Venus Dynamics Tracer (VdT) - a mission dedicated for in-situ measurements of the Venus atmosphere.

<p><span lang="EN-US">Recent Venus missions (Venus Express and Akatsuki) provided a large-scale view of Venus atmosphere and discovered new phenomena, such as high-altitude extension of the mountain wave to the cloud layer and a dawn-dusk asymmetry in the ionospheric motion.&#160; The superrotation of the cloud layer is assumed to be driven by the thermal tide but its relation to any meridional convection or waves is still unknown.&#160; The key to understand all these phenomena is to determine the multi-step re-distribution of the absorbed solar radiation to other forms of energy: (1) internal energy; including temperature, latent heat, and chemical energy (2) kinetic energy both in large scale flows/waves and in minor deviations of convection motions, (3) electric energy including ionization. </span></p> <p><span lang="EN-US">To understand how the motion of Venus atmosphere is driven by the energy originating from the absorption of solar radiation, we proposed Venus Dynamics Tracer (VdT), a mission for in-situ measurements, as a response&#160;to the ESA call for new M-class missions.&#160; Specific targets were two major energy absorption regions: the cloud layer and the ionized upper atmosphere. The scientific goals were to investigate (a) the roles&#160;of the vertical and meridional circulation in maintaining major atmospheric dynamics near the&#160;cloud layer where visible light is absorbed and drives the vertical motions of the air, and to understand the (b) global dynamics of ions and neutrals&#160;in the upper atmosphere where EUV is absorbed both by neutrals and ions and where energy&#160;and momentum are transferred between them.&#160; </span></p> <p><span lang="EN-US">For the first target, multiple-balloons are deployed for in situ observations with supporting camera/s on an orbiter giving global context. For the second target, the motions of ions and neutrals are directly measured.&#160; This presentation discusses required measurements to answer the scientific goals. &#160;</span></p>