Data Set Overview
    =================
      Line of sight (LOS) gravity data were obtained as part of the
      Radio Science Experiment by tracking 351 orbits of the Pioneer
      Venus Orbiter.  The data set consists of a table with the
      following columns: spacecraft latitude, longitude (degrees),
      accelerations, and altitude (km).  The acceleration data were
      determined from differentiation of raw Doppler residuals and
      are expressed as units of mm/s**2.  To obtain LOS gravity in
      milligals, accelerations need to be multiplied by 100.  An
      acceleration of 1.20 mm/s**2, therefore, corresponds to 120
      mgal, a large gravity anomaly.
 
      An accompanying file contains ancillary data to supplement the
      gravity data file.  The accompanying file has one record for
      each orbit in which LOS gravity data were acquired.  Each
      record contains the minimum and maximum latitude and longitude,
      and altitudes for the orbit, along with the sub-earth point
      latitude and longitude, and the spacecraft location and
      velocity in a Venus centered coordinate system.  Each record
      also contains a pointer to the first record for that orbit in
      the gravity data file, and the number of records for that
      orbit.
 
 
      Processing Level Id            : 4
      Software Flag                  : N
      Processing Start Time          : 1978
      Processing Stop Time           : 1990
 
 
    Parameters
    ==========
 
      Data Set Parameter 'LINE OF SIGHT ACCELERATION'
      -----------------------------------------------
        The acceleration of the spacecraft due to planet mass
        anomalies, where acceleration is measured along the line of
        sight between the spacecraft antenna and the Deep Space Net.
        Obtained by tracking Doppler changes in telemetry frequency.
 
        Data Set Parameter Name        : LINE OF SIGHT ACCELERATION
        Data Set Parameter Unit        : MM/S**2
        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              : P12
      Data Set Parameter Name         : LINE OF SIGHT ACCELERATION
      Instrument Parameter Name       : RSSDETEB POWER
      Important Instrument Parameters : 1
 
 
    Processing
    ==========
      N/A

Overview
    ========
      There are several possible sources for error, including the
      Earth's troposphere and ionosphere, Venus' atmosphere, and
      space plasma.  The noise levels were very dynamic and changed
      from day to day.  For specific information see Sjogren et al.,
      1980.