Data Set Overview
    =================
      This Voyager 2 Neptune data set is available on CD-ROM and
      magnetic tape.
 
      NASA's Voyager Project and the Planetary Data System (PDS) have
      created an archive of planetary digital images acquired by the
      twin Voyager spacecraft (Voyager 1 and Voyager 2).
 
      This data set includes images acquired by Voyager 2 as it
      passed by the planet Neptune, its' satellites and rings.
      Important to note is the fact that while geometry information
      and calibration files exist for all these data sets, they do
      not exist in the Experiment Data Record (EDR) data set but are
      available separately through the Imaging Node.  Neither does
      the data set include starfields, calibrations, Plasma Radio
      Astronomy (PRA), or Plasma Wave Spectrometer (PWS)
      image-formatted information.
 
      The Voyager Neptune archive resides on magnetic tape in EDR
      format (this format is explained in the Multimission Image
      Processing Laboratory (MIPL) Real-Time Processing Subsystem
      Software Design Document (1985), an internal JPL document
      available from JPL vellum files) and also on three CD-ROM
      volumes.
 
      In addition to the images, supplemental information exists on
      the CD-ROMs.  This includes documentation providing a user with
      information about the organization and contents of the disk.
      Software source code is included to provide programmers with
      tools to process the image files.  There are browse images,
      sub-sampled versions of the full-resolution images, which allow
      users to rapidly view the archive collection with their
      interactive display.
 
      Finally, there are image index files containing information
      about all the images stored in the archive.
 
      The set of images on the magnetic tapes are raw; no processing
      has been performed other than organizing the original telemetry
      into raster-formatted files.  The set of images on CD-ROM are
      also raw, however they have been compressed using a Huffman
      encoding algorithm.
 
      Detail Target Clarification:
 
      There are two targets which may prove to be confusing for the
      unfamiliar user; PLAQUE and CAL LAMPS, both are used as
      calibration targets.  PLAQUE is an image of a flat piece of
      metal illuminated by the sun.  CAL LAMPS are lamps inside the
      camera used for illumination.
 
      The target DARK is a dark current image when the camera mode is
      BODARK and the exposure is zero.  DARK SKY and SKY are
      shuttered images, non-zero exposures looking at dark sky.
 
      SCAT_LIGHT images are used to measure how much light is
      scattered in a particular direction.
 
      Definition Clarification:
 
      Planetodetic latitude of a point on the planet surface is the
      angle between the surface normal and the equatorial plane.  For
      a spherical body, the latitude is incidental to the
      planetocentric latitude.
 
      The p5 point is one of 6 static points on all images.  It is
      the point located in the center of the image.  The p1 point is
      located in the top left corner, p2 top right corner, p3 bottom
      left corner, p4 bottom right corner, p5 center, p6 center right
      edge.  If the target is not on the p5 point then that point
      does not have latitude and longitude coordinates associated
      with it nor does the target have a p5 point.
 
      The spacecraft coordinate system is a coordinate system defined
      by the spacecraft structure.  The antenna points alone the +z
      axis, the booms are along the +y and the -y axes, creating a
      unique coordinate system for each spacecraft.
 
      The Canopus coordinate system is the coordinate system defined
      by one axis pointing at Canopus, one pointing at the Sun and
      one pointing somewhere else.
 
      These systems are not used for describing images or points on
      images.  Because our interest is in where the pixels lie, not
      relative to the spacecraft or stars but relative to the
      target's own system.
 
      Processing Level Id            : 2
      Software Flag                  : N
      Processing Start Time          : 1988-08-01
      Processing Stop Time           : 1990-04-01
 
 
    Parameters
    ==========
 
      Data Set Parameter 'DATA NUMBER'
      --------------------------------
        Data Number is an integer expressing the digital value of an
        experiment's telemetry data.
 
        Sampling Parameter Name        : PIXEL
        Data Set Parameter Name        : DATA NUMBER
        Data Set Parameter Unit        : DIMENSIONLESS
 
 
    Source Instrument Parameters
    ============================
      Instrument Host ID              : VG2
      Data Set Parameter Name         : DATA NUMBER
      Instrument Parameter Name       : RADIANCE
      Important Instrument Parameters : 1
 
    Processing
    ==========
 
      Processing History
      ------------------
        Source Data Set ID          : FRAMSINK
        Software                    : VIMBUILD
        Product Data Set ID         : UNPROCESSED DATA RECORD
 
        Source Data Set ID          : UNPROCESSED DATA RECORD
        Software                    : MERGE
        Product Data Set ID         : RAW DATA RECORD
 
        Source Data Set ID          : RAW DATA RECORD
        Software                    : EDRGEN
        Product Data Set ID         : VG2-N-ISS-2-EDR-V1.0
 
      Software 'VIMBUILD'
      -------------------
        The functions of VIMBUILD include: 1) to receive,
        reconstruct, and format high rate telemetry data into
        'images' 2) decompress data and fill edited data as required,
        and 3) extract and store selected spacecraft and sensor
        engineering data from telemetry.
 
 
        Source Data Set ID          : FRAMSINK
        Software Name               : VIMBUILD
        Product Data Set ID         : UNPROCESSED DATA RECORD
        Software Type               : N/A
        Software Release Date       : 1985-10-01
        Node ID                     : IMAGING
        Cognizant Engineer          : SUSAN K. LAVOIE
        Software Access Description : NOT ACCESSIBLE THROUGH PDS
                                      CATALOG - CONTACT NODE.
 
      Software 'MERGE'
      ----------------
        The MERGE program creates a new Voyager image from all
        version of a specified image.  This program is part of the
        VICAR system (see VICAR).
 
        Source Data Set ID          : UNPROCESSED DATA RECORD
        Software Name               : MERGE
        Product Data Set ID         : RAW DATA RECORD
        Software Type               : N/A
        Software Release Date       : 1989-09-01
        Node ID                     : IMAGING
        Cognizant Engineer          : SUSAN K. LAVOIE
        Software Access Description : NOT ACCESSIBLE THROUGH PDS
                                      CATALOG - CONTACT NODE.
 
      Software 'EDRGEN'
      -----------------
        The EDRGEN program generates Voyager EDR formatted tapes.
        This program is a part of the VICAR system (see VICAR).
 
        Source Data Set ID          : RAW DATA RECORD
        Software Name               : EDRGEN
        Product Data Set ID         : VG2-N-ISS-2-EDR-V1.0
        Software Type               : N/A
        Software Release Date       : 1989-09-01
        Node ID                     : IMAGING
        Cognizant Engineer          : SUSAN K. LAVOIE
        Software Access Description : NOT ACCESSIBLE THROUGH PDS
                                      CATALOG - CONTACT NODE.

Overview
    ========
      This data set represents a complete collection of raw images
      from the Voyager 2 Neptune encounter beginning with the
      Observatory Phase.  To make full scientific use of the image
      collection, it is necessary to obtain (from the Imaging Node)
      and understand the radiometric and geometric properties of the
      camera system and perform corrections to the data.  Geometry
      and basic pointing information is included for all Image
      Observation Types including Calibration, Stars, and very small
      Satellites (or 'Rocks').  Non primary planetary bodies, like
      rocks may have geometry that refers to the primary planetary
      body (NEPTUNE, TRITON and NEREID).
 
      We recommend obtaining a copy of the 'Software Interface
      Specification, ISS PI SEDR Processor, Rev.b, SIS 4-7008-2', an
      internal JPL document available from the JPL vellum files for
      reference while using this data set.  This document will
      clarify some questions which may arise when using the geometry
      data, particularly for non primary planetary bodies.  For
      example; the original predict Supplemental Experiment Data
      Record (SEDRs) had a target for each image.  Some targets have
      been changed as information about that particular image has
      been refined.  However the geometry still refers to the
      original target from the SEDR.  We suggest contacting the
      Imaging Node for more information, clarification or assistance.
 
      The values for emissions and incidence angles contain errors
      and were received that way on the original set of SEDR tapes.
      We intend to update these values when the entire set of SEDR
      tapes are regenerated.
 
      While using more than one Voyager data set some confusion can
      occur due to duplications in the Flight Data Subsystem(FDS)
      counts (a.k.a.  spacecraft clock times).  This is due first to
      the fact that Voyager 1 and 2 flew concurrently, so there is
      inter-spacecraft duplication, and second because of spacecraft
      clock resets and rollovers that occurred, causing duplication
      within data sets.  Users are cautioned therefore, that the FDS
      count is not a unique identifier for an image.  A unique query
      must include the spacecraft ID, the FDS count, and the target.
 
      There are two targets which may prove to be confusing for the
      unfamiliar user; PLAQUE and CAL LAMPS, both are used as
      calibration targets.  PLAQUE is an image of a flat piece of
      metal illuminated by the sun.  CAL LAMPS are lamps inside the
      camera used for illumination.
 
      The target DARK is a dark current image when the camera mode is
      in bodark and the exposure is zero.  SKY is a shuttered image,
      non-zero exposure looking at dark sky.