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The Lorenz energy cycle was often used to analyze energy conversions related to instabilities in planetary atmospheres using zonal means as basic states. Alternatively, the bred vector (BV) energy equations use the control run as basic states and detect longitudinal dependency of the energy conversions. Additionally, it quantifies contributions from baroclinic and barotropic instabilities separately. We apply this method to understand energy conversions of the Venus atmosphere. BVs are obtained from breeding cycles emphasizing perturbation growths in the cloud layer. The BV potential energy in the pressure coordinate is newly derived. Energy conversions at different latitudes in the cloud layer are examined. Results show that baroclinic conversions are stronger at higher latitudes and exceed barotropic conversions at mid‐ to high‐latitudes. Thermal tides increase energy conversions in the morning hemisphere at mid‐latitudes. This study offers new insights into energy conversions of the Venus atmosphere, with potential applications to other planetary atmospheres. Plain Language Summary The atmospheres of planets such as Earth, Mars, and Venus, have various instabilities. Energy conversions occur when instabilities are triggered. The Lorenz energy cycle was typically used to understand energy conversions. However, this method considers zonal averages as basic flow, which works better for Earth's atmosphere than for Venus’s, where longitudinal dependency due to planetary‐scale disturbances is important. We applied an alternative approach, the Bred Vector (BV) energy equations, to analyze energy conversions of the Venusian atmosphere. This method has been used to study Earth’s ocean and the Martian atmosphere but has never been applied to the Venusian atmosphere. The advantage of this method is that it can detect longitudinal dependency of the energy conversion and quantify contributions of instabilities from meridional temperature gradient (baroclinic instability) and from horizontal wind shear (barotropic instability). Our findings show that the energy conversion related to baroclinic instability is stronger at higher latitudes and exceeds those related to barotropic instability in mid‐ to high‐latitude regions. We also found that thermal tides, excited by solar heating, increase energy conversions related to both instabilities in the morning hemisphere at mid‐latitudes. This study provides new insights into understanding energy conversions related to instabilities in the Venusian atmosphere. Key Points Energy conversions of the Venus atmosphere were examined for the first time using bred vector kinetic and potential energy equations Baroclinic energy conversion is stronger than barotropic energy conversion in the cloud layer at the mid‐ and high‐latitudes Thermal tide increases the baroclinic and barotropic energy conversions in the morning hemisphere at the mid‐latitudes

The spectroscopic detection of SO2 and unknown UV absorber substance in the H2SO4 cloud layer of Venus’ atmosphere is currently a focal point in the study of the habitability of Venusian atmospheric clouds. This paper addresses the simultaneous detection requirements of multiple substances in the ultraviolet range of Venus’ atmosphere and proposes a multi-channel hyperspectral imaging system design using pupil separation prisms and grating multilevel spectra. The system achieves a multi-channel design by splitting the entrance pupil of the telescope using prisms. Spectra from different channels are diffracted to the same detector through different orders of the grating. The system features a single spectrometer and detector, enabling simultaneous detection of spectra from different channels. It also boasts advantages such as compact size, ultra-high spectral resolution, and simultaneous multi-channel detection. The system design results indicate that within the working spectral range of three channels, the spectral resolution is better than 0.15 nm, surpassing previous in-orbit or current in-orbit planetary atmospheric detection spectrometers. With a Nyquist frequency of 56 lp/mm, the full-field MTF exceeds 0.7. The system’s smile is less than 0.05 μm, and the keystone is less than 0.04 μm, meeting the requirements for imaging quality.

We present aeronomical observations collected using remote sensing instruments on board Venus Express, complemented with ground-based observations and numerical modeling. They are mostly based on VIRTIS and SPICAV measurements of airglow obtained in the nadir mode and at the limb above 90 km. They complement our understanding of the behavior of Venus’ upper atmosphere that was largely based on Pioneer Venus observations mostly performed over thirty years earlier. Following a summary of recent spectral data from the EUV to the infrared, we examine how these observations have improved our knowledge of the composition, thermal structure, dynamics and transport of the Venus upper atmosphere. We then synthesize progress in three-dimensional modeling of the upper atmosphere which is largely based on global mapping and observations of time variations of the nitric oxide and O 2 nightglow emissions. Processes controlling the escape flux of atoms to space are described. Results based on the VeRA radio propagation experiment are summarized and compared to ionospheric measurements collected during earlier space missions. Finally, we point out some unsolved and open questions generated by these recent datasets and model comparisons.

At the cloud top of the Venus atmosphere, equatorial Kelvin waves have been observed and are considered to play an important role in the super-rotation. We were able to reproduce the wave in a general circulation model (GCM) by conducting an observing system simulation experiment (OSSE) with the help of a data assimilation system. The synthetic horizontal winds of the Kelvin wave produced by the linear wave propagating model are assimilated at the cloud top (~70 km) in realistic conditions, assuming they are obtained from cloud tracking of ultra-violet images (UVI) taken by the Venus orbiters. It is demonstrated using Eliassen–Palm (EP) fluxes that the reproduced Kelvin wave transports angular momentum and plays an important role in the magnitude and structure of the super-rotation, causing the acceleration and deceleration of zonal wind of ~0.1 m/s day−1. The conditions required in order to reproduce the Kelvin wave have also been investigated. It is desirable to have 24 hourly dayside satellite observations in an equatorial orbit, such as the Akatsuki Venus climate orbiter. The results of this type of data assimilation study will be useful in the planning of future observation missions to the atmospheres of planets.

The conceptual design of a hybrid aerial vehicle for the exploration of the upper Venus atmosphere is presented. The vehicle will float like a balloon and harvest solar energy which is stored in batteries. The neutral buoyancy reduces the energy consumption and makes the vehicle robust and durable. Energy stored in the batteries can be used for powered flight with good horizontal and vertical mobility to explore aspects of the atmosphere. The vehicle is intended to operate near 55.3 km altitude and to explore the cloud layer of the planet. The vehicle takes its inspiration from the Stingray inflatable wing by Prospective Concepts. Based on a trade study, the wing span was set to 25 m. Equations are developed for the altitude, gas and skin temperature, and skin stress during neutrally buoyant flight. To keep the equations in a simplified analytical form, the complex compartmentalized gas pockets of the vehicle are lumped into a single gas sphere. The equations take into account the volumetric expansion of the structure and the requirement that the differential pressure needs to be large enough to allow for brief periods of powered flight without significant structural deformation. An aerodynamic analysis provides the lift and drag coefficient curves and indicates that the vehicle is pitch-stable. A powered flight analysis shows that an airspeed of 30 m/s can be maintained for 31 min at 55 km and 69 min at 69 km altitude.

Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a unique opportunity to search for atmospheres on small planets outside the Solar System 1 . Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO 2 ) are now detectable 2 , 3 . Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO 2 in its atmosphere 4 . Here we report the detection of thermal emission from the dayside of TRAPPIST-1 c with the Mid-Infrared Instrument (MIRI) on JWST at 15 µm. We measure a planet-to-star flux ratio of f p / f ⁎  = 421 ± 94 parts per million (ppm), which corresponds to an inferred dayside brightness temperature of 380 ± 31 K. This high dayside temperature disfavours a thick, CO 2 -rich atmosphere on the planet. The data rule out cloud-free O 2 /CO 2 mixtures with surface pressures ranging from 10 bar (with 10 ppm CO 2 ) to 0.1 bar (pure CO 2 ). A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6 σ confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO 2 -rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than 9.5 − 2.3 + 7.5 Earth oceans of water. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system. The detection of thermal emission from the rocky exoplanet TRAPPIST-1 c using the Mid-Infrared Instrument on the James Webb Space Telescope reveals a dayside brightness temperature that disfavours a thick, CO 2 -rich atmosphere.

The possible presence of life in the atmosphere of Venus has been debated frequently over the last 60 years. The discussion was recently reignited by the possible detection of phosphine (PH3), but several other chemicals potentially relevant for life processes are also found in the middle atmosphere. Moreover, the reasons for the heterogeneous ultraviolet (UV) absorption between 320 and 400 nm in the altitude range ∼40–70 km are still not well understood. These aspects could be further studied in-situ by UV Raman and fluorescence instruments. Here, the conceptual design of a small balloon probe (<20 kg) is presented, including a science payload comprising a UV laser, spectrometer, and a telescope. The goal of the proposed mission is to analyse the absorption of UV light in Venus’ atmosphere, to study the atmospheric composition, and to verify the possible presence of biomarkers. Current state-of-the-art technologies would allow a more cost-efficient and easy to develop mission, as compared to previous Venus probes. This article is focused on the scientific instrumentation, as well as on the mass and power budgets required to realise the proposed mission.

Venus was the first of the planets of the Solar System in the atmosphere of which electrical phenomena similar to lightning in the Earth’s atmosphere were discovered. Electrical discharges (lightning in the atmosphere of Venus) were discovered in 1978 in the Venera-12 , -11 , and Pioneer Venus missions, based on their electromagnetic radiation. The paradox, however, was that the search for optical flares remained unsuccessful for the past 40 years. In 2015, the Akatsuki spacecraft of the Japan Aerospace Exploration Agency was launched into orbit Venus satellite. It was designed to search for lightning and other studies of the meteorology of Venus by recording radiation in selected spectral ranges. In 2016, the Akatsuki orbiter successfully performed detailed observations of Venus in the near-infrared range in the “transparency windows” of the planet’s atmosphere, as well as in the ultraviolet and other ranges. The article presents the results of an alternative search for and successful detection of lightning flashes according to the Akatsuki project, but not in the ultraviolet or visible ranges, but in the near-IR range. A comparison of the results of calculations based on models of terrestrial lightning with the results of measurements made by the IR2 camera of the Akatsuki mission on Venus at a wavelength of 2.26 μm shows a close agreement between the experimental and calculated data.

The radio occultation measurements of the signal intensity (λ = 32 cm) of the Venera-15 and -16 satellites, carried out from October 16 to October 31, 1983, are used to analyze the activity of internal waves in the northern polar atmosphere of Venus. Observations of the intensity of radio waves provide important information about the fine-scale structure of the planet’s atmosphere. Comparison of radio occultation measurements and the results of the standard wave theory shows that small-scale fluctuations of the received signal intensity are caused by the spectrum of vertically propagating internal gravity waves. The vertical length of these fluctuations at altitudes of more than 61.5 km is about ~1 km. The model developed for the radiative damping of intensity fluctuations with altitude in the atmosphere of Venus assumes that the intrinsic frequencies of the identified internal waves (measured in a frame of reference moving together with the undisturbed flow) in the sessions under study vary from 3.5 × 10 –4 to 9.5 × 10 –4 rad/s, and the ratio of horizontal and vertical wavelengths is in the range from 57 to 21.