A Study of the Jovian Atmospheric Structure using SWS and CAM-CVF

Th. Encrenaz 1 - E. Lellouch 1 - P. Drossart 1 - H. Feuchtgruber 2 - Th. de Graauw 3 - B. Altieri 2 - F. Lacombe 1 - D. Rouan 1 - D. Tiphène 1

The spectrum of Jupiter between 2.5 and 45 m extends over a very large dynamical range (100 000). It is characterized by a reflected solar component which dominates at short wavelengths and a thermal component which strongly increases beyond 4 m. The solar component gives access to the albedo and the altitude of the NH₃ cloud around 0.5 bar. The thermal radiation probes different altitude ranges, from the deep troposphere at several bars (at 5 m) up to the lower stratosphere at the mbar level (in the CH₄ emission at 7.7 m) or even the upper stratosphere at the bar level (in the CH₄ emission at 3.3 m, in the H₃⁺ lines around 4 m, and in the H₂O lines around 40 m).

We are using two sets of ISO data to retrieve the Jovian atmospheric structure and its spatial variations: the SWS grating spectra, recorded between 2.3 and 16.5 m at the center and between 2.3 and 45 m at the poles (R=1500), and the CAM-CVF images recorded between 2.3 and 11 m (R=50). The comparison of the 3 SWS spectra should provide information on the latitudinal variations of the thermal stratospheric profile, from the analysis of the CH₄ emission bands (Encrenaz et al, 1996), and on the vertical distributions of several species: NH₃, PH₃, hydrocarbons - including the recently detected CH₃C₂H - and possibly stratospheric H₂O (Feuchtgruber et al, 1997) and CO₂ (Lellouch et al, 1997). The CAM-CVF images provide a new information about the spatial structure of the NH₃ cloud and the temperature field in the lower stratosphere. The reduction of these data is in progress.

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