Evidence for Raman Scattering in HST FOS Spectra

Y. Bétrémieux, R. V. Yelle (CSP, Boston University)

Spectroscopic observations conducted May 5 and 6 1993 by HST along Jupiter's central meridian at 65, 48, 6, 0, -6, -12, -25, -33, -48 and -65 degree planetographic latitude are analyzed to deduce the latitudinal variation of acetylene abundance in Jupiter's upper atmosphere. The measurements were obtained with the G190H grating and Red detector combination of the FOS (Faint Object Spectrograph) spanning 1573-2330Å at about 3.5Å resolution. The data were corrected for scattered light, and careful modeling of the Line Spread Function of the instrument was performed to accurately degrade the solar spectrum obtained by SOLSTICE to that of the FOS. The I/F obtained displayed features consistent with Raman scattering by molecular hydrogen at wavelength of 2300, 2290, 2268, 2217, 2211 and 2124Å . We have modified the DISORT radiative transfer code to incorporate Raman scattering under the assumption that the Raman component of the scattering phase function is isotropic. Rotational and vibrational Raman scattering for the first few lowest energy rotational states of molecular hydrogen are considered for this analysis.