The character of the thermal emission from Venus

Images of the thermal infrared emission from 10.6 to 12.6 microns from the earth-facing hemisphere of Venus were made from earth on each available opportunity over a 26-day period in 1977 and a 106-day period in 1978-1979, using a 1.5 m telescope. Compact, variable thermal features exist at latitudes higher than about 50 deg, some of which repeat at 5-day intervals. No such repeatability is observed for features near the equator. Day-to-day variations in limb darkening and the contrast of high latitude features appear to differ in the conjunction and post-conjunction images. A strong, solar-fixed component of the emission exists and exhibits wave number 1, 2, and 4 components. The thermal tides provide constraints upon the atmosphere structure. The solar-fixed structure shows significant asymmetries with respect to the equator.