title: Galileo ultraviolet spectrometer experiment: initial venus and interplanetary cruise results.
abstract: The Galileo Extreme Ultraviolet Spectrometer obtained a spectrum of Venus atmospheric emissions in the 55.0- to 125.0-nanometer (nm) wavelength region. Emissions of helium (58.4 nm), ionized atomic oxygen (83.4 nm), and atomic hydrogen (121.6 nm), as well as a blended spectral feature of atomic hydrogen (Lyman-beta) and atomic oxygen (102.5 nm), were observed at 3.5-nm resolution. During the Galileo spacecraft cruise from Venus to Earth, Lyman-alpha emission from solar system atomic hydrogen (121.6 nm) was measured. The dominant source of the Lyman-alpha emission is atomic hydrogen from the interstellar medium. A model of Galileo observations at solar maximum indicates a decrease in the solar Lyman-alpha flux near the solar poles. A strong day-to-day variation also occurs with the 27-day periodicity of the rotation of the sun.
authors.forename: C W
authors.initials: CW
authors.lastname: Hord
authors.forename: C A
authors.initials: CA
authors.lastname: Barth
authors.forename: L W
authors.initials: LW
authors.lastname: Esposito
authors.forename: W E
authors.initials: WE
authors.lastname: McClintock
authors.forename: W R
authors.initials: WR
authors.lastname: Pryor
authors.forename: K E
authors.initials: KE
authors.lastname: Simmons
authors.forename: A I
authors.initials: AI
authors.lastname: Stewart
authors.forename: G E
authors.initials: GE
authors.lastname: Thomas
authors.forename: J M
authors.initials: JM
authors.lastname: Ajello
authors.forename: A L
authors.initials: AL
authors.lastname: Lane
authors.forename: R W
authors.initials: RW
authors.lastname: West
authors.forename: B R
authors.initials: BR
authors.lastname: Sandel
authors.forename: A L
authors.initials: AL
authors.lastname: Broadfoot
authors.forename: D M
authors.initials: DM
authors.lastname: Hunten
authors.forename: D E
authors.initials: DE
authors.lastname: Shemansky