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D. M. Kuehn (Physics Dept., Pittsburg State U.), N. J. Chanover, A. A. Simon, R. F. Beebe (Astronomy Dept., New Mexico State U.)
Analysis of high-resolution infrared images of Jupiter that we obtained in September, 1997 using the HST Near Infrared Multi-Object Spectrometer (NICMOS) is presented. These images were obtained using narrow bandpass filters centered at 1.9 and 2.12 \mum and a broader filter at 2.37 \mum, the location of a strong methane absorption band.
We focused our analysis on four latitude regions on Jupiter: N. Temperate Belt (+27o), N. Tropical Zone (+20o), the southern part of the Equatorial Zone (-5o) and the South Equatorial Belt (-15o). The data were fit using a vertically inhomogenous atmospheric model which includes the effects of multiple scattering calculated using a doubling/adding algorithm. At these particular wavelengths, only the atmosphere above the ammonia clouds are sampled. Thus, we paid particular attention to the modeling of the pressure level, optical depth, and scale height of the stratospheric haze that was previously detected in visible and near-IR methane band imaging (West, 1979; Kuehn and Beebe, 1993).
We were unable to fit any of the 1.9 \mum center-to-limb curves using the Pioneer-derived scattering phase function for the haze. At these wavlengths, the haze phase function seems to have less asymmetry than at visible wavlengths, with a Henyey-Greenstein “g” of about 0.5 at 1.9 \mum. The center-to-limb curve fitting performed on the 2.12 \mum data does not conflict with earlier results which have the haze layer altitude at somewhat less than 100 mbar. However, these vertical structure models are not able to fit the data at 2.37 \mum, which is more sensitive to higher altitudes (lower pressures). We will present modified vertical structure models of the stratospheric haze that attempt to rectify these problems and fit within the constraints set by the other two wavelengths.