Composite infrared spectrometer (CIRS) on Cassini

Jennings, Donald E.; Flasar, F. M.; Kunde, V. G.; Nixon, C. A.; Segura, M.; Romani, P. N.; Gorius, N.; Albright, S. A.; Brasunas, J. C.; Carlson, R.; Mamoutkine, A. A.; Guandique, E.; Kaelberer, M. S.; Aslam, Shahid; Achterberg, R. K.; Bjoraker, G.; Anderson, C. M.; Cottini, V.; Pearl, J. C.; Smith, M. D.; Hesman, B. E.; Barney, Richard D.; Calcutt, S. B.; Vellacott, Tim; Spilker, L. J.; Edgington, S. G.; Brooks, S. M.; Ade, Peter A. R.; Schinder, P. J.; Coustenis, A.; Courtin, R.; Molenaers, Guy; Fettig, Rainer K.; Pilorz, S.; Ferrari, C.

doi:10.1364/ao.56.005274

Cited by 44 publications

(31 citation statements)

References 44 publications

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“…Each pixel has a 0.27×0.27 mrad 2 field-of-view corresponding to a vertical resolution varying from 10 to 40 km (comparable to a pressure scale height), depending on the distance of the spacecraft to Titan during the flyby. More details on the CIRS instrument are given in Kunde et al (1996), Flasar et al (2004) and Jennings et al (2017), and more details on the different types of observations are given in Nixon et al (2019).…”

Section: Observationsmentioning

confidence: 99%

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Seasonal changes in the middle atmosphere of Titan from Cassini/CIRS observations: Temperature and trace species abundance profiles from 2004 to 2017

Mathé

Vinatier

Bézard

et al. 2020

Icarus

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The Cassini/Composite InfraRed Spectrometer (CIRS) instrument has been observing the middle atmosphere of Titan over almost half a Saturnian year. We used the CIRS dataset processed through the up-to-date calibration pipeline to characterize seasonal changes of temperature and abundance profiles in the middle atmosphere of Titan, from mid-northern winter to early northern summer all around the satellite. We used limb spectra from 590 to 1500 cm −1 at 0.5-cm −1 spectral resolution, which allows us to probe different altitudes. We averaged the limb spectra recorded during each flyby on a fixed altitude grid to increase the signal-to-noise ratio. These thermal infrared data were analyzed by means of a radiative transfer code coupled with an inversion algorithm, in order to retrieve vertical temperature and abundance profiles. These profiles cover an altitude range of approximately 100 to 600 km, at 10-or 40-km vertical resolution (depending on the observation). Strong changes in temperature and composition occur in both polar regions where a vortex is in place during the winter. At this season, we observe a global enrichment in photochemical compounds in the mesosphere and stratosphere and a hot stratopause located around 0.01 mbar, both linked to downwelling in a pole-to-pole circulation cell. After the northern spring equinox, between December 2009 and April 2010, a stronger enhancement of photochemical compounds occurred at the north pole above the 0.01-mbar region, likely due to combined photochemical and dynamical effects. During the southern autumn in 2015, above the South pole, we also observed a strong enrichment in photochemical compounds that contributed to the cooling of the stratosphere above 0.2 mbar (∼300 km). Close to the northern spring equinox, in December 2009, the thermal profile at 74 • N exhibits an oscillation that we interpret in terms of an inertia-gravity wave.

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Section: Observationsmentioning

confidence: 99%

“…We used the CIRS "global calibration" database described in Jennings et al (2017). We selected limb spectra with a spectral resolution of 0.5 cm −1 for which gas molecular emission bands are well separated.…”

Section: Observationsmentioning

confidence: 99%

Seasonal changes in the middle atmosphere of Titan from Cassini/CIRS observations: Temperature and trace species abundance profiles from 2004 to 2017

Mathé

Vinatier

Bézard

et al. 2020

Icarus

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“…The spectral resolution is the same on both instruments and is set by the scan mirror travel distance, with a maximum resolution (smallest FWHM) of 0.5 cm −1 . For more details on the CIRS instrument, see Flasar et al (2004) and Jennings et al (2017).…”

Section: Observationsmentioning

confidence: 99%

D/H Ratios on Saturn and Jupiter from Cassini CIRS

Pierel¹,

Nixon²,

Lellouch³

et al. 2017

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We present new measurements of the deuterium abundance on Jupiter and Saturn, showing evidence that Saturn's atmosphere contains less deuterium than Jupiter's. We analyzed far-infrared spectra from the Cassini Composite Infrared Spectrometer to measure the abundance of HD on both giant planets. Our estimate of the Jovian D/H = (2.95 ± 0.55) × 10 −5 is in agreement with previous measurements by ISO/SWS: (2.25 ± 0.35) × 10 −5 , and the Galileo probe: (2.6 ± 0.7) × 10 −5 . In contrast, our estimate of the Saturn value of (2.10 ± 0.13) × 10 −5 is somewhat lower than on Jupiter (by a factor of 0.71 0.15), contrary to model predictions of a higher ratio: Saturn/ Jupiter = 1.05-1.20. The Saturn D/H value is consistent with estimates for hydrogen in the protosolar nebula (2.1 ± 0.5) × 10 −5 , but its apparent divergence from the Jovian value suggests that our understanding of planetary formation and evolution is incomplete, which is in agreement with previous work.

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“…A detailed description of the instrument is given in Jennings et al (2017), while some key facts are given here that are most relevant to the Titan observation planning. The CIRS instrument was a dual spectrometer, which used a field-splitting beamsplitter to direct the incoming light from a 50 cm diameter telescope into mid-and far-infrared spectrometers.…”

Section: Cirs Instrument Overviewmentioning

confidence: 99%

Cassini Composite Infrared Spectrometer (CIRS) Observations of Titan 2004–2017

Nixon

Ansty

Lombardo

et al. 2019

ApJS

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From 2004 to 2017, the Cassini spacecraft orbited Saturn, completing 127 close flybys of its largest moon, Titan. Cassini's Composite Infrared Spectrometer (CIRS), one of 12 instruments carried on board, profiled Titan in the thermal infrared (7-1000 µm) throughout the entire 13-year mission. CIRS observed on both targeted encounters (flybys) and more distant opportunities, collecting 8.4 million spectra from 837 individual Titan observations over 3633 hours. Observations of multiple types were made throughout the mission, building up a vast mosaic picture of Titan's atmospheric state across spatial and temporal domains. This paper provides a guide to these observations, describing each type and chronicling its occurrences and global-seasonal coverage. The purpose is to provide a resource for future users of the CIRS data set, as well as those seeking to put existing CIRS publications into the overall context of the mission, and to facilitate future inter-comparison of CIRS results with those of other Cassini instruments, and ground-based observations.

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Composite infrared spectrometer (CIRS) on Cassini

Cited by 44 publications

References 44 publications

Seasonal changes in the middle atmosphere of Titan from Cassini/CIRS observations: Temperature and trace species abundance profiles from 2004 to 2017

Seasonal changes in the middle atmosphere of Titan from Cassini/CIRS observations: Temperature and trace species abundance profiles from 2004 to 2017

D/H Ratios on Saturn and Jupiter from Cassini CIRS

Cassini Composite Infrared Spectrometer (CIRS) Observations of Titan 2004–2017

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