PDS_VERSION_ID                   = PDS3
RECORD_TYPE                      = STREAM
OBJECT                           = TEXT
  PUBLICATION_DATE               = 1998-06-26
  NOTE                           = "Description of the GEOMETRY 
    directory contents for the MGS Sampler CD-ROM."
END_OBJECT                       = TEXT
END


                      GEOMETRY Directory Contents

     The GEOMETRY directory contains SPICE kernels from the Navigation
and Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory.
See the file VOLINFO.TXT in the DOCUMENT directory for a description of 
SPICE files. Also in this directory is a set of files containing the
sub-spacecraft locations for orbits during the MGS Assessment Subphase,
and a summary file containing time and geometry parameters for each
orbit, all generated by NAIF using the SPICE kernels.

     SPICE kernels for UNIX computers and for PCs are given in the UNIX
and PC subdirectories respectively. The following SPICE kernels are 
found in each subdirectory.

Kernel  File          Size   Contents
Type    Name          (Mb)
-----------------------------------------------------------------------

SPK     MGS_AERO.BSP  10.8   Ephemeris for the MGS spacecraft (ID=-94) 
                             relative to the Mars barycenter (ID=4)

        DE403S.BSP     3.4   Ephemeris for Mars barycenter (ID=4), Mars 
                             (ID=499), Earth barycenter (ID=3), Earth 
                             (ID=399) and Sun (ID=10) relative to solar 
                             system barycenter (ID=0). (Also contains 
                             data for all other planet barycenters and 
                             the Earth's moon.)

PCK     PCK00006.TPC   0.09  Size, shape and orientation for Mars (and 
                             all other planets and satellites)

CK      M013.BC        2.1   Spacecraft orientation for a period of 
                             time centered at periapsis number 13.
                             SPICE ID code for the spacecraft-fixed
                             frame is -94000.

        M019-036.BC   25.0   Spacecraft orientation for a period of 
                             time centered at periapsis numbers 19 - 36

        M073.BC        2.7   Spacecraft orientation for a period of 
                             time centered at periapsis number 73

        M077-079.BC    3.4   Spacecraft orientation for a period of
                             time centered at periapsis numbers 77-79

        M084.BC        1.9   Spacecraft orientation for a period of 
                             time centered at periapsis number 84

        M100.BC        1.7   Spacecraft orientation for a period of 
                             time centered at periapsis number 100

LSK     NAIF0006.TLS   0.004 Current Leapseconds kernel, used in 
                             covering between UTC and ephemeris time 
                             (ET) time systems

SCLK    MGS_SCLK.TSC   0.003 Current SPICE Spacecraft Clock file, used 
                             in converting between spacecraft clock 
                             (SCLK) and ET time systems
-----------------------------------------------------------------------

     Additional files in the GEOMETRY directory:

GEOMINFO.TXT - The file you are reading.

ORBnnnnC.TAB - Sub-spacecraft locations for orbit nnnn in
               planetocentric (areocentric) coordinates.

ORBnnnnC.LBL - PDS label for ORBnnnnC.TAB.

ORBnnnnG.TAB - Sub-spacecraft locations for orbit nnnn in
               planetographic (areographic) coordinates.

ORBnnnnG.LBL - PDS label for ORBnnnnG.TAB.

ORBITSUM.TAB - A summary of time and geometry parameters for each
               orbit.

ORBITSUM.LBL - PDS label for ORBITSUM.TAB.