METHANE, AMMONIA, AND TEMPERATURE-MEASUREMENTS OF THE JOVIAN PLANETS AND TITAN FROM CCD-SPECTROPHOTOMETRY

Full-disk albedo spectra of the jovian planets and Titan were derived from observations at the European Southern Observatory in July 1995. T he spectra extend from 300 to 1050 nm wavelength. The spectral resolut ion is 0.4 nm between 520 and 995 nm, and 1 nm elsewhere, The accuracy of the albedo calibration is 4%. UBV magnitudes were also determined. Raman scattering was quantified for each planet. Methane and ammonia bands are shown at 0.4 nm spectral resolution, including a new band at 930 nm wavelength which is probably due to ammonia. Maps of the varia tion of these absorptions across the disks of Jupiter and Saturn are d isplayed. Saturn's spectrum is undisturbed by light from its rings due to the edge-on geometry during the observations. The albedo of Uranus near 1 mu m wavelength has dropped almost 10% between 1993 and 1995, while there has been no change in the ultraviolet. The signature of li ght from Titan's surface yielded a path length of 4 km-am of methane i n Titan's atmosphere. The temperature dependence of the width of the 8 90-nm methane band was used to measure temperature variations at three altitude levels, resulting in the first temperature maps of Jupiter a nd Saturn based on reflected sunlight. Jupiter displays a banded tempe rature structure with some discrete features of a few Kelvin amplitude , Saturn's north-south temperature asymmetry has reversed since the Vo yager observations. (C) 1998 Academic Press.