The recently selected missions to Venus have opened a new era for the exploration of this planet. These missions will provide information about the chemistry of the atmosphere, the geomorphology, local-to-regional surface composition, and the rheology of the interior. One key scientific question to be addressed by these future missions is whether Venus remains volcanically active, and if so, how its volcanism is currently evolving. Hence, it is fundamental to analyze appropriate terrestrial analog sites for the study of possibly active volcanism on Venus. To this regard, we propose Mount Etna - one of the most active and monitored volcanoes on Earth - as a suitable terrestrial laboratory for remote and in-situ investigations to be performed by future missions to Venus. Being characterized by both effusive and explosive volcanic products, Mount Etna offers the opportunity to analyze multiple eruptive styles, both monitoring active volcanism and identifying the possible occurrence of pyroclastic activity on Venus. We directly compare Mount Etna with Idunn Mons, one of the most promising potentially active volcanoes of Venus. Despite the two structures show a different topography, they also show some interesting points of comparison, and in particular: a) comparable morpho-structural setting, since both volcanoes interact with a rift zone, and b) morphologically similar volcanic fields around both Mount Etna and Idunn Mons. Given its ease of access, we also propose Mount Etna as an analog site for laboratory spectroscopic studies to identify the signatures of unaltered volcanic deposits on Venus.

Серии последовательных УФ-изображений (365 нм) облачного покрова Венеры позволяют исследовать динамику мезосферы. Беспрецедентный по продолжительности ряд таких изображений получен камерами VMC на борту космического аппарата (КА) Venus Express (ESA) и UVI на борту КА Akatsuki (JAXA) c 2006 по 2022 гг. На 10° ю. ш. наблюдаются долговременные изменения средней зональной и меридиональной скоростей ветра с периодом 12.5 ± 0.5 лет. Анализ поведения среднего зонального ветра около полудня 12 ± 1 ч. при фазовых углах 60°–90° в ограниченные по времени интервалы наблюдения показывает, что вблизи минимума долгопериодической зависимости торможение горизонтального потока наблюдается над областью Овды, наиболее высокой частью Земли Афродиты, как для VMC, так и для UVI. И наоборот, ускорение наблюдается над областью Овды вблизи максимума долгопериодической зависимости. Рассматриваемые долготные вариации зональной скорости простираются от экватора до средних широт (0°–40°). Меридиональная скорость показывает долготные вариации, связанные с рельефом подстилающей поверхности, вне зависимости от того, торможение или ускорение горизонтального потока наблюдается над высокогорной частью Земли Афродиты.

Series of consecutive UV (365 nm) images of Venus cloud coverage provide a way to investigate dynamics of the mesosphere. An unprecedented series of such images was obtained by the VMC/Venus Express (ESA) and UVI/Akatsuki (JAXA) cameras from 2006 to 2022. At 10°S long-term variations in the mean zonal and meridional wind speed are observed with a period of 12.5 ± 0.5 years. Analysis of the of the mean zonal wind behavior around noon (12 ± 1 h) at phase angles of 60°–90° in limited observation time intervals shows that near the minimum of the long-term dependence the deceleration of the horizontal flow is observed above the highest part of Aphrodite Terra, Ovda Regio, for both VMC and UVI. Conversely, acceleration is observed above the Ovda Regio near the maximum of the long-term dependence. The considered longitudinal variations of the zonal wind speed extend from the equator to middle latitudes (0°–40°). The meridional wind speed shows longitudinal variations associated with the topography of the underlying surface, regardless of whether the horizontal flow is slowing down or accelerating above the highlands of Aphrodite Terra.

This paper presents a method for solving the inverse problem of thermal sounding using calibrated data from the ACS TIRVIM experiment on board the ExoMars Trace Gas Orbiter . The 1.7–17 µm range TIRVIM Fourier spectrometer as part of the ACS instrument complex aboard the ExoMars TGO operates in the nadir and solar occultation modes in orbit around Mars. The main scientific goal of TIRVIM in the nadir observation mode is the long-term constant monitoring of the thermal structure of the Martian atmosphere and the general content of aerosols and water vapor from measurements in the range of 5–16.7 µm (600–2000 cm –1 ). To process the TIRVIM nadir measurements, an algorithm was developed, allowing the retrieval of the vertical temperature profile from the surface to 60 km, the surface temperature, and the general content of dust and water ice in the atmosphere from the TIRVIM spectrum in the range of 600–1250 cm –1 , as well as the water vapor column abundance according to measurements in the range of 1250–1830 cm –1 . The processing method widely uses the achievements of previous similar experiments, taking into account the features of the TIRVIM spectra. Using the developed method 2.28 × 10 6 spectra obtained by TIRVIM in nadir by regular measurements, were processed with retrieval of the thermal structure up to 60 km altitude and the aerosol content in the atmosphere as well as additional 2.3 × 10 5 specially averaged TIRVIM spectra, were processed with retrieval of the water vapor column abundancein the Martian atmosphere.

In this work we discuss various selected mission concepts addressing Venus evolution through time. More specifically, we address investigations and payload instrument concepts supporting scientific goals and open questions presented in the companion articles of this volume. Also included are their related investigations (observations & modeling) and discussion of which measurements and future data products are needed to better constrain Venus’ atmosphere, climate, surface, interior and habitability evolution through time. A new fleet of Venus missions has been selected, and new mission concepts will continue to be considered for future selections. Missions under development include radar-equipped ESA-led EnVision M5 orbiter mission (European Space Agency 2021 ), NASA-JPL’s VERITAS orbiter mission (Smrekar et al. 2022a ), NASA-GSFC’s DAVINCI entry probe/flyby mission (Garvin et al. 2022a ). The data acquired with the VERITAS, DAVINCI, and EnVision from the end of this decade will fundamentally improve our understanding of the planet’s long term history, current activity and evolutionary path. We further describe future mission concepts and measurements beyond the current framework of selected missions, as well as the synergies between these mission concepts, ground-based and space-based observatories and facilities, laboratory measurements, and future algorithmic or modeling activities that pave the way for the development of a Venus program that extends into the 2040s (Wilson et al. 2022 ).

This research studies the O 2 (a 1 Δ g ) nightglow distribution in 1.27 μm to understand the dynamics of the atmosphere of Venus. Several factors were considered in the retrieval process, such as thermal emission of the lower atmosphere, reflection by the clouds. Results show deviation from SS-AS circulation mode: the area where horizontal flows from the dayside converge and where oxygen recombines and emits shifts from the midnight to 22–23 hours local time. This shift is caused by solar-induced thermal tide on Venus nightside. Some conclusions about the upper mesosphere dynamics are also presented.

In the framework of the project "Venera-D" a problem of landing the descent module in a given area of the surface of Venus is considered. With the standard approach to selection of the launch window and with limitations on the value of the re-entry angle into the atmosphere, as well as on the maximum allowable overload for lander during descent, a significant part of the planet’s surface is inaccessible for landing. The simplest way to expand the landing area could be to increase the launch window by moderate reducing the payload mass. However, the potential for such an increase is significantly limited, primarily by the required characteristic velocity cost. In this study a new approach is proposed to ensure landing of the descent module at any point on the surface of Venus. The basis of the proposed approach is the use of the gravitational field of the planet to transfer the spacecraft to the heliocentric orbit, resonant at a ratio of 1:1 with the orbit of Venus, and the subsequent return to its original position in one Venusian year, when another part of the surface will be available for landing. In the presented paper it is shown that application of new approach allows to provide radical expansion of achievable landing areas, and also to provide access to any point on the surface of Venus due to increase of duration of flight and small increase of characteristic velocity costs

We present joint analysis of the UV (365 nm) images captured by the cameras on board ESA’s Venus Express and JAXA’s Akatsuki spacecraft. These observations enabled almost continuous characterization of the cloud top circulation over the longest period of time so far (2006–2021). More than 46,000 wind vectors were derived from tracking the UV cloud features and revealed changes in the atmospheric circulation with the period of 12.5 ± 0.5 years. The zonal wind component is characterized by an annual mean of −98.6 ± 1.3 m/s and an amplitude of 10.0 ± 1.6 m/s. The mean meridional wind velocity is −2.3 ± 0.2 m/s and has an amplitude of 3.4 ± 0.3 m/s. Plausible physical explanations of the periodicity include both internal processes and external forcing. Both missions observed periodical changes in the UV albedo correlated with the circulation variability. This could result in acceleration or deceleration of the winds due to modulation of the deposition of the radiative energy in the clouds. The circulation can be also affected by the solar cycle that has a period of approximately 11 years with a large degree of deviation from the mean. The solar cycle correlated with the wind observations can probably influence both the radiative balance and chemistry of the mesosphere. The discovered periodicity in the cloud top circulation of Venus, and especially its similarity with the solar cycle, is strongly relevant to the study of exoplanets in systems with variable “suns”.

Wind vectors derived by processing data of UV (365 nm) images obtained by Venus Monitoring Camera (VMC) onboardVenus Express spacecraft from 2006 to 2013 and by Ultraviolet Imager (UVI) onboard Akatsuki from 2016 to 2019 wereused to study mesosphere dynamics. We found that the trend of the mean zonal wind speed at South equatorial latitudesof Venus changed from upward to downward in time period from 2014 to 2015. Analysis of the longitudinal dependence ofthe average zonal velocity, obtained from both the VMC and the UVI data, reveals decrease in wind speed associated withAphrodite Terra.

The horizontal wind velocity vectors at the lower cloud layer were retrieved by tracking the displacement of cloud features using the 1.74 µm images of the full Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M) dataset. This layer was found to be in a superrotation mode with a westward mean speed of 60–63 m s−1 in the latitude range of 0–60° S, with a 1–5 m s−1 westward deceleration across the nightside. Meridional motion is significantly weaker, at 0–2 m s−1; it is equatorward at latitudes higher than 20° S, and changes its direction to poleward in the equatorial region with a simultaneous increase of wind speed. It was assumed that higher levels of the atmosphere are traced in the equatorial region and a fragment of the poleward branch of the direct lower cloud Hadley cell is observed. The fragment of the equatorward branch reveals itself in the middle latitudes. A diurnal variation of the meridional wind speed was found, as east of 21 h local time, the direction changes from equatorward to poleward in latitudes lower than 20° S. Significant correlation with surface topography was not found, except for a slight decrease of zonal wind speed, which was connected to the volcanic area of Imdr Regio.

This study discusses the usage of Venus gravity assist in order to choose and reaching any point on Venusian surface. The launch of a spacecraft to Venus during the launch windows of 2029 to 2031 is considered for this purpose. The constraints for the method are the re-entry angle and the maximum possible overload. The primary basis of the proposed strategy is to use the gravitational field of Venus to transfer the spacecraft to an orbit resonant to the Venusian one – with the aim of expanding accessible landing areas. Results of the current research show that this strategy provides an essential increase in accessible landing areas and, moreover, may provide an access to any point on the surface of Venus with a small increase in ∆V required for launch from the Earth and in the flight duration. The comparison with the landing without using gravity assist near planet is also given.

The baseline Venera-D mission, proposed to be launched after 2026, consists of an orbiter and a landing module, which includes a lander and a small long-lived station. In this work, we present the possibility of augmenting the mission with one or two micro-spacecraft in Lagrange point orbits to significantly enhance the science return. Both L1 and L2 collinear points, situated at about 1 million km from Venus, are considered for scientific objectives. The paper focuses on trajectory design for the micro-spacecraft to be deployed by the Venera-D mission. The transfer scenario we propose performs the insertion of micro-spacecraft into Lagrange point orbit by making use of the main orbiter’s propulsion, while the propulsion on board micro-spacecraft is used only for trajectory correction and station-keeping manoeuvres. This scenario allows the Venera-D mission to add one or two micro-spacecraft of mass about 50 kg with only a total ΔV budget 30 m/s over 3 years on orbit.

This research is aimed to understand circulation of the Venusian atmosphere at the lower cloud level (44-48 km) and its variations with time, latitude, longitude and local time. On the nightside winds at these altitudes can be tracked from the orbit by using infrared imaging instruments. Here we compare results obtained in the same spectral window of 1.74 μm by two instruments flown on two most recent missions to Venus. Comparison of the results shows accordance in the meridional component direction and magnitude, however a significant difference in the values of the zonal component of the wind. Mean zonal speed measured from IR2 data in 2016 exceeds that of VIRTIS-M data in 2006-2008 by a value up to 16 m s -1 . Because of recent investigations of the stationary gravity waves and their potential influence on the atmospheric circulation [3], we examined longitude-latitude dependence of the wind velocities and found variations that can be attributed to such mechanisms.

The paper focuses on a future mission to Venus, Venera-D, which is presently at the stage of defining the scientific objectives and shaping the preliminary mission architecture. The main scientific goals regarding the atmosphere, magnetosphere and internal structure of Venus are considered. The current configuration, baseline, and additional elements of the mission are described.

The article describes the trajectory scenario for the Venera-D mission. The main aspects of optimal launch dates are considered. A scenario, which enables insertion of an orbiter into a highly elliptical orbit and a lander on the surface of Venus is described. Characteristics of the choice for operational orbit and scenario ensuring scientific data transfer from the lander on the surface of Venus to the Earth are justified. In addition, possibilities of transfer of a small satellite to the vicinity of the collinear Lagrangian point of the Sun-Venus system, and also a subsatellite into the orbit of the main orbiter, are considered.