title: Ground-based near-infrared imaging observations of venus during the galileo encounter.
abstract: Near-infrared images of Venus, obtained from a global network of ground-based observatories during January and February 1990, document the morphology and motions of the night-side near-infrared markings before, during, and after the Galileo Venus encounter. A dark cloud extended halfway around the planet at low latitudes (>+/-40 degrees ) and persisted throughout the observing program. It had a rotation period of 5.5 +/- 0.15 days. The remainder of this latitude band was characterized by small-scale (400 to 1000 kilometers) dark and bright markings with rotation periods of 7.4 +/- 1 days. The different rotation periods for the large dark cloud and the smaller markings suggests that they are produced at different altitudes. Mid-latitudes (+/-40 degrees to 60 degrees ) were usually occupied by bright east-west bands. The highest observable latitudes (+/-60 degrees to 70 degrees ) were always dark and featureless, indicating greater cloud opacity. Maps of the water vapor distribution show no evidence for large horizontal gradients in the lower atmosphere of Venus.
authors.forename: D
authors.initials: D
authors.lastname: Crisp
authors.forename: S
authors.initials: S
authors.lastname: McMuldroch
authors.forename: S K
authors.initials: SK
authors.lastname: Stephens
authors.forename: W M
authors.initials: WM
authors.lastname: Sinton
authors.forename: B
authors.initials: B
authors.lastname: Ragent
authors.forename: K W
authors.initials: KW
authors.lastname: Hodapp
authors.forename: R G
authors.initials: RG
authors.lastname: Probst
authors.forename: L R
authors.initials: LR
authors.lastname: Doyle
authors.forename: D A
authors.initials: DA
authors.lastname: Allen
authors.forename: J
authors.initials: J
authors.lastname: Elias