EUVE Science Highlights -
October 4, 1999
EUVE Science Highlights -
October 4, 1999
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This science highlight was submitted by G.R. Gladstone of the Southwest Research Institute.
G. R. Gladstone, S.A. Stern, D.C. Slater, and L.J. Paxton, to be presented at the October 15,1999 meeting of the AAS Division of Plantary Sciences.
During April 7-11, 1998, the EUVE satellite performed observations of Venus (not long after western elongation on March 27). About 20 ks of data were obtained in about 50 400 s pointings (one per orbit), performed while the spacecraft was in Earth's shadow. Large slews were required before and after each pointing to ensure that EUVE's look direction was >90 deg from the Sun when the satellite was in direct sunlight. These data comprise the first extreme ultraviolet spectrum of Venus in the 7-76 nm range (although a short Galileo EUVS spectrum at 55-125 nm was recorded during the February 1990 flyby, two excellent spectra were obtained by the Hopkins Ultraviolet Telescope in the 82-184 nm range, and rocket observations covering the 82.5-111 nm range have been acquired). The EUVE spectra indicate a brightness of 145 +/- 5 R for the HeI 58.4 nm emission, and 40 +/- 8 R for a combination of the HeI 53.7 nm and OII 53.9 nm emissions. For comparison, the Galileo EUVS measured a HeI 58.4 nm brightness of 200-280 R. We will present detailed simulations of these and other Venus EUV dayglow emissions. We are grateful to the EUVE project for their heroic efforts to plan and make these observations, which put the satellite at considerable risk.