Microwave absorptivity by sulfuric acid in the Venus atmosphere: First results from the Venus Express Radio Science experiment VeRa

The main cloud deck within Venus' atmosphere, which covers the entire planet between approx. 50 and 70 km altitude, is believed to consist mostly of liquid sulfuric acid. The temperature below the main clouds is high enough to evaporate the H2SO4 droplets into gaseous sulfuric acid forming a haze layer which extends to altitudes as deep as 35 km. Gaseous sulfuric acid in Venus&#8217; lower atmosphere is responsible for a strong absorption of radio waves as seen in Mariner, Pioneer Venus, Magellan and Venera radio science observations. Radio wave absorption measurements can be used to derive the amount of H2SO4 in Venus&#8217; atmosphere. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2014 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. The orbit of the Venus Express spacecraft allowed to sound the atmosphere over a wide range of latitudes and local times providing a global picture of the sulfuric acid vapor distribution. We present the global H2SO4(g) distribution derived from the X-band radio signal attenuation for the time of the entire Venus Express mission. The observation is compared with results obtained from a 2-D transport model. The VeRa observations were additionally used to estimate the abundance of SO2 near the cloud bottom. The global distribution of SO2 at these altitudes is presented and compared with results obtained from other experiments. Eight years of VEX observation allow to study the long-term evolution of H2SO4 and SO2. The latter is presented for the northern polar region.

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Calibration Techniques for Studying Venus and Mars Atmospheres

Aerotecnica Missili & Spazio ◽

10.1007/s42496-020-00066-y ◽

2020 ◽

Vol 99 (4) ◽

pp. 255-261

Author(s):

Edoardo Gramigna

Keyword(s):

Radio Occultation ◽

European Space Agency ◽

Point Of View ◽

Mars Atmosphere ◽

Radio Science ◽

Space Agency ◽

Spacecraft Trajectory ◽

Venus Express ◽

Calibration Techniques ◽

Venus Atmosphere

AbstractThe European Space Agency Venus Express mission (VEX) was sent to Venus in 2005 to unveil the unsolved mysteries regarding its atmosphere, the plasma environment and its temperatures. Radio occultation experiments performed by VeRa radio science instrument probed the planet’s atmosphere by studying the frequency shift on the radio signal sent by the spacecraft to Earth-based ground stations. This study carries out the calibration of the radio frequencies within a radio occultation experiment in order to correct the main sources of error as: thermal noise, spacecraft clock, spacecraft trajectory, and plasma noise. Any uncalibrated effects will bias the retrieval of atmospheric properties. A comparison of the occultation experiments between Venus and Mars is presented, both from the engineering and scientific point of view, through the analysis of Venus Express and Mars Global Surveyor (MGS) occultations data, highlighting stronger calibrations required for VEX, the extreme, hostile, thick Venus’ atmosphere, and a friendly, thin Mars’ atmosphere. This investigation analyzes Venus Express data recorded by the NASA Deep Space Network in 2014, and the results are compatible to previous studies of Venus atmosphere with VEX between 2006 and 2009.

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Structure of the Venus neutral atmosphere as observed by the Radio Science experiment VeRa on Venus Express

Journal of Geophysical Research Atmospheres ◽

10.1029/2008je003204 ◽

2009 ◽

Vol 114 ◽

Cited By ~ 107

Author(s):

Silvia Tellmann ◽

Martin Pätzold ◽

Bernd Häusler ◽

Michael K. Bird ◽

G. Leonard Tyler

Keyword(s):

Neutral Atmosphere ◽

Radio Science ◽

Venus Express

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Sulfuric acid vapor and sulfur dioxide in the atmosphere of Venus as observed by VeRa

10.5194/epsc2020-139 ◽

2020 ◽

Author(s):

Janusz Oschlisniok ◽

Bernd Häusler ◽

Martin Pätzold ◽

Silvia Tellmann ◽

Michael Bird

Keyword(s):

Sulfuric Acid ◽

Sulfur Dioxide ◽

Local Times ◽

Cloud Base ◽

Acid Vapor ◽

X Band ◽

Upper Limits ◽

Wide Range ◽

Venus Express ◽

Atmosphere Of Venus

The main Venus clouds, covering the entire planet between approx. 50 and 70 km altitude, are believed to consist mostly of liquid sulfuric acid. Below the clouds, the temperature is high enough to evaporate those droplets into gaseous sulfuric acid forming a haze layer which extends to altitudes as deep as 35 km. H2SO4(g) is the main absorber of radio waves as was observed in Mariner, Pioneer Venus, Magellan and Venera radio occultation measurements. Radio wave absorption measurements can be used to derive the amount of H2SO4 as well as to estimate upper limits of SO2 in Venus&#8217; atmosphere. The radio science experiment VeRa onboard Venus Express probed the atmosphere of Venus between 2006 and 2014 with radio signals at 13 cm (S-band) and 3.6 cm (X-band) wavelengths. Thanks to the orbit of VEX, a wide range of latitudes and local times was covered so that a global picture of the H2SO4(g) ditribution was obtained. We present H2SO4(g) profiles as well as upper limits of sulfur dioxide near the cloud base derived from the X-band radio signal from the entire Venus Express mission. More than 600 H2SO4(g) profiles show the global sulfuric acid vapor distribution covering the northern and southern hemisphere on the day- and night side of the planet. A distinct latitudinal&#160;H2SO4(g) and SO2 variation and a southern northern symmetry are clearly visible. Observations over 8 years allow to study also long-term variations. Indications for temporal H2SO4(g) and SO2 variations are found, at least at northern polar latitudes. The results shall be compared with observations retrieved by other experiments onboard Venus Express. Additionally, the observed H2SO4(g) distribution will be compared with results obtained from a mass transport model.

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The Challenges and Opportunities for International Cooperative Radio Science; Experience with Mars Express and Venus Express Missions

SpaceOps 2008 Conference ◽

10.2514/6.2008-3556 ◽

2008 ◽

Cited By ~ 2

Author(s):

Dwight Holmes ◽

Thomas Thompson ◽

Richard Simpson ◽

G. Tyler ◽

Veronque Dehant ◽

...

Keyword(s):

Mars Express ◽

Radio Science ◽

Challenges And Opportunities ◽

Venus Express ◽

Science Experience

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Frequency domain interferometry mode observations of PMSE using the EISCAT VHF radar

Annales Geophysicae ◽

10.1007/s00585-001-1599-8 ◽

2000 ◽

Vol 18 (12) ◽

pp. 1599-1612 ◽

Cited By ~ 6

Author(s):

P. B. Chilson ◽

S. Kirkwood ◽

I. Häggström

Keyword(s):

Frequency Domain ◽

Middle Atmosphere ◽

Lower Boundary ◽

Doppler Velocity ◽

Vhf Radar ◽

Radio Science ◽

First Results ◽

Summer Echoes ◽

Polar Mesosphere Summer Echoes ◽

Frequency Coherence

Abstract. During the summer of 1997 investigations into the nature of polar mesosphere summer echoes (PMSE) were conducted using the European incoherent scatter (EISCAT) VHF radar in Norway. The radar was operated in a frequency domain interferometry (FDI) mode over a period of two weeks to study the frequency coherence of the returned radar signals. The operating frequencies of the radar were 224.0 and 224.6 MHz. We present the first results from the experiment by discussing two 4-h intervals of data collected over two consecutive nights. During the first of the two days an enhancement of the FDI coherence, which indicates the presence of distinct scattering layers, was found to follow the lower boundary of the PMSE. Indeed, it is not unusual to observe that the coherence values are peaked around the heights corresponding to both the lower- and upper-most boundaries of the PMSE layer and sublayers. A Kelvin-Helmholtz mechanism is offered as one possible explanation for the layering structure. Additionally, our analysis using range-time-pseudocolor plots of signal-to-noise ratios, spectrograms of Doppler velocity, and estimates of the positions of individual scattering layers is shown to be consistent with the proposition that upwardly propagating gravity waves can become steepened near the mesopause.Key words: Ionosphere (polar ionosphere) · Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) · Radio Science (Interferometry)

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The ESA-JAXA BepiColombo mission: status and first results

10.5194/epsc2021-365 ◽

2021 ◽

Author(s):

Johannes Benkhoff ◽

Joe Zender ◽

Go Murakami ◽

Elsa Montagnon

Keyword(s):

Electric Propulsion ◽

Gamma Ray ◽

European Space Agency ◽

Terrestrial Planet ◽

Neutron Spectrometer ◽

Laser Altimeter ◽

Joint Project ◽

X Ray ◽

Radio Science ◽

First Results

BepiColombo was launched on 20 October 2018 from the European spaceport Kourou in French Guyana and is now on route to Mercury to unveil Mercury&#8217;s secrets. BepiColombo a joint project between the European Space Agency (ESA) and the Japanese Aerospace Exploration Agency (JAXA) consists of two orbiters, the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (Mio). It will perform measurements to increase our knowledge on the fundamental questions about Mercury&#8217;s evolution, composition, interior, magnetosphere, and exosphere. &#160;During its 7-year long journey to the innermost terrestrial planet Mio and MPO are connected to each on-top of the Mercury Transfer Module (MTM). The MTM contains a solar electric propulsion engine and will bring the two spacecraft to Mercury. In late 2025, this &#8216;stack&#8217; configuration is abandoned, the MTM will be jettisoned and the individual elements spacecraft are brought in to their final Mercury orbit: 480x1500km for MPO, and 590x11640km for Mio. &#160;On its way BepiColombo with its state of the art and very comprehensive payload has several opportunities for scientific observations - during the cruise into the inner solar system and during its nine planetary flybys (one at Earth, two at Venus and six at Mercury). However, since the spacecraft is in a stacked configuration not all of the instruments can be operated during the cruise phase.Some of the instruments have been already operated regularly or partially during the flybys in their &#8220;scientific&#8221; observation mode: e.g. the magnetometer (MPO-MAG), the accelerometer (ISA), the environmental sensor (BERM), the gamma-ray and neutron spectrometer (MGNS), the solar intensity x-ray and particle spectrometer (SIXS), the radio science experiment (MORE), using the X-band and the Ka-band, the thermal infrared spectrometer (MERTIS), the UV spectrometer (PHEBUS) and some sensors of the SERENA suite. Also, instruments or some parts of the instruments of the Japanese Mio spacecraft like the dust monitor (MDM), the plasma wave instrument (PWI), the particle and plasma experiments of MPPE and the magnetometer (MGF) were already successfully operated in their science modes. BepiColombo also took regular &#8220;selfie&#8221; images with their three monitoring cameras on the MTM. These cameras were also able to take a sequence of outreach images during the flybys at Earth and Venus in 2020. Other instruments such as cameras and NIR spectrometer (SIMBIO-SYS), the laser altimeter (BELA), the x-ray spectrometer (MIXS), and parts of the electron, neutron, and iron sensors of SERENA on MPO and MSASI and some dedicated sensors of PWI and MPPE are operational, but can only be used in their scientific modes after the Mercury in-orbit commissioning in early 2026 because their field of view is blocked by the underlying Transfer Module.Despite the reduced instrument availability, scientific and engineering operations has been scheduled during the cruise phase, especially during the swing-bys. A status of the mission and instruments and a summary of first results from measurements taken during the first three years en route to Mercury will be given.

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