Absolute Wind Measurements in the Lower Thermosphere of Venus Using Infrared Heterodyne Spectroscopy

Absolute Wind Measurements in the Lower Thermosphere of Venus Using Infrared Heterodyne Spectroscopy Jeffrey Jay Goldstein Supervisor, University of Pennsylvania: Benjamin S.P. Shen Supervisor, NASA/Goddard Space Flight Center: Michael J. Mumma In the atmosphere of Venus, observed diurnal and latitudinal temperature gradients over altitude imply a transition from retrograde zonal to subsolar-antisolar circulation at -i00 km altitude. Descent probe in situ investigations and orbital remote sensing have, to date, provided no direct measurements of winds above the cloud-tops (-65 km). Early ground-based heterodyne observations at Ii0 and -75 km (Betz et al. 1977b; Betz 1977) yielded dynamically unreasonable wind velocities, possibly due to laser local oscillator drift and/or offset. The first absolute wind velocities above the cloud-tops were obtained using NASA/Goddard Space Flight Center infrared heterodyne spectrometers at the NASA IRTF and the McMath Solar Telescope, December 1985 to March 1987, during four planetary phases spanning 82% of a synodic period. Beam-integrated Doppler displacements in the nonthermal emission core of 12C1602 10.33 _m R(8) (obtained at sub-Doppler resolution: _/A_=107), sampled the line of sight projection of the