A model of Titan's aerosols based on measurements made inside the atmosphere

Tomasko, M. G.; Doose, L. R.; Engel, S.; Dafoe, L. E.; West, Robert A.; Lemmon, M. T.; Karkoschka, Erich; See, C.

doi:10.1016/j.pss.2007.11.019

Cited by 267 publications

(382 citation statements)

References 20 publications

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“…A study of Titan's emission function from VIMS T38 observations of Ontario Lacus imply a 2-micron normal scattering optical depth of 1.12 for Titan's full atmosphere [10], consistent with an extrapolation of the DISR observations [156]. Using the DISR extrapolation and applying it to AVIATR, however, as in Fig.…”

Section: Science Instrumentssupporting

confidence: 63%

“…As observed in details by the Huygens probe near the equator during its descent into Titan's atmosphere in 2005 January-the only in situ measurement of vertical haze properties so far-the distribution of haze particles is not homogeneous with altitude [156]. The haze presents two abrupt changes in properties at ∼80 and ∼30 km.…”

Section: Task 23a Constrain Global Patterns Of Haze Transport and Timentioning

confidence: 95%

“…In the lowest a b Fig. 13 a The haze number density and aerosol size and shape as a function of altitude at tropical latitudes as inferred from the Huygens observations (from Tomasko et al [156]). b Twodimensional planetary distribution of Titan's haze scaled extinction (from [118]).…”

Section: Task 23a Constrain Global Patterns Of Haze Transport and Timentioning

confidence: 99%

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AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

et al. 2011

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We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVI-ATR). With independent delivery and direct-to-Earth communications, AVI-ATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan's global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments-2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector-AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan's atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earthyear nominal mission. We propose a novel 'gravity battery' climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead

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Section: Science Instrumentssupporting

confidence: 63%

Section: Task 23a Constrain Global Patterns Of Haze Transport and Timentioning

confidence: 95%

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AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

et al. 2011

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“…Synthetic spectra calculated using models of the aerosol scattering and structure made using DISR (Tomasko et al, 2008) can overestimate the observed intensities by a factor of up to ∼2. Reducing the aerosol single scattering albedo, ω H , reducing the aerosol opacity, or changing the scattering phase function can each reduce intensities in synthetic spectra.…”

Section: Resultsmentioning

confidence: 97%

Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

Ádámkovics

Mitchell

Hayes

et al. 2016

Icarus

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The spatial distribution of the tropospheric methane on Titan was measured using near-infrared spectroscopy. Ground-based observations at 1.5 µm (H-band) were performed during the same night using instruments with adaptive optics at both the W. M. Keck Observatory and at the Paranal Observatory on 17 July 2014 UT. The integral field observations with SINFONI on the VLT covered the entire H-band at moderate resolving power, R = λ/∆λ ≈ 1, 500, while the Keck observations were performed with NIRSPAO near 1.5525 µm at higher resolution, R ≈ 25, 000. The moderate resolution observations are used for flux calibration and for the determination of model parameters that can be degenerate in the interpretation of high resolution spectra. Line-by-line calculations of CH 4 and CH 3 D correlated k distributions from the HITRAN 2012 database were used, which incorporate revised line assignments near 1.5 µm. We fit the surface albedo and aerosol distributions in the VLT SINFONI observations that cover the entire H-band window and used these quantities to constrain the models of the high-resolution Keck NIRSPAO spectra when retrieving the methane abundances. Cassini VIMS images of the polar regions, acquired on 20 July 2014 UT, are used to validate the assumption that the opacity of tropospheric aerosol is relatively uniform below 10 km. We retrieved methane abundances at latitudes between 42 • S and 80 • N. The tropospheric methane in the Southern mid-latitudes was enhanced by a factor of ∼10-40% over the nominal profile that was measured using the GCMS on Huygens. The Northern hemisphere had ∼90% of the nominal methane abundance up to polar latitudes (80 • N). These measurements suggest that a source of saturated polar air is equilibrating with dryer conditions at lower latitudes.

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“…Furthermore, thanks to the joint NASA-ESA Cassini-Huygens satellite mission, Titan's surface and atmospheric structure are known in great detail. In particular, the measurements made inside Titan's atmosphere, made available by the Huygens landing probe, have provided accurate scattering and polarization parameters for the haze particles (e.g., Brown et al 2010;Tomasko et al 2008).…”

Section: Introductionmentioning

confidence: 99%

HST observations of the limb polarization of Titan

Bazzon

Schmid

Buenzli

2014

A&A

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Context. Titan is an excellent test case for detailed studies of the scattering polarization from thick hazy atmospheres. Accurate scattering and polarization parameters have been provided by the in situ measurements of the Cassini-Huygens landing probe. For Earth-bound observations Titan can only be observed at a backscattering situation, where the disk-integrated polarization is close to zero. However, with resolved imaging polarimetry a second order polarization signal along the entire limb of Titan can be measured. Aims. We present the first limb polarization measurements of Titan, which are compared as a test to our limb polarization models. Methods. Previously unpublished imaging polarimetry from the HST archive is presented, which resolves the disk of Titan. We determine flux-weighted averages of the limb polarization and radial limb polarization profiles, and investigate the degradation and cancelation effects in the polarization signal due to the limited spatial resolution of our observations. Taking this into account we derive corrected values for the limb polarization in Titan. The results are compared with limb polarization models, using atmosphere and haze scattering parameters from the literature. Results. In the wavelength bands between 250 nm and 2 μm a strong limb polarization of about 2−7% is detected with a position angle perpendicular to the limb. The fractional polarization is highest around 1 μm. As a first approximation, the polarization seems to be equally strong along the entire limb. The comparison of our data with model calculations and the literature shows that the detected polarization is compatible with expectations from previous polarimetric observations taken with Voyager 2, Pioneer 11, and the Huygens probe. Conclusions. Our results indicate that ground-based monitoring measurements of the limb-polarization of Titan could be useful for investigating local haze properties and the impact of short-term and seasonal variations of the hazy atmosphere of Titan. Planets with hazy atmospheres similar to Titan are particularly good candidates for detection with the polarimetric mode of the upcoming planet finder instrument at the VLT. Therefore, a good knowledge of the polarization properties of Titan is also important for the search and investigation of extra-solar planets.

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A model of Titan's aerosols based on measurements made inside the atmosphere

Cited by 267 publications

References 20 publications

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

AVIATR—Aerial Vehicle for In-situ and Airborne Titan Reconnaissance

Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

HST observations of the limb polarization of Titan

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