PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2015-06-03
   NOTE                 = "This file describes the files in the
                           extras/orbnum directory of this volume."
END_OBJECT              = TEXT

END


Orbit Number Files for the Mars Reconnaissance Orbiter Mission
==============================================================

   This directory contains the orbit number files generated during the
   mission using the NAIF's ORBNUM utility program for some the final
   merged spacecraft trajectory SPK files for the orbital phases of the
   mission. Normally the orbit number files have the same names as the
   corresponding SPK files but with the extension ``.bsp'' replaced by
   ``.orb'' or ``.nrb''. In a few cases more than one orbit number file
   may exist for a given SPK, with only one file having the same name
   as the SPK and other files having a version token appended to the
   SPK name. In such cases the orbit number file with the latest
   version in the name supersedes all other orbit number files for that
   SPK.

   The orbit number files are plain ASCII text files that have lines
   terminated with a line feed character, LF (ASCII 10).
 
   The orbit number files with the ``.orb'' extension contain data that
   follow the ``periapsis-to-periapsis'' orbit numbering scheme -- with
   the orbit number changing at periapsis.
 
   The orbit number files with the ``.nrb'' extension contain data that
   follow the ``node-to-node'' orbit numbering scheme -- with the orbit
   number changing at the descending node.
 
   The information contained in the orbit number files includes the
   orbit number (``No.''), periapsis or descending node UTC time
   (``Event UTC PERI'' or ``Event UTC D-NODE'') and SCLK time (``Event
   SCLK PERI'' or ``Event SCLK D-NODE'' ), apoapsis or ascending UTC
   time (``OP-Event UTC APO'' or ``OP-Event UTC A-NODE''). It also
   includes a few additional items computed at the time of periapsis or
   descending node such as planetocentric subsolar longitude and
   latitude (``SolLon'' and ``SolLat'') in the Mars body-fixed frame
   based on the IAU 2000 Mars rotation model, planetocentric
   subspacecraft longitude and latitude (``SC Lon'' and ``SC Lat'') in
   the Mars body-fixed frame based on the IAU 2000 Mars rotation model,
   spacecraft altitude above Mars (``Alt'') relative to the IAU 2000
   Mars ellipsoid, and Sun-Mars distance (``Sol Dist'').


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

   Regarding Mars Reconnaissance Orbiter project specific information
   provided in this data set and for general information about SPICE
   system, contact:
   
      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