Venus Dynamics on the framework of Bepicolombo flyby to Venus and Akatsuki UVI coordinated observations with TNG HARPS-N observations

With this work we present new results of studies of zonal and meridional winds in both Venus’ hemispheres, using ground- and space-based coordinated observations. The wind velocities retrieved from space used an improved cloud-tracked technique and the results obtained from telescope observations were retrieved with a Doppler velocimetry method, both described below. There is evidence that the altitude level sensed by the Doppler velocimetry method is approximately four kilometres higher than that using ground-tracked winds which is shown by models which predict wind profiles developed at the Laboratoire de Meteorologie Dynamique (Machado et al., Atmosphere,2021).

Initially developed by Thomas Widemann (Widemann et al., Planetary and Space Science 56, 2008), the Doppler velocimetry method was further evolved by Pedro Machado for both long slit and fibre-fed spectrographs, using UVES/VLT and ESPaDOnS/CFHT respectively. This technique is based on solar light scattered on Venus’ dayside and provides instantaneous wind velocities measurements of its atmosphere. (Machado et al., Icarus, 2012; Icarus 2014; Icarus 2017).

The cloud-tracking method consists of an analysis of a pair of navigated and processed images, provided that the time interval between both is known. It is possible to probe the motion of cloud features between the initial and second image, either by matching specific areas or points in both images. This matching process allows us to measure velocities of cloud features and deduct the average velocity for a certain cloud layer of the atmosphere, selected in the wavelength range of the observations (Peralta et al., The Astrophysical Journal Supplement Series 239, 2018).

An evolved tool of cloud tracking based on phase correlation between images and other softwares (Hueso et al., Advances in Space Research, 2010) allowed to explore Venus' atmospheric dynamics based on coordinated space and ground observations including Akatsuki UVI instrument, TNG/HARPS-N, and data from BepiColombo’s first Venus' flyby.

The main goal of this work was to build wind profiles in different wavelengths, allowing us to analyse several layers of the Venusian atmosphere. We present some results of this study following the works of Sánchez-Lavega et al., Geophysical Research Letters 35, 2008; Hueso et al. 2013 and Horinouchi et al., Planets and Space, 2018 and compare them with ground-based Doppler measurements (Machado et al., Atmosphere,2021).

Acknowledgements
We thank the JAXA’s Akatsuki team for support with coordinated observations. We gratefully acknowledge the collaboration of the TNG staff at La Palma (Canary Islands, Spain) - the observations were made with the Italian Telescopio Nazionale Galileo operated on the island of La Palma by the Fundación Galileo Galilei of the Istituto Nazionale di Astrofisica at the Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. We acknowledge support from the Portuguese Fundação Para a Ciência e a Tecnologia project PTUGA (ref. PTDC/FIS-AST/29942/2017) through national funds and by FEDER through COMPETE 2020 (ref. POCI-01-0145 FEDER-007672) and through a grant of reference 2020.06389.BD.