The 2003 November 14 occultation by Titan of TYC 1343-1865-1

Abstract

We observed a stellar occultation by Titan on 2003 November 14 from La Palma Observatory using ULTRACAM with three Sloan filters: u , g , and i (358, 487, and 758 nm, respectively). The occultation probed latitudes 2 • S and 1 • N during immersion and emersion, respectively. A prominent central flash was present in only the i filter, indicating wavelength-dependent atmospheric extinction. We inverted the light curves to obtain six lower-limit temperature profiles between 335 and 485 km (0.04 and 0.003 mb) altitude. The i profiles agreed with the temperature measured by the Huygens Atmospheric Structure Instrument [Fulchignoni, M., and 43 colleagues, 2005. Nature 438, 785-791] above 415 km (0.01 mb). The profiles obtained from different wavelength filters systematically diverge as altitude decreases, which implies significant extinction in the light curves. Applying an extinction model [Elliot, J.L., Young, L.A., 1992. Astron. J. 103, 991-1015] gave the altitudes of line of sight optical depth equal to unity: 396 ± 7 and 401 ± 20 km (u immersion and emersion); 354 ± 7 and 387 ± 7 km (g immersion and emersion); and 336 ± 5 and 318 ± 4 km (i immersion and emersion). Further analysis showed that the optical depth follows a power law in wavelength with index 1.3 ± 0.2. We present a new method for determining temperature from scintillation spikes in the occulting body's atmosphere. Temperatures derived with this method are equal to or warmer than those measured by the Huygens Atmospheric Structure Instrument. Using the highly structured, three-peaked central flash, we confirmed the shape of Titan's middle atmosphere using a model originally derived for a previous Titan

ULTRASPEC: a high-speed imaging photometer on the 2.4-m Thai National Telescope

“…For example, one can use high time-resolution observations of the eclipses, transits and occultations of exoplanets, brown dwarfs and solar system objects to provide unsurpassed spatial resolution, as well as to search for small variations in their orbits due to the presence of other bodies, e.g. Zalucha et al (2007), Ortiz et al (2012), Marsh et al (2014), Richichi et al (2014). Some of these targets, e.g.…”

Titan's atmosphere and climate

“…Although Titan's atmosphere is colder than Earth's, Titan's atmosphere is more extended, with scale heights of 15 to 50 km (compared to 5 to 8 km on Earth) due to Titan's lower gravity [ Flasar et al , ]. Finer‐scale structure in temperature measurements attributed to atmospheric waves has also been observed throughout the atmosphere [see, e.g., Sicardy et al , ; Fulchignoni et al , ; Müller‐Wodarg et al , ; Sicardy et al , ; Strobel , ; Zalucha et al , ; Aboudan et al , ; Koskinen et al , ; Lorenz et al , ]. Temperatures in the thermosphere are similar to those in the mesosphere, despite the significant EUV heating rates in the thermosphere, due to efficient cooling by HCN rotational lines [ Yelle , ].…”

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

“…Coustenis & Bézard 1995;Lebonnois et al 2001;Vinatier et al 2006), wind measurements through occultation and Doppler observations (e.g. Hubbard et al 1993;Sicardy et al 1999Sicardy et al , 2006Bouchez 2004;Kostiuk et al 2005;Zalucha et al 2007) and the haze density (Lorenz et al 1999;Rannou et al 2006) that manifest Titan's general circulation. The atmospheric opacity structure further establishes the solar energy partitioning, including the surface insolation (figure 3).…”