High spectral resolution ground-based observations of Venus in the 450- to 1250-cm−1 region

Abstract Ground-based observations of Venus were made with a 5-cm drive Michelson interferometer during December 1970 and December 1973. The thermal emission spectrum of the central portion of the apparent disk was recorded from 450–1250 cm−1 with an apodized spectral resolution of 0.25 cm−1. All statistically significant sharp line absorption features in the spectrum have been identified with gaseous CO2. Comparison between the observed spectrum and a synthetic spectrum computed from a model atmosphere, assuming gaseous CO2 and a sulfuric acid haze as opacity sources, indicates good agreement. A broad diffuse absorption feature associated with the sulfuric acid haze is evident in the 870- to 930 cm−1 region. With the exception of the rotational lines of the 927-cm−1 CO2 band, the above feature appears as a continuum down to 0.25 cm−1 resolution. In the 750- to 1250-cm−1 range, the spectrum exhibits moderate thermal contrast with maximum brightness temperatures of 234–238°K occurring near 825 cm−1. These temperatures are in general agreement with previous measurements.