Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer

Flasar, F. M.; Kunde, V. G.; Abbas, M. M.; Achterberg, R. K.; Ade, Peter A. R.; Barucci, A.; Bézard, Bruno; Bjoraker, G. L.; Brasunas, J. C.; Calcutt, S. B.; Carlson, R.; Césarsky, C. J.; Conrath, B. J.; Coradini, A.; Courtin, R.; Coustenis, A.; Edberg, Stephen J.; Edgington, S. G.; Ferrari, C.; Fouchet, Thierry; Gautier, D.; Gierasch, P. J.; Grossman, K.; Irwin, Patrick; Jennings, Donald E.; Lellouch, E.; Mamoutkine, A. A.; Marten, A.; Meyer, J. P.; Nixon, C. A.; Orton, Glenn S.; Owen, Tobias; Pearl, J. C.; Prangé, Renée; Raulin, F.; Read, P. L.; Romani, P. N.; Samuelson, R. E.; Segura, M.; Showalter, M. R.; Simon-Miller, A. A.; Smith, M. D.; Spencer, J. R.; Spilker, L. J.; Taylor, F. W.

doi:10.1007/s11214-004-1454-9

Cited by 281 publications

(127 citation statements)

References 286 publications

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“…A detailed description of CIRS technical characteristics and observing modes can be found in Flasar et al (2004). Here we report on the analysis of unapodized spectra acquired in limb viewing geometry by FP3 and FP4.…”

Section: Cassini/cirs Limb Observationsmentioning

confidence: 99%

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Guerlet

Fouchet

Vinatier

et al. 2015

A&A

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Context. Saturn's polar upper atmosphere exhibits significant auroral activity; however, its impact on stratospheric chemistry (i.e. the production of benzene and heavier hydrocarbons) and thermal structure remains poorly documented. Aims. We aim to bring new constraints on the benzene distribution in Saturn's stratosphere, to characterize polar aerosols (their vertical distribution, composition, thermal infrared optical properties), and to quantify the aerosols' radiative impact on the thermal structure. Methods. Infrared spectra acquired by the Composite Infrared Spectrometer (CIRS) on board Cassini in limb viewing geometry are analysed to derive benzene column abundances and aerosol opacity profiles over the 3 to 0.1 mbar pressure range. The spectral dependency of the haze opacity is assessed in the ranges 680-900 and 1360-1440 cm −1 . Then, a radiative climate model is used to compute equilibrium temperature profiles, with and without haze, given the haze properties derived from CIRS measurements. Results. On Saturn's auroral region (80• S), benzene is found to be slightly enhanced compared to its equatorial and mid-latitude values. This contrasts with the Moses & Greathouse (2005, J. Geophys. Res., 110, 9007) photochemical model, which predicts a benzene abundance 50 times lower at 80• S than at the equator. This advocates for the inclusion of ion-related reactions in Saturn's chemical models. The polar stratosphere is also enriched in aerosols, with spectral signatures consistent with vibration modes assigned to aromatic and aliphatic hydrocarbons, and presenting similarities with the signatures observed in Titan's stratosphere. The aerosol mass loading at 80• S is estimated to be 1−4 × 10 −5 g cm −2 , an order of magnitude less than on Jupiter, which is consistent with the order of magnitude weaker auroral power at Saturn. We estimate that this polar haze warms the middle stratosphere by 6 K in summer and cools the upper stratosphere by 5 K in winter. Hence, aerosols linked with auroral activity can partly account for the warm polar hood observed in Saturn's summer stratosphere.

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Section: Cassini/cirs Limb Observationsmentioning

confidence: 99%

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Guerlet

Fouchet

Vinatier

et al. 2015

A&A

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“…CIRS scans Titan's atmosphere through three separate focal planes that share the same telescope: FP1 (10-600 cm −1 ), FP3 (600-1100 cm −1 ), and FP4 (1100-1500 cm −1 ) (Flasar et al 2004). We focus here mainly on FP3 and FP4 high-resolution observations (0.5 cm −1 ) but also some medium resolution ones (2.5 cm −1 ).…”

Section: Context and Observationsmentioning

confidence: 99%

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Bampasidis

Coustenis

Achterberg

et al. 2012

ApJ

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We have developed a line-by-line Atmospheric Radiative Transfer for Titan code that includes the most recent laboratory spectroscopic data and haze descriptions relative to Titan's stratosphere. We use this code to model Cassini Composite Infrared Spectrometer data taken during the numerous Titan flybys from 2006 to 2012 at surface-intercepting geometry in the 600-1500 cm −1 range for latitudes from 50 • S to 50 • N. We report variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varies significantly with latitude during the 6 years investigated here, with increased mixing ratios toward the northern latitudes. In particular, we monitor and quantify the amplitude of a maximum enhancement of several gases observed at northern latitudes up to 50 • N around mid-2009, at the time of the NSE. We find that this rise is followed by a rapid decrease in chemical inventory in 2010 probably due to a weakening north polar vortex with reduced lateral mixing across the vortex boundary.

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“…We refer to Flasar et al [2004] for a detailed description of the instrument and to Spilker et al [2005Spilker et al [ , 2006 for associated methods. The CIRS data set is absolutely unique by its geometrical coverage.…”

Section: Introductionmentioning

confidence: 99%

Thermal phase curves observed in Saturn's main rings by Cassini‐CIRS: Detection of an opposition effect?

Altobelli¹,

Spilker²,

Pilorz³

et al. 2009

Geophysical Research Letters

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We report on thermal phase curve measurements of Saturn's main rings by the CIRS infrared spectrometer on‐board the CASSINI spacecraft. The extensive data set acquired by Cassini since its insertion in orbit around Saturn provides for the first time spatially resolved temperature measurements over broad phase angle ranges and for different solar elevations. Each of these curves exhibit a nonlinear variation in temperature with phase angle, with pronounced surges at medium to low phase angles that we interpret as an opposition effect in thermal infrared. The transition from a relatively flat linear regime to an exponential behavior in the A and B rings occurs at phase angles of 30° to 40° and is significantly broader in the C ring and Cassini Division. Analytical description of the phase curves is provided to serve as basis for future modeling work. The role played by mutual shadowing as possible origin of the broad thermal surge in thicker ring regions is emphasized. In turn, regolith properties might be inferred from the thermal phase curves in the optically thin ring regions.

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Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer

Abstract: The Composite Infrared Spectrometer (CIRS) is a remote-sensing Fourier Transform Spectrometer (FTS) on the Cassini orbiter that measures thermal radiation over two decades in wavenumber,

Cited by 281 publications

References 286 publications

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

Stratospheric benzene and hydrocarbon aerosols detected in Saturn’s auroral regions

THERMAL AND CHEMICAL STRUCTURE VARIATIONS IN TITAN'S STRATOSPHERE DURING THECASSINIMISSION

Thermal phase curves observed in Saturn's main rings by Cassini‐CIRS: Detection of an opposition effect?

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