THE DARK SIDE OF VENUS - NEAR-INFRARED IMAGES AND SPECTRA FROM THE ANGLO-AUSTRALIAN-OBSERVATORY

Near-infrared images and spectra of the night side of Venus taken at the Anglo-Australian Telescope during February 1990 reveal four new thermal emission windows at 1.10, 1.18, 1.27, and 1.31 micrometers (mu-m), in addition to the previously discovered windows at 1.74 and 2.3-mu-m. Images of the Venus night side show similar bright and dark markings in all windows, but their contrast is much lower at short wavelengths. The 1.27-mu-m window includes a bright, high-altitude O2 airglow feature in addition to a thermal contribution from the deep atmosphere. Simulations of the 1.27- and 2.3-mu-m spectra indicate water vapor mixing ratios near 40 +/- 20 parts per million by volume between the surface and the cloud base. No large horizontal gradients in the water vapor mixing ratios were detected at these altitudes.