Dataset Description:

This data set contains wave electric field amplitudes measured 
at four different frequencies by the Pioneer Venus Orbiter Electric
Field Detector.  The data are averaged over 2 spin periods (approximately
24 seconds. The averaging intervals are overlapped and data are output
on single spin period centers, the time stamp corresponding to the center
of the averaging window.  This reults in an unevenly sampled dataset as
the spin period varies.  The amplitude of the ''flutter'' in the averaging
window size is generally less than 0.004 seconds in the 12 second
period of an orbit. Orbits that have spin period adjustment thruster
firings will have larger variations in the output time steps, but such
adjustments are seldom, if ever, done in the hour surrounding periapsis.
 Each averaging interval contains both the minimum   
amplitude, average amplitude and peak amplitude for that interval at
each of the four frequencies.  The four frequencies are 100 Hz,
730 Hz, 5.4 kHz, 30 kHz.  The frequency filters are narrow-band,
with a 30% bandwidth.  Thus wave amplitudes are given in V/m/root(Hz).
The filters are continuously active, but data are only provided at a
rate determined by the spacecraft telemetry rate.  The wave antenna
is oriented perpendicular to the spacecraft spin axis, and so the wave 
instrument measures only wave fields in the spacecraft spin plane.
The wave antenna is a small Y-shaped structure, with effective 
separation of 0.76 meters.
  Other datasets on the CD-ROM are the Ephemeris which contains spacecraft    
position in Venus Solar Orbital coordinates, spacecraft altitude, solar zenith
angle, Venus centered longitude and latitude, spacecraft spin axis components,
celestial longitude and latitude of the spacecraft, celestial longitude of the
earth, and the Sun-spacecraft range.
  Other ancillary datasets are the: 1) phase and offset which contains the phase
amplitude of sun synchronous modulation of the 4 signals (E100, E730,
E5.4 and E30K), and offsets of the G sensor. 2) The engineering dataset which
contains temperatures, magnetometer modes, magnetometer sample format,    
magnetometer spin average select, telemetry data format, telemetry bit rate,
spacecraft spin period, pulse time, the difference between the Sun pulse time
and the Rip pulse time, and the pulse time flag. 3) The instrument status
dataset which contains amplitudes of spin ripple, differences between amplitudes, ratio of the amplitudes, phase differences between pseudosensors, average
field seen by the pseudosensors, cosine amplitude, and sine amplitude." 

Confidence Level Note:

The instrument noise level (and hence sensitivity) is determined
by the ambient environment at the time of observation.  Photo-
electrons emitted from various spacecraft surfaces appear to be
a strong source of electric field interference.  As a consequence
data acquired when the spacecraft is in sunlight often are contaminated
by spin modulated interference, especially when the spacecraft is
in the low density solar wind, where the Debye length is several
meters.  The noise is usually lowest when the antenna elements
are in the spacecraft shadow.  The noise level is also reduced
when the spacecraft is deep within the dayside ionosphere,
where the Debye length is much smaller than the antenna size.
The noise is not present when the spacecraft is within the
optical shadow of the planet.  In this case, however, additional 
noise features are observed (mainly at 100 Hz) when the
spacecraft is at low altitude within the nightside ionosphere.  This
interference is readily discriminated in the high resolution data,
where the noise is present as a sharp pulse occurring twice per
spin.  
The averaging scheme used can be subject to temporal aliasing when
the data rate is sufficiently low, such that only one or two data
are obtained per 24 second interval.  Since the sampling interval
and spin period are not exactly synchronized, periodic noise signals,
such as the interference, are aliased by the low sampling frequency.
In this case the data display periodic structure, but with a period
much longer than the spin period.
The instrument was calibrated in air.  No attempt to incorporate
changes in antenna-plasma coupling due to changes in Debye
length have been included in the data processing."
   
Selected References:

      Scarf,F.L., W.W.L. Taylor, and I.M. Green, 'Plasma waves
      near Venus:  Initial observations', Science, vol. 203, p.
      748, 1979."

      Taylor,W.W.L., F.L. Scarf, C.T. Russell, and L.H.
      Brace, 'Evidence for lightning on Venus', Nature, vol. 279,
      p. 614, 1979."
      
      Taylor,W.W.L, F.L. Scarf, C.T. Russell, and
      L.H. Brace, 'Absorption of whistler mode waves in the
      ionosphere of Venus', Science, vol. 205, p. 112, 1979."
      
      Scarf,F.L., W.W.L. Taylor, and P.F. Virobik,
      'The Pioneer Venus Orbiter Plasma Investigation',IEEE
      Trans. Geoscience and Remote Sensing, Jan. 1980,
      Volume GE-18 Number 1, pg 36."
      
      Scarf,F.L., W.W.L. Taylor, and C.T. Russell, and L.H. Brace,
      'Lightning on Venus: Orbiter detection of whistler signals,
      J. Geophys. Res.,vol 85, p. 8158, 1980."
      
      Scarf,F.L., W.W.L. Taylor, and C.T. Russell, and R.C. Elphic,
      'Pioneer Venus plasma wave observations: The solar wind - Venus 
      interaction', J. Geophys. Res., vol. 85, p. 7599, 1980."
      
      Scarf,F.L., and C.T. Russell, 'Lightning measurements from the
      Pioneer Venus orbiter, Geophys. Res. Lett., vol.10, p.1192, 1983."
      
      C.T. Russell, 'Venus Lightning', Space Science Review, vol. 55,
      p. 317, 1991."
      
      R.J. Strangeway, 'Plasma waves at Venus', Space Science Review,
      vol. 55, p.317, 1991."