JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

The Galileo Near Infrared Mapping Spectrometer has returned thousands of Jovian atmospheric spectra. Previous work has inverted a handful of these observations to obtain atmospheric properties in or near a hot spot region, but the process is slow and thus impractical for large scale use. We shall develop a "turn-key" retrieval algorithm capable of rapidly processing entire spectral sequences to return gas abundances and cloud properties at many locations on the planet. Maps of these retrievals will be produced. There are two interrelated approaches to achieving this goal: the development of much faster (yet still fully scattering) retrieval routines than currently exist, and an analysis of phase angle studies of reflected sunlight. For the first, the time required can be substantially reduced by using precalculated dependencies of intensity with atmospheric parameters. The inversion procedure will be capable of processing spectra both sequentially (for spatial mapping sequences such as the "hotmap" observations) and simultaneously (for consistent retrieval from multiple observations of the same region, e.g. the white oval feature track campaign). Secondly, analysis of cloud particle properties from studies of reflected sunlight at a wide range of viewing geometries will determine particle size and distribution as a function of height and region (belts, hot spots, etc.). These results will provide improved cloud models for use in inversion of NIMS spectra. Simultaneously, the increased retrieval speed will allow analysis of the many phase angle observations obtained. Thus these two methods will be developed in parallel and in support of one another. Retrieved properties will vary by observation depending upon the spectral range, but will include some or all of the following; abundances of ammonia, upper tropospheric water, deuterated methane, and phosphine; and cloud pressure levels, thicknesses, and scattering properties. Maps will be made and results compared to analysis by other groups using both NIMS and SSI data. These products will address the nature of Jovian atmospheric structure (e.g. belt/zone differences) and, through dynamical interpretation, the possible reasons therefor.