PDS_VERSION_ID      = PDS3
RECORD_TYPE         = STREAM

OBJECT     = TEXT
  PUBLICATION_DATE = 2017-05-12
  NOTE             = "Description of the GEOMETRY directory contents for
                      the MESSENGER MLA archive volume."
END_OBJECT = TEXT

END

All MESSENGER geometry data are contained in a separate data set. This data
set was cumulatively delivered in conjunction with each archive delivery
as described in the MESSENGER Data Management and Archiving Plan (DMAP). This
data set contains geometry data in the form of SPICE kernels. The data set is
archived by the PDS NAIF Node in the messsp_1000 volume, PDS data set ID
mess-e/v/h/spice-6-v1.0. It is available from the NAIF online archives at
http://naif.jpl.nasa.gov.

The SPICE data sets contain:
----------------------------

.ti  (ik)   -- SPICE system for providing instrument field of view
               definitions and other ancillary data.

.bc  (ck)   -- SPICE system for providing attitude information for
               spacecraft and instrument platforms.

.tpc (pck)  -- Planetary constants kernels. Models used for rotations of
               solar system bodies and shapes (constants and matrices of
               planets and satellites). Includes mission specific overlay
               for Mercury shape.

.tf  (fk)   -- MESSENGER reference frame file. Also known as the Frames
               Kernel. Contains the MESSENGER spacecraft, science
               instrument, and communications antennae frame definitions.

.tls (lsk)  -- Leapsecond kernel for providing information to convert
               between UTC times and any other time system.

.bsp (spk)  -- MESSENGER spacecraft ephemeris file. Also known as the
               Planetary Spacecraft Ephemeris Kernel (SPK) file.

.tsc (sclk) -- MESSENGER spacecraft clock coefficients file. Also known as
               the Spacecraft clock kernel (SCLK) file. Models the
               spacecraft clock against the Terrestrial Dynamical Time (TDT)
               time system.


MLA SPK Kernels
---------------
The MLA RDR products in the data set MESS-E/V/H-MLA-3/4-CDR/RDR-DATA-V2.0 in
the MESSMLA_2101 volume were processed using SPKs (ephemeris kernels) produced
by the MLA team at GSFC from on-orbit MLA and Radio Science data. These SPKs
provide more precise solutions for the spacecraft trajectory. These SPKs are
identified in the SPICE_FILE_NAME fields in the RDR labels as
MSGR_GSFCrecon_110318_140430.bsp and MSGR_GSFCrecon_140501_150430.bsp and
cover the periods 2011-03-18 through 2014-04-30 and 2014-05-01 through
2015-04-30 respectively.

These ephemeris data are archived at the NAIF PDS node in the usual MESSENGER
data set described above, but under different filenames. In order to reduce
the sizes of the files, the two files above are broken up into five files,
each covering shorter intervals of the MESSENGER mission orbital phases. These
files are archived in the messsp_1000 volume in the data/spk/ directory as:

   msgr_110318_110714_recon_gsfc_0.bsp
   msgr_110716_120430_recon_gsfc_0.bsp
   msgr_120501_130430_recon_gsfc_0.bsp
   msgr_130501_140430_recon_gsfc_0.bsp
   msgr_140501_150430_recon_gsfc_0.bsp

See the associated documentation in the MESSENGER SPICE kernel archive for
details.