Data Set Overview
  =================
    The best description of this data set is [KARKOSCHKA1998] which
    can be found in ASCII form in /DOCUMENT/ICARUS98.ASC on this
    volume.  Some of the text in this DATASET.CAT file is quoted
    from this reference.  Additionally, the previous version (1993)
    of this data set is included as well.  The reference for that
    portion of the data set is [KARKOSCHKA1994] and can be found in
    /DOCUMENT/ICARUS94.ASC.
 
    Full-disk albedo spectra of the jovian planets and Titan were
    derived from observations at the European Southern Observatory
    in July 1995.  The spectra extend from 300 to 1050 nm
    wavelength.  The spectral resolution is 0.4 nm between 520 and
    995 nm, and 1 nm elsewhere.  The accuracy of the albedo
    calibration is 4 percent.  UBV magnitudes were also determined.
    Raman scattering was quantified for each planet.  Methane and
    ammonia bands are shown at 0.4 nm spectral resolution,
    including a new band at 930 nm wavelength which is probably due
    to ammonia.  Maps of the variation of these absorptions across
    the disks of Jupiter and Saturn are displayed.  Saturn's
    spectrum is undisturbed by light from its rings due to the
    edge-on geometry during the observations.  The albedo of Uranus
    near 1 micro-m wavelength has dropped almost 10 percent between
    1993 and 1995, while there has been no change in the
    ultraviolet.  The signature of light from Titan's surface
    yielded a path length of 4 km-am of methane in Titan's
    atmosphere.  The temperature dependence of the width of the
    890-nm methane band was used to measure temperature variations
    at three altitude levels, resulting in the first temperature
    maps of Jupiter and Saturn based on reflected sunlight.
    Jupiter displays a banded temperature structure with some
    discrete features of a few Kelvin amplitude.  Saturn's
    north-south temperature asymmetry has reversed since the
    Voyager observations.
 
 
  Data
  ====
    The tables present the methane absorption coefficient and
    albedos of Jupiter, Saturn, Uranus, Neptune and Titan at 1 nm
    resolution and 0.4 nm sampling from 300-1050 nm and at 0.4 nm
    resolution and 0.1 nm sampling from 520-995 nm.

Confidence Level Overview
  =========================
    Table II in [KARKOSCHKA1998] summarizes the UBV magnitudes,
    calculated from the albedo spectra by the same method as
    [KARKOSCHKA1994].  Note that for Jupiter, Saturn, and Titan,
    their full-disk albedos shown are not geometric albedos and the
    listed magnitudes are not opposition magnitudes due to their
    finite phase angles during the observation.  Geometric albedos
    of Jupiter and Saturn are probably some 5 percent larger than
    the given albedos.  Accordingly, their opposition magnitudes
    are about 0.05 more negative than the listed magnitudes.
 
    As stated in [KARKOSCHKA1994], relative albedos are good to 2
    percent and absolute albedos are good to 4 percent, mostly due
    to the uncertainty in the solar-to-stellar flux ratio.  The 2
    percent accuracy applies also to the 2-year variations which
    are not influenced by solar or stellar flux errors since the
    same comparison stars were used in both years.  These
    percentages are relative to the albedo value, thus an albedo of
    0.1 is accurate to 0.004.
 
 
  Review
  ======
    This data set underwent PDS peer review in January 1999.
    Members of the peer review panel were Lyle Huber and Ron Joyner
    representing PDS, Erich Karkoschka as data provider and Don
    Banfield and David Kuehn as external reviewers.
 
 
  Data Coverage and Quality
  =========================
    The spectrograph has scattered light near the ends of the CCD
    which was not known during the observations in 1993.  Thus, the
    albedos of 1993 below 330 nm, above 970 nm, and near 650 nm
    wavelength are less reliable.  In 1995, this problem was known
    and avoided by appropriate placement.  Lower levels of
    scattered light may be present elsewhere since they are
    difficult to detect.  If this were the case, spectral regions
    with low data numbers may be influenced, which are the ends of
    the wavelength region, the deep methane bands, and wavelengths
    where the earth's atmosphere is almost opaque (cf. Fig.  1 of
    [KARKOSCHKA1994]).  The fact that the ratios between the 1993
    and 1995 data display some unexpected features of a few percent
    in the deepest methane bands indicates that the relative
    accuracy at those wavelengths may be significantly worse than
    the 2 percent estimate made above.
 
    Section IV of [KARKOSCHKA1998] describes a few systematic
    discrepancies of about 1 percent.  Many wavelength regions do
    not show such a discrepancy indicating that the spectral shape
    may have been recorded to better than the 1 % level at those
    wavelengths.
 
    The indirect determination of methane absorption coefficients
    is likely to give more approriate values for the purpose of
    modeling the jovian planets' atmospheres than previous
    laboratory measurements at room temperature, but likely to be
    less reliable than recent laboratory measurements at low
    temperature for selected spectral regions.  The levels of
    absorption coefficients derived here depend on Benner's values
    (cf. [KARKOSCHKA1994]).  If some of Benner's values were wrong
    by 10 %, the inferred absorption coefficients could be off by
    20 % in some spectral regions.