Winds on Titan from ground‐based tracking of the Huygens probe

Abstract

[1] Large radio telescopes on Earth tracked the radio signal transmitted by the Huygens probe during its mission at Titan. Frequency measurements were conducted as a part of the Huygens Doppler Wind Experiment (DWE) in order to derive the velocity of the probe in the direction to Earth. The DWE instrumentation on board Huygens consisted of an ultrastable oscillator which maintained the high Doppler stability required for a determination of probe horizontal motion during the atmospheric descent. A vertical profile of the zonal wind velocity in Titan's atmosphere was constructed from the Doppler data under the plausible assumption of generally small meridional wind, as validated by tracked images from the Huygens Descent Imager/Spectral Radiometer (DISR). We report here on improved results based on data with higher temporal resolution than that presented in the preliminary analysis by Bird et al. (2005), corroborating the first in situ measurement of Titan's atmospheric superrotation and a region of strong vertical shear reversal within the lower stratosphere. We also present the first high-resolution display and interpretation of the winds near the surface and planetary boundary layer.

Temporal variations of Titan’s middle-atmospheric temperatures from 2004 to 2009 observed by Cassini/CIRS

“…2. Following Achterberg et al (2008a), we use as a boundary condition a wind in solid body rotation at 10 mbar with an angular velocity of four times the solid body rotation rate, consistent with the winds at that level measured by the Huygens Doppler Wind Experiment (Bird et al, 2005;Folkner et al, 2006). The resulting winds are shown in Fig.…”

Twilight on Ligeia: Implications of communications geometry and seasonal winds for exploring Titan’s seas 2020–2040

“…Of presently-published models, TitanWRF produces the strongest superrotation, and while it does predict somewhat faster zonal wind speeds in the lower stratosphere near the equator than were observed by the Huygens probe (Bird et al, 2005;Folkner et al, 2006) it offers the best agreement with thermal infrared observations by Cassini (Achterberg et al, 2011) Fig. 7 shows zonal wind profiles for several sea targets in the coming decades.…”

Storms, polar deposits and the methane cycle in Titan's atmosphere

“…Griffith et al 1991;Brown et al 2002Brown et al , 2006Roe et al 2002;Porco et al 2005), three temperature profiles of Titan's tropical atmosphere (Lindal et al 1983;Fulchignoni et al 2005) and one measurement of Titan's methane abundance profile (figure 2) at the probe landing site (Niemann et al 2005). The drift of clouds and of the Huygens probe provide a few spotted measurements of tropospheric zonal winds, and indicate prograde winds of 10-35 m s K1 at 20-40 km that decrease with altitude to speeds less than 1 m s K1 below 5 km altitude (Bird et al 2005;Griffith et al 2005;Porco et al 2005;Folkner et al 2006). Upper atmosphere measurements also bear on the topic, particularly temperature maps (Flasar et al 2005), and the latitude profiles of minor species (e.g.…”