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We have obtained spatially resolved spectra of Titan in the near-infrared J,H and K bands at a resolving power of ~5000 using the near-infrared integralfield spectrometer (NIFS) on the Gemini North 8m telescope. Using recent datafrom the Cassini/Huygens mission on the atmospheric composition and surface andaerosol properties, we develop a multiple-scattering radiative transfer modelfor the Titan atmosphere. The Titan spectrum at these wavelengths is dominatedby absorption due to methane with a series of strong absorption band systemsseparated by window regions where the surface of Titan can be seen. We use aline-by-line approach to derive the methane absorption coefficients. Themethane spectrum is only accurately represented in standard line lists down to~2.1 {\mu}m. However, by making use of recent laboratory data and modeling ofthe methane spectrum we are able to construct a new line list that can be useddown to 1.3 {\mu}m. The new line list allows us to generate spectra that are agood match to the observations at all wavelengths longer than 1.3 {\mu}m andallow us to model regions, such as the 1.55 {\mu}m window that could not bestudied usefully with previous line lists such as HITRAN 2008. We point out theimportance of the far-wing line shape of strong methane lines in determiningthe shape of the methane windows. Line shapes with Lorentzian, andsub-Lorentzian regions are needed to match the shape of the windows, butdifferent shape parameters are needed for the 1.55 {\mu}m and 2 {\mu}m windows.After the methane lines are modelled our observations are sensitive toadditional absorptions, and we use the data in the 1.55 {\mu}m region todetermine a D/H ratio of 1.77 \pm 0.20 x 10-4, and a CO mixing ratio of 50 \pm11 ppmv. In the 2 {\mu}m window we detect absorption features that can beidentified with the {\nu}5+3{\nu}6 and 2{\nu}3+2{\nu}6 bands of CH3D.

The Near-IR Spectrum of Titan Modeled with an Improved Methane Line List