Data Set Overview
    =================
      After the digital data were transmitted to Earth and received
      at the Jet Propulsion Laboratory, they were subject to a
      variety of processes to produce the final digital tapes and
      photoproducts.  The first step was to strip out all the
      non-video data and produce a System Data Record (SDR).  This
      was compiled into video format, and an Experiment Data Record
      (EDR) was produced.  The EDR data consist of unprocessed (raw)
      instrument data.  Substantial processing is required to
      reconstruct each image owing to the unique manner in which data
      were transmitted to earth.  Images were initially recorded on
      7-track magnetic tape recorders on the spacecraft.  Each raw
      data frame retrieved from the tracking station thus contains
      every seventh pixel arranged in either increasing or decreasing
      order.  Image data reconstructed from these raw data frames by
      the Mission Test Imaging System (MTIS) form the EDR digital
      archive tape.
 
      The Orbiter Visual Imaging Subsystem (VIS) consists of two
      high-resolution, slow-scan television framing cameras, each
      with a telescope having 475-mm focal length and a
      37-mm-diameter vidicon, the central region of which is scanned
      with a raster format of 1056 lines by 1182 samples.  Each field
      of view is 1.54 deg.  X 1.69 deg., and each picture element
      subtends 24.8 microradians.  The optic axes are offset by 1.38
      deg.  so that the fields overlap slightly.  The cameras are
      shuttered and read out alternately, providing a single
      contiguous digital data stream, the interval between pictures
      (one frame time) being 4.48 s.  This interval determine the
      basic timing of the other two science instruments as well.
      Each camera has five color filters and one clear 'filter'.
 
      The objectives of the Viking Orbiter imaging investigation were
      to characterize potential landing sites in sufficient detail to
      support the site choice topographic, photometric, and
      colorimetric characteristics of the surface features (volcanos,
      canyons, channels, faults, polar cap formations, etc.) that
      have been discovered by Mariner 9 to improve our knowledge of
      the geologic evolution of Mars document changes in cloud
      structure, polar caps, polar hoods, and in the contrast of the
      surface features observe the vertical structure of the
      atmosphere.
 
      The orbiter photographed 100% of Mars at a resolution of at
      least 260 meters per pixel, 84% at 240 meters per pixel, 60% at
      220 meters per pixel, 44% at 200 meters per pixel, 30% at 180
      meters per pixel, 17% at 160 meters per pixel, 6% at 140 meters
      per pixel, 5% at 100 - 60 meters per pixel, and less than 1% at
      30 meters per pixel.
 
      The Planetary Conversion Task rerecorded JPL's digital archive
      of planetary images (EDR) onto 9-track 12in tape reels at 6250
      bpi with 32,000 bytes per block (VSFEDR format).  The VSFEDR
      format consists of a VICAR standard header label, mission
      dependent VICAR labels, the digital image lines (1056 lines
      with 1204 pixels per line), engineering data (396 bytes)
      appended to each line, and mission dependent EDR header record.
      Pixel values are stored as 8-bit integers with a range of 0 to
      254.  The values represented on the EDR tape are actually two
      times the value received in the telemetry stream.  Because of
      the nature of the recording and playback system, strings of
      missing bits appear as vertical bars at 7-pixel intervals.
      Missing pixels are set to zero in the EDR tape.  Further
      details describing this format and tape contents will be
      supplied with the tape.
 
      Additional mission products are also available.  These include
      systematic photoproducts and Supplementary Experimental Data
      Record (SEDR).  Systematic processing of the EDR to clean up
      and enhance the images produced a shading-corrected and
      contrast enhanced version called the SCR-2 and two filtered
      versions, orthographic and rectilinear, called the NGF.  The
      geometric data were compiled into the SEDR.
 
 
      Processing Level Id            : 2
      Software Flag                  : N
      Processing Start Time          : 1976
 
 
    Parameters
    ==========
 
      Description
      -----------
        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
        Noise Level                    : UNK
 
 
    Source Instrument Parameters
    ============================
      Instrument Host ID              : VO1
      Data Set Parameter Name         : DATA NUMBER
      Instrument Parameter Name       : RADIANCE
      Important Instrument Parameters : 1
 
      Instrument Host ID              : VO2
      Data Set Parameter Name         : DATA NUMBER
      Instrument Parameter Name       : RADIANCE
      Important Instrument Parameters : 1
 
 
    Processing
    ==========
 
      Processing History
      ------------------
        Source Data Set ID          : P30 CARDS
        Software                    : VISRAP (MTIS SOFTWARE)
        Product Data Set ID         : VO1/VO2-M-VIS-2-EDR-V1.0
 
        Source Data Set ID          : SYSTEM DATA RECORD (SDR)
        Software                    : VISRAP (MTIS SOFTWARE)
        Product Data Set ID         : VO1/VO2-M-VIS-2-EDR-V1.0
 
 
      Software 'VISRAP'
      -----------------
        Software Name               : VISRAP (MTIS SOFTWARE)
        Software Type               : N/A
        Software Release Date       : 1976
        Node ID                     : PIN
        Cognizant Engineer          : RICH BENSON
        Software Access Description : N/A

N/A