Data Set Overview
  =================
    This data set contains images of the Saturn system taken by the
    Wide Field/Planetary Camera 2 (WFPC2) aboard the Hubble Space
    Telescope (HST) through November 1995.  This period includes all
    images taken during the Saturn ring plane crossings of 1995.  (No
    WFPC2 images of Saturn were obtained during the last ring plane
    crossing in February 1996 because Saturn was too close to the
    Sun.)
 
    Every WFPC2 image showing Saturn, its rings or the region of the
    inner satellites has been included in this data set, regardless of
    the original intended purpose.  Note that some images were not
    specifically intended for ring or inner satellite observations and
    so are not optimally exposed for this use.
 
    The HST observing programs whose results are included in this
    data set are as follows:
 
     Proposal: 5219
     Title:    Saturn's Aurora, Airglow, and Extended Atmosphere
     PI:       John Trauger (Jet Propulsion Laboratory)
 
     Proposal: 5508
     Title:    Tracking Features in Titan's Lower Atmosphere and on
               its Surface
     PI:       Peter Smith (Lunar and Planetary Laboratory)
 
     Proposal: 5776
     Title:    Observations of the 1994 Spot on Saturn
     PI:       Reta Beebe (New Mexico State University)
 
     Proposal: 5782
     Title:    Saturn Ring-Plane Crossing, May 1995
     PI:       Amanda Bosh (Lowell Observatory)
 
     Proposal: 5824
     Title:    Occultation of GSC5249-01240 by Saturn: Atmospheric
               and Ring Studies
     PI:       Amanda Bosh (Lowell Observatory)
 
     Proposal: 5836
     Title:    Saturn Ring Plane Crossing Observations in August
               and November 1995
     PI:       Philip Nicholson (Cornell University)
 
     Proposal: 6030
     Title:    Clouds and Aerosols on Saturn and Uranus
     PI:       Martin Tomasko (Lunar and Planetary Lab)
 
     Proposal: 6215
     Title:    Saturn's Aurora and Airglow
     PI:       John Trauger (Jet Propulsion Laboratory)
 
     Proposal: 6216
     Title:    Saturn's Ring Atmosphere during Ring Plane Crossing
     PI:       John Trauger (Jet Propulsion Laboratory)
 
     Proposal: 6295
     Title:    Imaging the Atmosphere of Titan and its Surface
     PI:       John Caldwell (York University)
 
     Proposal: 6328
     Title:    Imaging and Spatial Scans of Saturn Near Ring-Plane
               Crossing
     PI:       John Caldwell (York University)
 
 
    In the specific case of the Titan proposals 5508 and 6295, some
    images show Titan but not Saturn or its rings.  These
    particular images have not been archived in this data set;
    however, they are obtainable from the HST Data Archive at:
 
        http://archive.stsci.edu/
 
    Files are distributed across this set of five CDROMs roughly
    chronologically, as follows:
 
  Volume    Directory          Proposal         Dates       # Images
   RPX_0001  199410XX/U2IQXXXX  5219, Trauger    1994-10-09    7
             199410XX/U2IZXXXX  5508, Smith      1994-10-05    6
                                                 1994-10-06    6
             199412XX/U2KRXXXX  5776, Beebe      1994-12-01    9
             199505XX/U2OOXXXX  6216, Trauger    1995-05-22    7
 
   RPX_0002  199505XX/U2ONXXXX  5782, Bosh       1995-05-22   48
 
   RPX_0003  199508XX/U2TFXXXX  5836, Nicholson  1995-08-09    8
                                                 1995-08-10   42
                                                 1995-08-11    4
 
   RPX_0004  199508XX/U2OOXXXX  6216, Trauger    1995-08-10    4
             199508XX/U2QEXXXX  6030, Tomasko    1995-08-06    8
             199510XX/U2VIXXXX  6295, Caldwell   1995-10-01    8
                                                 1995-10-09    8
             199510XX/U2WCXXXX  6215, Trauger    1995-10-15    4
                                                 1995-10-31    4
             199511XX/U2QEXXXX  6030, Tomasko    1995-11-17   16
 
   RPX_0005  199511XX/U2OOXXXX  6216, Trauger    1995-11-20    3
             199511XX/U2TFXXXX  5836, Nicholson  1995-11-21   20
                                                 1995-11-27    8
             199511XX/U2ZNXXXX  6328, Caldwell   1995-11-18   10
             199511XX/U2ZYXXXX  5824, Bosh       1995-11-21    2
                                                 1995-11-22    4
 
 
  Parameters
  ==========
    WFPC2 observations record the image brightness of Saturn and or
    its rings and moons in a particular filter for the specified
    exposure time.
 
    The PDS label for each file contains a broad variety of
    additional parameters enabling the user to determine image
    geometry and to convert pixel values to physically meaningful
    quantities.
 
 
  Processing
  ==========
    The calibrated images have been passed through the Space
    Telescope Science Institute's processing 'pipeline' which
    includes: analog-to-digital conversion, bias level correction,
    bias correction, dark current correction, and flat field
    correction.  For a detailed outline, see [BIRETTAETAL1993].
 
 
  Data
  ====
    The data provided here are images and tables in FITS format, as
    provided by the Space Telescope Archive.  For each data file, a
    detached PDS label is provided containing additional
    parameters.
 
    Most users will prefer to focus on the fully calibrated images
    found in the CALIMAGE subdirectories of these volumes.  Such
    files have been through the full HST processing pipeline and so
    are relatively straightforward to interpret both geometrically
    and photometrically.  The detached PDS label files contain the
    key parameters needed to perform this interpretation.
 
    The other especially useful subdirectories are those entitled
    BROWSE, which contain easy-to-display GIF files showing the
    images at compressed scale and with the four fields of view
    (PC1, WF2, WF3, WF4) mosaicked into a single image.  These
    files are especially useful when the user desires only a quick
    look at what the images contain.
 
    All additional data files on this disk have been compressed
    using Zip 2.1, as provided by the Info-Zip web site at:
 
       http://www.cdrom.com/pub/infozip/
 
    To use these files, it will first be necessary to run UnZip,
    also available at the same site.  (See also the discussion of
    software below).  These additional data files are generally
    only needed by more sophisticated users who need to re-process
    the data; this should rarely be necessary.  The files are as
    follows:
 
     Subdirectory  STScI file   File contents
                   extension
 
       CALMASK       .c1f       quality mask for calibrated image.
       ENGDATA       .x0f       extracted engineering data.
       ENGMASK       .q1f       quality mask for engineering data.
       HEADER        .shf       standard header containing
                                observation parameters.
       RAWIMAGE      .d0f       raw image.
       RAWMASK       .q0f       data quality mask for raw image.
 
    See Chapter 25 of the HST Data Handbook for more information
    about these files.
 
 
  Ancillary Data
  ==============
    Additional geometry and calibration files are provided to
    assist in the analysis and interpretation of the data.
 
    On each volume, the CALIBRATION subdirectory contains filter
    profiles for (most of) the filters used in this data set.  It
    also contains a model solar spectrum.
 
    The first volume of this set contains a GEOMETRY subdirectory,
    containing ephemeris files for Saturn and its satellites, plus
    the Sun, Earth, and Moon.  These files are provided in SPICE
    format for a variety of platforms.  For more information about
    SPICE data and toolkits, consult the PDS Navigation and
    Ancillary Information (NAIF) Node at:
 
       http://pds.nasa.gov/naif.html
 
 
  Coordinate System
  =================
    All geometric quantities appearing in the labels are in J2000
    coordinates.  In this coordinate frame, the z-axis points
    northward along the Earth's J2000 rotation axis and the x-axis
    points toward the First Point of Aries.
 
 
  Software
  ========
    Included on this disk is the source code for Unzip 5.32, needed
    to decompress many of the data files on this disk.  This is
    found in the SOFTWARE subdirectory.  However, most users will
    probably prefer to download a pre-built binary for their
    particular platform from the Info-Zip web site at:
 
       http://www.cdrom.com/pub/infozip/
 
 
  Media/Format
  ============
    This data set is archived on compact disc (CDROM) media.
    Organization and formats are according to PDS and ISO 9660
    level 1 standards.
 
    Compressed files have been generated using Zip 2.1 as
    distributed by Info-Zip.  Details of the Zip format and
    decompression source code are included in the SOFTWARE
    directory of this data set.
 
    Decompressed files are in FITS format, with detached PDS
    labels.  The FITS file standard is described in 'Definition of
    the Flexible Image Transport System (FITS) Standard', from the
    NASA/Science Office of Standards and Technology.  Specific
    information about STScI's usage of FITS keywords is found in
    the HST Data Handbook.

Confidence Level Overview
  =========================
    The well-known problems of HST's mirrors and the corrections
    for the WFPC2 are discussed in [BIRETTAETAL1996].  Filter
    characteristics, calibration procedures and a description of
    the methane filter are also included in this reference.
 
 
  Review
  ======
    This data set passed peer review on September 30, 1999.  The
    members of the peer review panel were Amanda Bosh, Richard French,
    Lyle Huber, Stephen Larson, Claude Roddier, and Philip Nicholson.
    Ron Joyner represented the PDS Central Node at JPL.
 
 
  Data Coverage and Quality
  =========================
    Saturn was imaged continuously during the hours surrounding
    Earth's crossings of the ring plane on May 22, 1995 and August
    10, 1995.  Saturn was too close to the Sun for observations on
    February 11, 1996.  Nearly-continuous imaging also occurred
    during the ring 'sunset' on November 21, 1995.  During these
    periods of ring-targeted observing, images are of extremely high
    quality.
 
    Naturally, images intended for observations of Saturn and/or
    Titan are not always exposed optimally for ring and ring-moon
    science.