Infrared limb sounding of Titan with the Cassini Composite InfraRed Spectrometer: effects of the mid-IR detector spatial responses

The composite infrared spectrometer (CIRS) instrument on board the Cassini Saturn orbiter employs two 1×10 HgCdTe detector arrays for mid-infrared remote sensing of Titan's and Saturn's atmospheres. In this paper we show that the real detector spatial response functions, as measured in ground testing before launch, differ significantly from idealized “boxcar” responses. We further show that neglecting this true spatial response function when modeling CIRS spectra can have a significant effect on interpretation of the data, especially in limb-sounding mode, which is frequently used for Titan science. This result has implications not just for CIRS data analysis but for other similar instrumental applications.

[1]  J. Flaud,et al.  Titan’s prolific propane: The Cassini CIRS perspective , 2009, 0909.1794.

[2]  B. Bézard,et al.  Titan’s stratospheric C2N2, C3H4, and C4H2 abundances from Cassini/CIRS far-infrared spectra , 2009 .

[3]  P. Gierasch,et al.  Titan’s winter polar vortex structure revealed by chemical tracers , 2008 .

[4]  A. Coustenis,et al.  Detection of C2HD and the D/H ratio on Titan , 2008 .

[5]  A. Coustenis,et al.  Isotopic Ratios in Titan’s Atmosphere from Cassini CIRS Limb Sounding: HC3N in the North , 2008 .

[6]  S. Calcutt,et al.  The NEMESIS planetary atmosphere radiative transfer and retrieval tool , 2008 .

[7]  A. Coustenis,et al.  Global and temporal variations in hydrocarbons and nitriles in Titan's stratosphere for northern winter observed by Cassini/CIRS , 2008 .

[8]  B. Bézard,et al.  The Titan 14N/15N and 12C/13C isotopic ratios in HCN from Cassini/CIRS , 2007 .

[9]  P. Irwin,et al.  Quantifying the effect of finite field-of-view size on radiative transfer calculations of Titan’s limb spectra measured by Cassini-CIRS , 2007 .

[10]  Athena Coustenis,et al.  Vertical abundance profiles of hydrocarbons in Titan's atmosphere at 15° S and 80° N retrieved from Cassini/CIRS spectra , 2007 .

[11]  Conor A. Nixon,et al.  Vertical profiles of HCN, HC3N, and C2H2 in Titan's atmosphere derived from Cassini/CIRS data , 2007 .

[12]  A. Coustenis,et al.  Latitudinal variations of HCN, HC3N, and C2N2 in Titan's stratosphere derived from Cassini CIRS data , 2006 .

[13]  Peter A. R. Ade,et al.  Cassini infrared Fourier spectroscopic investigation , 1996, Optics & Photonics.

[14]  P. Gierasch,et al.  The Voyager infrared spectroscopy and radiometry investigation , 1977 .

[15]  D. H. Martin,et al.  Polarised interferometric spectrometry for the millimetre and submillimetre spectrum , 1970 .

[16]  T. Owen,et al.  Exploring The Saturn System In The Thermal Infrared: The Composite Infrared Spectrometer , 2004 .

[17]  C. Nixon.  Remote sounding of the atmosphere of Titan , 1998 .