HST detection of H-2 Raman scattering in the Jovian atmosphere

Citation
Y. Betremieux et Rv. Yelle, HST detection of H-2 Raman scattering in the Jovian atmosphere, ICARUS, 142(2), 1999, pp. 324-341
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Space Sciences
Journal title
ICARUS
ISSN journal
0019-1035 → ACNP
Volume
142
Issue
2
Year of publication
1999
Pages
324 - 341
Database
ISI
SICI code
0019-1035(199912)142:2<324:HDOHRS>2.0.ZU;2-7
Abstract
Raman scattered features by molecular hydrogen have been detected in Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) observations of Jupi ter. The measurements were obtained with the G190H grating and red detector combination spanning 158.0-232.0 nm at about 0.3 nm resolution. The data w ere corrected for scattered light, and careful modeling of the line spread function (LSF) of the instrument was performed to accurately degrade the so lar spectrum obtained by SOLSTICE (solar-stellar irradiance comparison expe riment) to the spectral resolution of the FOS. A cross-correlation method w as used to align features in the planetary spectra to those in the SOLSTICE solar spectrum. At all latitudes longward of 210.0 nm, the resulting I/F d isplayed discrete features up to 20% of the continuum level that anticorrel ate with the solar spectrum. A radiative transfer code was developed to inc lude the effect of rotational and vibrational multiple Raman scattering for the first few lowest energy rotational states of molecular hydrogen under the approximation that the Raman component of the scattering phase function is isotropic. Simulations show not only that the detected features are ind eed due to Raman scattering by H-2, but are sensitive to its ortho-para rat io as well. An analysis of the equatorial spectrum reveals that the feature s are consistent with an equilibrium or normal population of H-2 at 130 K. (C) 1999 Academic Press.