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Abstract: We present the results of six soundings of the atmosphere of Titan by the radio occultation technique using the Cassini spacecraft currently in orbit around Saturn. These occultations occurred during four separate targeted Titan encounters in both the Prime and Equinox missions of Cassini over 3years. They cover a wide range of latitude from 75°S to 79°N, split so that three soundings are in the northern hemisphere and three are in the southern hemisphere. Techniques and error analysis are similar to Schinder et al. (2011). The six temperature-altitude profiles presented here are compared to those earlier results. Of special interest is the sudden cooling observed at altitudes of ∼80–100km in the two high northern (winter) soundings at 74°N and 80°N, where the temperature drops by about 10K over the course of 20km. The northern profiles also exhibit a transition between the troposphere and stratosphere that is much more abrupt than in the south, and the northern tropopause temperatures are much cooler. [Copyright &y& Elsevier]

Abstract: We present results from the two radio occultations of the Cassini spacecraft by Titan in 2006, which probed mid-southern latitudes. Three of the ingress and egress soundings occurred within a narrow latitude range, 31–34°S near the surface, and the fourth at 52.8°S. Temperature–altitude profiles for all four occultation soundings are presented, and compared with the results of the Voyager 1 radio occultation (Lindal, G.F., Wood, G.E., Hotz, H.B., Sweetnam, D.N., Eshleman, V.R., Tyler, G.L. [1983]. Icarus 53, 348–363), the HASI instrument on the Huygens descent probe (Fulchignoni, M. et al. [2005]. Nature 438, 785–791), and Cassini CIRS results (Flasar, F.M. et al. [2005]. Science 308, 975–978; Achterberg, R.K., Conrath, B.J., Gierasch, P.J., Flasar, F.M., Nixon, C.A. [2008b]. Icarus 194, 263–277). Sources of error in the retrieved temperature–altitude profiles are also discussed, and a major contribution is from spacecraft velocity errors in the reconstructed ephemeris. These can be reduced by using CIRS data at 300km to make along-track adjustments of the spacecraft timing. The occultation soundings indicate that the temperatures just above the surface at 31–34°S are about 93K, while that at 53°S is about 1K colder. At the tropopause, the temperatures at the lower latitudes are all about 70K, while the 53°S profile is again 1K colder. The temperature lapse rate in the lowest 2km for the two ingress (dawn) profiles at 31 and 33°S lie along a dry adiabat except within ∼200m of the surface, where a small stable inversion occurs. This could be explained by turbulent mixing with low viscosity near the surface. The egress profile near 34°S shows a more complex structure in the lowest 2km, while the egress profile at 53°S is more stable. [Copyright &y& Elsevier]