Multispectral near-IR imaging of Venus nightside cloud features

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 lambda/Delta lambda = 422 at 2.3 mu m. The observations;were made at several discrete wavelengths in the 2.3 mu m 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 similar to 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.