Bruce Hapke

Relative spectrophotometry of Venus from 3067 to 5960 A

Abstract The relative spectral reflectivity from 3067 A to 5960 A for the integrated disk of Venus is presented. The reflectivity is essentially flat from 5960 to about 5200 A then decreases smoothly to a flat region between 3950 and 3400 A at 55% of the value at 5960 A. Below 3300 A the reflectivity appears to drop again to possibly another flat region between 3200 and 3100 A. Temporal changes in the reflectivity curve are of the same magnitude as the changes over a range of phase angle from 40° to 76°. These changes appear to be only in the amount of UV absorption and not in the shape of the reflectivity curve. The narrow-band data of Irvine et al. are compared to the average reflectivity curve. The relative reflectivity curve of a dark UV feature compared to a bright UV feature has the same shape as the curve for the integrated disk of Venus. The comparison of these two curves leads to the conclusion that at least a significant amount of the UV absorption must occur above even the bright UV features.