Venus upper atmosphere winds from ground-based heterodyne spectroscopy of CO2 at 10 μm 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 groundbased 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 mu m) to determine wind velocity. Spatial resolution was similar to 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 sigma) at the equator to a maximum of 32 +/- 4 m/s (1 sigma) at southern mid-latitude (45 degrees 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 degrees 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 sigma). Retrieved velocities are lower than previous results, suggesting spatial and/or temporal variability of dynamics in the mesosphere/thermosphere of Venus. (C) 2008 Elsevier Ltd. All rights reserved.