Pioneer 11 HVM Cruise Data Archive

Description

The Helium Vector Magnetometer (HVM) measurements of interplanetary magnetic fields were averaged at fifteen minute or one hour intervals with respect to Ground Received Time (UT) and Spacecraft Event Time (UT). Measured parameters included the three orthogonal components of the magnetic field, the Z component being along the spacecraft spin axis towards Earth. Other calculated parameters included time averages of these components, squares and products of the components, direction cosines, and values and squares of field magnitude. Heliocentric positions of the spacecraft and Earth, referred to the ecliptic and equinox of date, were also included. In 1987 and afterward, the cyclic switching on and off of other instruments on Pioneer 11 caused random fluctuations of the magnetometer's Z axis zero levels. These fluctuations were of the order of 0.05 nT with a period of several days and were mostly, but not completely removed. Measured vector components were transformed into Pioneer Ecliptic (PE) coordinates. Before 1976 the PE components were converted to Solar Heliospheric (SH) or Jovian Encounter (SJ) coordinates, whereas some data in 1976 and all data thereafter were kept in PE coordinates. A coordinate system identifier field designated whether a record had PE, SH, or SJ coordinates. The PE system was defined with the Z axis along Pioneer's spin axis, nominally pointing toward the Earth, and the X axis as the unit vector in the direction E x Z, where E was the northern direction perpendicular to the Ecliptic. SH coordinates were defined with X in the sun-to-spacecraft direction and Y parallel to the solar equator and positive in the direction of planetary motion around the sun. Each data record consists of 372 bytes with 29 data fields in ASCII format. The dataset was packaged in SFDU format with descriptive metadata files and separate data files for each six months of consecutive years from launch. The metadata includes detailed descriptions of the parameters and coordinate systems. For more information, refer to Smith, E. J., B. V. Connor, and G. T. Foster, Jr., "Measuring the magnetic fields of Jupiter and the outer solar system, "IEEE Trans. Magn., vol. MAG-11, pp.962-980, 1975.