One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature1,2 and evidence for the presence of strong zonal winds3. It was realized that the motion of an atmospheric probe could be used to study the winds, which led to the inclusion of the Doppler Wind Experiment4 on the Huygens probe5. Here we report a high resolution vertical profile of Titan's winds, with an estimated accuracy of better than 1 m s-1. The zonal winds were prograde during most of the atmospheric descent, providing in situ confirmation of superrotation on Titan. A layer with surprisingly slow wind, where the velocity decreased to near zero, was detected at altitudes between 60 and 100 km. Generally weak winds (∼1 m s-1) were seen in the lowest 5 km of descent.
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This Letter presents results of a research project partially funded by the Deutsches Zentrum für Luft- und Raumfahrt (DLR). Parts of the research described here were carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA, and by NASA's Goddard Institute for Space Studies. We thank R. Kohl, K.-P. Wagner and M. Heyl for their efforts during the DWE development programme. We appreciate the support provided by the National Radio Astronomy Observatory (NRAO) and the Australia Telescope National Facility (ATNF). NRAO is operated by Associated Universities, Inc., under a cooperative agreement with the NSF. The ATNF, managed by the Commonwealth Scientific and Industrial Research Organization (CSIRO), is funded by the Commonwealth of Australia.
Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.
This file contains the Supplementary Discussion, Supplementary Figures 1–3, Supplementary Tables 1–2. Supplementary Figure 1 details Huygens signal frequency measurements at the Green Bank and Parkes radio telescopes. Supplementary Figure 2 presents Huygens frequency measurements and predictions at the Green Bank Telescope. Supplementary Figure 3 details Huygens frequency measurements and predictions at the Parkes Telescope. Supplementary Table 1 lists radio telescopes participating in the Earth-based DWE network. Supplementary Table 2 presents the Radio link budget: Huygens-to-Green Bank Telescope. (PDF 70 kb)
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Bird, M., Allison, M., Asmar, S. et al. The vertical profile of winds on Titan. Nature 438, 800–802 (2005). https://doi.org/10.1038/nature04060
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