Data Set Overview : This data set consists of magnetic field vector data recorded by the Vector Helium Magnetometer onboard the Pioneer 10 spacecraft, during the close encounter to Jupiter (inside 7 RJ). The vector data are provided in a Jupiter-centered JG coordinates (see descriptions in Sections of Data Format and Coordinate System for Data). Also included are the spacecraft trajectory data (distance from Jupiter, latitude, and longitude) in the same coordinates. Data Sampling : These data are provided in 1 minute averages. The resolution from which the 1 minute averages were generated is unknown. The magnetometer measures the three field components over a frequency range from 0 to 10 Hz. At encounter the data rate was 1024 bits/sec and the magnetometer sampling rate was one vector measurement every 3/16 second, corresponding to 5.33 samples/sec. Data Format : The Pioneer 10 magnetometer data for the close encounter to Jupiter were originally written on a 9-track, 1600 bpi, ASCII encoded magnetic tape. The original file was re-formatted into ASCII. The data file contains the following data columns: -------------------------------------------------------------------- Column Column Column Name Format Description -------------------------------------------------------------------- TIME A24 Ground received time in yyyy-mm-ddThh:mm:ss.sss R F12.4 Distance of Pioneer 10 from Jupiter in Rj LAT F12.4 Latitude of Pioneer 10 in JG coordinates LON F12.4 Longitude of Pioneer 10 in JG coordinates BX F12.4 X component of the magnetic field in JG coordinates BY F12.4 Y component of the magnetic field in JG coordinates Bz F12.4 Z component of the magnetic field in JG coordinates -------------------------------------------------------------------- Coordinate System for Data : JG coordinates is defined as the X axis in the direction of G, the equatorial vector lying in the System III (1957.0) Prime Meridian; the Z axis in the direction of J, the spin axis of Jupiter; and the Y axis parallel to Jupiter's equatorial plane and completing the right-handed orthogonal system. Instrument Calibration : The in-flight calibration consists of impressing eight precisely known currents on the sensor coil system and measuring the resulting fields with the magnetometer. The instrument is designed to carry out a nominal mission with only one instrument-on command. The instrument comes on in the automatic ranging/spectrum analyzer mode and automatically ranges to the proper scale by comparing the +X and |Z| axis outputs with fixed reference voltages. The only function commands sent to this instrument during the Pioneer F&G missions were those to initiate the in-flight calibration sequence periodically during the cruise phase. At the conclusion of this sequence the instrument automatically returned to the automatic ranging mode. A 6-bit digital house-keeping word indicates the operating mode of the instrument. The in-flight calibration onboard the Pioneer spacecraft was done by ground command once or twice a week. The low range sensors were calibrated at field magnitude of 13 GAMMA and 26 GAMMA during the interplanetary cruise period. While the high range sensors were calibrated near planetary encounter where the field magnitude was as high as +/-43,000 GAMMA and 86,800 GAMMA. There are two kind of instrument calibration parameters, sensor scale factor (gain) and offset. The conventional approach to checking the magnetometer scale factors in flight is to apply calibration field changes, dB to the sensors so that the corresponding voltage change dV can be determined. Normally several step changes are applied sequentially so that the linearity can be tested directly. After two years of in-flight calibrations, no change has been detected in the Pioneer 10 or 11 scale factors which were then known to an accuracy of 1 percent or better. The sensor offsets were determined in-flight using two different techniques. For the two sensors in the spin plane, the offset was calculated by averaging the spinning data in a time interval of an integral number of spin period. The offset of the spin axis sensor was determined by an adaptation of a variance technique developed by L. Davis [BELCHER1973]. The essential assumption was made that over short intervals of time (5 minutes), the fluctuations in the interplanetary field are principally changes in direction and tend to conserve the magnitude of the field.

Confidence Level Overview : The vector helium magnetometer noise spectrum is independent of frequency (white) with a field equivalent power spectral density of 10**-4 GAMMA**2/HZ. For signal bandwidths less than 1 Hz, corresponding for example to values averaged over a few seconds or more, fields smaller than 0.01 GAMMA can be detected. The maximum relative error of the magnetometer sensors is given by dB/B <: dB0/B + dk/k where B0 is the total offset error and dk is the scale factor error. The scale factor accuracy is as good as 1%. And the total offset error is mainly caused by the spin axis sensor error because it is not readily determined as the two in spin-plane sensors. The ratio of the standard deviation of the offset in spinning axis to the field magnitude is about 0.05. Thus, the maximum relative error in the magnetic field measurement is 0.06. Data Coverage and Quality : This data set has a nearly 2-hour data gap between 1973-12-04T04:08:58 and 1973-12-04T05:51:05 in this data set, on top of sporadic missing data points after 1973-12-04T06:18:00.000. There are no flagged values in this data set.