Multispectral near‐IR imaging of Venus nightside cloud features

Abstract

Near‐infrared imaging observations of the Venus nightside were made on May 17–23, 1996, at the Apache Point Observatory. The data were taken with an acousto‐optic tunable filter camera (AOTF), which is a newly developed, RF‐tunable imager with a spectral resolution of λ/Δλ = 422 at 2.3 μm. The observations were made at several discrete wavelengths in the 2.3 μm spectral window in the Venus atmosphere that correspond to molecular absorption minima and maxima of several species. These data are sensitive to properties of the lower cloud deck of Venus; we examined the zonal wind speeds near an altitude of 50 km and studied the implications of the brightness contrasts seen in the images. We confirmed the ∼ 5‐day rotational period of the cloud features previously seen at this altitude level. We also confirmed previously reported contrast ratios between the brightest and darkest regions of 20:1 and found that this contrast ratio corresponds to a variation in optical depth of at least 8. We demonstrated the new technology of the near‐IR AOTF camera by illustrating one of its many applications for planetary science.