Data Set Overview
      =================
      The data set covers the period Jan 25 through Feb 18, 1992
      (days 25 to 48 inclusive).

      Files VHMxx_xx.TAB and FGMxx_xx.TAB contain one minute
      averages of the magnetic field components and magnitude
      measured by either the VHM (Vector Helium Magnetometer) or FGM
      (Fluxgate Magnetometer), where xx_xx = Days of Year covered
      (25 = Jan 25). The three days of closest approach (38-40) are
      FGM; the others are VHM.

      Data
      ====
      Each line in the VHM/FGM files contains time in the format
      yyyy-mm-ddThh:mm:ss.sssZ (0000 hrs on Jan 25, 1992 would be
      1992-01-25T00:00:00.000Z), BR, BTHETA, BPHI, BMAGNITUDE in the
      format (1x,a24, 4f10.3). The time tag is the midpoint of the
      one minute averaging interval. BMAGNITUDE is the average of
      the field magnitude, not the magnitude of the average field
      vector. Field units are nT. BR, BTHETA and BPHI are one-minute
      averages of the field components in R-THETA-PHI coordinates
      (see below).

      Processing
      ==========
      VHM files were produced by first averaging high resolution (1s
      or 2s) field data in inertial spacecraft coordinates. Then the
      averages were transformed into R-THETA-PHI coordinates, using
      parameters from the Final SEDR (Supplementary Experiment Data
      Records). FGM files were produced in a similar manner by R.J.
      Forsyth at Imperial College. All files were then reformatted
      at the PDS/PPI Node to provide time tags consistent with those
      used on the rest of the ULYSSES JUPITER ENCOUNTER CD-ROM
      (ULY_0001), and merged into multiple day files.

      Coordinate System
      =================
      The field components are given in the R-THETA-PHI system,
      which is that conventionally used for comparison with models.
      The R axis is from Jupiter to Ulysses; the THETA axis is
      perpendicular to R and lies in the plane containing R and
      Jupiter's rotation axis and is positive southward; PHI
      completes the orthogonal right-handed system.

      The Ulysses at Jupiter EPHEM data includes all the parameters
      necessary to transform the field components into System III,
      ECL50, or inertial spacecraft coordinates. See Computation of
      Coordinate Transformations, below.

      The paragraphs below give methods for computing transformation
      matrices using trajectory parameters from the EPHEM files. As
      an alternative, note that the appendix in [SMITH&WENZEL1993]
      contains the orbital elements of Ulysses with respect to
      Jupiter and demonstrates how to calculate the position of
      Ulysses in System III and other coordinate systems without
      recourse to trajectory data files.

      The transformation matrix from R-THETA-PHI to System III
      (1965.0) consists of the column vectors of the R, THETA, and
      PHI axes expressed in System III. The R-axis in System III is
      cos(RLATJG) cos(360-RLONJG), cos(RLATJG) sin(360-RLONJG),
      sin(RLATJG). The PHI axis is the normalized crossproduct J x
      R, where J is the rotation axis which is just 0,0,1, so the
      unit vector in the PHI direction is -sin(360-RLONJG),
      cos(360-RLONJG), 0. The unit vector in the THETA direction is
      the crossproduct PHI x R = sin(RLATJG) cos(360-RLONJG),
      sin(RLATJG) sin(360-RLONJG), -cos(RLATJG).

      The transformation matrix from R-THETA-PHI back to ECL50
      consists of the column vectors of the R, THETA, and PHI axes
      expressed in ECL50. R is cos(RLATEC) cos(RLONEC), cos(RLATEC)
      sin(RLONEC), sin(RLATEC). PHI is the normalized crossproduct J
      x R, where J (North Pole of Jupiter) is given in the reference
      [SMITH&WENZEL1993] as -92.002 RA, 64.504 DEC, Earth Mean
      Equinox and Equator 1950.0. Rotating by 23.4458 deg (1950.0
      obliquity) gives J in ECL50 = (-.015037545, -.035534090,
      0.999255323). The THETA axis is PHI x R.

      Inertial spacecraft coordinates are defined as follows: Z is
      the Ulysses spin axis, which points approximately towards
      Earth; X is is perpendicular to Z and lies in the plane
      containing Z and S, where S is the Ulysses-to-Sun vector. X is
      positive toward the Sun. Z in ECL50 is cos(AXISLAT)
      cos(AXISLON), cos(AXISLAT) sin(AXISLON), sin(AXISLAT). S in
      ECL50 is -XSU, -YSU, -ZSU. The Y axis is the normalized
      crossproduct Z x S, and the X axis is Y x Z. The
      transformation matrix from ECL50 back to inertial spacecraft
      coordinates consists of the column vectors X, Y, and Z.

      The EPHEM data in this submission include all the parameters
      necessary to calculate the above transformations. In a few
      cases where the direction of the spin axis was not available
      in the SEDR, the Ulysses-to-Earth direction was substituted in
      the EPHEM data. It is suggested that interpolations in time be
      performed on vector components rather than angles in order to
      avoid difficulties near 0 or 360, and that double precision
      arithmetic be used in matrix multiplication.

Confidence Level Overview
      =========================
      Since the VHM sensor has greater resolution (4 pT in the +/- 8
      nT range), it was decided that the best quality dataset would
      consist of VHM data for the majority of the encounter period
      and FGM for days 38-40 when the VHM was in saturation.

      We feel that both VHM and FGM datasets have been individually
      calibrated to the best level that we can achieve at this time.
      It is possible that further small improvements could be made
      in the cross calibration between the two sensors; in the
      present dataset the differences between VHM and FGM at the
      beginning of day 38 and at the end of day 40 are less than 0.5
      nT.