Data Set Overview
    =================
      The Goldstone Solar System Radar observations of Venus from
      1972 until 1988 are included in this data set.  The system
      operated at 12.6 cm up until 1977; afterward the system
      operated at 12.9 cm.  The data consist of radar scaled
      backscatter cross sections in image format and, in most cases,
      associated altimetry observations.  The data were acquired over
      52 separate observing runs.  In total the observations cover
      the region between approximately 260 degrees (leftmost) east
      longitude to 30 degrees (rightmost) east longitude, within
      approximately 20 degrees of the equator.  Backscatter data were
      acquired with opposite sense circular polarization with
      incidence angles typically less than 10 degrees.  Associated
      altimetric data were acquired using a two or three station
      interferometric system.  Data are presented in Mercator
      projection with degrees/pixel in longitude dependent on the
      individual data file.
 
 
      Processing Level Id            : 5
      Software Flag                  : N
      Processing Start Time          : 1972-06-01
      Processing Stop Time           : 1990-04-01
 
 
    Parameters
    ==========
 
      Data Set Parameter 'RADAR SCALED BACKSCATTER CROSS SECTION'
      -----------------------------------------------------------
        Cross section values that are scaled by some procedure, such
        as dividing by theoretical or empirical scattering laws.
 
        Data Set Parameter Name        : RADAR SCALED BACKSCATTER
                                           CROSS SECTION
        Data Set Parameter Unit        : DIMENSIONLESS
        Sampling Parameter Name        : PIXEL
        Sampling Parameter Unit        : N/A
        Minimum Sampling Parameter     : N/A
        Maximum Sampling Parameter     : N/A
        Sampling Parameter Resolution  : N/A
        Sampling Parameter Interval    : N/A
        Minimum Available Sampling Int : N/A
        Noise Level                    : UNK
 
 
    Source Instrument Parameters
    ============================
      Instrument Host ID              : GSSR
      Data Set Parameter Name         : RADAR SCALED BACKSCATTER
                                          CROSS SECTION
      Instrument Parameter Name       : RADAR ECHO POWER
      Important Instrument Parameters : 1
 
 
    Measurement Information
    =======================
 
      Atmospheric Conditions
      ----------------------
        NOT APPLICABLE
 
 
      Source
      ------
        The transmitter was the 64 meter antenna at the Goldstone
        Deep Space Network station.
 
 
      Calibration Standard
      --------------------
        NOT APPLICABLE
 
 
      Wavelength Calibration
      ----------------------
        The transmitter frequency is calibrated with a hydrogen
        maser.
 
 
    Processing
    ==========
      N/A

Overview
    ========
      Pre-1977 backscatter images are normalized relative to the
      square root of the scattering properties for an annulus about
      the sub-Earth point including the data.  The 1977 and later
      images are normalized relative to the average scattering
      properties for the annulus.  Most of the backscatter images are
      speckle noise limited as opposed to thermal noise.  The
      confidence is usually limited by the number of looks.  The
      errors in the altimetry data are difficult to estimate and vary
      greatly over the image.  These errors depend upon the accuracy
      of the ephemeris, the variation of the interferometer fringe
      spacings, the signal to noise ratio and therefore the
      scattering law appropriate for each day's observation.  The
      maximum likelihood estimator also does not provide an estimate
      of the errors.  Errors range from 30 meters near the sub-radar
      region to a few kilometers at the outer edge of the image.