title: Venus Thermosphere: In situ Composition Measurements, the Temperature Profile, and the Homopause Altitude.
abstract: The neutral mass spectrometer on board the Pioneer Venus multiprobe bus measured composition and structral parameters of the dayside Venus upper atmosphere on 9 December 1978. Carbon dioxide and helium number densities were 6 x 10(6) and 5 x 10(6) per cubic centimeter, respectively, at an altitude of 150 kilometers. The mixing ratios of both argon-36 and argon-40 were approximately 80 parts per million at an altitude of 135 kilometers. The exospheric temperature from 160 to 170 kilometers was 285 +/- 10 K. The helium homopause was found at an altitude of about 137 kilometers.
authors.forename: U
authors.initials: U
authors.lastname: VON Zahn
authors.forename: D
authors.initials: D
authors.lastname: Krankowsky
authors.forename: K
authors.initials: K
authors.lastname: Mauersberger
authors.forename: A O
authors.initials: AO
authors.lastname: Nier
authors.forename: D M
authors.initials: DM
authors.lastname: Hunten