The Jovian Stratosphere in the ultraviolet

The center-of-disk reflectivity of Jupiter in the wavelength range from 1500 A to 3000 A was computed from 31 low dispersion IUE spectra taken during solar maximum in 1979/80. The spectra were normalized to a reflectivity scale with the improved solar spectrum of July, 1980. Consideration of wavelength shifts between different IUE spectra and within the solar spectrum improved the apparent noise, especially longward of 2000 A. Six out of seven ammonia bands between 1900 A and 2200 A were detected. A vertically inhomogeneous radiative transfer program is used to compute model reflectivities for various stratospheric compositions. In addition to ammonia, the abundance of acetylene is also well determined because these molecules show narrow absorption bands in the ultraviolet. The abundances of the other molecules in the models (C3H4, C2H4, C4H2, C2H6, C3H6) are very uncertain and therefore are quoted only as upper limits. The best model fit is consistent with infrared observations by Voyager IRIS.