Spectroscopic Observations of Winds on Venus

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Abstract
We have measured the differential Doppler shift between various points on Venus using a high-resolution PEPSIOS interferometer (three Fabry-Perot etalons in series). Using both a CO2 line and a Fraunhofer line we find a mean zonal wind velocity near the equator of −83 ± 10 m s−1 (retrograde); the velocity appears to vary from about −2 to −125 m s−1, with a time scale of greater than one week. Meridional velocities are measured to be weak (on the order of 30 m s−1 or less). The equatorial zonal velocity appears to be smaller (−73 m s−1) in the “morning” than in the “afternoon” (−111 m s−1) where the times of day are for retrograde rotation. A comparison with reported velocities of the ultraviolet dark markings reveals general agreement in that both find the motion to be retrograde, variable, and accelerated during the day. A new potential source of systematic error in all spectroscopic determinations of the differential Doppler shift of nonuniformly illuminated objects is pointed out.

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