  We report interferometric observations of carbon monoxide (CO) and its
isotopologues in Titan's atmosphere using the Atacama Large
Millimeter/submillimeter Array (ALMA). The following transitions were detected:
CO (J = 1-0, 2-1, 3-2, 6-5), $^{13}$CO (J = 2-1, 3-2, 6-5), C$^{18}$O (J = 2-1,
3-2), and C$^{17}$O (J = 3-2). Molecular abundances and the vertical
atmospheric temperature profile were derived by modeling the observed emission
line profiles using NEMESIS, a line-by-line radiative transfer code. We present
the first spectroscopic detection of $^{17}$O in the outer solar system with
C$^{17}$O detected at > 8$\sigma$ confidence. The abundance of CO was
determined to be 49.6 ${\pm}$ 1.8 ppm, assumed to be constant with altitude,
with isotopic ratios $^{12}$C/$^{13}$C = 89.9 ${\pm}$ 3.4, $^{16}$O/$^{18}$O =
486 ${\pm}$ 22, and $^{16}$O/$^{17}$O = 2917${\pm}$359. The measurements of
$^{12}$C/$^{13}$C and $^{16}$O/$^{18}$O ratios are the most precise values
obtained in Titan's atmospheric CO to date. Our results are in good agreement
with previous studies and suggest no significant deviations from standard
terrestrial isotopic ratios.
