PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM

OBJECT                  = TEXT
   INTERCHANGE_FORMAT   = ASCII
   PUBLICATION_DATE     = 2017-07-01
   NOTE                 = "This file describes the files in the
                           extras/orbnum directory of this volume."
END_OBJECT              = TEXT

END


Orbit number files for the Venus Climate Orbiter mission
========================================================

   This directory contains the orbit number file generated during the
   Venus Climate Orbiter (VCO, also known as PLANET-C and AKATSUKI)
   mission using the NAIF's ORBNUM utility program for the spacecraft
   trajectory SPK files of the mission. The orbit number files are
   named vco_vVV.orb, where VV is the version number. The file with
   the latest version supersedes all files with earlier versions.
   The orbit number files are plain ASCII text files that have lines
   terminated with a line feed character, LF (ASCII 10).

   The files included in this dataset are the most recent files
   available at the moment of the compilation of each release of this
   dataset, which should span at least the same time interval as all
   the SPK files included in the dataset.

   They contain data that follow the "periapsis-to-periapsis" orbit
   numbering scheme -- with the orbit number changing at periapsis.

   The information contained in the orbit number files includes:

    - Orbit number ("No".)
    - Periapsis UTC time ("Event UTC PERI")
    - SCLK time ("Event SCLK PERI" )
    - Apoapsis UTC time ("OP-Event UTC APO")
    - Sub-solar geodetic longitude and latitude (SolLon, SolLat), in
      the IAU_VENUS reference frame.
    - Sub-spacecraft geodetic longitude and latitude (SC Lon, SC Lat),
      in the IAU_VENUS reference frame.
    - Altitude of the vehicle above the primary body (Alt)
    - Inclination of the vehicle orbit (Inc)
    - Eccentricity of the orbit plane about the primary body (Ecc)
    - Longitude of the ascending node of the orbit (LonNode)
    - Argument of periapsis of the orbit (Arg Per)
    - Solar distance the time of the orbit event (Sol Dist)
    - Semimajor axis of the orbit (Semi Axis)

   All the orbital elements are calculated in the VME2000 reference
   frame. See rssd0002.tf for details about this frame.


Important Note Regarding Orbit Number Files
===========================================

   Orbit number 1 corresponds to the first orbit, started from
   2015-12-07.
 
   All derived quantities provided on each record -- sub-solar lon/lat,
   sub-spacecraft lon/lat/alt, and orbital elements -- are computed for
   the time of pericenter.


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

   Regarding the PLANET-C Project specific information provided in this
   data set and for general information about SPICE system, contact:
 
      Yukio Yamamoto
      +81-50-3362-2612
      yukio@planeta.sci.isas.jaxa.jp
 
   , or 
 
      Boris Semenov   
      (818)-354-8136  
      Boris.Semenov@jpl.nasa.gov