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See detailAn Overview Of Spicav/soir Results On The Atmosphere Of Venus From Venus Express Mission
Bertaux, Jean-Loup; Vandaele, A.; Korablev, O. et al

in AAS/Division for Planetary Sciences Meeting Abstracts (2009, September 01)

SPICAV/SOIR is a suite of three spectrometers in the UV and IR range flying on ESA Venus Express orbiter, dedicated to the study of the atmosphere of Venus : UV (110-320 nm), Vis-Nir (0.65-1.65 µm), and ... [more ▼]

SPICAV/SOIR is a suite of three spectrometers in the UV and IR range flying on ESA Venus Express orbiter, dedicated to the study of the atmosphere of Venus : UV (110-320 nm), Vis-Nir (0.65-1.65 µm), and mid IR (2.3-4.4 µm). The UV spectrometer discovered a high altitude layer of SO2 ( 85-105 km), apparently correlated with the density of haze particles. Ozone is detected for the first time in the atmosphere of Venus. The night side γ and δ bands of NO intensities are maximal at 2 am (influence of super-rotation), while the O2 emission mapped simultaneously by Virtis peaking at 95 km altitude ( 10 km below NO emission) is centered at midnight, a puzzle for general circulation models. The hot hydrogen component of the exosphere, extending at more than 30,000 km, is variable. The SPICAV VIS-IR sensor (0.7-1.7 μm, resolution 0.5-1.2 nm) employs a pioneering technology: acousto-optical tunable filter (AOTF). Day side observations indicate a variable latitude distribution of cloud top altitude (decreasing toward the pole) and water vapor mixing ratio. The SOIR spectrometer is a new Solar Occultation IR spectrometer in the range λ=2.2-4.3 µm, with a spectral resolution λ/Πλ>20,000, the highest ever flown in a planetary mission. This new concept includes a combination of an echelle grating and an AOTF crystal to sort out one order at a time. Vertical profiles of CO, HDO, H2O, HCl, SO[SUB]2[/SUB], CO[SUB]2[/SUB] isotopes and temperature are regularly retrieved, as well as aerosols. The CO mixing ratio (80-130 km), a tracer of atmospheric exchange from thermosphere to lower atmosphere, is 10 times less than the VIRA model prescription, showing also some time variability. [less ▲]

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See detailA warm layer in Venus' cryosphere and high-altitude measurements of HF, HCl, H[SUB]2[/SUB]O and HDO
Bertaux, Jean-Loup; Vandaele, Ann-Carine; Korablev, Oleg et al

in Nature (2007), 450

Venus has thick clouds of H[SUB]2[/SUB]SO[SUB]4[/SUB] aerosol particles extending from altitudes of 40 to 60km. The 60-100km region (the mesosphere) is a transition region between the 4day retrograde ... [more ▼]

Venus has thick clouds of H[SUB]2[/SUB]SO[SUB]4[/SUB] aerosol particles extending from altitudes of 40 to 60km. The 60-100km region (the mesosphere) is a transition region between the 4day retrograde superrotation at the top of the thick clouds and the solar-antisolar circulation in the thermosphere (above 100km), which has upwelling over the subsolar point and transport to the nightside. The mesosphere has a light haze of variable optical thickness, with CO, SO[SUB]2[/SUB], HCl, HF, H[SUB]2[/SUB]O and HDO as the most important minor gaseous constituents, but the vertical distribution of the haze and molecules is poorly known because previous descent probes began their measurements at or below 60km. Here we report the detection of an extensive layer of warm air at altitudes 90-120km on the night side that we interpret as the result of adiabatic heating during air subsidence. Such a strong temperature inversion was not expected, because the night side of Venus was otherwise so cold that it was named the `cryosphere' above 100km. We also measured the mesospheric distributions of HF, HCl, H[SUB]2[/SUB]O and HDO. HCl is less abundant than reported 40years ago. HDO/H[SUB]2[/SUB]O is enhanced by a factor of ~2.5 with respect to the lower atmosphere, and there is a general depletion of H[SUB]2[/SUB]O around 80-90km for which we have no explanation. [less ▲]

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See detailSPICAV on Venus Express: Three spectrometers to study the global structure and composition of the Venus atmosphere
Bertaux, Jean-Loup; Nevejans, D.; Korablev, O. et al

in Planetary and Space Science (2007), 55

Spectroscopy for the investigation of the characteristics of the atmosphere of Venus (SPICAV) is a suite of three spectrometers in the UV and IR range with a total mass of 13.9 kg flying on the Venus ... [more ▼]

Spectroscopy for the investigation of the characteristics of the atmosphere of Venus (SPICAV) is a suite of three spectrometers in the UV and IR range with a total mass of 13.9 kg flying on the Venus Express (VEX) orbiter, dedicated to the study of the atmosphere of Venus from ground level to the outermost hydrogen corona at more than 40,000 km. It is derived from the SPICAM instrument already flying on board Mars Express (MEX) with great success, with the addition of a new IR high-resolution spectrometer, solar occultation IR (SOIR), working in the solar occultation mode. The instrument consists of three spectrometers and a simple data processing unit providing the interface of these channels with the spacecraft. A UV spectrometer (118-320 nm, resolution 1. 5 nm) is identical to the MEX version. It is dedicated to nadir viewing, limb viewing and vertical profiling by stellar and solar occultation. In nadir orientation, SPICAV UV will analyse the albedo spectrum (solar light scattered back from the clouds) to retrieve SO2, and the distribution of the UV-blue absorber (of still unknown origin) on the dayside with implications for cloud structure and atmospheric dynamics. On the nightside, 7 and 6 bands of NO will be studied, as well as emissions produced by electron precipitations. In the stellar occultation mode the UV sensor will measure the vertical profiles of CO2, temperature, SO2, SO, clouds and aerosols. The density/temperature profiles obtained with SPlCAV will constrain and aid in the development of dynamical atmospheric models, from cloud top (similar to 60 km) to 160 km in the atmosphere. This is essential for future missions that would rely on aerocapture and acrobraking. UV observations of the upper atmosphere will allow studies of the ionosphere through the emissions of CO, CO+, and CO2+, and its direct interaction with the solar wind. It will study the H corona, with its two different scale heights, and it will allow a better understanding of escape mechanisms and estimates of their magnitude, crucial for insight into the long-term evolution of the atmosphere. The SPICAV VIS-IR sensor (0.7-1.7 mu m, resolution 0.5-1.2 nm) employs a pioneering technology: an acousto-optical tunable filter (AOTF). On the nightside, it will study the thermal emission peeping through the clouds, complementing the observations of both VIRTIS and Planetary Fourier Spectrometer (PFS) on VEX. In solar occultation mode this channel will study the vertical structure of H2O, CO2, and aerosols. The SOIR spectrometer is a new solar occultation IR spectrometer in the range lambda=2.2-4.3 mu m, with a spectral resolution lambda/Delta lambda > 15,000, the highest on board VEX. This new concept includes a combination of an echelle grating and an AOTF crystal to sort out one order at a time. The main objective is to measure HDO and H2O in solar occultation, in order to characterize the escape of D atoms from the upper atmosphere and give more insight about the evolution of water on Venus. It will also study isotopes of CO2 and minor species, and provides a sensitive search for new species in the upper atmosphere of Venus. It will attempt to measure also the nightside emission, which would allow a sensitive measurement of HDO in the lower atmosphere, to be compared to the ratio in the upper atmosphere, and possibly discover new minor atmospheric constituents. (C) 2007 Elsevier Ltd. All rights reserved. [less ▲]

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See detailDYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields
Chassefière, E.; Nagy, A.; Mandea, M. et al

in Advances in Space Research (2004), 33

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to ... [more ▼]

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure and evolution of Mars is thought to have influenced climate evolution. The collapse of the primitive magnetosphere early in Mars history could have enhanced atmospheric escape and favored transition to the present arid climate. These objectives are achieved by using a low periapsis orbit. DYNAMO has been proposed in response to the AO released in February 2002 for instruments to be flown as a complementary payload onboard the CNES Orbiter to Mars (MO-07), foreseen to be launched in 2007 in the framework of the French PREMIER Mars exploration program. MO-07 orbital phase 2b (with an elliptical orbit of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate. Ultraviolet remote sensing is an essential complement to characterize high, tenuous, layers of the atmosphere. One Martian year of operation, with about 5,000 low passes, should allow DYNAMO to map in great detail the residual magnetic field, together with the gravity field. Additional data on the internal structure will be obtained by mapping the electric conductivity, sinergistically with the NETLANDER magnetic data. Three options have been recommended by the International Science and Technical Review Board (ISTRB), who met on July 1st and 2nd, 2002. One of them is centered on DYNAMO. The final choice, which should be made before the end of 2002, will depend on available funding resources at CNES. [less ▲]

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