The Ultraviolet Reflectivity of Jupiter at 3.5 Å Resolution from Astro-1 and Astro-2

Patrick F. Morrissey and Paul D. Feldman
Department of Physics and Astronomy, The Johns Hopkins University
Charles and 34th Streets, Baltimore, MD 21218

Melissa A. McGrath
Space Telescope Science Institute
3700 San Martin Drive, Baltimore, MD 21218

Brian C. Wolven and H. Warren Moos
Department of Physics and Astronomy, The Johns Hopkins University
Charles and 34th Streets, Baltimore, MD 21218

June 30, 1995

Abstract:

The reflectivity of Jupiter in the wavelength band from 1450 Å to 1850 Å at 3.5 Å resolution has been determined from measurements of Jovian equatorial spectra obtained by the Hopkins Ultraviolet Telescope (HUT), which was flown on the Space Shuttle Columbia during the December 1990 Astro-1 mission and then on the Endeavour during the March 1995 Astro-2 mission. Good model fits to the data were obtained with only three hydrocarbon absorbers and an electron-impacted dayglow source. We have determined the abundances of acetylene, ethane and ethylene to be 35 ppb, 3 ppm and 0.25 ppb, respectively. Small changes in the reflectivity at the limit of the mission-to-mission instrument calibrations were observed; these resulted in somewhat different hydrocarbon abundances in 1990 and 1995. Mixing ratios derived from these HUT spectra are consistent with results from recent International Ultraviolet Explorer spectra at lower resolution. The integrated contribution of the dayglow was 800 Rayleighs in 1990 and 200 Rayleighs in 1995, which was a period spanning solar maximum and solar minimum.

Subject headings: planets: individual (Jupiter) --- ultraviolet: solar system, spectra, reflectivity, albedo



pfm@pha.jhu.edu