  Accurate fundamental parameters of stars are mandatory for the asteroseismic
investigation of the Kepler mission to succeed. We will determine the
atmospheric parameters for a sample of 6 well-studied bright K giants to
confirm that our method produces reliable results. We then apply the same
method to 14 K giants that are targets for the Kepler mission. We have used
high-resolution, high signal-to-noise spectra from the FIES spectrograph on the
Nordic Optical Telescope. We used the iterative spectral synthesis method VWA
to derive the fundamental parameters from carefully selected high-quality iron
lines and pressure-sensitive Calcium lines. We find good agreement with
parameters from the literature for the 6 bright giants. We compared the
spectroscopic values with parameters based on photometric indices in the Kepler
Input Catalogue (KIC). We identify serious problems with the KIC values for
[Fe/H] and find a large RMS scatter of 0.5 dex. The log g values in KIC agree
reasonably well with the spectroscopic values with a scatter of 0.25 dex, when
excluding two low-metallicity giants. The Teffs from VWA and KIC agree well
with a scatter of about 85 K. We also find good agreement with log g and Teff
derived from asteroseismic analyses for seven Kepler giant targets. We have
determined accurate fundamental parameters of 14 giants using spectroscopic
data. The large discrepancies between photometric and spectroscopic values of
[Fe/H] emphasize the need for further detailed spectroscopic follow-up of the
Kepler targets. This is mandatory to be able to produce reliable constraints
for detailed asteroseismic analyses and for the interpretation of possible
exo-planet candidates found around giant stars.
