Small-scale temperature fluctuations seen by the VeRa Radio Science Experiment on Venus Express

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T.; Bird, M. K.; Imamura, Takeshi; Pätzold, M.; Remus, S.

doi:10.1016/j.icarus.2012.08.023

Cited by 65 publications

(92 citation statements)

References 64 publications

(99 reference statements)

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“…This estimation of the vertical wavelength is also consistent with previous studies: Fels (1986) showed that vertically propagating diurnal tides should have vertical wavelengths <10 km, while numerical modeling studies by Pechmann and Ingersoll (1984) showed that the diurnal tide between altitudes of 60 and 90 km is characterized by an upward wave with a vertical wavelength of about 7 km. Recent results from the VeRa instrument onboard Venus Express also allowed temperature fluctuations with vertical wavelengths of only a few kilometres to be detected that could indicate the presence of the diurnal tide between 40 and 90 km (Tellmann et al, 2011) but their horizontal structure remains to be determined.…”

Section: Spatial Structure For the Diurnal Tidementioning

confidence: 99%

Solar migrating atmospheric tides in the winds of the polar region of Venus

Peralta

Luz

Berry

et al. 2012

Icarus

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a b s t r a c tWe study the effects of migrating solar tides on the winds at the cloud tops of the polar region of Venus.The winds were measured using cloud tracking on images obtained at wavelengths of 3.9 and 5.0 lm by the instrument VIRTIS-M onboard Venus Express. These wavelengths probe about the same altitude close to the cloud tops, allowing for the first time to retrieve winds simultaneously in the day and nightside of the planet. We use a dataset with observations from 16 orbits, covering a time span of 289 days and a latitude range between 70°S and 85°S, the region where the so called cold collar resides. Diurnal and quarter-diurnal tides (wavenumbers 1 and 4) were detected in the wind field, with a decoupled influence on the zonal and meridional directions. The diurnal tide is the dominant harmonic with amplitudes of about 4.7 m/s exclusively affecting the meridional component of the wind and forcing a solar-to-antisolar circulation at the polar region. The quarter-diurnal mode is only apparent in the zonal wind in a restricted latitude range with amplitudes $2.2 m/s. The spatial structure of the diurnal tide has also been investigated, obtaining a vertical wavelength of about 8 km, in accordance with predictions by models. Finally, a theoretical relation between the amplitudes of tidal temperature and tidal wind has been derived and its validity tested with models and results from previous missions.

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Section: Spatial Structure For the Diurnal Tidementioning

confidence: 99%

Solar migrating atmospheric tides in the winds of the polar region of Venus

Peralta

Luz

Berry

et al. 2012

Icarus

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“…Radio occultation has played a crucial role in determining the structures of the planetary atmospheres (e.g., Eshleman 1973;Tyler 1987;Pätzold et al 2007;Imamura et al 2012). In a radio occultation experiment conducted with a spacecraft equipped with a stable frequency source, the spacecraft transmits radio waves toward the Earth, while it goes behind the planet and reemerges as seen from the Earth.…”

Section: Introductionmentioning

confidence: 99%

“…The static stability is near neutral in the middle and lower cloud regions (50-58 km), suggesting occurrence of vertical convection (Pollack et al 1980;Tellmann et al 2009). At altitudes above ~ 58 km, propagation of gravity waves is suggested from wavelike features in the temperature profiles (Hinson and Jenkins 1995;Tellmann et al 2012;Ando et al 2015a). In spite of these findings, the relationship among the variations of the temperature field, the wind field and the cloud distribution has not been studied.…”

Section: Introductionmentioning

confidence: 99%

Initial performance of the radio occultation experiment in the Venus orbiter mission Akatsuki

Imamura

Ando

Tellmann

et al. 2017

Earth Planets Space

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After the arrival of Akatsuki spacecraft of Japan Aerospace Exploration Agency at Venus in December 2015, the radio occultation experiment, termed RS (Radio Science), obtained 19 vertical profiles of the Venusian atmosphere by April 2017. An onboard ultra-stable oscillator is used to generate stable X-band downlink signals needed for the experiment. The quantities to be retrieved are the atmospheric pressure, the temperature, the sulfuric acid vapor mixing ratio, and the electron density. Temperature profiles were successfully obtained down to ~ 38 km altitude and show distinct atmospheric structures depending on the altitude. The overall structure is close to the previous observations, suggesting a remarkable stability of the thermal structure. Local time-dependent features are seen within and above the clouds, which is located around 48-70 km altitude. The H 2 SO 4 vapor density roughly follows the saturation curve at cloud heights, suggesting equilibrium with cloud particles. The ionospheric electron density profiles are also successfully retrieved, showing distinct local time dependence. Akatsuki RS mainly probes the low and middle latitude regions thanks to the near-equatorial orbit in contrast to the previous radio occultation experiments using polar orbiters. Studies based on combined analyses of RS and optical imaging data are ongoing.

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“…New measurements made by various instruments on the VEx spacecraft have provided important advances concerning the vertical characterization of the Venus atmospheric thermal structure, but this applies mostly below about 100 km. For example, radio occultation probed from 40 to 90 km (Tellmann et al 2009(Tellmann et al , 2012, while sensing the night-time emission at selected IR wavelengths, allows us to sense between 65 and 96 km (Grassi et al 2010;Migliorini et al 2012;GarateLopez et al 2015). Temperatures in the altitude range between 90 and 150 km have been inferred, but only on the nightside with stellar occultation (Piccialli et al 2015), and in the morning and evening terminators with solar occultation techniques (Mahieux et al 2015b).…”

Section: Introductionmentioning

confidence: 99%

Dayside temperatures in the Venus upper atmosphere from Venus Express/VIRTIS nadir measurements at 4.3μm

Peralta

López‐Valverde

Gilli

et al. 2015

A&A

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In this work, we analysed nadir observations of atmospheric infrared emissions carried out by VIRTIS, a high-resolution spectrometer on board the European spacecraft Venus Express. We focused on the ro-vibrational band of CO 2 at 4.3 µm on the dayside, whose fluorescence originates in the Venus upper mesosphere and above. This is the first time that a systematic sounding of these non-local thermodynamic equilibrium (NLTE) emissions has been carried out in Venus using this geometry. As many as 143,218 spectra have been analysed on the dayside during the period 14/05/2006 to 14/09/2009. We designed an inversion method to obtain the atmospheric temperature from these non-thermal observations, including a NLTE line-by-line forward model and a pre-computed set of spectra for a set of thermal structures and illumination conditions. Our measurements sound a broad region of the upper mesosphere and lower thermosphere of Venus ranging from 10 −2 -10 −5 mb (which in the Venus International Reference Atmosphere, VIRA, is approximately 100-150 km during the daytime) and show a maximum around 195 ± 10 K in the subsolar region, decreasing with latitude and local time towards the terminator. This is in qualitative agreement with predictions by a Venus Thermospheric General Circulation Model (VTGCM) after a proper averaging of altitudes for meaningful comparisons, although our temperatures are colder than the model by about 25 K throughout. We estimate a thermal gradient of about 35 K between the subsolar and antisolar points when comparing our data with nightside temperatures measured at similar altitudes by SPICAV, another instrument on Venus Express (VEx). Our data show a stable temperature structure through five years of measurements, but we also found episodes of strong heating/cooling to occur in the subsolar region of less than two days.

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Small-scale temperature fluctuations seen by the VeRa Radio Science Experiment on Venus Express

Cited by 65 publications

References 64 publications

Solar migrating atmospheric tides in the winds of the polar region of Venus

Solar migrating atmospheric tides in the winds of the polar region of Venus

Initial performance of the radio occultation experiment in the Venus orbiter mission Akatsuki

Dayside temperatures in the Venus upper atmosphere from Venus Express/VIRTIS nadir measurements at 4.3μm

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