Data Set Overview
    =================

      This dataset contains Voyager 2 magnetometer data from the
      interplanetary cruise averaged to 48 second samples in Heliographic
      coordinates.

    Data Processing
    ===============
      The high resolution data submitted to the NSSDC has its origins in the
      original MVS 'Summary' data sets formally produced on the NSSC IBM MVS
      mainframe system.  The original data sets contain a mix of engineering,
      electron, magnetic field and plasma data.  The Voyager magnetometer
      (MAG) experiment now resides on a dedicated workstation where only MAG
      data are processed.

      All Voyager MAG data submitted to the NSSDC consists wholly of high
      resolution LFM averages.  These files consist of a set of averages
      applied across all of the mission's differing telemetry modes.  In the
      case of the Magnetometer Experiment, the records contain both
      1.92 second, 9.6 second and 48 second averages.  1.92 second averages
      are created from the detail detail data, 9.6 second averages are created
      from 1.92 second averages and 48 second averages are created from the
      9.6 second averages.

      All data in this NSSDC data set are interplanetary and in heliographic
      coordinates (see below). An ASCII formated data set containing key
      components of the 48 second magnetic field data and ephemeris data has
      been created allowing more convenient access to high resolution Voyager
      magnetometer data.

    Coordinate System
    =================

      Interplanetary magnetic field studies make use of two important
      coordinate systems, the Inertial Heliographic (IHG) coordinate system
      and the Heliographic (HG) coordinate system.

      The IHG coordinate system is use to define the spacecraft's position.
      The IHG system is defined with its origin at the Sun.  There are three
      orthogonal axes, X(IHG), Y(IHG), and Z(IHG).  The Z(IHG) axis points
      northward along the Sun's spin axis.  The X(IHG) - Y(IHG) plane lays in
      the solar equatorial plane.  The intersection of the solar equatorial
      plane with the ecliptic plane defines a line, the longitude of the
      ascending node, which is taken to be the X(IHG) axis.  The X(IHG) axis
      drifts slowly with time, approximately one degree per 72 years.

      Magnetic field orientation is defined in relation to the spacecraft.
      Drawing a line from the Sun's center (IHG origin) to the spacecraft
      defines the X axis of the HG coordinate system.  The HG coordinate
      system is defined with its origin centered at the spacecraft.  Three
      orthogonal axes are defined, X(HG), Y(HG), and Z(HG).  The X(HG) axis
      points radially away from the Sun and the Y(HG) axis is parallel to the
      solar equatorial plane and therefore parallel to the X(IHG)-Y(IHG) plane
      too.  The Z(HG) axis is chosen to complete the orthonormal triad.

      An excellent reference guide with diagrams explaining the IHG and HG
      systems may be found in Space and Science Reviews, Volume 39 (1984),
      pages 255-316, MHD Processes in the Outer Heliosphere, L. F. Burlaga
      [BURLAGA1984].

    Data Format
    ===========
      field  descriptor  (pre 1990 data)
      -----  ----------------------------------
        1.   s/c identification (FLT1=Voyager 1)
                                (FLT2=Voyager 2)

        2.   coordinate system
                                (HG=heliographic)used for this data set

        3.   Time (UTC) format  YY DDD HH MM SS MSS
                                YY  = year
                                DDD = day of year
                                HH  = hour
                                MM  = minute
                                SS  = second
                                MSS = millisecond
        4.   field magnitude (nT)
        5.   field component 1 (nT) - HG
        6.   field component 2 (nT) - HG
        7.   field component 3 (nT) - HG
        8.   spacecraft radial distance (AU)
        9.   spacecraft x position (AU) - IHG
       10.   spacecraft y position (AU) - IHG
       11.   spacecraft z position (AU) - IHG

      field  descriptor  (temiantion shock data)
      -----  ----------------------------------
        1.   s/c identification (2=Voyager 2)
        2.   Time (UTC) format  YYYY DDD.DDDD
                                YY       = year
                                DDD.DDDD = decimal day of year
        3.   F1 average field magnitude (nT)
        4.   Br field component (nT) - HG
        5.   Bt field component (nT) - HG
        6.   Bn field component (nT) - HG
        7.   1 sigma error in F1
        8.   1 sigma error in Br
        9.   1 sigma error in Bt
       10.   1 sigma error in Bn

    Contact Information
    ===================

      Principal Investigator:

      Prof. Norman F. Ness
      Bartol Research Institute
      Univerity of Delaware
      Newark, Delaware 19716-4793
      Phone: (302) 831-8116
      Fax: (302) 831-1843
      Email: norman.ness@mus.udel.edu

    Acknowledgement
    ===============

       Use of these data in publications should be accompanied at minimum by
       acknowledgements of the National Space Science Data Center and the
       responsible Principal Investigator defined in the experiment
       documentation provided here.

These data have been extracted from the NSSDC archive for distribution
      by the PDS along with other Voyager solar wind data sets.  These data
      were not submitted to the PDS for archive and have not been through
      the PDS peer review process.  These data are provided by the PDS for
      the convenience of PDS users.  Please exercise caution when using these
      data.

      Comments on the Voyager 2 48 sec termination shock data

      The average magnetic field strength produced by the spacecraft at the
      location of the outboard magnetometer of the dual magnetometers system
      on V2 varies between 0.1 - 0.2 nT, comparable to the most probable
      magnetic field strength in the inner heliosheath and significantly
      larger than the most probable magnetic field strength in the distant
      supersonic solar wind. The spacecraft magnetic field is a complex,
      time-dependent signal that must be removed from the measured magnetic
      field signal in order to derive the ambient magnetic fields of the
      solar wind and heliosheath.  Corrections must also be made for spurious
      magnetic signals and noise associated with the telemetry system, ground
      tracking systems, and other factors. A non-periodic modulation of the
      spacecraft's magnetic field, with amplitudes comparable to the average
      ambient magnetic field strength and periods in the range from 1 to
      12 hours, has been present approximately half the time in the V2 data
      since ~1990, beginning in ~1985.  Finally, a spacecraft systems command
      during late 2006 had the unintended consequence of exposing the sensors
      to temperatures well beyond their design limits for more than one week.
      This command also rotated one set of dual triaxial sensors through a
      large angle and produced additional noise, drifts and spurious signals
      as a result of damage to the sensor assembly. Extracting the signal
      describing the solar wind and heliosheath from the many sources of
      uncertainty is a complex and partly subjective process that requires
      understanding of the instrument and judgment based on experience in
      dealing with the ever-changing extraneous signals. We estimate that
      the 1-sigma uncertainty in the 48 sec averages in the components of
      the magnetic field is typically ~ +/-0.03 nT. The uncertainties in
      F1, BR, BT, and BN can differ from one another and they may vary with
      time, but there is no practical way to determine these uncertainties
      more precisely at present.