Data Set Overview
  =================
    This dataset contains the Galileo spacecraft trajectory data sampled
    every minutes for Oct. 29 and 30, 1991. The spacecraft closest
    approach to the asteroid was at 22:36:40 at a range of about 1600
    km.  The trajectory data are provided in two coordinate systems,
    Gaspra-centric Solar Ecliptic (GaSE) and Heliographic (HG)
    coordinates. The position of the spacecraft has been extracted from
    the SPICE kernels provided by the project. The time tags are the
    exact times for which the S/C position was calculated. The time tag
    is spacecraft event time (SCET) given in universal time (UT).

    Primary Dataset Reference:

      Kivelson, M.G., L.F. Bargatze,  K.K. Khurana, D.J. Southwood,
      R.J. Walker, P.J. Coleman, 'Magnetic Field Signatures Near
      Galileo's Closest Approach to Gaspra', Science, Vol. 261,
      p331-334, 16 July, 1993. [KIVELSONETAL1993]


  Data
  ====

    ------------------------------------------------------------------
    Table 1. Data record structure
    ------------------------------------------------------------------
    Column   Description
    ------------------------------------------------------------------
     time    S/C event time (UT) given in PDS time format
             YYYY-MM-DDThh:mm:ss.sssZ
     X       S/C distance from Gaspra in the X-direction in GaSE
             coordinates 
     Y       S/C distance from Gaspra in the Y-direction in GaSE
             coordinates 
     Z       S/C distance from Gaspra in the Z-direction in GaSE
             coordinates 
     R       S/C radial distance from the Sun 
     LAT     S/C solar latitude 
     LON     S/C solar (east) longitude 

     Missing data values = 9999999.9 and 99999.999
     Fortran Format of the data file: (1X, A24, 3F11.1,3F11.5)


  Coordinate Systems
  ==================
    The data are archived in two coordinate systems, GaSE and IHG
    (1950).  GaSE Gaspracentric Solar Ecliptic (GaSE) is a Gaspra
    centered coordinate system defined by the primary vector along the
    instantaneous Gaspra->Sun (GSun) line and the Earth's ecliptic north
    pole (ENP) as the secondary vector. In this coordinate system:

      X is the GSun unit vector taken to be positive towards the Sun.
      Y is the formed by the unitized cross product ENP x GSun
      Z completes the right handed set (Z = X x Y)

    such that the X-Z plane contains the ecliptic north pole.

    The data are also provided in inertial heliographic (epoch 1950)
    coordinates. The radial direction is taken along the instantaneous
    Sun->S/C line, positive away from the Sun. Latitude is the angle the
    radial vector makes with the Sun's equatorial plane at the reference
    epoch, positive above the equator. Longitude is measured from the
    longitude of the ascending node.  At the reference epoch, the
    inclination of the Sun's north pole was 7 deg 15 min and the
    longitude of the ascending node can be computed using the formula:

      Node =  74 deg 22 min + 0.84 min (year - 1900)

Confidence Level Overview
  =========================
    These data have been extracted from SPICE kernels that were created
    using post encounter ephemeris data. The data should be of the
    highest possible quality.