Saturn'S Bulk Atmosphere Above The Homopause And The Implications For Cassini'S End Of Mission
Abstract
We present results of the current model of the Saturn's upper atmosphere and its implications for the end of life scenario of the Cassini spacecraft. Stellar occultations of δOri and ζOri observed by Cassini's Ultraviolet Imaging Spectra (UVIS) have recently shown Saturn's bulk atmosphere to vary with latitude (Shemansky and Liu, submitted). In particular, they show that the scale height differs significantly between 42.7°S and 15.2°N, with the latter being consistent with previous results by Voyager observations at 3.8°N. This can potentially lead to significant differences in the atmosphere's total mass density that directly influences how Cassini traverses Saturn's upper atmosphere.
Preliminary results for the stellar occultation at 42.7°S have been used to generate an engineering model of Saturn's atmosphere to examine the conditions that the Cassini orbiter would encounter at the end of its Solstice Mission. We examine the impact of the new constraints placed by the recent UVIS analysis, on the Cassini's current engineering model atmosphere. After further constraining and improving the engineering model, we will improve our determination of the region between the D-ring and Saturn's upper atmosphere where it is safe for Cassini to fly through. In the construction of the improved atmospheric model, we examine the differences that arise from treating the problem in the context of a multi-component (e.g. H2, He, and H) diffusion model versus traditional hydrostatic equilibrium models. We also look at hydrocarbon concentrations near the homopause produced by the inclusion of the new UVIS atmospheric profiles in photochemical models. The modeling results for CH4, C2H2, and C2H4 will be compared to the results published by Shemansky and Liu. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.- Publication:
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AAS/Division for Planetary Sciences Meeting Abstracts #41
- Pub Date:
- September 2009
- Bibcode:
- 2009DPS....41.3908E