Submillimeter observations of Titan:: Global measures of stratospheric temperature, CO, HCN, HC3N, and the isotopic ratios 12C/13C and 14N/15N

Interferometric observations of the atmosphere of Titan were performed with the Submillimeter Array on two nights in 2004 February to investigate the global average vertical distributions of several molecular species above the tropopause. Rotational transitions of CO, isomers of HCN, and HC3N were simultaneously recorded. The abundance of CO is determined to be parts per million (ppm), constant with altitude. The vertical profile 51 +/- 4 of HCN is dependent on the assumed temperature but generally increases from 30 parts per billion at the condensation altitude (similar to83 km) to 5 ppm at similar to300 km. Furthermore, the central core of the HCN emission is strong and can be reproduced only if the upper stratospheric temperature increases with altitude. The isotopic ratios are determined to be C-12/C-13 = 132 +/- 25 and N-14/N-15 = 94 +/-13 assuming the Coustenis & Bezard temperature profile. If the Lellouch temperature profile is assumed, the ratios decrease to C-12/C-13 =108 +/- 20 and N-14/N-15 = 72 +/- 9. The vertical profile of HC3N is consistent with that derived by Marten et al.