Data Set Overview
  =================
    This shape model of Phobos is based on 224 Viking Orbiter 1 VIS-A and
    VIS-B camera images taken in 1976-1978, and eight Phobos 2 VSK images
    taken in 1989. The shape model was prepared by Robert Gaskell on March 11,
    2006.
 
    The geometrical coordinate system of this model is defined by the
    planetary constants file pck00006.tpc, available in PDS from the NAIF
    node.  To find the file in PDS, go to the NAIF SPICE archive at
    http://naif.jpl.nasa.gov/naif/data_archived.html.  In the table of data
    links, select the volume FTP link for the Viking Orbiter mission.
    Within the volume, go to the data/pck directory, and download the desired
    file (pck00006.tpc).
 
The parameters of the model are as follows:
 
    Number of landmarks: 456
    Formal position uncertainty: 18 m/component
    Number of images: 232
    Pointing uncertainty: .018 mrad
    S/C position uncertainty: N/A (positions treated as given)
    Pointing residuals: (initial pointings treated as unknown)
    range residuals N/A
    Number of measurement pairs: 18345
    Number of measurements per landmark: 40
    RMS LMK location residual: 25 m/component
 
    The models were originally prepared in the Implicitly Connected
    Quadrilateral (ICQ) format.  Vertex-facet format versions, derived from
    the ICQ versions, are also provided.  The filenames are
    phobos_quad512q.tab and phobos_ver512q.tab, where 512 is the value of Q
    (an indicator of the resolution). Files with three selections of lower
    resolution are also provided for each format, with similar filenames but
    lower values of q.
 
    The file 'phobosimagelist.tab' is a list of the Viking Orbiter 1 VIS-A and
    VIS-B camera images and Phobos 2 VSK-FREGAT images used to generate this
    model.  (VSK-FREGAT is a three-channel television camera which flew on the
    Soviet Phobos 2 mission.)
 
    A text file, 'icqmodel.asc' is provided in the 'document' directory which
    describes the ICQ format and the derivation of the vertex-facet versions.

Confidence Level Overview
  =========================
    Note that the vertex-facet versions of the model have some duplicate
    vertices on the edges and corners of the cube.  The duplicate vertices are
    not used in the facet table, resulting in the presence of some vertices in
    the vertex table which do not appear in the facet table.  This does not
    affect the correctness of the vertex-facet version.