  The upsilon Andromedae system was the first multi-planet system discovered
orbiting a main sequence star. We describe the detection of water vapor in the
atmosphere of the innermost non-transiting gas giant ups~And~b by treating the
star-planet system as a spectroscopic binary with high-resolution, ground-based
spectroscopy. We resolve the signal of the planet's motion and break the
mass-inclination degeneracy for this non-transiting planet via deep combined
flux observations of the star and the planet. In total, seven epochs of Keck
NIRSPEC $L$ band observations, three epochs of Keck NIRSPEC short wavelength
$K$ band observations, and three epochs of Keck NIRSPEC long wavelength $K$
band observations of the ups~And~system were obtained. We perform a multi-epoch
cross correlation of the full data set with an atmospheric model. We measure
the radial projection of the Keplerian velocity ($K_P$ = 55 $\pm$ 9 km/s), true
mass ($M_b$ = 1.7 $^{+0.33}_{-0.24}$ $M_J$), and orbital inclination \big($i_b$
= 24 $\pm$ 4$^{\circ}$\big), and determine that the planet's opacity structure
is dominated by water vapor at the probed wavelengths. Dynamical simulations of
the planets in the ups~And~system with these orbital elements for ups~And~b
show that stable, long-term (100 Myr) orbital configurations exist. These
measurements will inform future studies of the stability and evolution of the
ups~And~system, as well as the atmospheric structure and composition of the hot
Jupiter.
