Preliminary results of interferometric observations of Venus at 11.1-cm wavelength

Radio interferometry measurements have been made of the temperature variation over Venus. The results imply that the temperature has no significant poleward variation. A limit of 12°K can be placed on the surface temperature difference between poles and equator. A small phase-dependent asymmetry was measured, corresponding to an 18.4 ± 9.2°K maximum brightness difference between the equatorial limbs. This maximum difference occurs near inferior conjunction. The data also indicate that the disk of Venus is limb brightened. The extent of the brightening can be fitted if Venus' atmosphere is composed of 95% CO
2
, with no water, and has an extensive isothermal layer at the surface.