Dataset OverviewThis dataset contains full resolution magnetometer data from the PioneerVenus Orbiter spacecraft beginning with orbit 3602 (Oct 16, 1988) andcontinuing until the orbiter was lost in the Venusian atmosphere (orbit5055, Oct 7, 1992). The dataset differs from the high resolution magnetometerdataset from theprevious orbits due to an anomaly in the multiplexor thatcontrolled the sampling of the magnetometer sensors. During orbit 3602, andfor the remainder of the mission, the spacecraft downlink containedmagnetometer data from only the P sensor. The P sensor is the sensor whichis aligned with the spacecraft spin axis, nominally in the direction of theecliptic normal.After the anomaly was first detected, the magnetometer team made asubstantial effort to recover the average magnetic field vector using thesingle sensor data. Since the sensor is not perfectly aligned with thespacecraft spin axis, a small amount of spin modulation is present in thesensor data. In theory, the amplitude of the spin plane field can bedetermined from the amplitude of the spin modulation and knowledge of thetrue sensor mounting geometry. In practice, this turned out to be a verydifficult task because the spin axis of the spacecraft is not sufficientlyconstant in body-fixed coordinates.Data ProcessingThis dataset has been calibrated to account for sensor zero levels, gains,and geometry. The data are given in units of nanoTesla. The data are at thefull downlink sampling resolution. They have not been resampled during thedata processing procedure. After the anomaly, the onboard calibrate signalcontinued to function and the calibration of the instrument was repeatedlychecked. No change in gain was detected. The technique used to check the zerolevels earlier in the mission could not be used after the anomaly occurred.Since the operations were limited to the low power available on thespacecraft, and since the magnetometer became a low priority instrument, itwas not possible to check the zero levels to the levels desirable. However,it is clear that towards the end of the mission the zero levels had driftedsignificantly. It is recommended that these data be used principally in avariometer mode, i.e. for changes only.The dataset contains the following columns:Column Description ___________________________________________________________________________UT S/C event time (UT) of the sample P1 Measured value of the P sensor at the sample time P2 Measured value of the P sensor at the sample time + 38 microsecs P2 Measured value of the P sensor at the sample time + 76 microsecs Bz The derived value of the spacecraft z-axis aligned magnetic field component at the sample time .Data SamplingThe data 'P' columns are values which have been sampled from the Psensor directly. The magnetometer samples each sensor 38 microseconds afterthe previous sensor sample. The data processing procedure uses the P1 sampleto determine the Bz value and hence it is sampled at the start of sweep(time-tag) time.Ancillary Products Other datasets on the CD-ROM are the Ephemeris which contains spacecraftposition in Venus Solar Orbital coordinates, spacecraft altitude, solarzenith angle, Venus centered longitude and latitude, spacecraft spin axiscomponents, celestial longitude and latitude of the spacecraft, celestiallongitude of the earth, and the Sun-spacecraft range. Other ancillary datasets are the: 1) phase and offset which contains thephase 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 whichcontains 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 timeand 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 courseof the mission. Each successive reprocessing has eliminated someof the problems found in earlier version of the data. Please bringto the attention of the original investigator any suspicious sectionof data. No zero level correction has been applied to the data.