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Science 27 September 1991:
Vol. 253. no. 5027, pp. 1548 - 1550
DOI: 10.1126/science.253.5027.1548
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Articles

Galileo Ultraviolet Spectrometer Experiment: Initial Venus and Interplanetary Cruise Results

C. W. HORD 1, C. A. BARTH 1, L. W. ESPOSITO 1, W. E. MCCLINTOCK 1, W. R. PRYOR 1, K. E. SIMMONS 1, A. I. F. STEWART 1, G. E. THOMAS 1, J. M. AJELLO 2, A. L. LANE 2, R. W. WEST 2, B. R. SANDEL 3, A. L. BROADFOOT 3, D. M. HUNTEN 3, and D. E. SHEMANSKY 3

1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80309
2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109
3 Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721

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-agr emission from solar system atomic hydrogen (121.6 nm) was measured. The dominant source of the Lyman-agr emission is atomic hydrogen from the interstellar medium. A model of Galileo observations at solar maximum indicates a decrease in the solar Lyman-agr flux near the solar poles. A strong day-to-day variation also occurs with the 27-day periodicity of the rotation of the sun

Revised on April 26, 1991
Accepted on August 9, 1991

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Science. ISSN 0036-8075 (print), 1095-9203 (online)