-3869,
      Charles.Acton@jpl.nasa.gov,

   or

      Boris Semenov
      (818)-354-8136
      Boris.Semenov@jpl.nasa.gov

   address:

      Navigation and Ancillary Information Facility (NAIF)
      Jet Propulsion Laboratory
      MS 301-121
      4800 Oak Grove Drive
      Pasadena CA 91109 USA