  We study Minkowski Functionals as probes of primordial non-Gaussianity in the
Cosmic Microwave Background, specifically for the estimate of the primordial
`local' bi-spectrum parameter f_NL, with instrumental parameters which should
be appropriate for the Planck experiment. We use a maximum likelihood approach,
which we couple with various filtering methods and test thoroughly for
convergence. We included the effect of inhomogeneous noise as well as
astrophysical biases induced by point sources and by the contamination from the
Galaxy. We find that, when Wiener filtered maps are used (rather than simply
smoothed with Gaussian), the expected error on the measurement of f_NL should
be as small as \Delta f_NL \simeq 10 when combining the 3 channels at 100, 143
and 217 GHz in the Planck extended mission setup. This result is fairly
insensitive to the non homogeneous nature of the noise, at least for realistic
hit-maps expected from Planck. We then estimate the bias induced on the
measurement of f_NL by point sources in those 3 channels. With the appropriate
masking of the bright sources, this bias can be reduced to a negligible level
in the 100 and 143 GHz channels. It remains significant in the 217 GHz channel,
but can be corrected for. The galactic foreground biases are quite important
and present a complex dependence on sky coverage: making them negligible will
depend strongly on the quality of the component separation methods.
