Dataset Overview

This dataset contains resampled magnetometer data from the Pioneer Venus
Orbiter spacecraft beginning with orbit 3602 (Oct 16, 1988) and continuing
until the orbiter was lost in the Venusian atmosphere (orbit 5055,
Oct 7, 1992). The dataset differs from the 2 spin period averaged mag dataset
from the previous orbits due to an anomaly in the multiplexor that controlled
the sampling of the magnetometer sensors. During orbit 3602, and for the
remainder of the mission, the spacecraft downlink contained magnetometer
data from only the P sensor. The P sensor is the sensor which is aligned with
the spacecraft spin axis, nominally in the direction of the ecliptic normal.

Version 2.0 of this data set includes new versions of some of the data
products. The ancillary engineering (ENGR) were regenerated
setting bad data to flag values. The original, unflagged data values
are available in the binary version of the same data.

After the anomaly was first detected, the magnetometer team made a
substantial effort to recover the average magnetic field vector using the
single sensor data. Since the sensor is not perfectly aligned with the
spacecraftspin axis, a small amount of spin modulation is present in the
sensor data. In theory, the amplitude of the spin plane field can be
determined from the amplitude of the spin modulation and knowledge of the
true sensor mounting geometry. In practice, this turned out to be a very
difficult task because the spin axis of the spacecraft is not sufficiently
constant in body-fixed coordinates.

Data Processing and Sampling

This dataset has been calibrated to account for  gains only.
The data are given in units of nanoTesla. The data have been
derived from the high resolution dataset PVO-V-OMAG-3-P-SENSOR-V1.0
by resampling. These data have been averaged over two spin period intervals
on one spin period centers. The time tag given to each record is the project
assigned time value for the spin period (UADS time tag).

The dataset contains the following columns:

Column  Description 
___________________________________________________________________________
UT      S/C event time (UT) of the sample 
Bz-SC   Calibrated/Averaged value of S/C coord. Z component of B 
Var-Bz  The variance of Bz-sc over the two spin period interval 
Bn      The magnetic field magnitude |B|. 

Ancillary Products

  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.

References:

      Russell, C.T., R.C. Snare, J.D. Means and R.C. Elphic, 'Pioneer
      Venus Orbiter Fluxgate Magnetometer', IEEE Trans. Geo. Elec.,
      vol. GE 18, no. 1 p. 32, 1980.

These data have been reprocessed several times during the course
of the mission. Each successive reprocessing has eliminated some
of the problems found in earlier version of the data.  Please bring
to the attention of the original investigator any suspicious section
of data.  No zero level correction has been applied to the data.