Venus upper atmosphere winds from ground-based heterodyne spectroscopy of CO2 at wavelength

We report observations of Venus atmospheric wind near 110 km altitude by means of high-resolution mid-infrared spectroscopy. Data were acquired May 28–June 4, 2007 at the McMath-Pierce Solar Telescope (Kitt Peak, Arizona, USA), during a coordinated ground-based observing campaign in support of Venus Express. The Cologne Tuneable Heterodyne Infrared Spectrometer (THIS) was used to measure the Doppler shift of fully resolved non-LTE emission lines of CO2 at 959.3917 cm - 1 ( 10.423 μ m ) to determine wind velocity. Spatial resolution was ∼ 1.7 arcsec on Venus’ apparent diameter of 20–22 arcsec. Zonal wind velocities were retrieved at six different latitudes close to the west limb. Retrieved zonal velocities—parallel to Venus’ retrograde solid body rotation—range 3 ± 7 m / s ( 1 σ ) at the equator to a maximum of 32 ± 4 m / s ( 1 σ ) at southern mid-latitude ( 45 ∘ S ) , decreasing at higher latitudes and thus suggesting a retrograde double jet structure for the zonal component. The subsolar-to-antisolar circulation component was measured at one position, 45 ∘ towards the sunlit limb from the central meridian, on the equator. The retrieved subsolar-to-antisolar component at this position implies a cross-terminator velocity of 52 ± 18 m / s ( 1 σ ) . Retrieved velocities are lower than previous results, suggesting spatial and/or temporal variability of dynamics in the mesosphere/thermosphere of Venus.