PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2013-04-09
   NOTE                 = "GRAIL SP-Kernel Information"
END_OBJECT              = TEXT
                                                                     
END

General Information About SPICE SP-Kernels
==========================================

   The purpose of the SP-kernel -- 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.
 
   The SPK files can be accessed and 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.
 
   To use SP-kernels, a Leapseconds (LSK) is required. Also, to use
   SP-Kernels containing positions given relative to the non-inertial
   and project-defined frames, a Frame Definitions (FK) and Planetary
   Constants (PCK) files are required.
 
   Refer to the ``spk.req'' document provided with the toolkit to get
   more information on how to access SP-kernel data.


GRAIL SP-kernels Provided in This Data Set
==========================================

   The following GRAIL SP-kernels are provided in this data set (only
   the name portion of the file name is shown; the extension of all
   file names is ``.bsp''):
 
   GRAIL Spacecraft Trajectory SPK files:

      grail_BEG_END_PROD_vVV      SPK files containing GRAIL spacecraft
                                  trajectory from BEG to END, created
                                  by PROD (``nav'' for the GRAIL NAV
                                  team; ``sci'' for the GRAIL Science
                                  team), with version VV. The two dates
                                  are specified in the YYMMDD format.
                                  Note that for the Moon orbital phases
                                  the trajectory provided in these SPKs
                                  is Moon-centric, meaning that the
                                  planetary ephemeris SPK must be
                                  loaded together with these SPKs in
                                  order to compute the s/c position
                                  relative to the Sun or other Solar
                                  system bodies. Because the ``sci''
                                  SPKs provide more accurate trajectory
                                  compared to the ``nav'' SPKs, they
                                  should be loaded with a higher
                                  priority (last).

   GRAIL Crash Site Location SPK files:

      grail_BEG_END_crashsite_vVV SPK files containing GRAIL crash
                                  site locations, and GRAIL spacecraft
                                  positions relative to the sites (zero
                                  offsets), covering from BEG to END,
                                  created by NAIF, version VV. The two
                                  dates are specified in the YYMMDD
                                  format.

   Solar System Bodies Ephemeris data SPK file:
   
      de421                       SPK file containing JPL's Planetary
                                  Ephemerides DE421.


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 utility programs COMMNT and
   SPACIT included into the NAIF Toolkit.
   

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

   Regarding GRAIL 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

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