  We examine the prospects for detecting gamma-rays from dark matter
annihilation in the six most promising dwarf spheroidal (dSph) satellite
galaxies of the Milky Way. We use recently-measured velocity dispersion
profiles to provide a systematic investigation of the dark matter mass
distribution of each galaxy, and show that the uncertainty in the gamma-ray
flux from mass modeling is less than a factor of ~ 5 for each dSph if we assume
a smooth NFW profile. We show that Ursa Minor and Draco are the most promising
dSphs for gamma-ray detection with GLAST and other planned observatories. For
each dSph, we investigate the flux enhancement resulting from halo
substructure, and show that the enhancement factor relative to a smooth halo
flux cannot be greater than about 100. This enhancement depends very weakly on
the lower mass cut-off scale of the substructure mass function. While the
amplitude of the expected flux from each dSph depends sensitively on the dark
matter model, we show that the flux ratios between the six Sphs are known to
within a factor of about 10. The flux ratios are also relatively insensitive to
the current theoretical range of cold dark matter halo central slopes and
substructure fractions.
