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1

Venus Express mission  

NASA Astrophysics Data System (ADS)

Venus Express is well and healthy and has now been providing exciting new data from Venus, our nearby twin planet, for over 2 years. Many of the new results are presented and discussed in the subsequent papers in this special section. The overall scientific objective of Venus Express is to carry out a detailed study of the atmosphere of Venus, including the interaction of the upper atmosphere with the solar wind and the interaction of the lowest part of the atmosphere with the surface of the planet. In addition, the plasma environment and magnetic fields as well as some aspects of the surface of the planet are addressed. For the first time, investigations make systematic use of the transparent infrared spectral windows in order to probe the atmosphere in four dimensions: three spatial dimensions plus time. The spacecraft design is taken from Mars Express with some modifications necessary owing to the specific environment around Venus. The payload is composed of three spectrometers, a camera, a magnetometer, an instrument for detecting energetic particles, and a radio science package. The orbit is polar and highly elliptic, with a pericenter altitude of about 200 km over the northern polar region and an apocenter altitude of 66,000 km. Presently, the coverage of the southern hemisphere is very good, but important gaps still do exist. The coverage of the northern hemisphere is much less dense. Venus Express is a part of the European Space Agency's program for the exploration of the inner solar system, which includes missions to study the Sun, Mercury, Venus, the Moon, Mars, and comets and asteroids.

Svedhem, H.; Titov, D.; Taylor, F.; Witasse, O.

2009-03-01

2

Venus Express: Mission Status and First Results  

Microsoft Academic Search

Venus Express is the first European mission to Venus. It aims at global investigation of the atmosphere, the plasma environment, and the surface from polar orbit. The Venus Express spacecraft was launched by the Russian Sojuz-Fregat launcher from Baykonur (Kazakhstan) on November 9, 2005. On April 11, 2006 after 153 days of interplanetary cruise Venus Express reached its destination and

Hakan Svedhem; D. Titov; S. Barabash; J. L. Bertaux; P. Drossart; V. Formisano; B. Häusler; W. Markiewicz; G. Piccioni; T. Zhang; O. Witasse

2006-01-01

3

Venus winds at cloud level from VIRTIS during the Venus Express mission  

NASA Astrophysics Data System (ADS)

The Venus Express (VEX) mission has been in orbit to Venus for almost four years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 ?m) map the opacity of the lower cloud deck at 48 km. Here we present our latest results on the analysis of the global atmospheric dynamics at these cloud levels using a large selection over the full VIRTIS dataset. We will show the atmospheric zonal superrotation at these levels and the mean meridional motions. The zonal winds are very stable in the lower cloud at mid-latitudes to the tropics while it shows different signatures of variability in the upper cloud where solar tide effects are manifest in the data. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present almost null global meridional motions at all latitudes but with particular features traveling both northwards and southwards in a turbulent manner depending on the cloud morphology on the observations. A particular important atmospheric feature is the South Polar vortex which might be influencing the structure of the zonal winds in the lower cloud at latitudes from the vortex location up to 55°S. Acknowledgements This work has been funded by the Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07.

Hueso, Ricardo; Peralta, Javier; Sánchez-Lavega, Agustín.; Pérez-Hoyos, Santiago; Piccioni, Giuseppe; Drossart, Pierre

2010-05-01

4

An Overview Of Spicav/soir Results On The Atmosphere Of Venus From Venus Express Mission  

NASA Astrophysics Data System (ADS)

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 ? and ? 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 ?m, 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 ?=2.2-4.3 µm, with a spectral resolution ?/??>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, SO2, CO2 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.

Bertaux, Jean-Loup; Vandaele, A.; Korablev, O.; Montmessin, F.; Marcq, E.; Chaufray, J.; Wilquet, V.; Fedorova, A.; Mahieux, A.; Belyaev, D.; Villard, E.; Gerard, J.; Royer, E.; Quemerais, E.

2009-09-01

5

An Overview Of Spicav\\/soir Results On The Atmosphere Of Venus From Venus Express Mission  

Microsoft Academic Search

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

Jean-Loup Bertaux; A. Vandaele; O. Korablev; F. Montmessin; E. Marcq; J. Chaufray; V. Wilquet; A. Fedorova; A. Mahieux; D. Belyaev; E. Villard; J. Gerard; E. Royer; E. Quemerais

2009-01-01

6

The Pioneer Venus Missions.  

ERIC Educational Resources Information Center

|This document provides detailed information on the atmosphere and weather of Venus. This pamphlet describes the technological hardware including the probes that enter the Venusian atmosphere, the orbiter and the launch vehicle. Information is provided in lay terms on the mission profile, including details of events from launch to mission end. The…

National Aeronautics and Space Administration, Mountain View, CA. Ames Research Center.

7

Venera-D -the future Russian mission to Venus  

Microsoft Academic Search

Venus was actively studied by Soviet and US mission in 60-80-th years of the last century. The investigations carried out both from the orbit and in situ were highly successful. After a 15-years break in space research of Venus, the ESA Venus Express mission, launched in 2005, successfully continues its work on orbit around Venus. In 2010 the launch of

Ludmila Zasova; Lev Zelenyi; Oleg Korablev; N. F. Sanko; Victor V. Khartov; Victor A. Vorontsov; A. T. Basilevsky; Konstantin M. Pichkhadze; Konstantin S. Elkin; Victor V. Voron

2010-01-01

8

The Venus Radar Mapper mission  

Microsoft Academic Search

The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface using a synthetic aperture mapping radar. This paper describes the VRM mission at its present state of design. The science objectives and project constraints are described. Key features of the spacecraft system and radar system are discussed.

E. Cutting; J. H. Kwok; S. N. Mohan

1984-01-01

9

A Venus Flagship Mission: Exploring a World of Contrasts  

Microsoft Academic Search

Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission

D. Senske; M. Bullock; T. Balint; A. Benz; B. Campbell; E. Chassefiere; A. Colaprete; J. Cutts; L. Glaze; S. Gorevan; D. Grinspoon; J. Hall; G. Hasimoto; J. Head; G. Hunter; N. Johnson; W. Kiefer; E. Kolawa; T. Kremic; J. Kwok; S. Limaye; S. Mackwell; M. Marov; C. Peterson; G. Schubert; T. Spilker; E. Stofan; H. Svedhem; D. Titov; A. Treiman

2008-01-01

10

Cloud Level Circulation on Venus from Venus Monitoring Camera on Venus Express  

Microsoft Academic Search

The Venus Monitoring Camera (VMC) on ESA's Venus Express mission has been taking images of Venus in four filters from UV to near infrared since April 2006. The images collected during the apoapsis portion of the orbit when a large portion of the day-side of Venus is captured have been used to measure the cloud level day side circulation. Both

Sanjay Limaye; Igor Khatuntsev; Wojciech J. Markiewicz; Dmitri Titov; Richard Moissl

2008-01-01

11

Venus Express: the spacecraft  

NASA Astrophysics Data System (ADS)

The Venus Express project began with the fortunate inheritance of a set of spare spacecraft units and an industrial setup from the Mars Express mission, as it was clear that this second "Express" mission would only be possible both financially and schedule-wise if new developments were kept to a minimum. Likewise for the payload, the strong legacy from Rosetta and Mars Express in terms of the scientific instruments was equally essential for mission success. Another critical factor was strict adherence to the spacecraft Assembly, Integration and Test campaign schedule, to ensure that the fixed launch window would be met.

Winton, Alistair J.; Schnorhk, Ared; McCarthy, Con; Witting, Michael; Sivac, Philippe; Eggel, Hans; Pereira, Joseph; Verna, Marco; Geerling, Frank

2005-11-01

12

The Venus Radar Mapper (VRM) mission  

Microsoft Academic Search

The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface of Venus using a synthetic aperture mapping radar. The spacecraft is scheduled to be launched in April 1988 using a Shuttle-Centaur G combination. The spacecraft arrives at Venus in late July 1988 and begins its mapping mission

E. Cutting; J. H. Kwok; S. N. Mohan

1984-01-01

13

Education and Public Outreach using Venus Express  

Microsoft Academic Search

Nearly two decades after NASA's Magellan radar mission to Venus, its atmosphere and surface is being investigated with new instruments by the Venus Express spacecraft from orbit. It was launched by the European Space Agency (ESA) on 11 November 2005, and has been orbiting Venus since April 2006. This mission provides an opportunity to focus on comparative planetary meteorology for

Rosalyn A. Pertzborn; S. S. Limaye; H. Y. Pi

2006-01-01

14

Venus space mission  

Microsoft Academic Search

One can read about the scientific results of the Pioneer Venus exploration program in a highly valued special issue of the Journal of Geophysical Research, 85(A13), December 30, 1980, but these results are only a part of the impact of what has been one of the most sophisticated scientific endeavors in history. In this program numerous spacecraft---the U.S. Mariner 2,

Peter M. Bell

1983-01-01

15

Challenges of a Venus entry mission  

Microsoft Academic Search

There have been numerous NASA and international orbiters, atmospheric probes, and landers that have explored Venus over the past 50 years. The Russian Space Agency (RSA) conducted over twenty missions to Venus from the 1960's to 1980's, including flybys, entry probes, landers and orbiters. NASA's first measurements of Venus came from a flyby of the Mariner 10 in 1973. Later

Anita Sengupta; Leslie Hall

2011-01-01

16

The Magellan Venus radar mapping mission  

Microsoft Academic Search

The NASA Magellan Venus Radar Mapper spacecraft, which will be placed into orbit around Venus on August 10, 1990, is described and its mission is discussed. The orbiter's 12-cm wavelength, multimode radar system is examined and the applications of its modes are addressed. In the SAR mode, it can image most of the Venus surface at a resolution of better

R. S. Saunders; G. H. Pettengill; R. E. Arvidson; W. L. Sjogren; W. T. K. Johnson; L. Pieri

1990-01-01

17

Mission concepts for Venus surface investigation  

Microsoft Academic Search

Mission concepts for the in situ investigation of the Venus atmosphere and surface in the period following the VOIR mission are discussed. The science issues in Venus exploration and possible means of meeting the scientific objectives are considered, including global mapping, surface composition determination, atmospheric composition determination and surface-atmosphere interactions. Particular attention is then given to the feasibility of buoyant

S. J. Hoffman; H. Feingold; A. Friedlander

1981-01-01

18

Compilation System for Venus Radar Mission (Magellan).  

National Technical Information Service (NTIS)

A synthetic aperture radar (SAR) compilation system was developed for extraction of topographic information of Venus from stereoradar imagery to be obtained from the Magellan mission. The system was developed for an AS-11AM analytical stereoplotter. Exten...

S. S. C. Wu F. J. Schafer A. Howington

1987-01-01

19

The Analyser of Space Plasmas and Energetic Atoms (ASPERA-4) for the Venus Express mission  

Microsoft Academic Search

The general scientific objective of the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) experiment is to study the solar wind–atmosphere interaction and characterise the plasma and neutral gas environment in the near-Venus space through energetic neutral atom (ENA) imaging and local charged particle measurements. The studies to be performed address the fundamental question: How strongly do the interplanetary plasma

S. Barabash; J.-A. Sauvaud; H. Gunell; H. Andersson; A. Grigoriev; K. Brinkfeldt; M. Holmström; R. Lundin; M. Yamauchi; K. Asamura; W. Baumjohann; T. L. Zhang; A. J. Coates; D. R. Linder; D. O. Kataria; C. C. Curtis; K. C. Hsieh; B. R. Sandel; A. Fedorov; C. Mazelle; J.-J. Thocaven; M. Grande; Hannu E. J. Koskinen; E. Kallio; T. Säles; P. Riihela; J. Kozyra; N. Krupp; J. Woch; J. Luhmann; S. McKenna-Lawlor; S. Orsini; R. Cerulli-Irelli; M. Mura; M. Milillo; M. Maggi; E. Roelof; P. Brandt; C. T. Russell; K. Szego; J. D. Winningham; R. A. Frahm; J. Scherrer; J. R. Sharber; P. Wurz; P. Bochsler

2007-01-01

20

The Analyser of Space Plasmas and Energetic Atoms (ASPERA-4) for the Venus Express mission  

Microsoft Academic Search

The general scientific objective of the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) experiment is to study the solar wind-atmosphere interaction and characterise the plasma and neutral gas environment in the near-Venus space through energetic neutral atom (ENA) imaging and local charged particle measurements. The studies to be performed address the fundamental question: How strongly do the interplanetary plasma

S. Barabasha; J.-A. Sauvaudb; H. Gunella; H. Anderssona; A. Grigorieva; M. Holmstroma; R. Lundina; M. Yamauchia; W. Baumjohannd Asamurac; T. L. Zhangd; A. J. Coatese; D. O. Katariae; A. Fedorovb; C. Mazelleb; J.-J. Thocavenb; E. Kallioi; T. Salesi; J. Kozyraj Riihelai; J. Luhmannl; S. McKenna-Lawlorm; S. Orsinin; R. Cerulli-Irellin; M. Muran; M. Milillon; M. Maggin; P. Brandto

21

A Venus Flagship Mission: Exploring a World of Contrasts  

NASA Astrophysics Data System (ADS)

Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission to Venus. This 3- to 4 billon mission, to launch in the post 2020 timeframe, should revolutionize our understanding of how climate works on terrestrial planets, including the close relationship between volcanism, tectonism, the interior, and the atmosphere. It would also more clearly elucidate the geologic history of Venus, including the existence and persistence of an ancient ocean. Achieving these objectives will provide a basis to understand the habitability of extra solar terrestrial planets. To address a broad range of science questions this mission will be composed of flight elements that include an orbiter that is highlighted by an interferometric SAR to provide surface topographic and image information at scales one to two orders of magnitude greater than that achieved by any previous spacecraft to Venus. Two balloons with a projected lifetime of weeks will probe the structure and dynamics of the atmosphere at an altitude of 50 to 70-km. In addition, two descent probes will collect data synergistic to that from the balloon and analyze the geochemistry of surface rocks over a period of hours. The technology road map focuses on key areas of science instruments and enabling engineering to provide greater in situ longevity in the hostile Venus environment.

Senske, D.; Bullock, M.; Balint, T.; Benz, A.; Campbell, B.; Chassefiere, E.; Colaprete, A.; Cutts, J.; Glaze, L.; Gorevan, S.; Grinspoon, D.; Hall, J.; Hasimoto, G.; Head, J.; Hunter, G.; Johnson, N.; Kiefer, W.; Kolawa, E.; Kremic, T.; Kwok, J.; Limaye, S.; Mackwell, S.; Marov, M.; Peterson, C.; Schubert, G.; Spilker, T.; Stofan, E.; Svedhem, H.; Titov, D.; Treiman, A.

2008-12-01

22

The Venusian induced magnetosphere: A case study of plasma and magnetic field measurements on the Venus Express mission  

Microsoft Academic Search

Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general

E. Kallio; T. L. Zhang; S. Barabash; R. Jarvinen; I. Sillanpaaa; P. Janhunen; A. Fedorov; J.-A. Sauvaud; C. Mazelle; J.-J. Thocaven; H. Gunell; H. Andersson; A. Grigoriev; K. Brinkfeldt; Y. Futaana; M. Holmström; R. Lundin; M. Yamauchi; K. Asamura; W. Baumjohann; H. Lammer; A. J. Coates; D. R. Linder; D. O. Kataria; C. C. Curtis; K. C. Hsieh; B. R. Sandel; M. Grande; H. E. J. Koskinen; T. Säles; W. Schmidt; P. Riihelä; J. Kozyra; N. Krupp; J. Woch; J. G. Luhmann; S. McKenna-Lawlor; S. Orsini; R. Cerulli-Irelli; A. Mura; A. Milillo; M. Maggi; E. Roelof; P. Brandt; C. T. Russell; K. Szego; J. D. Winningham; R. A. Frahm; J. R. Scherrer; J. R. Sharber; P. Wurz; P. Bochsler

2008-01-01

23

Venera-D -the future Russian mission to Venus  

NASA Astrophysics Data System (ADS)

Venus was actively studied by Soviet and US mission in 60-80-th years of the last century. The investigations carried out both from the orbit and in situ were highly successful. After a 15-years break in space research of Venus, the ESA Venus Express mission, launched in 2005, successfully continues its work on orbit around Venus. In 2010 the launch of the Japanese Climate Orbiter (Planeta-C) mission is planned. However, many questions concerning the structure, and evolu-tions of planet Venus, which are the key questions of comparative planetology, very essential for understanding the evolution of the terrestrial climate, cannot be solved by observations from an orbit. Now in Russia the new investigation phase of Venus begins: the mission Venera-D is included in the Russian Federal Space Program to be launched in 2016. This mission includes the lander, balloons, and the orbiter. The long living balloons are planned to be deployed at different heights, in the clouds and under the clouds. Scientific goals of the mission include: -investigation of structure, chemical composition of the atmosphere, including noble gases abundance and isotopic ratio, structure and chemistry of the clouds; -study of dynamics of the atmosphere, nature of the superrotation, radiative balance, nature of an enormous greenhouse effect; -study of structure, mineralogy and geochemistry of the surface, search for seismic and volcanic activity, the lightening, interaction of the atmosphere and the surface; -investigation of the upper atmosphere, ionosphere, magnetosphere, and the escape rate; -study of the evolution of the atmosphere and the surface of Venus. The complex of experiments on the orbiter includes, among the others, several spectrometers in the spectral range from UV to MW, the mapping spectrometers and the plasma package. On the lander there are instruments to work during the descent, and on the surface: gas-chromatograph, PTW (meteo), nephelometer and the particle sizes spectrometer, optical package, active gamma-spectrometer, TV-complex, which includes panoramic, high resolution and descending cameras.. On the balloon which has to work near the lower boundary of clouds, the devices will be installed to study the lower atmosphere and to get the surface images with high resolution at 1 mkm. Successful realization of the project Venera-D will allow to solve the important scientific problems of comparative planetology. In particular it will help to understand why do Venus and the Earth (sister-planets), similar in many aspects, being formed at similar conditions in the protoplanet nebula, evolve by such a different way.

Zasova, Ludmila; Zelenyi, Lev; Korablev, Oleg; Sanko, N. F.; Khartov, Victor V.; Vorontsov, Victor A.; Basilevsky, A. T.; Pichkhadze, Konstantin M.; Elkin, Konstantin S.; Voron, Victor V.

24

A study of a potential venus radar topography mission  

Microsoft Academic Search

Radar has been shown to be the best way to view the surface of Venus as was demonstrated by Pioneer Venus Orbiter, Veneras 15 and 16, and Magellan Missions. Each of these missions progressively increased our knowledge of the surface and it has been nearly twenty years since Magellan covered nearly all the surface with SAR images from 120 to

W. Johnson; R. Jordan; L. Veilleux; R. Hodges; L. Giersch

2009-01-01

25

Planet-C: Venus Climate Orbiter mission of Japan  

Microsoft Academic Search

The Venus Climate Orbiter mission (PLANET-C), one of the future planetary missions of Japan, aims at understanding the atmospheric circulation of Venus. Meteorological information will be obtained by globally mapping clouds and minor constituents successively with four cameras at ultraviolet and infrared wavelengths, detecting lightning with a high-speed imager, and observing the vertical structure of the atmosphere with radio science

Masato Nakamura; Takeshi Imamura; Munetaka Ueno; Naomoto Iwagami; Takehiko Satoh; Shigeto Watanabe; Makoto Taguchi; Yukihiro Takahashi; Makoto Suzuki; Takumi Abe; George L. Hashimoto; Takeshi Sakanoi; Shoichi Okano; Yasumasa Kasaba; Jun Yoshida; Manabu Yamada; Nobuaki Ishii; Takahiro Yamada; Kazunori Uemizu; Tetsuya Fukuhara; Koh-Ichiro Oyama

2007-01-01

26

Venus Express first results - An Overview  

Microsoft Academic Search

The Venus Express spacecraft arrives to Venus and will be inserted into orbit on 11 April 2006 Venus Express will carry out an in depth study of the atmosphere of Venus and will study the plasma environment and its intearaction with the solar wind as well as investigating selected surface related topics The paylod is composed of seven instruments ASPERA

H. Svedhem; D. Titov; S. Barabash; J.-L. Bertaux; P. Drossart; V. Formisano; B. Häusler; W. Markiewicz; G. Piccioni; T. Zhang; O. Witasse

2006-01-01

27

Experimental Aerobraking with Venus Express  

NASA Astrophysics Data System (ADS)

Venus Express has successfully orbited Venus in its polar 24 hour, 250km by 66000 km, orbit since April 2006 and has provided a wealth of new data from our sister planet. Approaching the end of the mission we are now planning an experimental campaign dedicated to aerobraking at altitudes down to as low as about 130km. These low pericentre passes will provide direct measurements of density, temperature, magnetic field and energetic particles in a region not accessible by other methods. Experience of operations and studies of spacecraft responses will be valuable knowledge for possible future missions that might need this techniques as a part of its nominal operations. Aerobraking was considered in the early design phase of the mission but it was fairly soon realised that the nominal mission would not need this. However, a few important design features were maintained in order to allow for this in case it should be needed at a later stage. The inherently stable geometry of the spacecraft configuration and the inclusion of a software mode for aerobraking are the two most important elements from this early design phase. An recent study by industry has determined the constraints for the spacecraft and identified several potential scenarios. The present highly elliptical orbit has as one of its inherent features a downward drift of the pericentre altitude of between 1 and 4 km/day. However, at certain times, when the Sun is in the orbital plane, this drift disappears for a period of up to two weeks. This is a very well suited time to carry out these initial experiments as it is makes operations safer and it reduces the heat input on the spacecraft as the solar panels will be edge-on towards the sun during the aerobraking. Already a number of low altitude operations have been carried out during the so called atmospheric drag campaigns. The spacecraft has then dipped down to altitudes as low as 165 km and a good characterisation of this region has been performed. This collected information will be helpful for the planning of the aerobraking itself.

Svedhem, Hakan

2013-10-01

28

Observing the surface of Venus with VIRTIS on Venus Express  

NASA Astrophysics Data System (ADS)

The M channel of VIRTIS will allow the first systematic mapping of the surface and of the near-surface atmosphere of Venus in the near infrared wavelengths range This will be done using the atmospheric windows located at 1 10 1 18 mu m and if possible additionally using the window at 1 02 mu m Wattson and Rothman 1986 Kamp et al 1988 Moroz 2002 The latter is unfortunately right at the low end of the wavelength range of the IR channel and at the upper end of the VIS channel Therefore the usability of this window is unclear until first data from Venus are obtained The atmospheric windows will allow measuring the thermal emission of the surface as was demonstrated by Galileo NIMS Carlson et al 1991 and Cassini VIMS Baines et al 2000 While the atmospheric windows show no or little CO 2 absorption the radiance from the surface is still affected by scattering in the clouds This effect varies based on the optical thickness of the clouds We have developed a quicklook processing procedure which allows deriving surface emissivity variations from nighttime observations correcting for the atmospheric effects We will present the first version of this algorithm During the mission the algorithm will be refined based on the data returned from the different instruments on Venus Express The final goal is to derive maps of the absolute surface emissivity Based on these data two main science tasks for the surface analysis will be pursued Classification of the surface composition and study the interaction between low atmosphere and

Helbert, J.; Mariangeli, L.; Baines, K. H.; Garcia, R.; Erard, S.; Piccioni, G.; Drossart, P.; Müller, N.; Hashimoto, G.; Kostama, P.; Virtis Team

29

The 2010 European Venus Explorer (EVE) mission proposal  

NASA Astrophysics Data System (ADS)

The European Venus Explorer (EVE) mission described in this paper was proposed in December 2010 to ESA as an `M-class' mission under the Cosmic Vision programme. It consists of a single balloon platform floating in the middle of the main convective cloud layer of Venus at an altitude of 55 km, where temperatures and pressures are benign (˜25°C and ˜0.5 bar). The balloon float lifetime would be at least 10 Earth days, long enough to guarantee at least one full circumnavigation of the planet. This offers an ideal platform for the two main science goals of the mission: study of the current climate through detailed characterization of cloud-level atmosphere, and investigation of the formation and evolution of Venus, through careful measurement of noble gas isotopic abundances. These investigations would provide key data for comparative planetology of terrestrial planets in our solar system and beyond.

Wilson, Colin Frank; Chassefière, Eric; Hinglais, Emmanuel; Baines, Kevin H.; Balint, Tibor S.; Berthelier, Jean-Jacques; Blamont, Jacques; Durry, Georges; Ferencz, Csaba S.; Grimm, Robert E.; Imamura, Takeshi; Josset, Jean-Luc; Leblanc, François; Lebonnois, Sebastien; Leitner, Johannes J.; Limaye, Sanjay S.; Marty, Bernard; Palomba, Ernesto; Pogrebenko, Sergei V.; Rafkin, Scot C. R.; Talboys, Dean L.; Wieler, Rainer; Zasova, Liudmila V.; Szopa, Cyrill

2012-04-01

30

The structure of Venus' Upper Atmosphere and forthcoming measurements by the Venus Express Atmospheric Drag Experiment  

NASA Astrophysics Data System (ADS)

A rich set of measurements of Venus' atmosphere above the top cloud layer (around 60-250 km) was provided by the Pioneer Venus mission between 1978 and 1992, with additional data from Radio Science and atmospheric drag measurements by the Magellan spacecraft. Some of these measurements were summarized in empirical models by Hedin et al. (1983) and Keating et al. (1985). These models have been used extensively for scientific and engineering purposes. One considerable shortcoming of these models has however been the lack of constraints at high latitudes and low solar activity. Venus Express is offering us a unique opportunity to fill this gap, given the orbital geometry that allows observations at high latitudes and the current solar minimum. We are presenting a new experiment, the Venus Express Atmospheric Drag Experiment (VEx- ADE) which uses two separate techniques to investigate atmospheric structure. Initial lowering of periapsis of Venus Express to around 180 km, as planned for mid-2008, should allow examining atmospheric effects on orbital decay. We expect to be able to obtain densities at periapsis altitude from several successive orbits and, with time, to build up vertical density profiles in the thermosphere at high latitudes and solar minimum, the first ever measurements for Venus at those locations and conditions. At later stages in the mission periapsis may be lowered even further, allowing potentially to use a second technique of determining densities, by analyzing the atmospheric drag from the on-board accelerometers used otherwise for engineering purposes. This talk will present our planned measurements and outline the scientific case for this experiment, presenting an assessment of our current knowledge of the atmospheric structure on Venus above 60 km altitude.

Mueller-Wodarg, Ingo; Bruinsma, Sean; Forbes, Jeffrey M.; Keating, Roger; Yelle Sci. Gerald, Sr.; Withers, Paul; Lopez-Valverde, Miguel Angel

31

A Conceptual Venus Rover Mission Using Advanced Radioisotope Power Systems  

Microsoft Academic Search

This concept study demonstrates that a long lived Venus rover mission could be enabled by a novel application of advanced RPS technology. General Purpose Heat Source (GPHS) modules would be employed to drive an advanced thermoacoustic Stirling engine, pulse tube cooler and linear alternator that provides electric power and cooling for the rover. The Thermoacoustic Stirling Heat Engine (TASHE) is

Michael Evans; James H. Shirley; Robert Dean Abelson

2006-01-01

32

Science considerations for an orbital radar mapping mission to Venus  

Microsoft Academic Search

A radar mapping mission to Venus is under consideration by NASA for the 1980s. The science objectives of the mission are to determine the geologic history of the planet; map the major topographic features and provide limited detailed geologic and terrain analysis of potential probe landing sites. Because of the thick Venusian atmosphere, a synthetic-aperture side-looking radar system has been

D. C. Wychgram

1974-01-01

33

European Venus Explorer: An in-situ mission to Venus using a balloon platform  

Microsoft Academic Search

Planetary balloons have a long history already. A small super-pressure balloon was flown in the atmosphere of Venus in the eighties by the Russian-French VEGA mission. For this mission, CNES developed and fully tested a 9m diameter super-pressure balloon, but finally replaced it by a smaller one due to mass constraints (when it was decided to send Vega to Halley’s

E. Chassefière; O. Korablev; T. Imamura; K. H. Baines; C. F. Wilson; D. V. Titov; K. L. Aplin; T. Balint; J. E. Blamont; C. G. Cochrane; Cs. Ferencz; F. Ferri; M. Gerasimov; J. J. Leitner; J. Lopez-Moreno; B. Marty; M. Martynov; S. V. Pogrebenko; A. Rodin; J. A. Whiteway; L. V. Zasova

2009-01-01

34

Venus Express observations of ULF and ELF waves in the Venus ionosphere: Wave properties and sources  

NASA Astrophysics Data System (ADS)

Electrical activity in a planetary atmosphere enables chemical reactions that are not possible under conditions of local thermodynamic equilibrium. In both the Venus and terrestrial atmospheres, lightning forms nitric oxide. Despite the existence of an inventory of NO at Venus like the Earth's, and despite observations of the signals expected from lightning at optical, VLF, and ELF frequencies, the existence of Venus lightning still is met with some skepticism. The Venus Express mission was equipped with a fluxgate magnetometer gradiometer system sampling at rates as high as 128 Hz, and making measurements as low as 200 km altitude above the north polar regions of Venus. However, significant noise levels are present on the Venus Express spacecraft. Cleaning techniques have been developed to remove spacecraft interference at DC, ULF, and ELF frequencies, revealing two types of electromagnetic waves, a transverse right-handed guided mode, and a linearly polarized compressional mode. The propagation of both types of signals is sensitive to the magnetic field in ways consistent with propagation from a distant source to the spacecraft. The linearly polarized compressional waves generally are at lower frequencies than the right-handed transverse waves. They appear to be crossing the usually horizontal magnetic field. At higher frequencies above the lower hybrid frequency, waves cannot enter the ionosphere from below when the field is horizontal. The arrival of signals at the spacecraft is controlled by the orientation of the magnetic field. When the field dips into the atmosphere, the higher frequency guided mode above the lower hybrid frequency can enter the ionosphere by propagating along the magnetic field in the whistler mode. These properties are illustrated with examples from five orbits during Venus Express' first year in orbit. These properties observed are consistent with the linearly polarized compressional waves being produced at the solar wind interface and the transverse guided waves being produced in the atmosphere.

Russell, C. T.; Leinweber, H.; Hart, R. A.; Wei, H. Y.; Strangeway, R. J.; Zhang, T. L.

2013-11-01

35

Venus orbiter: Ishtar  

Microsoft Academic Search

ISHTAR or VENUS ORBITER is a mission to Venus similar to the mission Mars Express to Mars, with the use, possibly, of the same spacecraft and subsystems. This mission has been proposed to ESA for a feasibility study as a small mission (F2, F3). We shall describe here briefly the scientific objectives of the mission, and how could be implemented.

V. Formisano

2002-01-01

36

ESA's Venus Express to reach final destination  

NASA Astrophysics Data System (ADS)

First step: catching Venus To begin to explore our Earth’s hot and hazy sister planet, Venus Express must complete a critical first step, the most challenging one following launch. This involves a set of complex operations and manoeuvres that will inject the spacecraft into orbit. The Venus Orbit Insertion (VOI) manoeuvre allows the spacecraft to reduce its speed relative to Venus, so that it can be captured by the planet’s gravitation. The manoeuvre is a critical one which must proceed at precisely the right place and time. The VOI phase officially started on 4 April and will not be completed until 13 April. It is split into three main sub-phases. The first consists in preparing or initialising the spacecraft for the actual capture manoeuvre so as to avoid the risk of the spacecraft going into safe mode, should parameters unrelated to VOI go off-range. The capture manoeuvre itself consists of a main-engine burn lasting about 50 minutes on the morning of 11 April starting at 09:17 (Central European Summer Time). This is the second main VOI sub-phase. The final sub-phase will be restoring all spacecraft functions, notably resuming communications with Earth and uplinking the commands to be executed during the preliminary ‘capture’ orbit. Orbital capture is controlled by an automatic sequence of predefined commands, uploaded to the spacecraft four days prior to VOI. This sequence is the minimum set needed to perform the main-engine burn. All spacecraft operations are controlled and commanded by the ground control team located at ESA’s European Spacecraft Operations Centre (ESOC) in Darmstadt, Germany. Timeeline of major VOI events (some times subject to change) 4 Aprilacecraft transmitter connected to low gain antenna is switched on. During its interplanetary cruise and during the scientific part of the mission to come, Venus Express communicates with Earth by means of its two high gain antennas. However, during the orbit capture phase (11 April), these two antennas become unusable because of the spacecraft’s required orientation at that time. The low gain antenna, carrying a feeble but instantly recognisable signal, will be transmitting throughout all VOI manoeuvres. This will allow ground controllers to monitor the velocity change during the burn, using NASA’s Deep Space Network’s 70-metre antenna near Madrid, Spain. No other means of communication with the Earth is possible during the capture burn. 5 and 9 April, targeting control manoeuvres. Two time slots are available to adjust course if needed. Given the high accuracy of the course correction performed end of March, Venus Express is currently on the right trajectory for a successful capture into orbit and it is therefore unlikely that either of these two extra slots will be required. 10 to 11 April, final preparations for VOI manoeuvre. 24 to 12 hours before VOI, spacecraft controllers will command Venus Express into its final configuration for the burn. Over the final 12 hours, they will monitor its status, ready to deal with any contingencies requiring last-minute trajectory correction or any revising of the main-engine burn duration. 11 April, 08:03 (CEST), ‘slew’ manoeuvre. This manoeuvre lasts about half an hour and rotates Venus Express so that the main engine faces the direction of motion. Thanks to this, the burn will slow down (rather than accelerate) the spacecraft. 11 April, 09:17 (CEST), main-engine burn starts. A few minutes after firing of the spacecraft thrusters to make sure the propellant settles in the feed lines to the main engine, the latter will begin its 50-minute long burn, ending at 10:07. This thrust will reduce the initial velocity of 29 000 kilometres per hour (in relation to Venus) by 15 percent, allowing capture. Venus Express will settle into its preliminary, elongated nine-day orbit. On capture, it will be at about 120 million kilometres from the Earth and, at its nearest point, within 400 km of the surface of Venus. During the burn, at 09:45 (CEST), Venus Express will disappear behind the planet and will not be visi

2006-04-01

37

Selection and Certification of TPS: Constraints and Considerations for Venus Missions  

Microsoft Academic Search

The science community is interested in planetary entry probe missions to improve our understanding of the atmospheres of Saturn, missions to Venus, and sample return missions from comets and asteroids. The In-Space Propulsion Program has completed aerocapture mission design studies that have defined requirements for the thermal protection system (TPS) to Venus, Mars, Titan and Neptune. There have been investments

E. Venkatapathy; B. Laub; G. J. Hartman; J. O. Arnold; M. J. Wright; G. A. Allen

38

A Conceptual Venus Rover Mission Using Advanced Radioisotope Power Systems  

NASA Astrophysics Data System (ADS)

This concept study demonstrates that a long lived Venus rover mission could be enabled by a novel application of advanced RPS technology. General Purpose Heat Source (GPHS) modules would be employed to drive an advanced thermoacoustic Stirling engine, pulse tube cooler and linear alternator that provides electric power and cooling for the rover. The Thermoacoustic Stirling Heat Engine (TASHE) is a system for converting high-temperature heat into acoustic power which then drives linear alternators and a pulse tube cooler to provide both electric power and coolin6g for the rover. A small design team examined this mission concept focusing on the feasibility of using the TASHE system in this hostile environment. A rover design is described that would provide a mobile platform for science measurements on the Venus surface for 60 days, with the potential of operating well beyond that. A suite of science instruments is described that collects data on atmospheric and surface composition, surface stratigraphy, and subsurface structure. An Earth-Venus-Venus trajectory would be used to deliver the rover to a low entry angle allowing an inflated ballute to provide a low deceleration and low heat descent to the surface. All rover systems would be housed in a pressure vessel in vacuum with the internal temperature maintained by the TASHE at under 50 °C.

Evans, Michael; Shirley, James H.; Abelson, Robert Dean

2006-01-01

39

Venus Lightning: Statistical Properties from Venus Express Magnetic Field Observations  

NASA Astrophysics Data System (ADS)

Lightning discharges are observed by the Venus Express magnetometer as right-hand circularly polarized (whistler-mode) waves propagating nearly parallel to the ionospheric magnetic field at low altitude. The strength of the signals that are oscillating at ELF frequencies is much larger than on Earth, sometimes over 1nT peak to peak compared to about 30 pT at Earth, but when the energy flux of these waves (that are propagating much more slowly than their terrestrial counterparts) is calculated the energy fluxes are similar. It is difficult to obtain a precise value for the world-wide flash rate but when we do make estimates, they are similar to the terrestrial rates. Thus to zeroth order, lightning appears to be similar at the two planets despite the differences in cloud altitudes, cloud particles and weather patterns. Now that over 3 years of Venus Express measurements have been analyzed, we have the statistical accuracy to separate the different spatial dependences. The signals are strongly local time-dependent with a late morning maximum. The frequency of occurrence also decreases with latitude and altitude. This behavior is consistent with, and very much complements, the observations of Pioneer Venus. PVO was blind to dayside signals and was able to only explore at low latitudes. Venus Express has completed the local time map and shown that lightning activity extends to the pole. In the coming year we are looking forward to undertaking joint observations in cooperation with Akatsuki’s lightning camera.

Daniels, J.; Russell, C. T.; Strangeway, R. J.; Wei, H.; Zhang, T.

2010-12-01

40

Venus O + pickup ions: Collected PVO results and expectations for Venus Express  

NASA Astrophysics Data System (ADS)

Observations of oxygen pickup ions by the plasma analyzer on the Pioneer Venus Orbiter (PVO) Mission arguably launched broad interest in solar wind erosion of unmagnetized planet atmospheres, and its potential evolutionary effects. Oxygen pickup ions may play key roles in the removal of the oxygen excess left behind from the photodissociation of water vapor by enabling direct escape, additional sputtering of oxygen when they impact the exobase, and escape as energetic neutrals produced in charge exchange reactions with the ambient exospheric oxygen and hydrogen. Although the PVO observations were compromised by an ˜8 keV energy limit for O + detection, a lack of ion composition capability, and the limited sampling and data rate of the plasma analyzer which was designed for solar wind monitoring, these measurements provide our best information about the extended O + exosphere and wake at Venus. Here we show the full picture of the spatial distribution and energies of the O + ion observations collected by the plasma analyzer during PVO's ˜5000 orbit tour. A model of O + test particles launched in the circum-Venus fields described by an MHD simulation of the solar wind interaction is used to help interpret the PVO observations and to anticipate the expanded view of Venus O + escape that will be provided by the ASPERA-4 experiment on Venus Express.

Luhmann, J. G.; Ledvina, S. A.; Lyon, J. G.; Russell, C. T.

2006-11-01

41

Venus Express Bistatic Radar Over Maxwell Montes  

NASA Astrophysics Data System (ADS)

Toward the end of the Magellan mission, several bistatic radar experiments were conducted using the spacecraft's linearly polarized transmissions at 13 cm wavelength. Ground reception was in right- and left- circular polarizations (RCP and LCP, respectively). Echoes from Maxwell Montes showed unusual polarization properties, which were interpreted as coming from a surface with a complex dielectric constant (Pettengill et al., Science, 272, 1628-1631, 1996). On early orbits of Venus Express (VEX) similar experiments were carried out, albeit with VEX's more conventional RCP transmissions and at lower signal-to-noise ratio than for Magellan. As expected, dielectric constants from VEX are generally higher than for other bodies (such as the Moon and Mars), based on echo power ratios (RCP/LCP). At the time of this writing, however, the expected change in polarization from preliminary coherent processing of RCP and LCP over Maxwell has not been detected.

Simpson, R. A.; Tyler, G. L.; Haeusler, B.; Paetzold, M.

2006-12-01

42

European Venus Explorer: An in-situ mission to Venus using a balloon platform  

NASA Astrophysics Data System (ADS)

Planetary balloons have a long history already. A small super-pressure balloon was flown in the atmosphere of Venus in the eighties by the Russian-French VEGA mission. For this mission, CNES developed and fully tested a 9 m diameter super-pressure balloon, but finally replaced it by a smaller one due to mass constraints (when it was decided to send Vega to Halley's Comet). Furthermore, several kinds of balloons have been proposed for planetary exploration [Blamont, J., in: Maran, S.P. (Ed.), The Astronomy and Astrophysics Encyclopedia. Cambridge University Press, p. 494, 1991]. A Mars balloon has been studied for the Mars-94 Russian-French mission, which was finally cancelled. Mars and Venus balloons have also been studied and ground tested at JPL, and a low atmosphere Venus balloon is presently under development at JAXA (the Japanese Space Agency). Balloons have been identified as a key element in an ongoing Flagship class mission study at NASA, with an assumed launch date between 2020 and 2025. Recently, it was proposed by a group of scientists, under European leadership, to use a balloon to characterize - by in-situ measurements - the evolution, composition and dynamics of the Venus atmosphere. This balloon is part of a mission called EVE (European Venus Explorer), which has been proposed in response to the ESA AO for the first slice of the Cosmic Vision program by a wide international consortium including Europe, Russia, Japan and USA. The EVE architecture consists of one balloon platform floating at an altitude of 50-60 km, one short lived probe provided by Russia, and an orbiter with a polar orbit to relay data from the balloon and probe, and to perform remote sensing science observations. The balloon type preferred for scientific goals is one, which would oscillate in altitude through the cloud deck. To achieve this flight profile, the balloon envelope would contain a phase change fluid. While this proposal was not selected for the first slice of Cosmic Vision missions, it was ranked first among the remaining concepts within the field of solar system science.

Chassefière, E.; Korablev, O.; Imamura, T.; Baines, K. H.; Wilson, C. F.; Titov, D. V.; Aplin, K. L.; Balint, T.; Blamont, J. E.; Cochrane, C. G.; Ferencz, Cs.; Ferri, F.; Gerasimov, M.; Leitner, J. J.; Lopez-Moreno, J.; Marty, B.; Martynov, M.; Pogrebenko, S. V.; Rodin, A.; Whiteway, J. A.; Zasova, L. V.; the EVE Team

43

Provision of noble gases to Venus atmosphere from comets and volcanoes: constraints from Venus Express data  

NASA Astrophysics Data System (ADS)

In light of new data from Venus Express providing more detailed profiles of the variation in concentration of major and minor constituents with depth in Venus' atmosphere, we readdress the issue of the source of noble gases and minor constituent volatiles in Venus' atmosphere. We re-examine two hypotheses that have already been proposed for the sources of the noble gases: cometary impact and volcanic activity. In order to test the plausibility of the first source, we collect from the literature and analyse data (of both comet and atmosphere composition) from many studies including those that utilise recent spacecraft missions that have sampled comets directly, such as Stardust and Deep Impact. Where data is unavailable for some noble gas concentrations of comets, we estimate the likely concentrations inferred from the noble gas data that is available. For the volcanic hypothesis, we model the delivery of noble gases through volcanism and estimate the required rate of volcanic activity to produce the near-surface abundances of noble gases and other constituents as observed by instruments on board Venus Express. For both sources, we find the upper limit on the required rate of source activity assuming that only one of the sources is active. We envisage that the most likely situation in reality is a combination of the two sources, with the proportion of delivery from each source being between the two calculated extremes. The results could have implications for comet formation because we test whether the noble gas abundances in Venus' atmosphere are consistent with the noble gases of comets condensing at very low temperatures, or else being trapped as clathrates, or else inconsistent with either hypothesis, in which case comets would probably not have been a major source of gases for Venus. The calculated upper limit on the rate of volcanic activity may have significant implications for the geological evolution of the planet.

Bargery, A. S.; Tobie, G.; Sotin, C.; Choblet, G.; Le Mouélic, S.

2009-04-01

44

Improved calibration of SOIR/Venus Express spectra.  

PubMed

The SOIR instrument on board the ESA Venus Express mission has been operational since the insertion of the satellite around Venus in April 2006. Since then, it has delivered high quality IR solar occultation spectra of the atmosphere of Venus. The different steps from raw spectra to archived data are described and explained in detail here. These consist of corrections for the dark current and for the non-linearity of the detector; removing bad pixels, as well as deriving noise. The spectral calibration procedure is described, along with all ancillary data necessary for the understanding and interpretation of the SOIR data. These include the full characterization of the AOTF filter, one of the major elements of the instrument. All these data can be found in the ESA PSA archive. PMID:24103989

Vandaele, Ann Carine; Mahieux, Arnaud; Robert, Séverine; Berkenbosch, Sophie; Clairquin, Roland; Drummond, Rachel; Letocart, Vincent; Neefs, Eddy; Ristic, Bojan; Wilquet, Valérie; Colomer, Frédéric; Belyaev, Denis; Bertaux, Jean-Loup

2013-09-01

45

Observations of Venus by VIRTIS aboard Venus Express  

NASA Astrophysics Data System (ADS)

After about two years since the orbit insertion, VIRTIS aboard the Venus Express spacecraft has addressed a significant amount of the planned scientific objectives, from the surface up to the lower thermosphere, in terms of mapping, composition, structure and dynamics. The VIR- TIS instrument consists of two channels: VIRTIS-M, an imaging spectrometer with moderate spectral resolution in the range from 0.25um to 5um and VIRTIS-H, a high spectral resolution spectrometer in the range from 2 to 5um co-aligned with the field of view of -M. The resolution of VIRTIS-M is 2nm from 0.25 to 1um and 10 nm from 1 to 5um. The resolution of VIRTIS-H is about 2nm. Venus is regularly observed by VIRTIS since the orbit insertion occurred about two years ago. The scientific objectives span from the surface up to the lower thermosphere, from dynamics to composition and structure, supported by nadir and limb view observations geometries. In the Venus nightside, the atmospheric windows at short wavelengths (1.18, 1.10, 1.01, 0.9, 0.85 microns) allow to penetrate the tick clouds and see the hot surface of Venus, while the radiance at about 1.7 and 2.3 microns give access to study the composition lower the clouds and also the dynamics at clouds level. Spectroscopy of the 4-5 micron range gives access to the cloud structure in the 60-95 km altitude levels. The atmosphere above the clouds is regularly observed both on day and night sides, in solar reflection and thermal emission in nadir geometry. Limb observations provide O2, CO2 and CO emissions, through nightglow and fluorescence observations. This talk gives an overview of the main results achieved by VIRTIS, while a more detailed description in the relevant field can be found in other specific papers.

Piccioni, Giuseppe

46

Results from Four Years of Venus Express  

NASA Astrophysics Data System (ADS)

Since arriving at Venus in April 2006 Venus Express has provided a wealth of information on a large variety of topics on the atmosphere, surface and plasma environment of the planet. The atmosphere in the southern hemisphere has been studied in detail by three instruments dedicated to atmospheric investigations, from the near IR to the UV and additional information has been derived from radio science measurements. The structure and composition of the atmosphere has been mapped in three dimensions from 40 km to 140 km altitude. Significant temporal and spatial variations have been found, both in composition, density and temperature. Imaging in the UV has revealed strong latitudinal variations and significant temporal changes in the global cloud top morphology as well as identification of various types of waves in the cloud layer. The cloud top altitude varies from about 72 km in the low and middle latitudes to about 64 km in the polar region, marking vast polar depressions, likely a result of the Hadley-type meridional circulation. A large amount of data on the atmospheric circulation has been collected and results include maps of wind speeds at different altitudes and movies of the dynamics of the southern polar vortex. A surface temperature map and an emissivity map of the full southern hemisphere have been constructed from IR images in the spectral windows. By correlating these results and the Magellan radar images and gravity data, regions of young unweathered surfaces likely due to recent volcanism have been identified. The induced magnetosphere with its boundaries and the escape of planetary matter have been characterized by a magnetometer and an energetic particle instrument, and escape rates of hydrogen, oxygen and helium have been determined.A decision to extend the mission until end 2014 is expected at the end of this year.

Svedhem, Hakan; Titov, D.; Taylor, F.

2010-10-01

47

SO2 measurements at Venus' cloud top: from Pioneer Venus Orbiter to Venus Express  

NASA Astrophysics Data System (ADS)

This talk will focus on UV nadir measurements of SO_2 at Venus cloud top level obtained with SPICAV/Venus Express from 2006 to 2010, using an expanded data set and updated version of Marcq et al. [2008] radiative transfer algorithm. Provisional results show a more complicated picture than thought based on the first 300 Venus Express orbits [Marcq et al., 2011; Belyaev et al., 2008]. Short-term variability as well as maximal values seem on par with 1980s UVS/Pioneer Venus data [Esposito et al., 1988], confirming the halt of the negative trend in SO_2 mean abundance observed in the 1980s and 1990s. Latitudinal gradient is usually negative, but positive in a handful of orbits, reminiscent of the situation in the 1980s [Zasova et al., 1993; Na et al., 1994]. This may point to frequent changes in the relative intensity of the processes ruling SO_2 abundance at cloud top level, leading to at least two distinct regimes for SO_2 with opposite latitudinal gradients. A positive correlation between the mean UV brightness (proxy for unknown UV absorber) and SO_2 mixing ratio has also been evidenced. Naive transport modeling as well as much more sophisticated chemical modeling [Krasnopolsky, 2012] seem able to reproduce much of the observed spatial and temporal variability of SO_2, indicating at least a qualitative understanding of the physical and chemical process at work. All these results will be compared when relevant to the band ratio SO_2 retrievals from Pioneer Venus era [Esposito et al., 1988] in order to investigate possible changes on a decadal timescale in Venus' lower mesosphere.

Marcq, Emmanuel; Belyaev, Denis; Montmessin, Franck; Bertaux, Jean-Loup; Fedorova, Anna

2012-07-01

48

Venus winds from ultraviolet, visible and near infrared images from the VIRTIS instrument on Venus Express  

NASA Astrophysics Data System (ADS)

After more than 6 years orbiting Venus the Venus Express mission has provided the largest database of observations of Venus atmosphere at different cloud layers with the combination of VMC and VIRTIS instruments. We present measurements of cloud motions in the South hemisphere of Venus analyzing images from the VIRTIS-M visible channel at different wavelengths sensitive to the upper cloud haze at 65-70 km height (dayside ultraviolet images) and the middle cloud deck (dayside visible and near infrared images around 1 ?m) about 5-8 km deeper in the atmosphere. We combine VIRTIS images in nearby wavelengths to increase the contrast of atmospheric details and measurements were obtained with a semi-automatic cloud correlation algorithm. Both cloud layers are studied simultaneously to infer similarities and differences in these vertical levels in terms of cloud morphologies and winds. For both levels we present global mean zonal and meridional winds, latitudinal distribution of winds with local time and the wind shear between both altitudes. The upper branch of the Hadley cell circulation is well resolved in UV images with an acceleration of the meridional circulation at mid-latitudes with increasing local time peaking at 14-16h. This organized meridional circulation is almost absent in NIR images. Long-term variability of zonal winds is also found in UV images with increasing winds over time during the VEX mission. This is in agreement with current analysis of VMC images (Kathuntsev et al. 2013). The possible long-term acceleration of zonal winds is also examined for NIR images. References Khatuntsev et al. Icarus 226, 140-158 (2013)

Hueso, Ricardo; Garate-Lopez, I.; Peralta, J.; Bandos, T.; Sánchez-Lavega, A.

2013-10-01

49

RAVEN - High-resolution Mapping of Venus within a Discovery Mission Budget  

Microsoft Academic Search

It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission

V. L. Sharpton; R. R. Herrick; F. Rogers; S. Waterman

2009-01-01

50

Venus Express Contribution to Space Plasma Physics  

NASA Astrophysics Data System (ADS)

Venus Express spacecraft (VEX) is magnetically non-clean spacecraft with a small plasma package that consists of FGM magnetometer and plasma instrument ASPERA. System Identification based methodology have been used to separate spacecraft generated interferences and natural signal. The implemented procedure of data cleaning resulted in a high quality magnetic field measurements. VEX FGM contributed not only to many aspects of Venus-Solar Wind interaction but also to fundamental plasma physics problems such physics of collisionless shocks, K-H intability and dynamics of mirror waves. These and other findings of VEX FGM are reviewed.

Balikhin, M.

2008-12-01

51

The structure of the Venus neutral atmosphere from the Radio Science Experiment VeRa on Venus Express  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment VeRa uses one-way radio signals at X-band and S-band for the sounding of the Venus neutral atmosphere and ionosphere. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for this one-way radio link. Simultaneous, coherent measurements at two wavelengths allow separation of dispersive media effects from the classical Doppler shift. Electron density profiles of the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere can be derived via an Abel transform with an altitude resolution of only a few hundred metres in the altitude range between about 40 and 100 km. Three occultation seasons could be covered during the nominal mission of Venus Express resulting in a data set of about 140 profiles of the neutral atmosphere. Another three occultation seasons are planned during the extended mission. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Day-night and latitudinal variations of the thermal structure, the high variability of the atmosphere above the troposphere and signal absorption effects caused by the H2SO4 vapour can be investigated with the resulting data set.

Tellmann, Silvia; Bird, Mike; Verweyen, Alice; Haeusler, Bernd; Paetzold, Martin; Tyler, G. L.

52

Venus Terminator Temperature Structure: Venus Express SOIR and VTGCM Comparisons  

NASA Astrophysics Data System (ADS)

Venus Express SOIR terminator profiles of CO2 densities and temperatures have been organized and presented for 100+ selected orbits obtained between 2006-2011. The SOIR instrument measures CO2 absorption across a broad spectral window. The observed atmospheric transmittance spectra are subsequently inverted to obtain vertical density (and inferred temperature) profiles at the Venusian terminator over approximately 70 to 160 km. These recently recalibrated measurements continue to show a striking permanent temperature minimum (at 125 km) and a weaker temperature maximum (over 100-115 km). These features are reflected in the corresponding CO2 density profiles, and provide detailed constraints for global circulation models of the upper atmosphere. New Venus Thermospheric General Circulation Model (VTGCM) simulations are conducted for conditions appropriate to these SOIR measurements. In particular, solar minimum fluxes are specified and mean values of eddy diffusion and wave drag parameters are utilized. Recent upgrades to the VTGCM code now include more realistic lower boundary conditions at 70 km near cloud tops. Model temperature profiles are extracted from the terminators that correspond to five latitude bins presently used in the SOIR data analysis. Averaging of VTGCM temperature profiles in each of these bins (at each terminator) is conducted to match SOIR sampling. Comparisons of these SOIR and VTGCM temperature profiles are made. Most notably, the observed temperature minimum near 125 km and the weaker temperature maximum over 100-115 km are generally reproduced by the VTGCM at the correct pressure level. However, magnitudes of simulated and measured temperatures are somewhat different. In addition, VTGCM evening terminator (ET) temperatures are simulated to be modestly warmer than corresponding morning terminator (MT) values, a result of stronger ET than MT zonal winds at/above about 130 km. The SOIR terminator temperatures thusfar only reveal rather weak ET versus MT asymmetries above 140 km. Details of the underlying thermal balance processes are identified that give rise to these VTGCM simulated temperatures.

Bougher, Stephen W.; Parkinson, C. D.; Schulte, R.; Brecht, A. S.; Fischer, J.; Vandaele, A.; Wilquet, V.; Mahieux, A.

2013-10-01

53

Investigation of air temperature on the nightside of Venus derived from VIRTIS-H on board Venus-Express  

NASA Astrophysics Data System (ADS)

We present the spatial distribution of air temperature on Venus' night side, as observed by the high spectral resolution channel of VIRTIS (Visible and Infrared Thermal Imaging Spectrometer), or VIRTIS-H, on board the ESA mission Venus Express. The present work extends the investigation of the average thermal fields in the northern hemisphere of Venus, by including the VIRTIS-H data. We show results in the pressure range of 100-4 mbar, which corresponds to the altitude range of 65-80 km. With these new retrievals, we are able to compare the thermal structure of the Venus' mesosphere in both hemispheres. The major thermal features reported in previous investigations, i.e. the cold collar at about 65-70°S latitude, 100 mbar pressure level, and the asymmetry between the evening and morning sides, are confirmed here. By comparing the temperatures retrieved by the VIRTIS spectrometer in the North and South we find that similarities exist between the two hemispheres. Solar thermal tides are clearly visible in the average temperature fields. To interpret the thermal tide signals (otherwise impossible without day site observations), we apply model simulations using the Venus global circulation model Venus GCM (Lebonnois, S., Hourdin, F., Forget, F., Eymet, V., Fournier, R. [2010b]. International Venus Conference, Aussois, 20-26 June 2010) of the Laboratoire de Météorologie Dynamique (LMD). We suggest that the signal detected at about 60-70° latitude and pressure of 100 mbar is a diurnal component, while those located at equatorial latitudes are semi-diurnal. Other tide-related features are clearly identified in the upper levels of the atmosphere.

Migliorini, A.; Grassi, D.; Montabone, L.; Lebonnois, S.; Drossart, P.; Piccioni, G.

2012-02-01

54

Venus O2 nightglow observations with VIRTIS/Venus Express  

NASA Astrophysics Data System (ADS)

The oxygen nightglow emissions in the visible spectral range are known since the early observations with the Venera spacecrafts. Recent observations with the VIRTIS instrument on board Venus-Express allowed to re-detect the Herzberg II system of O2. In particular, the (0-7), (0-8), (0-9), (0-10), and (0-11) bands of the Herzberg II system have been observed in the limb data. These bands peak at about 95 km, with a mean total integrated intensity of about 200 kR. Moreover, 3 bands of the Chamberlain system, centred at 0.56 ?m, 0.605 ?m, and 0.657 ?m were also detected. For the first time, the O2 nightglow emissions were investigated simultaneously in the visible and in the IR spectral range, reporting a good agreement of the peak altitude values for the Herzberg II and the O2(a1?g-X3?- g) band. Finally a 1-D atmospheric model was applied in order to interpret our results. The model, starting from realistic O and CO2 vertical distribution, allows to well reproduce the observed profiles for the O2 systems both in the visible and IR spectral ranges.

Migliorini, A.; Piccioni, G.; Gérard, J. C.; Slanger, T.; Politi, R.; Snels, M.; Nuccilli, F.; Drossart, P.

2012-09-01

55

Dynamics of Venus' southern polar vortex from over two years of VIRTIS/Venus Express observations  

NASA Astrophysics Data System (ADS)

polar region of Venus, using measurements from the VIRTIS instrument from the Venus Express Mission, revealed it to be in constant dynamic change, with the southern polar vortex displaced from the rotational geometry of the planet [1]. Here, we place these results in the context of measurements taken over a two year period. We examine the dynamics of the southern polar region based on measurements of winds at the 45 and 65 km levels, detected from cloud motion monitoring by the VIRTIS instrument. The wind velocity components were determined by an automatic cloud-tracking technique based on evaluating the similarity between pairs of images of cloud structures at a specific atmospheric altitude, separated by a short time interval. The images were obtained at infrared wavelengths of 1.74 and 2.3 ?m, for the night side, and 3.9 and 5.0 ?m, for both the day and night sides. These wavelengths are sensitive to radiation originating from levels close to the base and to the top of the cloud deck, respectively. The technique assumes that the clouds are passive tracers of the atmospheric mass flow, and that the cloud structure does not change substantially between the two images. Our objectives have been 1) to provide horizontal maps of direct wind measurements at cloud tops and in the lower cloud level with a high spatial resolution; 2) to characterize the southern polar vortex as to its motion, rotation rate and dynamical stability; 3) to constrain the contribution of the circumpolar circulation to the angular momentum budget; and 4) to provide valuable information for Venus climate modelling, for the planning of future probe or balloon missions, and to examine the Venus polar vortex in the context of other planetary vortices. The circulation in the southern polar region is dominated by the zonal flow, which is much stronger than the meridional circulation. The latitudinal profiles show a relatively smooth variation and the vertical shear between the 45-km and 65-km levels is on the order of 5-10 ms-1. The horizontal structure of the zonal and meridional wind components indicate that wavenumber-2 thermal tides are likely to be present.

Luz, D.; Berry, D. L.; Peralta, J.; Piccioni, G.

2011-10-01

56

Dynamics of Venus' Southern hemisphere and South Polar Vortex from VIRTIS data obtained during the Venus Expres Mission  

NASA Astrophysics Data System (ADS)

The VIRTIS instrument onboard Venus Express observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. The images have been used to trace the motions of the atmosphere at different layers of clouds [1-3]. We review the VIRTIS cloud image data and wind results obtained by different groups [1-3] and we present new results concerning the morphology and evolution of the South Polar Vortex at the upper and lower cloud levels with data covering the first 900 days of the mission. We present wind measurements of the South hemisphere obtained by cloud tracking individual cloud features and higher-resolution wind results of the polar region covering the evolution of the South polar vortex. The later were obtained by an image correlation algorithm run under human supervision to validate the data. We present day-side data of the upper clouds obtained at 380 and 980 nm sensitive to altitudes of 66-70 km, night-side data in the near infrared at 1.74 microns of the lower cloud (45-50 km) and day and night-side data obtained in the thermal infrared (wavelengths of 3.8 and 5.1 microns) which covers the dynamical evolution of Venus South Polar vortex at the cloud tops (66-70 km). We explore the different dynamics associated to the varying morphology of the vortex, its dynamical structure at different altitudes, the variability of the global wind data of the southern hemisphere and the interrelation of the polar vortex dynamics with the wind dynamics at subpolar and mid-latitudes. Acknowledgements: Work funded by Spanish MICIIN AYA2009-10701 with FEDER support and Grupos Gobierno Vasco IT-464-07. References [1] A. Sánchez-Lavega et al., Geophys. Res. Lett. 35, L13204, (2008). [2] D. Luz et al., Science, 332, 577-580 (2011). [3] R. Hueso, et al., Icarus doi:10.1016/j.icarus.2011.04.020 (2011)

Hueso, R.; Garate-Lopez, I.; Sanchez-Lavega, A.

2011-12-01

57

Magellan - Early results from the Venus mapping mission  

Microsoft Academic Search

Some results obtained with the Magellan Venus Radar Mapper are presented. Mapping was initiated on October 26, 1990 and has completed over 714 orbits of image data, covering 40 percent of the surface of Venus. Mapping began at 330 deg east longitude, mapping from the north pole to about 78 deg south latitude. Included are the regions of Ishtar Terra,

R. S. Saunders

1991-01-01

58

Venus O + pickup ions: Collected PVO results and expectations for Venus Express  

Microsoft Academic Search

Observations of oxygen pickup ions by the plasma analyzer on the Pioneer Venus Orbiter (PVO) Mission arguably launched broad interest in solar wind erosion of unmagnetized planet atmospheres, and its potential evolutionary effects. Oxygen pickup ions may play key roles in the removal of the oxygen excess left behind from the photodissociation of water vapor by enabling direct escape, additional

J. G. Luhmann; S. A. Ledvina; J. G. Lyon; C.T. Russell

2006-01-01

59

Venus Express en route to probe the planet's hidden mysteries  

NASA Astrophysics Data System (ADS)

Venus Express will eventually manoeuvre itself into orbit around Venus in order to perform a detailed study of the structure, chemistry and dynamics of the planet's atmosphere, which is characterised by extremely high temperatures, very high atmospheric pressure, a huge greenhouse effect and as-yet inexplicable "super-rotation" which means that it speeds around the planet in just four days. The European spacecraft will also be the first orbiter to probe the planet's surface while exploiting the "visibility windows" recently discovered in the infrared waveband. The 1240 kg mass spacecraft was developed for ESA by a European industrial team led by EADS Astrium with 25 main contractors spread across 14 countries. It lifted off onboard a Soyuz-Fregat rocket, the launch service being provided by Starsem. The lift-off from the Baikonur Cosmodrome in Kazakstan this morning took place at 09:33 hours local time (04:33 Central European Time). Initial Fregat upper-stage ignition took place 9 minutes into the flight, manoeuvring the spacecraft into a low-earth parking orbit. A second firing, 1 hour 22 minutes later, boosted the spacecraft to pursue its interplanetary trajectory. Contact with Venus Express was established by ESA's European Space Operations Centre (ESOC) at Darmstadt, Germany approximately two hours after lift-off. The spacecraft has correctly oriented itself in relation to the sun and has deployed its solar arrays. All onboard systems are operating perfectly and the orbiter is communicating with the Earth via its low-gain antenna. In three days' time, it will establish communications using its high-gain antenna. Full speed ahead for Venus Venus Express is currently distancing itself from the Earth full speed, heading on its five-month 350 million kilometre journey inside our solar system. After check-outs to ensure that its onboard equipment and instrument payload are in proper working order, the spacecraft will be mothballed, with contact with the Earth being reduced to once daily. If needed, trajectory correction manoeuvres can go ahead at the half-way stage in January. When making its closest approach, Venus Express will face far tougher conditions than those encountered by Mars Express on nearing the Red Planet. For while Venus's size is indeed similar to that of the Earth, its mass is 7.6 times that of Mars, with gravitational attraction to match. To resist this greater gravitational pull, the spacecraft will have to ignite its main engine for 53 minutes in order to achieve 1.3 km/second deceleration and place itself into a highly elliptical orbit around the planet. Most of its 570 kg of propellant will be used for this manoeuvre. A second engine firing will be necessary in order to reach final operational orbit: a polar elliptical orbit with 12-hour crossings. This will enable the probe to make approaches to within 250 km of the planet's surface and withdraw to distances of up to 66 000 km, so as to carry out close-up observations and also get an overall perspective. Exploring other planets to better understand planet Earth "The launch of Venus Express is a further illustration of Europe's determination to study the various bodies in our solar system", stressed Professor David Southwood, the Director of ESA's science programmes. "We started in 2003 with the launch of Mars Express to the Red Planet and Smart-1 to the Moon and both these missions have amply exceeded our expectations. Venus Express marks a further step forward, with a view to eventually rounding off our initial overview of our immediate planetary neighbours with the BepiColombo mission to Mercury to be launched in 2013." "With Venus Express, we fully intend to demonstrate yet again that studying the planets is of vital importance for life here on Earth", said Jean Jacques Dordain, ESA Director General. "To understand climate change on Earth and all the contributing factors, we cannot make do with solely observing our own planet. We need to decipher the mechanics of the planetary atmosphere in

2005-11-01

60

Venus  

Microsoft Academic Search

Venus is Earth's nearest planetary neighbor, and has fascinated mankind since the dawn of history. Venus' clouds reflect most of the sunlight shining on the planet and make it the brightest object in the sky after the Sun and Moon. Venus is visible with the naked eye as an evening star until a few hours after sunset, or as a

B. Fegley Jr.

2003-01-01

61

Cloud level winds from the Venus Express Monitoring Camera imaging  

NASA Astrophysics Data System (ADS)

Six years of continuous monitoring of Venus by European Space Agency's Venus Express orbiter provides an opportunity to study dynamics of the atmosphere our neighbor planet. Venus Monitoring Camera (VMC) on-board the orbiter has acquired the longest and the most complete so far set of ultra violet images of Venus. These images enable a study the cloud level circulation by tracking motion of the cloud features. The highly elliptical polar orbit of Venus Express provides optimal conditions for observations of the Southern hemisphere at varying spatial resolution. Out of the 2300 orbits of Venus Express over which the images used in the study cover about 10 Venus years. Out of these, we tracked cloud features in images obtained in 127 orbits by a manual cloud tracking technique and by a digital correlation method in 576 orbits. Total number of wind vectors derived in this work is 45,600 for the manual tracking and 391,600 for the digital method. This allowed us to determine the mean circulation, its long-term and diurnal trends, orbit-to-orbit variations and periodicities. We also present the first results of tracking features in the VMC near-IR images. In low latitudes the mean zonal wind at cloud tops (67 ± 2 km following: Rossow, W.B., Del Genio, A.T., Eichler, T. [1990]. J. Atmos. Sci. 47, 2053-2084) is about 90 m/s with a maximum of about 100 m/s at 40-50°S. Poleward of 50°S the average zonal wind speed decreases with latitude. The corresponding atmospheric rotation period at cloud tops has a maximum of about 5 days at equator, decreases to approximately 3 days in middle latitudes and stays almost constant poleward from 50°S. The mean poleward meridional wind slowly increases from zero value at the equator to about 10 m/s at 50°S and then decreases to zero at the pole. The error of an individual measurement is 7.5-30 m/s. Wind speeds of 70-80 m/s were derived from near-IR images at low latitudes. The VMC observations indicate a long term trend for the zonal wind speed at low latitudes to increase from 85 m/s in the beginning of the mission to 110 m/s by the middle of 2012. VMC UV observations also showed significant short term variations of the mean flow. The velocity difference between consecutive orbits in the region of mid-latitude jet could reach 30 m/s that likely indicates vacillation of the mean flow between jet-like regime and quasi-solid body rotation at mid-latitudes. Fourier analysis revealed periodicities in the zonal circulation at low latitudes. Within the equatorial region, up to 35°S, the zonal wind show an oscillation with a period of 4.1-5 days (4.83 days on average) that is close to the super-rotation period at the equator. The wave amplitude is 4-17 m/s and decreases with latitude, a feature of the Kelvin wave. The VMC observations showed a clear diurnal signature. A minimum in the zonal speed was found close to the noon (11-14 h) and maxima in the morning (8-9 h) and in the evening (16-17 h). The meridional component peaks in the early afternoon (13-15 h) at around 50°S latitude. The minimum of the meridional component is located at low latitudes in the morning (8-11 h). The horizontal divergence of the mean cloud motions associated with the diurnal pattern suggests upwelling motions in the morning at low latitudes and downwelling flow in the afternoon in the cold collar region.

Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Limaye, S. S.; Markiewicz, W. J.; Almeida, M.; Roatsch, Th.; Moissl, R.

2013-09-01

62

Global Mapping of Venus' Atmosphere Using Accumulated Projections of Virtis Venus Express Observations  

Microsoft Academic Search

The VIRTIS instrument onboard Venus Express has been using its Mapping channel successfully since the Venus orbit insertion on 11th April 2005. The hyper-spectral images obtained in the near-Infrared and Visible cover a wide spectral range (5um-250nm) with good sampling capabilities, which make them highly useful for the study of morphology, dynamics and composition of the atmosphere and the surface.

A. Cardesín Moinelo; G. Piccioni; A. Migliorini; P. Drossart

2008-01-01

63

Chemistry of the Venus atmosphere and clouds: New insights from Venus Express  

NASA Astrophysics Data System (ADS)

Venus Express arrived at Venus in April 2006 and commenced routine scientific operations two months later. The first two years of operations have provided a large volume of data on the composition and chemistry of Venus' atmosphere and clouds. These observations by Venus Express cover a broad altitude range-from airglow emission, which has been seen by VIRTIS and SPICAV up to about 120 km altitude, to measurements of water vapour by VIRTIS near the surface. The observations reported to date have focused on the night side, but SOIR has derived abundance profiles for several species near the terminator in the north polar region and information on the day side composition is starting to emerge. Significant spatial and temporal variations in species abundances and temperatures have been reported by VIRTIS, SPICAV, and SOIR, and the magnetometer has reported evidence for whistler-mode waves that are consistent with lightning in the clouds. These observations provide insight into the complex and time-varying interactions between dynamics and chemistry in Venus' atmosphere. This talk will summarize the chemistry and composition observations from the first two years of Venus Express, review the new insight we have gained from these observations, and discuss what lies ahead.

Mills, Franklin

64

Calibration pipeline of VIRTIS-M onboard Venus Express  

NASA Astrophysics Data System (ADS)

The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) is flying on board the ESA mission Venus Express and orbiting around the planet Venus since April 11 2006, providing very valuable remote sensing data of the planet. The instrument combines a double capability: high-resolution visible and infrared imaging in the 0.28-5 mum range at moderate spectral resolution (VIRTIS-M channel) and high-resolution spectroscopy in the 2-5 mum range (VIRTIS-H channel). The scientific objectives of VIRTIS cover a large field and span from the study of the surface up to the upper atmosphere. The team is composed by people coming from institutes abroad from more than 10 countries. About 2.5 Gbit of raw compressed data are coming in average every day from the spacecraft to be further processed and distributed to the team for the data analysis. Here we described how the pipeline is structured and the various different steps performed from the telemetry to the calibrated data products but focused on VIRTIS-M. We also present some example of data product.

Cardesín Moinelo, Alejandro

2009-08-01

65

A recommended entry reconstruction process for the Pioneer Venus multi-probe mission  

Microsoft Academic Search

A method for determining the entry trajectories for the Pioneer Venus multi-probe mission is presented that utilizes earth based Doppler and onboard accelerometry as observables to provide updates for the spacecraft state and atmospheric parameters. The evolution of this method, based on error analyses and actual simulation results, is discussed. A derivative of the Viking radio science orbit determination software

J. T. Findlay; G. M. Kelly

1978-01-01

66

The Rationale for a New High-resolution Imaging Radar Mission to Venus  

NASA Astrophysics Data System (ADS)

Magellan, NASA’s last geoscience mission to Venus, provided synthetic aperture radar (SAR) images at ~100-m resolution, topography at ~10-km resolution, and the gravity field at ~300-km resolution. Although that mission provided a major advance in our understanding of the planet, basic questions about the geologic history of Venus remain unresolved. For example, hypotheses on the planet’s surface evolution range from uniformitarian to catastrophic, and assessments of current geologic activity range from earth-comparable levels of volcanic and tectonic activity to a surface shaped only by occasional impact and eolian processes. It is now feasible to send a mission to Venus that could provide SAR imaging at 1-5-m resolution; topography with tens-of-meters spatial resolution by utilizing interferometric SAR (InSAR) and stereo radargrammetry; and surface deformation at centimeter-scale vertical resolution through InSAR. Such a mission would substantially further our understanding of Venus by means of: (1) assessing the fundamental framework of the planet's geologic history (e.g., catastrophic change, slow evolution, uniformitarian) by imaging key stratigraphic contacts; (2) expanding the global framework of geomorphic unit types and relative stratigraphy with reconnaissance surveys of large geographic provinces; (3) directly detecting volcanic and tectonic activity through imaging of flows and fault-related activities (e.g., landslides) that occur between imaging passes; (4) monitoring present-day volcanic and tectonic activity with repeat-pass InSAR deformation studies; (5) constraining the nature of Venusian geologic volcanic and tectonic processes, and their relationship to mantle convective processes; (6) understanding the role of eolian processes in modifying the surface and the use of eolian features as stratigraphic markers (e.g., parabolic features) through detailed examination; (7) constraining Venusian impact processes, particularly the role of the atmosphere in the ejecta emplacement process; (8) constraining the processes responsible for the abrupt decrease in emissivity at high altitudes; (9) selecting landing sites for future missions; and (10) identifying past landers/probes to place them in geologic context. Our state of knowledge about Venus is currently analogous to our knowledge of Mars in the post-Viking era, and a high-resolution imaging radar mission to Venus could revolutionize our understanding of Venus in the way that the Mars Global Surveyor mission did for Mars.

Herrick, R. R.; Sharpton, V. L.; Gens, R.; Ghent, R. R.; Gilmore, M. S.; Grimm, R. E.; Johnson, C. L.; McGovern, P. J.; Meyer, F.; Mouginis-Mark, P. J.; Plaut, J. J.; Sandwell, D. T.; Simons, M.; Solomon, S. C.

2009-12-01

67

Concept study for a Venus Lander Mission to Analyze Atmospheric and Surface Composition  

NASA Astrophysics Data System (ADS)

We present a concept-level study of a New Frontiers class, Venus lander mission that was developed during Session 1 of NASA's 2011 Planetary Science Summer School, hosted by Team X at JPL. Venus is often termed Earth's sister planet, yet they have evolved in strikingly different ways. Venus' surface and atmosphere dynamics, and their complex interaction are poorly constrained. A lander mission to Venus would enable us to address a multitude of outstanding questions regarding the geological evolution of the Venusian atmosphere and crust. Our proposed mission concept, VenUs Lander for Composition ANalysis (VULCAN), is a two-component mission, consisting of a lander and a carrier spacecraft functioning as relay to transmit data to Earth. The total mission duration is 150 days, with primary science obtained during a 1-hour descent through the atmosphere and a 2-hour residence on the Venusian surface. In the atmosphere, the lander will provide new data on atmospheric evolution by measuring dominant and trace gas abundances, light stable isotopes, and noble gas isotopes with a neutral mass spectrometer. It will make important meteorological observations of mid-lower atmospheric dynamics with pressure and temperature sensors and obtain unprecedented, detailed imagery of surface geomorphology and properties with a descent Near-IR/VIS camera. A nepholometer will provide new constraints on the sizes of suspended particulate matter within the lower atmosphere. On the surface, the lander will quantitatively investigate the chemical and mineralogical evolution of the Venusian crust with a LIBS-Raman spectrometer. Planetary differentiation processes recorded in heavy elements will be evaluated using a gamma-ray spectrometer. The lander will also provide the first stereo images for evaluating the geomorphologic/volcanic evolution of the Venusian surface, as well as panoramic views of the sample site using multiple filters, and detailed images of unconsolidated material and rock textures from a microscopic imager. Our mission proposal will enable the construction of a unique Venus test facility that will attract a new generation of scientists to Venus science. With emphasis on flight heritage, we demonstrate our cost basis and risk mitigation strategies to ensure that the VULCAN mission can be conducted within the requirements and constraints of the New Frontiers Program.

Kumar, K.; Banks, M. E.; Benecchi, S. D.; Bradley, B. K.; Budney, C. J.; Clark, G. B.; Corbin, B. A.; James, P. B.; O'Brien, R. C.; Rivera-Valentin, E. G.; Saltman, A.; Schmerr, N. C.; Seubert, C. R.; Siles, J. V.; Stickle, A. M.; Stockton, A. M.; Taylor, C.; Zanetti, M.; JPL Team X

2011-12-01

68

Venus NIR Surface Emissivity estimated from VIRTIS on Venus Express Observations  

NASA Astrophysics Data System (ADS)

Spectral window regions close to 1?m allow for the transfer of thermal radiation from the surface through the atmosphere of Venus. Results of radiative transfer modeling are used to invert VIRTIS images at 1.02, 1.10 and 1.18?m for thermal emission of the surface. Local atmospheric transmittance is derived from the VIRTIS band at 1.31?m. Several hundreds of VIRTIS images covering in total most of the southern hemisphere of Venus have thus been analyzed and stacked for improvement of signal to noise ratio. The results of this approach are to some extent ambiguous since neither surface emissivity nor surface temperature are well known. Furthermore aerosols or a gradient of absorbing gaseous constituents near the surface might affect the interpretation. But neglecting any effects of the near surface atmosphere and assuming parameters of the radiative transfer model within reasonable ranges it is possible to estimate either surface emissivity or surface temperature. Temperature of surface and atmosphere is mostly a function of altitude, no large diurnal, seasonal or latitudinal variations are expected in the lower atmosphere. The lapse rate is constrained by the adiabatic lapse rate. A hint for global average of surface emissivity is given by the dominance of probably basaltic volcanic plains on the southern hemisphere. It is however imaginable that temperature dependant weathering leads to a trend of emissivity with altitude similar to that seen in the Magellan radiothermal emissivity observations. Regardless of any global variations of lapse rate or emissivity with altitude, spatial variations of emissivity independent from topography can be examined by assuming constant emissivity and fitting surface temperature accordingly to the global relation of thermal emission to topography. This spatial variation of thermal emission is assumed to be due to variation of surface emissivity and shows correlation with some geological features known from Magellan radar images. In the Lada Terra region large lava streams, Cavillaca - and Juturna Fluctus, show increased emissivity with respect to neighboring regions of the same altitude. Other large lava streams in the region show a similar but less obvious relative emissivity. Large areas of tessera terrain on the contrary consistently show relative low emissivity. While this variation of emissivity might be related to content of mafic minerals it is also conceivable that weathering and thus age of the terrain in question is responsible. The accumulation of observations by VIRTIS during the Venus Express mission will allow us to study with a larger database these correlations and to further disentangle possible atmospheric from surface contributions and thus to increase understanding of surface composition as well as of composition and temperature of the atmosphere in contact with the surface.

Mueller, N.; Helbert, J.; Hashimoto, G.; Kostama, P.; Marinangeli, L.; Erard, S.; Piccioni, G.; Drossart, P.; Venus Express Team

2007-12-01

69

Venus, Mars, and the Ices on Mercury and the Moon: Astrobiological Implications and Proposed Mission Designs  

NASA Astrophysics Data System (ADS)

Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have adapted to live in these ecological niches by the evolutionary force of directional selection. Missions to our neighboring planets should therefore be planned to explore these potentially life-containing refuges and return samples for analysis. Sample return missions should also include ice samples from Mercury and the Moon, which may contain information about the biogenic material that catalyzed the early evolution of life on Earth (or elsewhere). To obtain such information, science-driven exploration is necessary through varying degrees of mission operation autonomy. A hierarchical mission design is envisioned that includes spaceborne (orbital), atmosphere (airborne), surface (mobile such as rover and stationary such as lander or sensor), and subsurface (e.g., ground-penetrating radar, drilling, etc.) agents working in concert to allow for sufficient mission safety and redundancy, to perform extensive and challenging reconnaissance, and to lead to a thorough search for evidence of life and habitability.

Schulze-Makuch, Dirk; Dohm, James M.; Fairén, Alberto G.; Baker, Victor R.; Fink, Wolfgang; Strom, Robert G.

2005-12-01

70

Venus, Mars, and the ices on Mercury and the moon: astrobiological implications and proposed mission designs.  

PubMed

Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have adapted to live in these ecological niches by the evolutionary force of directional selection. Missions to our neighboring planets should therefore be planned to explore these potentially life-containing refuges and return samples for analysis. Sample return missions should also include ice samples from Mercury and the Moon, which may contain information about the biogenic material that catalyzed the early evolution of life on Earth (or elsewhere). To obtain such information, science-driven exploration is necessary through varying degrees of mission operation autonomy. A hierarchical mission design is envisioned that includes spaceborne (orbital), atmosphere (airborne), surface (mobile such as rover and stationary such as lander or sensor), and subsurface (e.g., ground-penetrating radar, drilling, etc.) agents working in concert to allow for sufficient mission safety and redundancy, to perform extensive and challenging reconnaissance, and to lead to a thorough search for evidence of life and habitability. PMID:16379531

Schulze-Makuch, Dirk; Dohm, James M; Fairén, Alberto G; Baker, Victor R; Fink, Wolfgang; Strom, Robert G

2005-12-01

71

Venus  

Microsoft Academic Search

Contents: Introduction. Early telescopic observations. Orbital and rotational motions. Earth-based radar observations of the surface. Spacecraft observations. Constraints on the composition of Venus. Venera Lander results. Eolian erosion and transport. Chemical weathering. Global topography and surface roughness. Surface roughness. Bright radar rings. Gravity. Plate tectonics on Venus.

R. S. Saunders; M. H. Carr

1984-01-01

72

Venus In Situ Explorer Mission design using a mechanically deployed aerodynamic decelerator  

NASA Astrophysics Data System (ADS)

The Venus In Situ Explorer (VISE) Mission addresses the highest priority science questions within the Venus community outlined in the National Research Council's Decadal Survey. The heritage Venus atmospheric entry system architecture, a 45° sphere-cone rigid aeroshell with a carbon phenolic thermal protection system, may no longer be the preferred entry system architecture compared to other viable alternatives being explored at NASA. A mechanically-deployed aerodynamic decelerator, known as the Adaptive Deployable Entry and Placement Technology (ADEPT), is an entry system alternative that can provide key operational benefits and risk reduction compared to a rigid aeroshell. This paper describes a mission feasibility study performed with the objectives of identifying potential adverse interactions with other mission elements and establishing requirements on decelerator performance. Feasibility is assessed through a launch-to-landing mission design study where the Venus Intrepid Tessera Lander (VITaL), a VISE science payload designed to inform the Decadal Survey results, is repackaged from a rigid aeroshell into the ADEPT decelerator. It is shown that ADEPT reduces the deceleration load on VITaL by an order of magnitude relative to a rigid aeroshell. The more benign entry environment opens up the VISE mission design environment for increased science return, reduced risk, and reduced cost. The ADEPT-VITAL mission concept of operations is presented and details of the entry vehicle structures and mechanisms are given. Finally, entry aerothermal analysis is presented that defines the operational requirements for a revolutionary structural-TPS material employed by ADEPT: three-dimensionally woven carbon cloth. Ongoing work to mitigate key risks identified in this feasibility study is presented.

Smith, B.; Venkatapathy, E.; Wercinski, P.; Yount, B.; Prabhu, D.; Gage, P.; Glaze, L.; Baker, C.

73

Venus atmospheric circulation: Known and unknown  

Microsoft Academic Search

After a pause of more than two decades, Venus' atmosphere is being explored again. Since April 2006, European Space Agency's Venus Express has been acquiring data, exploiting the near-infrared windows that allow us to peer into the deep night-side atmosphere. In June 2007, NASA's MESSENGER mission will fly past Venus on its way to Mercury, collecting useful data for a

Sanjay S. Limaye

2007-01-01

74

Collapse of Venus' polar thermosphere density as detected by Venus Express.  

NASA Astrophysics Data System (ADS)

The Venus Express (VEX) spacecraft offers the opportunity to probe in-situ the density of the polar atmosphere of Venus at altitude range between 165- 185 km. Two methods have been used to derive the density at dedicated campaigns of the Venus Express Atmospheric Drag Experiment (VExADE). The first method uses the tracking data of the spacecraft to precisely compute the drag acceleration of its motion when passing through the thermosphere at the periapsis pass of its orbit [1]. The second method uses the inertial wheels on board the spacecraft to measure the torque generated by the atmospheric drag during the periapsis pass [2]. Both methods provide reliable and similar estimates of the density at the periapsis pass. The estimated density from the first three campaigns is about 2-3 times lower than the one predicted from available empirical models. It suggests either polar collapse of the thermospheric structure or colder thermospheric temperatures than predicted by the models.

Rosenblatt, P.; Bruinsma, S.; Müller-Wodarg, I. C. F.; Svedhem, H.; Häusler, B.

2011-10-01

75

First Observations of Venus UV dayglow at limb from SPICAV/Venus Express  

NASA Astrophysics Data System (ADS)

The thermospheres of Venus and Mars are similar in their composition, structure, and temperatures. The aeronomic UV dayglow reflects the CO2 composition, and the products of ionization/ dissociation CO2+, CO, C, O, in addition to H at Lyman alpha. While Mars dayglow has been well studied in the past with Mariner 9 and Mars Express with limb viewing observations of the thermosphere, to our knowledge there are no observations at the limb for Venus. Also, limb or disc, no day glow spectra above ~180 nm was ever reported. With SPICAV on Venus Express, we had also great difficulties to get some spectra of the dayglow. The main reason is that the detector of SPICAV UV is an image intensifier with a CsI cathode, sensitive up to 315 nm. The disc of Venus is orders of magnitude brighter than the dayglow above 200 nm, from solar UV backscattered by the clouds. We will report the first detection of the UV dayglow of Venus at the limb, obtained with a coarse spectral resolution (6-7 nm), owing to some spacecraft conservative constraints. The dayglow extends from 115 km up to 180 km; its spectrum is similar to Mars dayglow (but much brighter). Similarities and differences between the two planets UV dayglow will be discussed.

Bertaux, J.-L.; Chaufray, J.-Y.; Leblanc, F.

2012-04-01

76

Integration of Radioisotope Heat Source with Stirling Engine and Cooler for Venus Internal-Structure Mission  

SciTech Connect

The primary mission goal is to perform long-term seismic measurements on Venus, to study its largely unknown internal structure. The principal problem is that most payload components cannot long survive Venus's harsh environment, 90 bars at 500 degrees C. To meet the mission life goal, such components must be protected by a refrigerated payload bay. JPL Investigators have proposed a mission concept employing a lander with a spherical payload bay cooled to 25 degrees C by a Stirling cooler powered by a radioisotope-heated Sitrling engine. To support JPL's mission study, NASA/Lewis and MTI have proposed a conceptual design for a hydraulically coupled Stirling engine and cooler, and Fairchild Space - with support of the Department of Energy - has proposed a design and integration scheme for a suitable radioisotope heat source. The key integration problem is to devise a simple, light-weight, and reliable scheme for forcing the radioisotope decay heat to flow through the Stirling engine during operation on Venus, but to reject that heat to the external environment when the Stirling engine and cooler are not operating (e.g., during the cruise phase, when the landers are surrounded by heat shields needed for protection during subsequent entry into the Venusian atmosphere.) A design and integration scheme for achieving these goals, together with results of detailed thermal analyses, are described in this paper. There are 7 copies in the file.

Schock, Alfred

1993-10-01

77

Neutral atmosphere composition from SOIR measurements on board Venus Express  

Microsoft Academic Search

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 ?m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection [1,2]. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the

A. Mahieux; R. Drummond; V. Wilquet; A. C. Vandaele; A. Federova; D. Belyaev; O. Korablev; E. Villard; F. Montmessin; J.-L. Bertaux

2009-01-01

78

Venus.  

National Technical Information Service (NTIS)

Recent investigations of the planet Venus are reviewed on the basis of a wide survey of domestic and foreign literature. The individual topics examined include the configuration and seasons of the planet; its mass, radius, rotation, internal structure, ma...

L. V. Samsonenko

1974-01-01

79

Venus thermal evolution and outgassing history: constraints from numerical simulations and Venus Express observations  

NASA Astrophysics Data System (ADS)

The Venus Express mission has revealed areas of high emissivity that are indicative of recent volcanism [1]. These areas are also characterized by gravity and topography signatures typical of the presence of active plumes. In an effort to understand the characteristics of these plumes, numerical simulations of heat transfer in a 3D spherical shell have been carried out [2]. These numerical simulations can handle large viscosity variations [3]. We have examined 16 cases with Temperature differences from 1140 to 2280°K, non dimensional internal heating of 0 to 10, and mantle viscosities of 10**20 and 10**21 Pa.s. The equivalent activation energy is ~485 kJ/mole. Convective Rayleigh numbers range from 10**5 to 3x10**7. Increasing internal heating increases the number of hot plumes. The limit occurs when the mantle temperature becomes so large that the temperature difference across the hot thermal boundary layer drops below the viscous temperature scale [4], at which point there is insufficient buoyancy to give rise to plumes. Such a case contradicts the observations. Including a lower mantle viscosity value of 10**20 Pa.s allows for larger values of internal heating that permit hot plumes. However, the highest non-dimensional heating rate in cases with mantle plumes achieved to date (HS = 10) is lower than the value of 50 than predicted by scaling internal heating from Earth to Venus. Partitioning of radiogenic elements into the crust would lower the mantle concentration, but is inconsistent with retaining volatiles in the mantle. Thus our simulations suggest that the mantle is heating up at a rate of about 100 K/byr. In half of the cases, the hot plumes produce pressure release melting over several 100s km beneath the conductive lid, intersecting the wet solidus, but not the dry solidus. Wet melting throughout much of the upper mantle suggests that it may be lacking in light elements and more fully outgassed than the lower mantle. Over time the upper mantle may have lost significant volatiles. Assuming 50 ppm water in the mantle, 10 plumes with a buoyancy flux of 500 kg/s erupting for 4 m.y. will outgas approximately the amount of water in the lower atmosphere [5]. Volcanism may have gone through a transition from more wide-spread, wet melting in the upper mantle to more localized melting in mantle plumes carrying unmelted, volatile rich material from depth. Part of this work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. Government sponsorship acknowledged.

Sotin, C.; Choblet, G.; Smrekar, S. E.

2012-04-01

80

Venus  

NASA Astrophysics Data System (ADS)

Venus is Earth's nearest planetary neighbor, and has fascinated mankind since the dawn of history. Venus' clouds reflect most of the sunlight shining on the planet and make it the brightest object in the sky after the Sun and Moon. Venus is visible with the naked eye as an evening star until a few hours after sunset, or as a morning star shortly before sunrise. Many ancient civilizations observed and worshipped Venus, which had a different name in each society, e.g., Ishtar to the Babylonians, Aphrodite to the Greeks, Tai'pei to the Chinese, and Venus to the Romans (Hunt and Moore, 1982). Venus has continued to play an important role in myth, literature, and science throughout history. In the early seventeenth century, Galileo's observations of the phases of Venus showed that the geocentric (Ptolemaic) model of the solar system was wrong and that the heliocentric (Copernican) model was correct. About a century later, Edmund Halley proposed that the distance from the Earth to the Sun (which was then unknown and is defined as one astronomical unit, AU) could be measured by observing transits of Venus across the Sun. These transits occur in pairs separated by eight years at intervals of 105.5 yr and 121.5 yr in an overall cycle of 243 yr, e.g., June 6, 1761, June 3, 1769; December 9, 1874, December 6, 1882, June 8, 2004, June 6, 2012, December 11, 2117, and December 8, 2125. The first attempted measurements of the astronomical unit during the 1761 transit were unsuccessful. However, several observers reported a halo around Venus as it entered and exited the Sun's disk. Thomas Bergman in Uppsala and Mikhail Lomonosov in St. Petersburg, independently speculated that the halo was due to an atmosphere on Venus. Eight years later observations of the 1769 solar transit (including those made by Captain Cook's expedition to Tahiti) gave a value of 1 AU=153 million kilometers, ~2.3% larger than the actual size (149.6 million kilometers) of the astronomical unit (Woolf, 1959; Maor, 2000).

Fegley, B., Jr.

2003-12-01

81

Venus Exploration Analysis Group (VEXAG)  

NASA Astrophysics Data System (ADS)

The Venus Exploration Analysis Group (VEXAG) was established by NASA in July 2005 to identify scientific priorities and strategy for exploration of Venus. This community-based forum is designed to provide scientific input and technology development plans for planning and prioritizing the exploration of Venus over the next several decades. VEXAG is currently composed of two co- chairs and several groups. The focus groups actively solicit input from the scientific community and meet during VEXAG meetings, held at least once a year. VEXAG reports its findings and provides input to NASA, but does not make recommendations. VEXAG holds meetings open to the global scientific community with interest in understanding Venus and receives input from the scientists and engineers around the world on the current open issues regarding understanding Venus as a planet. VEXAG regularly evaluates Venus exploration goals, scientific objectives, investigations and critical measurement requirements, including especially recommendations in the National Academy of Sciences Decadal Survey and the Solar System Exploration Strategic Roadmap. VEXAG is coordinating the preparation of several White papers on different topics, including science, technology, and the recent flagship study, relevant to Venus exploration for the current Decadal Survey can be found on the VEXAG website (http://www.lpi.usra.edu/vexag). VEXAG provides a forum for learning about international efforts in exploring Venus and facilitates collaboration in combined observation programs from space and earth based observatories. At present, Venus Express mission launched by European Space Agency in November 2005 is the only active mission collecting data from orbit around Venus since April 2006. It will soon be joined in December 2010 by Japan's Venus Climate Orbiter which is under development for a launch in May 2010. Other missions to Venus are being considered by NASA (Venus Flagship mission), Russia (Venera D) and in the European community (European Venus Explorer). In addition, it is anticipated that several mission concepts will be proposed to NASA's Discovery (Announcement of Opportunity anticipated winter 2010). The three New Frontiers proposals selected by NASA in December 2009 include a proposal for a mission to Venus - Surface and Atmosphere and Geochemical Explorer. The Venus community recognizes that science return can be maximized by coordinating observations as much as feasible. VEXAG is one forum where the discussions can take place and the community is invited to actively participate in the VEXAG meetings and activities. The next VEXAG meeting and a workshop on the Venus atmosphere and its interaction with the surface will be held in Madison, Wisconsin, during 30 August - 2 September 2010. VEXAG's past activities, current efforts and future plans will be presented. The scientific community interested in Venus is invited to participate in VEXAG and support the exploration of Venus by the interested space agencies.

Limaye, Sanjay; Smrekar, Sue

2010-05-01

82

A Venus atmospheric model at the Venus terminator obtained from SOIR solar occultations on board Venus Express  

NASA Astrophysics Data System (ADS)

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 ?m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere at the terminators in the upper mesosphere and lower thermosphere (70 to 170 km) with an emphasis on vertical distribution of the gases. In particular, measurements of CO2 density and rotational temperature vertical profiles have been routinely performed. Using the Asimat algorithm, CO2 density, temperature, total density and total pressure are derived from the SOIR data. Depending on the wavenumber region scanned, CO2 density profiles were obtained from 170 km down to 70 km from a subset of 70 occultations, that allowed to build an atmospheric model only valid at the Venus terminator for different latitudinal regions. This terminator model is described, and the atmospheric dynamics that it implies are investigated. The model is also compared to previous models.

Mahieux, A.; Robert, S.; Wilquet, V.; Drummond, R.; Vandaele, A. C.; Bertaux, J.-L.

2012-04-01

83

Structure Of The Core Of The Southern Vortex On Venus: VMC And VIRTIS Observations From Venus Express  

Microsoft Academic Search

In April 2007, a special observational campaign was conducted from Venus Express using the high data rate transmissions available through a NASA DSN to obtain a movie of the South pole region of Venus. Previously, the VIRTIS observations showed a remarkable view of the hemispheric vortex centered roughly over the South pole with a well defined \\

Sanjay Limaye; K. H. Baines; W. Markiewicz; G. Piccione; D. Titov

2007-01-01

84

Exploring the surface of Venus  

Microsoft Academic Search

The VIRTIS instrument on the ESA mission Venus Express has produced the first in-orbit mapping of the surface of Venus using the atmospheric windows near 1 micron. Based on the data returned by VIRTIS a map of surface brightness variations could be obtained which are indicative of emissivity variations on the surface. The mapping in general indiactes three surface types,

J. Helbert; N. T. Mueller; S. E. Smrekar; G. Piccioni; P. Drossart

2009-01-01

85

Reassessing the possibility of life on venus: proposal for an astrobiology mission.  

PubMed

With their similar size, chemical composition, and distance from the Sun, Venus and Earth may have shared a similar early history. Though surface conditions on Venus are now too extreme for life as we know it, it likely had abundant water and favorable conditions for life when the Sun was fainter early in the Solar System. Given the persistence of life under stabilizing selection in static environments, it is possible that life could exist in restricted environmental niches, where it may have retreated after conditions on the surface became untenable. High-pressure subsurface habitats with water in the supercritical liquid state could be a potential refugium, as could be the zone of dense cloud cover where thermoacidophilic life might have retreated. Technology based on the Stardust Mission to collect comet particles could readily be adapted for a pass through the appropriate cloud layer for sample collection and return to Earth. PMID:12469368

Schulze-Makuch, Dirk; Irwin, Louis N

2002-01-01

86

Reassessing the Possibility of Life on Venus: Proposal for an Astrobiology Mission  

NASA Astrophysics Data System (ADS)

With their similar size, chemical composition, and distance from the Sun, Venus and Earth may have shared a similar early history. Though surface conditions on Venus are now too extreme for life as we know it, it likely had abundant water and favorable conditions for life when the Sun was fainter early in the Solar System. Given the persistence of life under stabilizing selection in static environments, it is possible that life could exist in restricted environmental niches, where it may have retreated after conditions on the surface became untenable. High-pressure subsurface habitats with water in the supercritical liquid state could be a potential refugium, as could be the zone of dense cloud cover where thermoacidophilic life might have retreated. Technology based on the Stardust Mission to collect comet particles could readily be adapted for a pass through the appropriate cloud layer for sample collection and return to Earth.

Schulze-Makuch, Dirk; Irwin, Louis N.

2002-06-01

87

O+ pickup ions outside of Venus' bow shock: Venus Express observation  

NASA Astrophysics Data System (ADS)

Pickup ions are ions of planetary origin that become assimilated into the solar wind flow through their interaction with the solar wind magnetic and electric field. The speed of pickup ions varies between zero and twice the underlying plasma flow component perpendicular to magnetic field vector. For the unmagnetized planet Venus and Mars, oxygen (O+) pickup ions are known to be important because they can modify the global configuration of planetary plasma environment and significantly contribute to the atmospheric O+ loss [1]. Since the kinetic energy of an O+ pickup ion can reach 64 times that of a co-moving proton, an instrument must be able to measure O+ ions with energy of at least tens of keV to investigate the O+ pickup ion distribution from planetary ionosphere to solar wind. The in-situ observations and simulations at Mars have shown that the energy of O+ pickup ions can be 55-72 keV outside of the bow shock [2]. For Venus case, the plasma analyzer (OPA) onboard Pioneer Venus Orbiter (PVO), which was designed for solar wind monitoring, has an 8 keV energy limit for O+ detection and the limited sampling and data rate [3]. Therefore, OPA can only measure the O+ pickup ions in the sheath flow or inside the induced magnetosphere where the speed of ambient plasma flow is significantly lower than that of the unshocked solar wind outside of the bow shock. The Ion Mass Analyzer (IMA), included in the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) package on board Venus Express (VEX), determines the composition, energy, and angular distribution of ions in the energy range ~10 eV/q to 30 keV/q. Note that an O+ ion moving at the typical solar wind speed 400 km/s has kinetic energy 13.4 keV. Therefore, IMA has ability to measure the O+ pickup ions outside of Venus' bow shock. We have examined the IMA data during the solar minimum period 2006-2010, and identified about ten cases with clear signature of O+ pickup ion. With these observations, we will determine the location and the scale height of the source region of O+ pickup ions and describe the relationship between the behavior of these O+ and the upstream solar wind condition. The results would provide new information for numerical simulation of plasma environment near Venus and contribute to estimation of total O+ ion loss from Venus.

Wei, Y.; Fraenz, M.; Dubinin, E.; Zhang, T. L.; Wan, W.; Barabash, S.; Woch, J.; Lundin, R.

2012-09-01

88

RAVEN - High-resolution Mapping of Venus within a Discovery Mission Budget  

NASA Astrophysics Data System (ADS)

It has been more than 15 years since the Magellan mission mapped Venus with S-band synthetic aperture radar (SAR) images at ~100-m resolution. Advances in radar technology are such that current Earth-orbiting SAR instruments are capable of providing images at meter-scale resolution. RAVEN (RAdar at VENus) is a mission concept that utilizes the instrument developed for the RADARSAT Constellation Mission (RCM) to map Venus in an economical, highly capable, and reliable way. RCM relies on a C-band SAR that can be tuned to generate images at a wide variety of resolutions and swath widths, ranging from ScanSAR mode (broad swaths at 30-m resolution) to strip-map mode (resolutions as fine as 3 m), as well as a spotlight mode that can image patches at 1-m resolution. In particular, the high-resolution modes allow the landing sites of previous missions to be pinpointed and characterized. Repeat-pass interferometric SAR (InSAR) and stereo radargrammetry provide options for constraining topography to better than 100-m horizontal and 10-m vertical resolution. InSAR also provides the potential for detecting surface deformation at centimeter precision. Performing InSAR requires precise knowledge and control of the orbital geometry, and for this reason a 600-km circular polar orbit is favored. This configuration causes the equatorial nadir point to move ~9 km per orbit. Considering both ascending and descending passes, the spacecraft will pass over every point on the planet in half a Venus day (~4 Earth months). The ability to transmit data back to Earth via the Deep Space Network is the primary limiting factor on the volume of data that can be collected. Our current estimates indicate that within an imaging cycle of one Venus day we can image 20-30 percent of the planet at 20-30-m resolution and several percent at 3-5 m resolution. These figures compare favorably to the coverage provided by recent imaging systems orbiting Mars. Our strategy calls for the first cycle of coverage to be devoted to imaging large geographic areas (e.g., Thetis Regio) at 20-30-m resolution with interleaved observation of pre-selected targets at high resolution. The second cycle will include additional imaging, but the focus will be repeat-pass coverage to obtain topography for a significant fraction of the first-cycle targets. A focus of the third cycle will be InSAR-based deformation studies of selected areas. All components of the spacecraft are expected to remain operational well beyond the nominal mission time, so global mapping at 10 m or better resolution during an extended mission is conceivable. RAVEN will allow us to determine both the broad framework of the planet’s geologic history (e.g, uniformitarian versus catastrophic evolution) and the nature of current geologic activity. It will substantially advance our understanding of Venus and reveal details, issues, and further questions that will benefit future site-specific missions such as probes and landers. Current RAVEN science team members are Buck Sharpton (PI), Rudi Gens, Rebecca Ghent, Martha Gilmore, Robert Grimm, Robert Herrick, Catherine Johnson, Patrick McGovern, Franz Meyer, Peter Mouginis-Mark, Jeff Plaut, David Sandwell, Mark Simons, and Sean Solomon.

Sharpton, V. L.; Herrick, R. R.; Rogers, F.; Waterman, S.

2009-12-01

89

Spectral inventory of the SOIR spectra onboard Venus Express  

NASA Astrophysics Data System (ADS)

The set of spectra recorded by the SOIR instrument on board Venus Express have been carefully studied from a spectroscopic point of view. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter for order selection. It performs solar occultation measurements in the IR region (2.2 - 4.4 ?m) at a resolution of 0.10 - 0.24 cm-1 [1]. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65 to 180 km) with emphasis on the vertical distribution of gases (CO2, CO, H2O, HCl, HF, ...). The sensitivity of the SOIR instrument and the high concentration of CO2 on Venus, coupled with the long absorption paths sounded during solar occultations, enable us to detect weak absorption bands of rare CO2 isotopologues [2, 3]. The spectra are analysed using ASIMAT, an in-house Matlab algorithm [4]. It is based on the Optimal Estimation Method [5] with the aim to deduce physical characteristics (densities, temperature) of the Venus atmosphere from the spectra recorded using SOIR. The spectra were fitted using HITRAN 2008 [6]. A tool of automatic assignment was developed and applied to each spectrum leading to the creation of the wavenumber list of each line visible in the SOIR spectra. The tools used to calibrate the spectra, to characterize the residuals and to produce the line list will be described extensively for a selected number of orbits. References 1. Nevejans, D., et al., Compact high-resolution space-borne echelle grating spectrometer with AOTF based on order sorting for the infrared domain from 2.2 to 4.3 micrometer. Applied Optics, 2006. 45(21): p. 5191-5206. 2. Wilquet, V., et al., Line parameters for the 01111-00001 band of 12C16O18O from SOIR measurements of the Venus atmosphere. J. Quant. Spectrosc. Radiat. Transfer, 2008. 109: p. 895-905. 3. Robert, S., et al., Assignment and rotational analysis of new absorption bands of carbon dioxide isotopologues in Venus spectra. J. Quant. Spectrosc. Radiat. Transfer, 2013. 114: p. 29-41. 4. Mahieux, A., et al., Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR onboard Venus Express: Retrieval technique. J. Geophys. Res., 2010. 115(E12014): p. 10.1029/2010JE003589. 5. Rodgers, C., Inverse methods for atmospheric sounding: Theory and practice. World Scientific, ed. N.J. Hackensack. 2000: University of Oxford. 6. Rothman, L.S., et al., The HITRAN 2008 molecular spectroscopic database. J. Quant. Spectrosc. Radiat. Transfer, 2009. 110(9-10): p. 533-572.

Robert, Séverine; Mahieux, Arnaud; Wilquet, Valérie; Drummond, Rachel; Carine Vandaele, Ann

2013-04-01

90

The Water Vapor Abundance Near the Surface of Venus from Venus Express / VIRTIS Observations  

NASA Astrophysics Data System (ADS)

We present an analysis of Venus Express/VIRTIS observations of the 1.18-?m window on Venus' night side. We used the infrared M-channel of the VIRTIS instrument, an imaging spectrometer for the range 1-5 ?m with a resolution of about 17 nm. The 1.18-?m window probes down to the surface and allows us to map and monitor the water abundance in the lowest scale height of the atmosphere. Besides CO2 and H2O molecular bands, an additional "continuum" source of absorption exists in the window, likely due to CO2 collision-induced bands and extreme far wings of strong CO2 bands. From the variation of the emission with surface elevation, we determined this absorption to be 1.1 ± 0.2 × 10-9 cm-1 amagat-2. From the best fit of the 1.18-micron window in various areas of Venus' southern hemisphere, we derived a H2O mole fraction of 32 ± 7 ppm in the altitude range 0-15 km. This result agrees with previous ground-based and Galileo/NIMS determinations (Taylor et al. 1997, in Venus II, pp. 325-351) but has significantly lower error bars. The derived mole fraction is similar to that inferred at higher altitudes from the 2.3- and 1.74-?m windows, suggesting a constant-with-height water profile from the surface up to 40 km. We also searched for spatial variations of the H2O near-surface abundance using various VIRTIS-M observational sequences and did not detect any latitudinal variations to within 1.5% (i.e. ± 0.5 ppm) in the range 60°S - 20°N.

Bezard, Bruno; Tsang, C. C. C.; Carlson, R. W.; Piccioni, G.; Marcq, E.; Drossart, P.; VIRTIS/Venus Express Team

2008-09-01

91

Mars Express and Venus Express Data Retention In-Flight Performance  

NASA Astrophysics Data System (ADS)

Venus, Mars and Earth, three out of the four inner or 'rocky' planets of the Solar System, have a lot in common: a solid surface you could walk on, a comparable surface composition, an atmosphere and a weather system. European Space Agency (ESA) Mars Express (MEx) and Venus Express (VEx) pioneer scientific missions aim at exploring these two neighbours of the Earth, in order to enrich our knowledge of our planet and of the Solar System. Both projects are based on the same spacecraft bus, and in particular on 'sister' Solid State Mass Memory (SSMM) units, in charge of the acquisition, storage and retrieval of all on board data, relevant both to the platform and to the instruments. This paper recalls the common SSMM design and the inner fault tolerant memory array module architecture based on Computer Off The Shelf (COTS) Samsung 64 Mbit Synchronous Dynamic Random Access Memory (SDRAM) chips, and presents the comparative in-flight data retention performance for both MEx and Vex units, since their respective June 2003 and November 2005 launches. Both units have shown to successfully withstand the radiative deep space environment, including during the outstanding October 2003 solar flare, and no uncorrectable data corruption was ever reported. Beyond this stable retention performance over time, the memory scrubbing correctable error accounting feedback allows evaluating the deep space Single Event Upset (SEU) rates, to be compared with the theoretical SSMM radiation assessment as well as with other previous missions in-flight qualitative reference performance records, and finally enables to derive a couple of recommendations from the lessons' learnt.

Lebrédonchel, J.; Rombeck, F.-J.

2007-08-01

92

The Venus Airglow  

NASA Astrophysics Data System (ADS)

Venus Express is scheduled to arrive at Venus in April, 2006, and atmospheric emissions will be studied with the SPICAV/SOIR spectrometer, which is similar to the SPICAM spectrometer on board the Mars Express orbiter. Because both atmospheres are predominantly CO2/N2, it is expected that emissions in the UV will be similar. Mars Express has already shown that the predominant 200-300 nm nightglow emission is from excited states of NO, as is known for Venus from the Pioneer Venus mission. From Mars Express, the presence of O(1S) from its nightglow emission at 297.2 nm is somewhat ambiguous, although in the dayglow this emission is strong, as shown earlier by the Mariner missions. Because it is now known that Venus O(1S-1D) emission at 557.7 nm can be as strong as the terrestrial green line, although very variable, we expect that Venus Express will be able to make observations of the O(1S-3P) 297.2 nm line, and measure its seasonal and spatial variations. The SOIR instrument measures the IR emissions to a blue cut-off of 700 nm. Thus, it is hoped that emission of the O2 Atmospheric 0-0 band at 762 nm is discernible, as well as the weak O2 Herzberg II and Chamberlain bands above 700 nm. The very variable O2 IR Atmospheric 0-0 band emission at 1270 nm should be easily observable.

Sharpee, B. D.; Slanger, T. G.

2005-12-01

93

VENUS EXPLORATION ANALYSIS GROUP (VEXAG)  

NASA Astrophysics Data System (ADS)

The Venus Exploration Analysis Group (VEXAG) was established by NASA in July 2005 to identify scientific priorities and strategy for exploration of Venus. This community-based forum is designed to provide scientific input and technology development plans for planning and prioritizing the exploration of Venus over the next several decades. VEXAG is currently composed of two co- chairs and several groups. The focus groups actively solicit input from the scientific community and meet during VEXAG meetings, held at least once a year. VEXAG reports its findings and provides input to NASA, but does not make recommendations. VEXAG holds meetings open to the global scientific community with interest in understanding Venus and receives input from the scientists and engineers around the world on the current open issues regarding understanding Venus as a planet. VEXAG regularly evaluates Venus exploration goals, scientific objectives, investigations and critical measurement requirements, including especially recommendations in the National Academy of Sciences Decadal Survey and the Solar System Exploration Strategic Roadmap. VEXAG is coordinating the preparation of several White papers on different topics, including science, technology, and the recent flagship study, relevant to Venus exploration for the current Decadal Survey can be found on the VEXAG website (http://www.lpi.usra.edu/vexag). VEXAG provides a forum for learning about international efforts in exploring Venus and facilitates collaboration in combined observation programs from space and earth based observatories. At present, Venus Express mission launched by European Space Agency in November 2005 is the only active mission collecting data from orbit around Venus since April 2006. It will soon be joined in December 2010 by Japan’s Venus Climate Orbiter which is under development for a launch in May 2010. Other missions to Venus are being considered by NASA (Venus Flagship mission), Russia (Venera D) and in the European community (European Venus Explorer). In addition, it is anticipated that several mission concepts will be proposed to NASA’s Discovery (Announcement of Opportunity anticipated by end of 2009). The Venus community recognizes that science return can be maximized by coordinating observations as much as feasible. VEXAG is one forum where the discussions can take place and the community is invited to actively participate in the VEXAG meetings and activities. The next VEXAG meeting will be held following the second Inner Planets Panel Meeting, in Irvine, California, October 28-29, 2009 (see website for details). VEXAG’s past activities, current efforts and future plans will be presented. A workshop focused on Venus Atmosphere is being planned for summer 2010 in conjunction with a VEXAG meeting is being tentatively planned for summer 2010.

Limaye, S. S.; Smrekar, S. E.

2009-12-01

94

Mars Express Science Results and Goals for the Extended Mission  

NASA Astrophysics Data System (ADS)

The ESA Mars Express mission was successfully launched on 02 June 2003 from Baikonur, Kazakhstan, onboard a Russian Soyuz rocket with a Fregat upper stage. The mission comprises an orbiter spacecraft, which has been placed in a polar martian orbit, and the small Beagle-2 lander, due to land in Isidis Planitia but whose fate remains uncertain. In addition to global studies of the surface, subsurface and atmosphere of Mars, with an unprecedented spatial and spectral resolution, the unifying theme of the mission is the search for water in its various states everywhere on the planet. A summary of scientific results from all experiments after more than one Martian year in orbit (687 days) will be presented. Mars Express is already hinting at a quantum leap in our understanding of the planet's geological evolution, to be complemented by the ground truth being provided by the American MER rovers. The nominal mission lifetime of one Martian year for the orbiter spacecraft has already been extended by another Martian year. During the extended mission, priority will be given to fulfill the remaining goals of the nominal mission (e.g., gravity measurements and seasonal coverage), to catch up with delayed MARSIS measurements during the nominal mission, to complete global coverage of high-resolution imaging and spectroscopy, as well as subsurface sounding with the radar, to observe atmospheric and variable phenomena, and to revisit areas where discoveries were made. Also, an effort to enlarge the scope of existing cooperation will be made, in particular with respect to other missions to Mars (such as MGS, MER, MRO) and also missions to other planets carrying the same instruments as Mars Express (i.e. Venus Express). For further details on the Mars Express mission and its science, see the web site: http://sci.esa.int/marsexpress/

Chicarro, A. F.

2006-08-01

95

Present Status and Future of Venus Express and Results from Atmospheric Drag measurements  

NASA Astrophysics Data System (ADS)

Venus Express has now been in its 24 hour polar orbit around our neighbour planet for six years since arriving at Venus in April 2006. The spacecraft and its scientific instruments are in an excellent condition barring a few items that have reached their end of life. The fuel situation is good and it is expected that the supply will last until at least early 2015 and possibly longer. From the six active instruments on board well above 3 Tbit data has been down-linked to ground. The Venus Express team has prepared for several new types of observations during the last years, including aerodrag measurements that started in 2009, solar spectral scans that started in 2011 and airglow measurements on the dayside that will start in 2012. Original observation plans for 2011 included exciting and unique joint measurements with the Akatsuki mission, but due to the unfortunate failure during its orbit insertion plans had to be changed. The atmospheric drag measurements have been performed during seven dedicated campaigns, when, due to solar gravity perturbations of the orbit, the pericentre altitude has reached levels below 200km and as far down as 165km. These measurements have revealed a much less dense atmosphere at the polar latitudes than what existing models predict. In addition the density seems to vary up to a factor three in a semi periodic manner. The mechanism causing this variation is not yet understood but it is possible that waves propagating from the polar vortex far below have some influence.

Svedhem, H.; Titov, D.; Wilson, C.

2012-04-01

96

Variability of CO concentrations in the Venus troposphere from Venus Express/VIRTIS using a Band Ratio Technique  

NASA Astrophysics Data System (ADS)

A fast method is presented for deriving the tropospheric CO concentrations in the Venus atmosphere from near-infrared spectra using the night side 2.3 ?m window. This is validated using the spectral fitting techniques of Tsang et al. [Tsang, C.C.C., Irwin, P.G.J., Taylor, F.W., Wilson, C.F., Drossart, P., Piccioni, G., de Kok, R., Lee, C., Calcutt, S.B., and the Venus Express/VIRTIS Team, 2008a. Tropospheric carbon monoxide concentrations and variability on Venus with Venus Express/VIRTIS-M observations. J. Geophys. Res. 113, doi: 10.1029/2008JE003089. E00B08] to show that monitoring CO in the deep atmosphere can be done quickly using large numbers of observations, with minimal effect from cloud and temperature variations. The new method is applied to produce some 1450 zonal mean CO profiles using data from the first eighteen months of operation from the Visible and Infrared Thermal Imaging Spectrometer infrared mapping subsystem (VIRTIS-M-IR) on Venus Express. These results show many significant long- and short-term variations from the mean equator-to-pole increasing trend previously found from earlier Earth- and space-based observations, including a possible North-South dichotomy, with interesting implications for the dynamics and chemistry of the lower atmosphere of Venus.

Tsang, C. C. C.; Taylor, F. W.; Wilson, C. F.; Liddell, S. J.; Irwin, P. G. J.; Piccioni, G.; Drossart, P.; Calcutt, S. B.

2009-06-01

97

Need for a mission to understand the Earth-Venus-Mars difference in Nitrogen  

NASA Astrophysics Data System (ADS)

This presentation is based on a satellite mission proposal that was submitted to ESA's call for a Small Mission in June 2012. Although the mission was not selected, its science was recommended by the Solar System Exploration Working Group. Nitrogen is a key element for life as an inevitable part of the amino acid and protein. While nitrogen is abundant on the Earth (the amount in the soil, crust, and ocean are small compared to the atmospheric amount) and on Venus (only 3% but pressure is 90 times of the Earth, resulting in three times as the Earth), Martian atmosphere has very little nitrogen, about only 0.01% of the Earth or Venus (with 10% of planetary mass). This contrasts the oxygen abundance, which is found in all three planets (Martian case, it is now believed to exist in the crust as oxidized rocks because the observed escape rate is equivalent only 10 m deep water). Considering the fact that nitrogen is much more difficult to be ionized than oxygen due to triple chemical binding and that dependence of the ion outflow from the ionosphere on the geomagnetic activity is more drastic for cold nitrogen ion than cold oxygen ions, absence of the nitrogen only on the Mars is a mystery, while this absence might explain the absence of life on Mars at the present knowledge. From these viewpoints, it is important to understand the dynamic of N+ and N2+ at different solar conditions, e.g., its difference from oxygen dynamics for whatever the planet. One reason for lack of such measurement except cold ions is the difficulty in separating hot N+ from O+ in the modern time-of-flight instruments, but it is now most likely possible to separate O+ and N+ using magnetic mass analyzer if we mask H+ and if we limit the angular coverage to minimize contamination. The nitrogen study in space requires a dedicated space mission that covers both the polar region and inner magnetosphere. Instrumentation for such a mission also benefits study of inner magnetospheric study, substorm studies, and basic plasma physics such as ion energization. We present the science and instrumentation of the proposed NITRO mission.

Yamauchi, Masatoshi; Dandouras, Iannis; Rathsman, Peter

2013-04-01

98

Understanding of the Venus upper atmosphere dynamics with O2(a1?) Venus Express observations  

NASA Astrophysics Data System (ADS)

The O2(a1?) nightglow emission at 1.27 ?m may be used as a tracer of the dynamics prevailing in the Venusian upper mesosphere. This emission has thus been observed with ground-based telescopes and from space with instruments such as VIRTIS on board Venus Express. Observations have shown that the emission maximum is statistically located close to the antisolar point at ~96 km. As originally suggested by Connes et al. (1979), such an emission results from the production of oxygen atoms on the Venus dayside by photodissociation and electron impact dissociation of CO2 and CO, which are then transported to the nightside by the subsolar to antisolar general circulation, where they recombine to create excited O2(a1?) molecules. Their radiative deexcitation produces the O2(a1?) nightglow with a maximum near the antisolar point. However, VIRTIS observations indicate that the O2(a1?) nightglow emission is highly variable, both in intensity and location. Actually, when considering individual observations, the patch of bright emission is rarely located at the antisolar point and the brighter area around this point is the result of statics accumulation. Also, when considering several individual observations acquired in a short period of time, it is possible to follow an individual emission patch and to deduce its displacement and its brightness variation due to activation or deactivation. In this study, we analyze several sequences of VIRTIS observations in order to understand the Venus upper mesosphere dynamics. We show that the intensity can vary by several megaRayleighs in a couple of hours with effective lifetimes on the order of several hours. The horizontal motion of the spots leads to the conclusion that winds in the 95-100 km region are in the range of 25 to 150 m s-1, in good agreement with the study by Hueso et al. (2008).

Soret, L.; Gérard, J.-C.; Piccioni, G.; Drossart, P.

2012-04-01

99

Models of the global cloud structure on Venus derived from Venus Express observations  

NASA Astrophysics Data System (ADS)

Spatially-resolved near-infrared spectra from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on Venus Express have been used to derive improved models of the vertical structure and global distribution of cloud properties in the southern hemisphere of Venus. VIRTIS achieved the first systematic, global mapping of Venus at wavelengths within transparency windows in the 1.6-2.6 ?m range, which are sensitive on the nightside to absorption by the lower and middle cloud layers of thermally-emitted radiation from the hot lower atmosphere ( Taylor, F.W., Crisp, D., Bézard, B. [1997]. Venus II: Geology, Geophysics, Atmosphere, and Solar Wind Environment, pp. 325-351). The cloud model used to interpret the spectra is based on previous work by Pollack et al. (Pollack, J., Dalton, J., Grinspoon, D., Wattson, R., Freedman, R., Crisp, D., Allen, D., Bézard, B., de Bergh, C., Giver, L. [1993]. Icarus 103, 1-42), Grinspoon et al. (Grinspoon, D.H., Pollack, J.B., Sitton, B.R., Carlson, R.W., Kamp, L.W., Baines, K.H., Encrenaz, T., Taylor, F.W. [1993]. Planet. Space Sci. 41, 515-542) and Crisp (Crisp, D. [1986]. Icarus 67, 484-514), and assumes a composition for the cloud particles of sulfuric acid and water, with acid concentration as a free parameter to be determined. Other retrieved parameters are the average size of the particles and the altitude of the cloud base in the model. Latitudinal variation in the atmospheric temperature structure was incorporated using data from the Venus Radio Science experiment (VeRa). Values are estimated initially using wavelength pairs selected for their unique sensitivity to each parameter, and then validated by comparing measured to calculated spectra over the entire wavelength range, the latter generated using the NEMESIS radiative transfer and retrieval code (Irwin, P.G.J., Teanby, N.A., de Kok, R., Fletcher, L.N., Howett, C.J.A., Tsang, C.C.C., Wilson, C.F., Calcutt, S.B., Nixon, C.A., Parrish, P.D. [2008]. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150). The sulfuric acid concentration in the cloud particles is found to be higher in regions of optically thick cloud. The cloud base altitude shows a dependence on latitude, reaching a maximum height near -50°. The increased average particle size near the pole found by Wilson et al. (Wilson, C.F., Guerlet, S., Irwin, P.G.J., Tsang, C.C.C., Taylor, F.W., Carlson, R.W., Drossart, P., Piccioni, G. [2008]. J. Geophys. Res. (Planets) 113, E12) and the finding of spatially variable water vapor abundance at35-40 km altitude first reported by Tsang et al. (Tsang, C.C.C., Wilson, C.F., Barstow, J.K., Irwin, P.G.J., Taylor, F.W., McGouldrick, K., Piccioni, G., Drossart, P., Svedhem, H. [2010]. Geophys. Res. Lett. 37, L02202) are both confirmed. The implications of these improved descriptions of cloud structure and variability for the chemistry, meteorology, and radiative energy balance on Venus are briefly discussed.

Barstow, J. K.; Tsang, C. C. C.; Wilson, C. F.; Irwin, P. G. J.; Taylor, F. W.; McGouldrick, K.; Drossart, P.; Piccioni, G.; Tellmann, S.

2012-02-01

100

Gravity Waves in the Atmosphere of Venus as Observed by VIRTIS on Venus Express  

NASA Astrophysics Data System (ADS)

Trains of mesoscale waves have been regularly observed in the opacity of the clouds of Venus through the images obtained by the VIRTIS-M spectral camera onboard Venus Express. They have been studied at two cloud levels characterized by a high stability: the top of the clouds (at a height of 66 km) observed using the solar reflected ultraviolet light (380 nm) from the dayside, and the lower cloud (at a height of 47 km) observed using the thermal emission (1.74 µm) from the nightside. These waves have been identified as gravity waves through the comparison of their temporal frequencies with the Brunt-Vaisalla and acoustic cut-off frequencies. They are nearly zonal, with wavelengths of 60-130 km and are confined in wave packets of 400 to 1,600 km. They propagate westward and with low phase velocities relative to the zonal flow, having the waves within the lower cloud the slowest values. An analytic study and a preliminary numerical modelling of these waves are also introduced.

Peralta, Javier; Hueso, R.; Sánchez-Lavega, A.; Piccioni, G.; Lanciano, O.; Drossart, P.

2008-09-01

101

Europe Scores New Planetary Success: Venus Express Enters Orbit around the Hothouse Planet  

NASA Astrophysics Data System (ADS)

During the next four weeks, the Venus Express probe will perform a series of manoeuvres to reach the scheduled operational orbit for its scientific mission. It will move from its current highly elongated 9-day orbit to a 24-hour polar orbit, culminating at 66,000 km. From this vantage point, the orbiter will conduct an in-depth observation of the structure, chemistry and dynamics of the atmosphere of Venus for at least two Venusian days (486 Earth days). Enigmatic atmosphere From previous missions to Venus as well as observations directly from Earth, we already know that our neighbouring planet is shrouded in a thick atmosphere where extremes of temperature and pressure conditions are common. This atmosphere creates a greenhouse effect of tremendous proportions as it spins around the planet in four days in an unexplained “super-rotation” phenomenon. The mission of Venus Express will be to carry out a detailed characterisation of this atmosphere, using state-of-the-art sensors in order to answer the questions and solve the mysteries left behind by the first wave of explorers. It will also be the first Venus orbiter to conduct optical observations of the surface through “visibility windows” discovered in the infrared spectrum.V The commissioning of the onboard scientific instruments will begin shortly and the first raw data are expected within days. The overall science payload is planned to be fully operational within two months. Europe explores the Solar System With this latest success, ESA is adding another celestial body to its range of solar system studies. ESA also operates Mars Express around Mars, SMART-1 around the Moon and is NASA’s partner on the Cassini orbiter around Saturn. In addition, ESA is also operating the Rosetta probe en route to comet 67P/Churyumov-Gerasimenko. It should reach its target and become the first spacecraft ever to enter orbit around a comet nucleus by 2014. Meanwhile, ESA also plans to complete the survey of our celestial neighbours with the launch of the BepiColombo mission to Mercury in 2013. “With the arrival of Venus Express, ESA is the only space agency to have science operations under way around four planets: Venus, the Moon, Mars and Saturn” underlines Professor David Southwood, the Director of ESA’s science programmes. “We are really proud to deliver such a capability to the international science community.” “To better understand our own planet, we need to explore other worlds in particular those with an atmosphere,” said Jean-Jacques Dordain, ESA Director General. “We’ve been on Titan and we already are around Mars. By observing Venus and its complex atmospheric system, we will be able to better understand the mechanisms that steers the evolution of a large planetary atmosphere and the change of climates. In the end, it will help us to get better models of what is actually going on in our own atmosphere, for the benefit of all Earth citizens.” State-of-the-art science package Venus Express was developed for ESA by a European industrial team led by EADS Astrium incorporating 25 main contractors from 14 European countries. Its design is derived from that of its highly successful predecessor, Mars Express, and its payload accommodates seven instruments including upgraded versions of three instruments developed for Mars Express and two for Rosetta. The PFS spectrometer will determine the temperature and composition profile of the atmosphere at very high resolution. It will also monitor the surface temperature and search for hot spots from possible volcanic activity. The UV/infrared SpicaV/SOIR spectrometer and the VeRa radioscience experiment will probe the atmosphere by observing the occultation of distant starts or the fading of radio signals on the planetary limb. SpicaV/SOIR will be particularly looking for traces of water molecules, molecular oxygen and sulphur compounds, which are suspected to exist in the atmosphere of Venus. The Virtis spectrometer will map the different layers of the atmosphere and provide imagery of the cloud systems at multipl

2006-04-01

102

First observations of SPICAV on board Venus Express.  

NASA Astrophysics Data System (ADS)

SPICAV (SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus) is a suite of three spectrometers in the UV and IR range with a total mass of 12.3 kg flying on Venus Express orbiter, dedicated to the study of the atmosphere of Venus from ground level to the outermost hydrogen corona at more than 40,000 km. 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 analyzes 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 day side with implications for cloud structure, and atmospheric dynamics. On the night side, ?gnd ? bands of NO have been detected. In the stellar occultation mode the UV sensor is measuring the vertical profiles of CO2 , temperature, SO2 , SO, clouds and aerosols. So far, occultations on the night side indicates a higher temperature than predicted by the VIRA model and an aerosol horizontal opacity of 1 at 90 km altitude. The SPICAV VIS-IR sensor (0.7-1.7 µµm, resolution 0.5-1.2 nm) employs a pioneering technology: acousto-optical tunable filter (AOTF). On the night side, it measures the thermal emission peeping through the clouds, complementing the observations of both VIRTIS and Planetary Fourier Spectrometer (PFS). In solar occultation mode this channel permits to study the vertical structure of H2 O, CO2 , and aerosols. The SOIR spectrometer is a new Solar Occultation IR spectrometer in the rangeg?=2.2-4.3 µm, with a spectral resolution ?v?? >15,000, the highest on board Venus Express (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 H2 O 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. The SOIR results are reported in another presentation.

Bertaux, J. L.; Korablev, O.; Villard, E.; Fedorova, A.; Nevejans, D.; Neefs, E.; Montmessin, F.; Quemerais, E.; Vandaele, A. C.; Muller, C.

103

Venus, Mars, and the Ices on Mercury and the Moon: Astrobiological Implications and Proposed Mission Designs  

Microsoft Academic Search

ABSTRACT Venus and Mars likely had liquid water bodies on their surface early in the Solar System his- tory. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reser- voirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial

Dirk Schulze-Makuch; James M. Dohm; Alberto G. Fairen; Victor R. Baker; Wolfgang Fink; Robert G. Strom

2005-01-01

104

Venus, Mars, and the Ices on Mercury and the Moon: Astrobiological Implications and Proposed Mission Designs  

Microsoft Academic Search

Venus and Mars likely had liquid water bodies on their surface early in the Solar System history. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reservoirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms may have

Dirk Schulze-Makuch; James M. Dohm; Alberto G. Fairén; Victor R. Baker; Wolfgang Fink; Robert G. Strom

2005-01-01

105

The OH Venus nightglow spectrum: Intensity and vibrational composition from VIRTIS—Venus Express observations  

NASA Astrophysics Data System (ADS)

Limb spectra of the OH nightglow emission corresponding to the ?v=1 and ?v=2 sequences have been collected with the VIRTIS infrared imaging spectrograph on board Venus Express between April 2006 and October 2008. A detailed statistical analysis shows that the peak intensity and altitude of the two vibrational sequences are significantly correlated, with a mean intensity ratio of the two sequences of 0.38±0.37. The altitude of the maximum of the ?v=2 emission is located ˜1 km lower than ?v=1. A spectral analysis shows that the ?v=1 sequence is composed at 44.6% by the (1-0) band, 9.3% by the (3-2) band and 7.1% by the (4-3) band. The ?v=2 emission is best fitted if solely including the (2-0) band.A non-LTE model of OH vibrational population by the O3+H reaction including radiative and collisional relaxation has been used to compare the expected spectral distribution, the altitude of the emission peak and the emission rate under different assumptions on the quenching processes to those observed with VIRTIS. The adopted carbon dioxide, atomic oxygen and ozone densities are based on recent Venus Express remote sensing measurements. We find that the “Sudden Death” quenching scheme by CO2 produces inadequate spectral distribution between the various bands and insufficient airglow brightness. Instead, the observed spectral distribution and the total emission intensity are reasonably well reproduced with the Single Quantum jump model, an O density profile peaking at 103.5 km with a maximum value of 1.9×1011 cm-3, a O3 density profile peaking at 5.8×106 cm-3 at 96.5 km and a H density profile close to 108 cm-3 between 90 and 120 km, in agreement with several photochemical models.

Soret, Lauriane; Gérard, Jean-Claude; Piccioni, Giuseppe; Drossart, Pierre

2012-12-01

106

Microwave absorptivity by sulfuric acid in the Venus atmosphere derived from the Venus Express Radio Science Experiment VeRa  

NASA Astrophysics Data System (ADS)

Earth's nearest planetary neighbour Venus is shrouded within a roughly 22 km thick three-layered cloud deck, which is located approximately 48 km above the surface and extends to an altitude of about 70 km. The clouds are mostly composed of sulfuric acid. The latter is responsible for a strong absorption of radio signals at microwaves, which is observed in radio occultation experiments. The absorption of the radio signal intensity is used to determine the abundance of H2SO4. This way a detailed study of the H2SO4 height distribution within the cloud deck is possible. The Venus Express spacecraft is orbiting Venus since 2006. The Radio Science Experiment VeRa onboard probes the atmosphere with radio signals at 3.4 cm (X-Band) and 13 cm (S-Band). Absorptivity profiles of the 3.4 cm radio wave and the resulting vertical sulfuric acid profiles in the cloud region of Venus' atmosphere are presented. The three-layered structure and a distinct latitudinal variation of H2SO4 are observed. Convective atmospheric motions within the equatorial latitudes, which transport absorbing material from lower to higher altitudes, are clearly visible. Results of the Venus Monitoring Camera (VMC) and the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) are compared with the VeRa results.

Oschlisniok, J.; Pätzold, M.; Häusler, B.; Tellmann, S.; Bird, M.; Andert, T.; Remus, S.; Krüger, C.; Mattei, R.

2011-10-01

107

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

Microsoft Academic Search

The European Space Agency Venus Express Radio Science experiment (VeRa) obtained 118 radio occultation measurements of the Venusian atmosphere between July 2006 and June 2007. Southern latitudes are uniformly sampled; measurements in the northern hemisphere are concentrated near the pole. Radial profiles of neutral number density derived from the occultations cover the altitude range 40–90 km, which are converted to

Silvia Tellmann; Martin Pätzold; Bernd Häusler; Michael K. Bird; G. Leonard Tyler

2009-01-01

108

Water abundance and hydrogen isotopic ratio in the upper atmosphere of Venus from SOIR measurements on board Venus Express  

NASA Astrophysics Data System (ADS)

Water on Venus is much more scarce than on Earth, with volume mixing ratios lower than a part per million. The reason for this has always been of great interest, because it may give clues to the difference of evolution between the two planets. Studying water gives also access to another important planetary parameter, which is the deuterium to hydrogen isotopic ratio. H _{2}O and HDO are measured together with CO _{2} in the SOIR wavelength range, in the region 2.5 to 2.6 ?m (3800 to 4000 cm ^{-1}) for H _{2}O and 3.35 to 3.85 ?m (2600 to 3000 cm ^{-1}) for HDO, which allows the derivation of their vertical density profiles together with the temperature and total density profiles obtained from CO2 measurements [1], which can be used to calculate VMR profiles. The measurements all occur at the Venus terminator, both the morning and evening side, covering all latitudes from the North Pole to the South Pole. The vertical resolution is very good from the North Pole to 40° North (resolution of 500 m), and is poorer in the Southern hemisphere (resolution between 1000 m and 2500 m). The maximum extent of the H _{2}O and the HDO profiles is from 120 to 70 km, with variations from orbit to orbit. We will present results from the simultaneous measurements of H _{2}O and HDO that occur during the first 5 occultation seasons of Venus Express, i.e. from 04/09/2006 to 22/08/2007. 1. Mahieux, A., A.C. Vandaele, S. Robert, V. Wilquet, R. Drummond, F. Montmessin, and J.L. Bertaux, Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express. Carbon dioxide measurements at the Venus terminator. J. Geophys. Res., (submitted) (2012)

Drummond, Rachel; Mahieux, Arnaud; Wilquet, Valerie; Bertaux, Jean-Loup; Robert, Severine; Vandaele, Ann C.; Matsui, Hiroki; Iwagami, Naomoto

2012-07-01

109

Characterizing the Venus atmospheric dynamics from ground-based Doppler velocimetry  

Microsoft Academic Search

We present an analysis of observations of Venus made with the UVES instrument (Ultraviolet and Visual Echelle Spectrograph) at ESO's Very Large Telescope (VLT). The observations were carried out in May and June 2007 with the aim of characterizing the zonal wind flow in the atmosphere of Venus during the nominal mission phase of Venus Express. Doppler velocimetry measurements are

Pedro Machado; David Luz; Thomas Widemann; Emmanuel Lellouch; Olivier Witasse; Jean-Loup Bertaux

2010-01-01

110

Electromagnetic waves observed by Venus Express at periapsis: Detection and analysis techniques  

Microsoft Academic Search

The magnetometer on Venus Express was designed to be able to obtain 128Hz samples of the magnetic field from two sensors in a gradiometer configuration. This mode is used around periapsis to determine whether the signals reported at low altitudes near 100Hz, had the properties of electromagnetic waves generated by electric discharges in the Venus atmosphere. The lack of a

C.T. Russell; T. L. Zhang; R. J. Strangeway; H. Y. Wei; M. Delva; W. Magnes

2008-01-01

111

Electromagnetic waves observed by Venus Express at periapsis: Detection and analysis techniques  

Microsoft Academic Search

The magnetometer on Venus Express was designed to be able to obtain 128 Hz samples of the magnetic field from two sensors in a gradiometer configuration. This mode is used around periapsis to determine whether the signals reported at low altitudes near 100 Hz, had the properties of electromagnetic waves generated by electric discharges in the Venus atmosphere. The lack

C. T. Russell; T. L. Zhang; R. J. Strangeway; H. Y. Wei; M. Delva; W. Magnes

2008-01-01

112

SPICAV/SOIR on board Venus express: an overview of two years of observations.  

NASA Astrophysics Data System (ADS)

SPICAV (SPectroscopy for the Investigation of the Characteristics of the Atmosphere of Venus) is a suite of three spectrometers in the UV and IR range with a total mass of 12.3 kg flying on Venus Express orbiter, dedicated to the study of the atmosphere of Venus from ground level to the outermost hydrogen corona at more than 40,000 km. The UV spectrometer (118 - 320 nm, resolution 1.5 nm) has detected on the night side, the ? and ? bands of NO. In the stellar occultation mode the UV sensor is measuring the vertical profiles of CO2, temperature, SO2, clouds and aerosols. So far, star occultations on the night side indicates a higher temperature than predicted by the VIRA model and an aerosol horizontal opacity of 1 at 90 km altitude (variable), with a haze extending up to 104 km. SO2 is detected also in solar occultation. 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). In solar occultation this channel allows to measure the aerosols characteristics. On the day side, it measures water vapor at cloud top level (65 km), which seems latitude dependent. The SOIR spectrometer is a new Solar Occultation IR spectrometer in the range ?=2.2-4.3 µm, with a spectral resolution ˜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, SO2 and CO2 isotopes have been retrieved, as well as aerosols. A new absorption signature near 2982 cm-1 was discovered, identified now with a previously unknown absorption band of CO2 isotope 12C16O18O. Details will not be discussed , since they are presented in various other contributed papers.

Bertaux, Jean-Loup; Vandaele, Ann-Carine; Korablev, Oleg; Montmessin, Franck; Wilquet, Valerie; Fedorova, Anna; Mahieux, Arnaud; Belyaev, Denis; Villard, Eric

113

Mariner-Venus 1967.  

National Technical Information Service (NTIS)

Detailed information on the spacecraft performance, mission operations, and tracking and data acquisition is presented for the Mariner Venus 1967 and Mariner Venus 1967 extension projects. Scientific and engineering results and conclusions are discussed, ...

1971-01-01

114

Nuclear Polar VALOR: An ASRG-Enabled Venus Balloon Mission Concept  

Microsoft Academic Search

In situ exploration of Venus is expected to answer high priority science questions about the planet's origin, evolution, chemistry, and dynamics as identified in the NRC Decadal Survey and in the VEXAG White Paper. Furthermore, exploration of the polar regions of Venus is key to understanding its climate and global circulation, as well as providing insight into the circulation, chemistry,

T. S. Balint; K. H. Baines

2008-01-01

115

Probing Venus' polar upper atmosphere in situ: Preliminary results of the Venus Express Atmospheric Drag Experiment (VExADE).  

NASA Astrophysics Data System (ADS)

On its highly elliptical 24 hour orbit around Venus, the Venus Express (VEx) spacecraft briefly reaches a pericenter altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008 (campaign1), October 2009 (cam-paign2), February and April 2010 (campaign3), for which the pericenter altitude was lowered to about 175 km in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in-situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the pericenter pass, allowing us to infer total atmospheric mass density at the pericenter altitude. The GINS software (Géodésie par Intégration Numérique e e Simultanées) is used to accurately reconstruct the orbital motion of VEx through an iterative least-squares fitting process to the Doppler tracking data. The drag acceleration is modelled using an initial atmospheric density model (VTS model, A. Hedin). A drag scale factor is estimated for each pericenter pass, which scales Hedin's density model in order to best fit the radio tracking data. About 20 density scale factors have been obtained mainly from the second and third VExADE campaigns, which indicate a lower density by a factor of about one-third than Hedin's model predicts. These first ever polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus' thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements. The preliminary results of the VExADE cam-paigns show that it is possible to obtain reliable estimates of Venus' upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from the planned further lowering of VEx pericenter altitude to below 170 Km.

Rosenblatt, Pascal; Bruinsma, Sean; Mueller-Wodarg, Ingo; Haeusler, Bernd

116

Water vapor abundance near the surface of Venus from Venus Express/VIRTIS observations  

NASA Astrophysics Data System (ADS)

Nightside observations of the 1.18-?m atmospheric window by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) aboard the Venus Express spacecraft were analyzed to measure and map the water vapor abundance in the lower atmosphere. Thermal emission in this window originates partly from the surface and partly from the first scale height (0-15 km) of the atmosphere. Constraints on the CO2 continuum absorption, which is the dominant source of gaseous opacity in the window, were obtained from the variation of the 1.185-?m intensity with surface elevation. An absorption coefficient of 1 ± 0.4 × 10-9 cm-1 amagat-2 best fits the observed variation. We retrieved a water vapor mole fraction of 44 ± 9 ppm from various selections of VIRTIS spectra in the southern hemisphere, in agreement with previous analyses of the nightside emission. This value is somewhat larger than that previously determined at higher altitudes from the 2.3- and 1.74-?m nightside windows, but the error bars still allow a constant with height H2O mole fraction from the surface up to 40 km. Using the intensity ratio in the two wings of the 1.18-?m window as a proxy, we searched for horizontal variations of the H2O abundance in various VIRTIS observational sequences. We derived stringent upper limits for any possible latitudinal variations on the night side: ±1.5% in the range 60°S-25°N and ±3% for the broader range 80°S-25°N. The lack of detectable latitudinal variations is consistent with a constant with height water profile in the lower atmosphere and probably precludes any strong concentration gradient near the surface.

Bézard, Bruno; Tsang, Constantine C. C.; Carlson, Robert W.; Piccioni, Giuseppe; Marcq, Emmanuel; Drossart, Pierre

2009-05-01

117

Climatology of the neutral atmosphere as measured by SOIR on board Venus Express  

Microsoft Academic Search

The SOIR instrument on board Venus Express performs solar occultation measurements in the IR region (2.2 - 4.3 µm) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection [1, 2]. The wavelength range probed by SOIR allows a detailed chemical inventory of

Arnaud Mahieux; Rachel Drummond; Séverine Robert; Valérie Wilquet; Ann Carine Vandaele; Franck Montmessin; Jean-Loup Bertaux

2010-01-01

118

A suggested trajectory for a Venus-sun, earth-sun Lagrange points mission, Vela  

Microsoft Academic Search

The possibility is suggested of investigating the existence of small, as-yet undiscovered, asteroids orbiting in the solar system near the earth-sun or Venus-sun stable Lagrange points by means of a spacecraft which traverses these regions. The type of trajectory suggested lies in the ecliptic plane and has a period of 5\\/6 years and a perihelion at the Venus orbital distance.

D. F. Bender

1979-01-01

119

The Structure of the Venus Neutral Atmosphere from the Radio Science Experiment VeRa on Venus Express  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment VeRa uses one-way radio signals at X-band and S-band for the sounding of the Venus neutral atmosphere and ionosphere. An Ultrastable Oscillator (USO) provides a high quality onboard frequency reference source for this dual-frequency one-way radio link. Simultaneous, coherent measurements at two wavelengths allow separation of dispersive media effects from the classical Doppler shift. Electron density profiles of the ionosphere and profiles of pressure, temperature and neutral number density of the neutral atmosphere can be derived via an Abel transform with an altitude resolution of only a few hundred metres from the cloud deck to ~ 100 km. Two occultation seasons took place in the first year of observation. A total number of 42 profiles occultation experiments were conducted. The polar orbit of Venus Express provides the opportunity to study the atmosphere at all planetocentric latitudes under varying illumination conditions. Special attention will be given to day-night variations of the atmospheric structure and the temperature distribution at high polar latitudes on both hemispheres ("cold collar region") and signal absorption effects caused by the H2SO4 vapour.

Tellmann, S.; Häusler, B.; Pätzold, M.; Bird, M.; Tyler, G. L.

2007-08-01

120

Morphology of the cloud tops as observed by the Venus Express Monitoring Camera  

NASA Astrophysics Data System (ADS)

Since the discovery of ultraviolet markings on Venus, their observations have been a powerful tool to study the morphology, motions and dynamical state at the cloud top level. Here we present the results of investigation of the cloud top morphology performed by the Venus Monitoring Camera (VMC) during more than 3 years of the Venus Express mission. The camera acquires images in four narrow-band filters centered at 365, 513, 965 and 1010 nm with spatial resolution from 50 km at apocentre to a few hundred of meters at pericentre. The VMC experiment provides a significant improvement in the Venus imaging as compared to the capabilities of the earlier missions. The camera discovered new cloud features like bright "lace clouds" and cloud columns at the low latitudes, dark polar oval and narrow circular and spiral "grooves" in the polar regions, different types of waves at the high latitudes. The VMC observations revealed detailed structure of the sub-solar region and the afternoon convective wake, the bow-shape features and convective cells, the mid-latitude transition region and the "polar cap". The polar orbit of the satellite enables for the first time nadir viewing of the Southern polar regions and an opportunity to zoom in on the planet. The experiment returned numerous images of the Venus limb and documented global and local brightening events. VMC provided almost continuous monitoring of the planet with high temporal resolution that allowed one to follow changes in the cloud morphology at various scales. We present the in-flight performance of the instrument and focus in particular on the data from the ultraviolet channel, centered at the characteristic wavelength of the unknown UV absorber that yields the highest contrasts on the cloud top. Low latitudes are dominated by relatively dark clouds that have mottled and fragmented appearance clearly indicating convective activity in the sub-solar region. At ˜50° latitude this pattern gives way to streaky clouds suggesting that horizontal, almost laminar, flow prevails here. Poleward from about 60°S the planet is covered by almost featureless bright polar hood sometimes crossed by dark narrow (˜300 km) spiral or circular structures. This global cloud pattern can change on time scales of a few days resulting in global and local "brightening events" when the bright haze can extend far into low latitudes and/or increase its brightness by 30%. Close-up snapshots reveal plenty of morphological details like convective cells, cloud streaks, cumulus-like columns, wave trains. Different kinds of small scale waves are frequently observed at the cloud top. The wave activity is mainly observed in the 65-80° latitude band and is in particular concentrated in the region of Ishtar Terra that suggests their possible orographic origin. The VMC observations have important implications for the problems of the unknown UV absorber, microphysical processes, dynamics and radiative energy balance at the cloud tops. They are only briefly discussed in the paper, but each of them will be the subject of a dedicated study.

Titov, Dmitrij V.; Markiewicz, Wojciech J.; Ignatiev, Nikolay I.; Song, Li; Limaye, Sanjay S.; Sanchez-Lavega, Agustin; Hesemann, Jonas; Almeida, Miguel; Roatsch, Thomas; Matz, Klaus-Dieter; Scholten, Frank; Crisp, David; Esposito, Larry W.; Hviid, Stubbe F.; Jaumann, Ralf; Keller, Horst U.; Moissl, Richard

2012-02-01

121

Scientific investigations of the Mars Express mission  

Microsoft Academic Search

The ESA Mars Express mission will be launched in May 2003 from Baikonur onboard a Russian Soyuz\\/Fregat launcher. The mission comprises an orbiter spacecraft to be placed in a quasi-polar martian orbit, with closest approach at 250 km and a mission lifetime of one martian year (687 days), and the small Beagle-2 probe to land at Isidis Planitia in December

A. F. Chicarro

2003-01-01

122

The plasma environment of Venus: comparison of Venus Express ASPERA-4 measurements with 3D hybrid simulations  

NASA Astrophysics Data System (ADS)

ABSTRACT We use data of the ASPERA-4 ion and electron spectrometers onboard Venus Express (VEX) to determine the locations and shapes of the plasma boundaries [1] (bow shock, ion composition boundary and mantle) at Venus. We also investigate the variation of the terminator bow shock position as a function of the solar wind dynamic pressure, total magnetic pressure and solar EUV flux. Additionally, we analyse the shock location as a function of the magnetosonic Mach number and IMF clock angle. We compare the results with a 3D hybrid simulation [3]. In the hybrid model, ions are treated as individual particles moving in self-consistently generated electromagnetic fields and electrons are modeled as a massless charge neutralizing fluid. The planetary heavy ion plasma is generated by an oxygen ionosphere and exosphere adapted to a profile, which depends on the solar zenith angle (Chapman layer). A comparison between observations and simulations indicates that the hybrid model is able to produce an adequate picture of the global plasma environment at Venus [2]. The positions of the plasma boundaries are well reproduced by the model but a significant disagreement appears in the absolute values of the considered parameters. References [1] Martinecz, C. et al. (2008), Planet Space Sci., doi:10.1016/j.pss.2007.01.014. [2] Martinecz, C. et al. (2008), JGR, submitted. [3] Bagdonat, T. and Motschmann, U. (2002), Earth Moon and Planets, 305-321.

Martinecz, C.; Boeswetter, A.; Fränz, M.; Roussos, E.; Krupp, N.; Woch, J.; Dubinin, E.; Motschmann, U.; Wiehle, S.; Simon, S.; Barabash, S.; Lundin, R.; Zhang, T. L.; Lammer, H.; Lichtenegger, H.; Kulikov, Y.

2008-09-01

123

Venus' nightside upper atmospheric density measurements by SPICAV UV on Venus Express  

NASA Astrophysics Data System (ADS)

The SPICAV UV instrument offers the possibility to probe the deep night side of Venus by means of stellar occultation. Measurements routinely yield vertical profiles of CO 2, SO 2, O 3 (recently detected) and aerosols from 70 to 150 km. After nearly six years of operations, SPICAV has allowed to assemble a dense and widespread (wrt. nightside) climatology of major and minor atmospheric components that shall provide important entries in view of updating the reference VIRA model. The 6 years of measurements, consisting of >500 individual profiles, show large temporal and spatial variability. The unique character of this dataset lies in the possibility to probe an otherwise poorly documented area of Venus climate; i.e. the nightside mesosphere and thermosphere. SPICAV results will be discussed in the context of joining the internnational effort of elaborating an updated version of VIRA.

Montmessin, Franck; Mahieux, Arnaud; Belyaev, Denis; Bertaux, Jean-Loup; Fedorova, Anna; Marcq, Emmanuel; Vandaele, Ann C.; Korablev, Oleg; Wilson, Colin

2012-07-01

124

Radio science investigations by VeRa onboard the Venus Express spacecraft  

Microsoft Academic Search

The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13cm (“X”- and “S”-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time,

B. Häusler; M. Pätzold; G. L. Tyler; R. A. Simpson; M. K. Bird; V. Dehant; J.-P. Barriot; W. Eidel; R. Mattei; S. Remus; J. Selle; S. Tellmann; T. Imamura

2006-01-01

125

Thermal zonal winds in the Venus mesosphere from the Venus Express temperature soundings  

Microsoft Academic Search

The Venus mesosphere (60-100 km altitude) is a transition region characterized by extremely complex dynamics: strong retrograde zonal winds dominate in the troposphere and lower meso-sphere while a solar-antisolar circulation can be observed in the upper mesosphere. The super-rotation extends from the surface up to the cloud top (˜65 km altitude) with wind speeds of only a few meters per

Arianna Piccialli; Dmitri Titov; Silvia Tellmann; Alessandra Migliorini; Peter Read; Davide Grassi; Martin Paetzold; Bernd Haeusler; Giuseppe Piccioni; Pierre Drossart

2010-01-01

126

Venus NIR Surface Emissivity estimated from VIRTIS on Venus Express Observations  

Microsoft Academic Search

Spectral window regions close to 1mum allow for the transfer of thermal radiation from the surface through the atmosphere of Venus. Results of radiative transfer modeling are used to invert VIRTIS images at 1.02, 1.10 and 1.18mum for thermal emission of the surface. Local atmospheric transmittance is derived from the VIRTIS band at 1.31mum. Several hundreds of VIRTIS images covering

N. Mueller; J. Helbert; G. Hashimoto; P. Kostama; L. Marinangeli; S. Erard; G. Piccioni; P. Drossart

2007-01-01

127

A dynamic upper atmosphere of Venus as revealed by VIRTIS on Venus Express  

Microsoft Academic Search

The upper atmosphere of a planet is a transition region in which energy is transferred between the deeper atmosphere and outer space. Molecular emissions from the upper atmosphere (90-120km altitude) of Venus can be used to investigate the energetics and to trace the circulation of this hitherto little-studied region. Previous spacecraft and ground-based observations of infrared emission from CO2, O2

P. Drossart; G. Piccioni; J. C. Gérard; M. A. Lopez-Valverde; A. Sanchez-Lavega; L. Zasova; R. Hueso; F. W. Taylor; B. Bézard; A. Adriani; F. Angrilli; G. Arnold; K. H. Baines; G. Bellucci; J. Benkhoff; J. P. Bibring; A. Blanco; M. I. Blecka; R. W. Carlson; A. Coradini; A. di Lellis; T. Encrenaz; S. Erard; S. Fonti; V. Formisano; T. Fouchet; R. Garcia; R. Haus; J. Helbert; N. I. Ignatiev; P. Irwin; Y. Langevin; S. Lebonnois; D. Luz; L. Marinangeli; V. Orofino; A. V. Rodin; M. C. Roos-Serote; B. Saggin; D. M. Stam; D. Titov; G. Visconti; M. Zambelli; C. Tsang; Eleonora Ammannito; Alessandra Barbis; Rainer Berlin; Carlo Bettanini; Angelo Boccaccini; Guillaume Bonnello; Marc Bouyé; Fabrizio Capaccioni; Alejandro Cardesin; Francesco Carraro; Giovanni Cherubini; Massimo Cosi; Michele Dami; Maurizio de Nino; Davide Del Vento; Marco di Giampietro; Alessandro Donati; Olivier Dupuis; Sylvie Espinasse; Anna Fabbri; Agnès Fave; Iacopo Ficai Veltroni; Gianrico Filacchione; Katia Garceran; Yamina Ghomchi; Maurizio Giustizi; Brigitte Gondet; Yann Hello; Florence Henry; Stefan Hofer; Gerard Huntzinger; Juergen Kachlicki; René Knoll; Driss Kouach; Alessandro Mazzoni; Riccardo Melchiorri; Giuseppe Mondello; Francesco Monti; Christian Neumann; Fabrizio Nuccilli; Jérôme Parisot; Claudio Pasqui; Stefano Perferi; Gisbert Peter; Alain Piacentino; Carlo Pompei; Jean-Michel Réess; Jean-Pierre Rivet; Antonio Romano; Natalie Russ; Massimo Santoni; Adelmo Scarpelli; Alain Soufflot; Douchane Stefanovitch; Enrico Suetta; Fabio Tarchi; Nazzareno Tonetti; Federico Tosi; Bernd Ulmer

2007-01-01

128

Structure of the Venus atmosphere  

Microsoft Academic Search

The structure of the Venus atmosphere is discussed. The data obtained in the 1980s by the last Soviet missions to Venus: orbiters Venera 15, 16 and the entry probes and balloons of Vega 1 and 2 are compared with the Venus International Reference Atmosphere (VIRA) model. VIRA is based on the data of the extensive space investigations of Venus in

L. V. Zasova; N. Ignatiev; I. Khatuntsev; V. Linkin

2007-01-01

129

High energy particles at Mars and Venus: Phobos-2, Mars Express and Venus Express observations and their interpretation by hybrid model simulations  

NASA Astrophysics Data System (ADS)

Mars and Venus can both be reached by Solar Energetic Particles (SEPs). Such high energy particles (protons, multiply charged heavy ions, electrons) penetrate the upper atmospheres of Mars and Venus because, in contrast to Earth, these bodies do not have a significant, global, intrinsic magnetic field to exclude them. One especially well documented, complex and prolonged SEP took in place in early 1989 (Solar Cycle 23) when the Phobos-2 spacecraft was orbiting Mars. This spacecraft had a dedicated high energy particle instrument onboard (SLED), which measured particles with energies in the keV range up to a few tens of MeV. There was in addition a magnetometer as well as solar wind plasma detectors onboard which together provided complementary data to support contemporaneous studies of the background SEP environment. Currently, while the Sun is displaying maximum activity (Solar Cycle 24), Mars and Venus are being individually monitored by instrumentation flown onboard the Mars Express (MEX) and Venus Express (VEX) spacecraft. Neither of these spacecraft carry a high energy particle instrument but their Analyzer of Space Plasmas and Energetic Atoms (ASPERA) experiments (ASPERA-3 on MEX and ASPERA-4 on VEX), can be used to study SEPs integrated over E ? ~30 MeV which penetrate the instrument hardware and form background counts in the plasma data. In the present work we present SEP events measured at Mars and Venus based on Phobos-2, 1989 data and on, more recent, MEX and VEX (identified from particle background) observations. We further introduce numerical global SEP simulations of the measured events based on 3-D self-consistent hybrid models (HYB-Mars and HYB-Venus). Through comparing the in situ SEP observations with these simulations, new insights are provided into the properties of the measured SEPs as well as into how their individual planetary bow shocks and magnetospheres affect the characteristics of their ambient Martian and Venusian SEP environments.

McKenna-Lawlor, Susan; Kallio, Esa; Fram, Rudy A.; Alho, Markku; Jarvinen, Riku; Dyadechkin, Sergey; Wedlund, Cyril Simon; Zhang, Tielong; Collinson, Glyn A.; Futaana, Yoshifumi

2013-04-01

130

Mars Express and Venus Express multi-point observations of geoeffective solar flare events in December 2006  

Microsoft Academic Search

In December 2006, a single active region produced a series of proton solar flares, with X-ray class up to the X9.0 level, starting on 5 December 2006 at 10:35UT. A feature of this X9.0 flare is that associated MeV particles were observed at Venus and Mars by Venus Express (VEX) and Mars Express (MEX), which were ?80° and ?125° east

Y. Futaana; S. Barabash; M. Yamauchi; S. McKenna-Lawlor; R. Lundin; J. G. Luhmann; D. Brain; E. Carlsson; J.-A. Sauvaud; J. D. Winningham; R. A. Frahm; P. Wurz; M. Holmström; H. Gunell; E. Kallio; W. Baumjohann; H. Lammer; J. R. Sharber; K. C. Hsieh; H. Andersson; A. Grigoriev; K. Brinkfeldt; H. Nilsson; K. Asamura; T. L. Zhang; A. J. Coates; D. R. Linder; D. O. Kataria; C. C. Curtis; B. R. Sandel; A. Fedorov; C. Mazelle; J.-J. Thocaven; M. Grande; Hannu E. J. Koskinen; T. Sales; W. Schmidt; P. Riihela; J. Kozyra; N. Krupp; J. Woch; M. Fränz; E. Dubinin; S. Orsini; R. Cerulli-Irelli; A. Mura; A. Milillo; M. Maggi; E. Roelof; P. Brandt; K. Szego; J. Scherrer; P. Bochsler

2008-01-01

131

Investigation of winds in Venus mesosphere by digital method using UV images from VMC aboard Venus Express.  

NASA Astrophysics Data System (ADS)

Investigation of winds at the top cloud layer is important for understanding the global circulation of the Venus atmosphere. The Venus Monitoring Camera (VMC) aboard Venus Express has acquired a huge number of UV (365 nm) images. UV images of top cloud layer are customary to obtain the wind velocity due to their high contrast. Visual estimation of wind velocities is a labor intensive procedure. Authors have developed a digital method to estimate velocities of shifts of cloud details. The method is based on analysis of correlations between two UV images acquired at different moments. The method takes into account the change of a correlation function due to latitudinal peculiarities of cloud morphology and eliminates image regions which are far from the sub-spacecraft point. The digital method provides with good vector coverage of the Venus day side (9-16 local time) from the equator to high latitudes. The best agreement between the digital and visual methods is observed at low latitudes (below 35S). The discrepancy at higher latitudes is related to complicated cloud morphology, namely domination of streaks, which increases errors in the zonal wind speed. The method is productive for long-scale circulation at the top cloud layer. Sizes of regions for correlation were chosen empirically as a trade-off of sensitivity against noise immunity and varies from 10x7.5 ° to 20x10 ° depending on grid step. 580 orbits covering ten Venus years have been processed by using the digital method. The database of shift vectors counts about 400000 records. The mean wind speed at low latitudes is about 100 m/s. Wind vector fields were obtained for every orbit. The zonal wind speed in the equatorial region exhibits short-period (about 4.8 days) and long-period variations (long-term trend). Vector field averaged by all orbits show deviations of the main stream up to 5 degrees poleward in the early afternoon (12.5-14.5h) at 45-55S. The mean absolute value of the wind speed increases from 59.38 m/s at 10-12h to 76.46 m/s at 12.5-14.5h at the same latitude interval.

Patsaeva, Marina; Khatuntsev, Igor; Ignatiev, Nikolai

2013-04-01

132

Preliminary results of the solar flux radiometer experiment aboard the Pioneer Venus multiprobe mission  

Microsoft Academic Search

An understanding of the thermal balance of Venus requires a detailed knowledge of the amount of sunlight absorbed at various levels in its atmosphere and at the planet's surface. To obtain measurements of solar flux near the cloud tops where the sun is still visible from a spinning probe suspended beneath a parachute, the measurement scheme adopted used narrow fields

M. G. Tomasko; L. R. Doose; J. Palmer; A. Holmes; W. Wolfe; N. D. Castillo; P. H. Smith

1979-01-01

133

The Vega project: A space mission to Venus and Halley's comet  

NASA Astrophysics Data System (ADS)

The launch of the Soviet space probes Vega 1 and Vega 2 to explore Venus, including its atmosphere, and flyby Halley's comet, a rare guest in the inner Solar System, added a vivid page to the history of space exploration. This paper is dedicated to Designer General Vyacheslav M. Kovtunenko.

Dolgopolov, V. P.; Pichkhadze, K. M.; Sukhanov, K. G.

2012-12-01

134

Wind-powered Rover for a Low-Cost Venus Mission.  

National Technical Information Service (NTIS)

Venus, with a surface temperature of 450 C and an atmospheric pressure 90 times higher than that of the Earth, is a difficult target for exploration. However, high-temperature electronics and power systems now being developed make it possible that future ...

A. J. Colozza G. Benigno G. A. Landis K. Hoza S. Motiwala

2013-01-01

135

Venus: Not evil, jus t a bit unfortunate  

NASA Astrophysics Data System (ADS)

The Venus Express mission, currently orbiting Earth's nearest planetary neighbour, has just had its mission extended until the end of 2012 by the European Space Agency (ESA). In December 2010 it will be joined by the Japanese Venus Climate Orbiter, which has similar goals of understanding the atmosphere and climate. In this article Fred Taylor looks at what has been learned so far and what remains mysterious about our nearby twin, with its torrid weather and its global warming issues.

Taylor, Fw

2010-02-01

136

Tracking of Mars Express and Venus Express spacecraft with VLBI radio telescopes  

NASA Astrophysics Data System (ADS)

The ESA Mars Express and Venus Express spacecraft (S/C) have been observed for the last two years with the European VLBI radio telescopes of Metsähovi (FI), Wettzell (GE), Yebes (SP), Medicina, Matera, Noto (IT), Puschino (RU) and Onsala (SW). The campaign is in the framework of the assessment study and preparation of the European VLBI Network to the upcoming ESA and other deep space missions. It also offers new opportunities for applications of radio astronomy techniques to planetary science, geophysics and geodesy. Observations are carried out either in single- or multi-dish modes when S/C is locked to the ESA’s ESTRACK ground stations (Cebreros or New Nortia) observing the two way link. Data are recorded locally at the stations using standard VLBI equipment and transferred to the Metsähovi for processing. Further on, the data are transferred from Metsähovi to Joint Institute for VLBI in Europe for further post-analysis. High dynamic range of the S/C signal detections allowed us to determine the apparent topocentric frequency of the S/C carrier line and accompanying ranging tones down to milli-Hz spectral accuracy and to extract the phase of the S/C signal carrier line. With multi-station observations, the respective phases can be calibrated on the per-baseline basis using VLBI phase referencing technique and observations of background quasars close to S/C in their celestial position using far-field VLBI delay model for quasars and near-field model for S/C. The post-analysis of the S/C tracking data enables us to study several parameters of the S/C signals. Of these, the phase fluctuations of the signal can be used for characterization of the interplanetary plasma density fluctuations along the signal propagation line at different spatial and temporal scales and different solar elongations. These fluctuations are well represented by a near-Kolmogorov spectrum. Multi-station observations can distinguish the contributions of propagation effects in the plasma along the up- and down-link paths as seen from different VLBI stations through different Fresnel channels. We also demonstrated high accuracy S/C Doppler tracking with 3 EVN stations (Metsähovi, Wettzell and Yebes) during the MEX-Phobos flyby, which occurred on 2010 march 03. These multi-station observing sessions could help to better determine the Phobos gravity field and together with phase referencing provide additional geometrical constrains on the orbiter/Phobos trajectories. VEX S/C signal detection with four VLBI antennae (23/08/2010).

Molera Calvés, G.; Pogrebenko, S. V.; Wagner, J.; Cimò, G.; Gurvits, L.; Duev, D.

2010-12-01

137

Oxygen nightglow emissions in the Venus atmosphere, observed by the visible channel of VIRTIS/Venus Express  

NASA Astrophysics Data System (ADS)

The oxygen nightglow emissions in the visible spectral range have been known since the early observations with the Venera spacecraft. The VIRTIS instrument on board Venus-Express allows extension of observations of the Herzberg II system of O2, and we report a mean value of 200 kR for the integrated intensity of the progression in limb view. Moreover, three bands of the Chamberlain system have been detected in the VIRTIS mean spectrum, with a mean intensity of 8-10 kR for the most intense of these bands. For the 0-v? progression of the Herzberg II system, with v? = 6-13, the maximum emission is typically observed at 95-96 km, with a full width at half maximum ranging from 12 to 15 km. A systematic observing campaign at limb is in progress from Venus Express, which will allow mapping the horizontal spatial distribution of these emissions. Once the map is enough populated, it will be possible to compare the results obtained both in the visible and IR for the O2 nightglow emissions, although not simultaneously.

Migliorini, A.; Piccioni, G.; Gérard, J.-C.; Slanger, T.; Snels, M.,; Drossart, P.

2012-04-01

138

Solar Tides in the winds of the southern polar region of Venus using VIRTIS-M/Venus Express images  

NASA Astrophysics Data System (ADS)

The effect of the solar tides on the winds at the top of the clouds in Venus has been studied using cloud tracking technique applied to the Venus Express/VIRTIS-M images taken at wavelengths of 3.8 and 5.0 ?m. Both these wavelengths probe about the same altitude on the clouds top, allowing for the first time to retrieve winds in the dayside and nightside simultaneously. The dataset included observations from 17 orbits, covering a time span of 290 days and a latitude range between 70ºS and 85ºS, a region where resides the so called cold collar. Both the diurnal (wavenumber 1) and the semidiurnal (wavenumber 2) tides are present, with the diurnal tide being the dominant harmonic for both the zonal and meridional components of the wind. The diurnal tide induces wind oscillations with amplitudes of about 4.5 m/s and 8.0 m/s for the zonal and meridional winds respectively. These amplitudes are in good accordance with the Rayleigh friction expected for this level of the Venus atmosphere, and support the important role of the diurnal tide in the maintenance of the mean zonal flow and in determining the sense of the meridional flow. While the tidal amplitude seems not to undergo important changes, the phase displays a temporal variability of about 1.4 hours in the local time coordinate. The rate of change of the phase seems different for the diurnal and semidiurnal component, indicative of a dispersive character of the solar tides, and is consistent with the expected change due to the tidal vertical propagation. Finally, a persistent lag is apparent in most cases between the tidal phases of zonal and meridional disturbances, implying that the diurnal tides tend to force equatorward winds when in the sense of the mean flow, and poleward winds when in the opposite sense.

Peralta, J.; Luz, D.; Berry, D. L.; Piccioni, G.; Drossart, P.; Hueso, R.; Sánchez-Lavega, A.

2011-10-01

139

Magellan Venus science plans  

Microsoft Academic Search

The Magellan mission to map the surface of the planet Venus is scheduled to be the next NASA planetary mission. It will also be the first planetary spacecraft to be launched by the Space Transportation System, or Shuttle. The launch period opens 29 April and closes 23 May 1989. Venus Orbit Insertion will occur about 10 August 1990. Following a

R. S. Saunders

1988-01-01

140

Correlations between Venus nightside near infrared emissions measured by VIRTIS/Venus Express and Magellan radar data  

NASA Astrophysics Data System (ADS)

Background The Venus Express Spacecraft images the nightside thermal emissions using the VIRTIS imaging spectrometer. At 1.02 micron thermal emission from the surface is penetrates the atmosphere but the signal is attenuated by scattering and absorption [1, 2]. Although the measured flux at top of the atmosphere is nonlinearly related to the original emission of the surface, it is still positively correlated with the product of surface temperature and surface emissivity [3]. The surface temperature of Venus is relatively well constrained as a monotonous function of altitude. Emissivity at 1 micron depends strongly on surface composition, in particular abundance of mafic minerals [3]. Mapping the thermal emission of the surface of Venus therefore supplements radar data as it allows to infer relative variation of surface composition. Data Processing This study examines the correlation of VIRTIS images showing a signal of the surface with all known parameters that govern radiance and applies semi empirical relations to remove the respective influences. 1. Stray sunlight is removed by subtraction of a spectrum template scaled to fit radiance at 1.4 ¹m [2] 2. Limb darkening is accounted for using a linear phase function consistent with results of radiative transfer modeling [4]. 3. Cloud opacity is determined from 1.31 ¹m and applied to 1.02 ¹m while accounting for multiple reflections between lower atmosphere and clouds [3]. Result is brightness temperature of thermal emission below the cloud deck but above the lowest 20 km of the atmosphere. 4. Influence of surface temperature and lower atmosphere absorption is determined by correlation of VIRTIS declouded brightness temperature and Magellan Topography data [5]. To further reduce the influence of cloud contrast and increase the signal of the surface, all suitable VIRTIS observations are map projected and stacked to create a map of the southern hemisphere of Venus. Observations and Interpretation As expected from the small diurnal, latitudinal and seasonal variations of temperature in the atmosphere of Venus, the map created from all retrieved brightness temperatures is highly correlated with Magellan altimetry (fig. 1). Local deviation from the globally averaged brightness to topography relation can be either ascribed to surface emissivity or unexpected temperature variations. Temperature variations e.g. due to active volcanism are unlikely to be persistent over the time of observations. The stacked data is here interpreted in terms of surface emissivity variation by removal of the influence of topography (fig. 2). The emissivity variation found is correlated with geomorphological features established from Magellan radar images. It is generally lower at tessera terrain. This might indicate felsic surface composition of tessera highlands, e.g. anorthosite or granite [6, 7]. Creation of felsic crust is unlikely under current conditions. Some, but not all volcanic edifices show increased emissivity. Large lava flows in the Lada terra - Lavinia planitia region also show an increased thermal emission. In particular Cavilaca and Juturna fluctus, emanating from Boala corona (70S 0E) inside Quetzalpetlatl corona, are characterized by an increased IR flux. This might be consistent with the large scale extrusive volcanism of ultramafic composition considered by [8] in the context of chemical differentiation in the upper mantle. Discussion These observations are however highly sensitive to errors in the altimetry applied. A known systematic error in the Magellan dataset stemming from spacecraft orbit determination uncertainty is qualitatively confirmed by comparison with VIRTIS data (see longitude -120 in fig. 1 and 2. Tessera terrain is known to strongly scatter radar waves which might influences accuracy of altimetry. An quantitative analysis and search for small scale systematic errors is in progress during the submission of this abstract. References [1] Lecacheux, J., P. Drossart, P. Laques, F. Deladerriere, and F. Colas (1993), Detection of the surface of Venus at 1.0 micromet

Mueller, N.; Helbert, J.; Hashimoto, G. L.; Tsang, C. C. C.; Erard, S.; Piccioni, G.; Drossart, P.

2008-09-01

141

Waves in the Mesosphere of Venus as seen by the Venus Express Radio Science Experiment VeRa  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment (VeRa) has retrieved more than 700 profiles of the mesosphere and troposphere of Venus. These profiles cover a wide range of latitudes and local times, enabling study of atmospheric wave phenomena over a range spatial scales at altitudes of 40-90 km. In addition to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves, and turbulence play a significant role in the development and maintenance of atmospheric super-rotation. Small-scale temperature variations with vertical wavelengths of 4 km or less have wave amplitudes reaching TBD km in the stable atmosphere above the tropopause, in contrast with much weaker temperature perturbations observed in the middle cloud layer below. The strength of gravity waves increases with latitude in both hemispheres. The results suggest that convection at low latitudes and topographical forcing at high northern latitudes—possibly in combination with convection and/or Kelvin-Helmholtz instabilities—play key roles in the genesis of gravity waves. Further, thermal tides also play an important role in the mesosphere. Diurnal and semi-diurnal wave modes are observed at different latitudes and altitudes. The latitudinal and height dependence of the thermal tide modes will be investigated.

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

2013-10-01

142

Minor gaseous constituents and aerosols of the Venus mesosphere measured by SPICAV/SOIR on board Venus Express  

NASA Astrophysics Data System (ADS)

The SOIR instrument performs solar occultation measurements in the IR region (2.2 - 4.3 ?m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. A brief description of the instrument and its in- flight measured performances will be presented. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65 to 150 km) with an emphasis on vertical distribution of the gases. In particular, measurements of HDO, H2O, HCl, HF, CO and CO2 vertical profiles have been routinely performed. Temperature retrieval will be described and tentative results presented. Aerosols extinction profiles are also simultaneously retrieved from the SOIR spectra. Some results for selected orbits will be investigated and discussed. It will be shown that size distribution can be addressed but only when considering all three channels of the SPICAV/SOIR instrument.

Mahieux, A.; Drummond, R.; Wilquet, V.; Vandaele, A.; Fedorova, A.; Korablev, O.; Villard, E.; Montmessin, F.; Bertaux, J.

2009-05-01

143

Vertical structure of the Venus cloud top from the VeRa and VIRTIS observations onboard Venus Express  

NASA Astrophysics Data System (ADS)

Vertical structure of the Venus clouds is important for understanding of the radiative energy balance and the atmospheric dynamics. The structure of the cloud tops (75-65 km) is especially poorly investigated since it falls between the altitude ranges sounded by solar/ stellar occultation and that studied by descent probes. In this work we analyse the data from the radio science experiment VeRa and Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard Venus Express. Radio sounding is insensitive to the clouds and provides 'true' temperature structure, while thermal IR spectra depend on both temperature and aerosol distribution. Thus the joint analysis allows one to constrain vertical structure of aerosol at the cloud tops and its latitudinal variations. Using VeRa temperature profiles we fit VIRTIS spectra in the wavelength range of 4.5 - 5 ?m by tuning two parameters in the exponential model of aerosol vertical distribution: cloud top altitude of a unity optical thickness and scale height. We found that the cloud top altitude decreased from ~66 km in the middle and low latitudes to 62-64 km in the polar regions. The scale height showed correlated changes from 3-4 km to less than 1 km. Radiative transfer modelling showed that thermal IR spectrum is more sensitive to the cloud top altitude than to the aerosol scale height.

Lee, Yeon Joo; Titov, Dmitriy; Tellmann, Silvia; Piccioni, Giuseppe; Piccialli, Arianna; Pätzold, Martin; Drossart, Pierre

2010-05-01

144

Hypothesis Paper Venus, Mars, and the Ices on Mercury and the Moon: Astrobiological Implications and Proposed Mission Designs  

Microsoft Academic Search

Venus and Mars likely had liquid water bodies on their surface early in the Solar System his- tory. The surfaces of Venus and Mars are presently not a suitable habitat for life, but reser- voirs of liquid water remain in the atmosphere of Venus and the subsurface of Mars, and with it also the possibility of microbial life. Microbial organisms

DIRK SCHULZE-MAKUCH; JAMES M. DOHM; ALBERTO G. FAIRÉN; VICTOR R. BAKER; WOLFGANG FINK; ROBERT G. STROM

145

Mars Express: Mission and Science Goals (Invited)  

Microsoft Academic Search

The ESA Mars Express mission includes an orbiter spacecraft and a small lander module to be launched in 2003 by a Soyuz rocket. The scientific objectives of the orbiter spacecraft include: global high-resolution photogeology at 10 m resolution, global mineralogical mapping at 100 m resolution, global atmospheric circulation and mapping of the atmospheric composition, subsurface structure at km scale down

A. F. Chicarro

1999-01-01

146

Atmospheric studies with the Mars Express mission  

Microsoft Academic Search

The Mars Express mission, including an orbiter sp acecraft and a small Beagle-2 lander, will be launched in 2003 by a Soyuz rocket from Baikonur. In addition to a wide variety of scientific objectives concerning the global coverage of the planet for studies of the surface geology and mineralogy, subsurface structure, and atmospheric circulation, composition and escape, as well as

A. Chicarro

2002-01-01

147

Preliminary results of the solar flux radiometer experiment aboard the pioneer venus multiprobe mission.  

PubMed

The solar flux radiometer aboard the Pioneer Venus large probe operated successfully during its descent through the atmosphere of Venus. Upward, downward, and net fluxes from 0.4 to 1.0 micrometers were obtained at more than 390 levels between 185 millibars (at an altitude of approximately 61 kilometers) and the surface. Fluxes from 0.4 to 1.8 micrometers were also obtained between 185 millibars and about the level at which the pressure was 2 atmospheres. Data from 80 to 185 millibars should be available after additional decoding by the Deep Space Network. Upward and downward intensities in a narrower band from 0.59 to 0.66 micrometers were also obtained throughout the descent in order to constrain cloud properties. The measurements indicate three cloud regions above the 1.3-atmosphere level (at an altitude of approximately 49 kilometers) and a clear atmosphere beneath that level. At the 67 degrees solar zenith of the probe entry site, some 15 watts per square meter are absorbed at the surface by a dark ground, which implies that about 2 percent of the solar energy incident on the planet is absorbed at the ground. PMID:17833001

Tomasko, M G; Doose, L R; Palmer, J; Holmes, A; Wolfe, W; Castillo, N D; Smith, P H

1979-02-23

148

Electromagnetic waves observed by Venus Express at periapsis: Detection and analysis techniques  

NASA Astrophysics Data System (ADS)

The magnetometer on Venus Express was designed to be able to obtain 128 Hz samples of the magnetic field from two sensors in a gradiometer configuration. This mode is used around periapsis to determine whether the signals reported at low altitudes near 100 Hz, had the properties of electromagnetic waves generated by electric discharges in the Venus atmosphere. The lack of a magnetic cleanliness program and the shortness of the magnetometer boom make this a challenging measurement. Fortunately the signals are sufficiently strong that they can be easily resolved with rather straightforward analysis techniques.

Russell, C. T.; Zhang, T. L.; Strangeway, R. J.; Wei, H. Y.; Delva, M.; Magnes, W.

149

In-flight performance and calibration of SPICAV SOIR onboard Venus Express.  

PubMed

Solar occultation in the infrared, part of the Spectoscopy for Investigation of Characteristics of the Atmosphere of Venus (SPICAV) instrument onboard Venus Express, combines an echelle grating spectrometer with an acousto-optic tunable filter (AOTF). It performs solar occultation measurements in the IR region at high spectral resolution. The wavelength range probed allows a detailed chemical inventory of Venus's atmosphere above the cloud layer, highlighting the vertical distribution of gases. A general description of the instrument and its in-flight performance is given. Different calibrations and data corrections are investigated, in particular the dark current and thermal background, the nonlinearity and pixel-to-pixel variability of the detector, the sensitivity of the instrument, the AOTF properties, and the spectral calibration and resolution. PMID:18449289

Mahieux, Arnaud; Berkenbosch, Sophie; Clairquin, Roland; Fussen, Didier; Mateshvili, Nina; Neefs, Eddy; Nevejans, Dennis; Ristic, Bojan; Vandaele, Ann Carine; Wilquet, Valérie; Belyaev, Denis; Fedorova, Anna; Korablev, Oleg; Villard, Eric; Montmessin, Franck; Bertaux, Jean-Loup

2008-05-01

150

Observing the surface of Venus after VIRTIS on VEX: new concepts and laboratory work  

NASA Astrophysics Data System (ADS)

The permanent cloud cover of Venus prohibits observation of the surface with traditional imaging techniques most of the visible spectral range. Venus' CO2 atmosphere is transparent in small spectral windows near 1 micron. These windows have been successfully used from ground observers, during the flyby of the Galileo mission at Jupiter and most recently by the VMC and VIRTIS instruments on the ESA VenusExpress spacecraft. Studying surface composition based on only a small number of spectral channels in a very narrow spectral range is very challenging. The task is further complicated by the fact that Venus has an average surface temperature of 460°C. Spectral signatures of minerals are affected by temperature and therefore a comparison with mineral spectra obtained at room temperature can be misleading. We report here about first laboratory measurements of Venus analog materials obtained at Venus surface temperatures. The spectral signatures show clear temperature dependence. Based on the experience gained from using the VIRTIS instrument to observe the surface of Venus combined with the high temperature laboratory experiments we have developed the concept for the Venus Emissivity Mapper (VEM). VEM is a multi-spectral mapper dedicated to the task of multi-spectral mapping the surface of Venus. VEM imposes minimal requirements on the spacecraft and mission design and can therefore added to any future Venus mission. Ideally the VEM instrument is combined with a high resolution radar mapper to provide accurate topographic data.

Helbert, Jörn; Müller, Nils; Maturilli, Alessandro; Nadalini, Riccardo; Smrekar, Suzanne; D'Incecco, Piero; D'Amore, Mario

2013-09-01

151

Magellan: The Unveiling of Venus.  

National Technical Information Service (NTIS)

In the late 1970s and early 1980s, the United States and the Soviet Union sent the Pioneer Venus and Venera spacecraft, respectively, to study Venus more closely and to image its surface with radar. These missions have answered many questions about Venus,...

1989-01-01

152

Stellar Occultation of the Ultraviolet Nitric Oxide Nightglow with SPICAV on Board Venus Express  

NASA Astrophysics Data System (ADS)

Ultraviolet nightglow have been detected on Venus for the first time by Barth and al., in 1968, from mariner 5, then identified like to be nitric oxide nightglow by Feldmann and al., and by Stewart and Barth, in 1979, with Pioneer. SPICAV (SPectroscopy for the Characteristics of the Atmosphere of Venus), currently in fly on board Venus Express, also see them. We descibe here a direct model allowed to reproduce this nitric oxide nightglows. It is a first approach in a better understanding of the dynamic phenomena of the venusian thermosphere. This nightglows are due to radiative recombinaison process. On the dayside of the planet, we have nitrogen and oxygen atoms created by UV disssociation of N2, CO2 and O2. This atoms are transported on the nightside, where they recombine themselves and emit an ultraviolet radiation. Thus NO nightglow are tracers of the descending branch of the solar, anti-solar circulation in the thermosphere of Venus. The model using geometric parameters who are fixed for each observation, simulate the travel of a ray of light inside the spectrometer and reproduce the spectra of nightglows. We model a nitric oxide layer, controled by his borderline altitudes and his brightness. Wa have to adjust the parameters of the layer to fit the data. The results, in the making, already are very supporting. Thus, fit the ultraviolet nitric oxide nightglows, as a tracer of the venusian thermospheric circulation, will lead to a better understanding of the dynamic phenomena in the same region of this atmosphere.

Royer, E.; Montmessin, F.; Bertaux, J.

2008-12-01

153

Mars Express—ESA's first mission to planet Mars  

Microsoft Academic Search

ESA’ Mars Express mission is a fully approved and funded project which has entered its spacecraft development (i.e. hardware) phase early January 2000. It is the first of ESA's new ‘F’ (flexible) missions which are based on a new implementation scenario to maintain overall mission cost below a stringent cost cap. The key features of an F-mission are streamlined management,

R. Schmidt

2003-01-01

154

Ionospheric photoelectrons at Venus: Initial observations by ASPERA-4 ELS  

Microsoft Academic Search

We report the detection of electrons due to photo-ionization of atomic oxygen and carbon dioxide in the Venus atmosphere by solar helium 30.4nm photons. The detection was by the Analyzer of Space Plasma and Energetic Atoms (ASPERA-4) Electron Spectrometer (ELS) on the Venus Express (VEx) European Space Agency (ESA) mission. Characteristic peaks in energy for such photoelectrons have been predicted

A. J. Coates; R. A. Frahm; D. R. Linder; D. O. Kataria; Y. Soobiah; G. Collinson; J. R. Sharber; J. D. Winningham; S. J. Jeffers; S. Barabash; J.-A. Sauvaud; R. Lundin; M. Holmström; Y. Futaana; M. Yamauchi; A. Grigoriev; H. Andersson; H. Gunell; A. Fedorov; J.-J. Thocaven; T. L. Zhang; W. Baumjohann; E. Kallio; H. Koskinen; J. U. Kozyra; M. W. Liemohn; Y. Ma; A. Galli; P. Wurz; P. Bochsler; D. Brain; E. C. Roelof; P. Brandt; N. Krupp; J. Woch; M. Fraenz; E. Dubinin; S. McKenna-Lawlor; S. Orsini; R. Cerulli-Irelli; A. Mura; A. Milillo; M. Maggi; C. C. Curtis; B. R. Sandel; K. C. Hsieh; K. Szego; A. Asamura; M. Grande

2008-01-01

155

Thermal structure of Venusian nighttime mesosphere as observed by VIRTIS-Venus Express  

Microsoft Academic Search

The mapping IR channel of the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS-M) on board the Venus Express spacecraft observes the CO2 band at 4.3 ?m at a spectral resolution adequate to retrieve the atmospheric temperature profiles in the 65–96 km altitude range. Observations acquired in the period June 2006 to July 2008 were used to derive average temperature fields

D. Grassi; A. Migliorini; L. Montabone; S. Lebonnois; A. Cardesìn-Moinelo; G. Piccioni; P. Drossart; L. V. Zasova

2010-01-01

156

Robotic exploration of the surface and atmosphere of Venus  

Microsoft Academic Search

Venus, the “greenhouse planet,” is a scientifically fascinating place. The US National Academies of Sciences listed a Venus surface in situ explorer as one of the highest priority planetary science missions. A mission concept for a robotic mission to study the surface and atmosphere of Venus has been designed. The mission includes both surface robots, designed with an operational lifetime

Geoffrey A. Landis

2006-01-01

157

Recent results obtained by the SOIR instrument on board Venus Express: Vertical profiles of carbon species  

NASA Astrophysics Data System (ADS)

The SOIR instrument (Solar Occultation in the IR) performs solar occultation measurements in the IR region (2.2 - 4.3 ?m) at a resolution of 0.12 cm-1, the highest on board Venus Express. It combines an echelle spectrometer and an AOTF (Acousto-Optical Tunable Filter) for the order selection. The wavelength range probed by SOIR allows for a detailed chemical inventory of the Venus atmosphere at the terminators in the upper mesosphere and lower thermosphere (80 to 180 km) with an emphasis on vertical distribution of the gases. In particular, measurements of CO2 and CO density and rotational temperature vertical profiles have been routinely performed. Comparisons with the hydrostatic equilibrium allowed us to derive information concerning the dynamical behavior of the atmosphere at the terminators. The approach as well as some results will be described.

Mahieux, A.; Robert, S.; Wilquet, V.; Drummond, R.; Vandaele, A. C.; Bertaux, J. L.; Spicav/Soir Team

2011-10-01

158

TECHNOLOGIES FOR FUTURE VENUS EXPLORATION  

Microsoft Academic Search

The purpose of this white paper is to provide an overview to the NRC Decadal Survey Inner Planets Sub-Panel on key technologies required for future Venus exploration missions. It covers both heritage technologies and identifies new technologies to enable future missions in all three mission classes. The technologies will focus on mission enabling and enhancing capabilities for in situ missions,

Tibor Balint; James Cutts; Mark Bullock; James Garvin; Stephen Gorevan; Jeffery Hall; Peter Hughes; Gary Hunter; Satish Khanna; Elizabeth Kolawa; Viktor Kerzhanovich; Ethiraj Venkatapathy

159

A solar storm observed from the Sun to Venus using the STEREO, Venus Express, and MESSENGER spacecraft  

NASA Astrophysics Data System (ADS)

The suite of SECCHI optical imaging instruments on the STEREO-A spacecraft is used to track a solar storm, consisting of several coronal mass ejections (CMEs) and other coronal loops, as it propagates from the Sun into the heliosphere during May 2007. The 3-D propagation path of the largest interplanetary CME (ICME) is determined from the observations made by the SECCHI Heliospheric Imager (HI) on STEREO-A (HI-1/2A). Two parts of the CME are tracked through the SECCHI images, a bright loop and a V-shaped feature located at the rear of the event. We show that these two structures could be the result of line-of-sight integration of the light scattered by electrons located on a single flux rope. In addition to being imaged by HI, the CME is observed simultaneously by the plasma and magnetic field experiments on the Venus Express and MESSENGER spacecraft. The imaged loop and V-shaped structure bound, as expected, the flux rope observed in situ. The SECCHI images reveal that the leading loop-like structure propagated faster than the V-shaped structure, and a decrease in in situ CME speed occurred during the passage of the flux rope. We interpret this as the result of the continuous radial expansion of the flux rope as it progressed outward through the interplanetary medium. An expansion speed in the radial direction of ˜30 km s-1 is obtained directly from the SECCHI-HI images and is in agreement with the difference in speed of the two structures observed in situ. This paper shows that the flux rope location can be determined from white light images, which could have important space weather applications.

Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Savani, N. P.; Sheeley, N. R.; Thernisien, A.; Zhang, T.-L.; Howard, R. A.; Anderson, B.; Carr, C. M.; Tsang, S.; Lockwood, M.; Davis, C. J.; Harrison, R. A.; Bewsher, D.; Fränz, M.; Crothers, S. R.; Eyles, C. J.; Brown, D. S.; Whittaker, I.; Hapgood, M.; Coates, A. J.; Jones, G. H.; Grande, M.; Frahm, R. A.; Winningham, J. D.

2009-07-01

160

Radio science investigations by VeRa onboard the Venus Express spacecraft  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13 cm ("X"- and "S"-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time, and polarization of the received signals. Simultaneous, coherent measurements at the two wavelengths allow separation of dispersive media effects from classical Doppler shift. VeRa science objectives include the following: Determination of neutral atmospheric structure from the cloud deck (approximately 40 km altitude) to 100 km altitude from vertical profiles of neutral mass density, temperature, and pressure as a function of local time and season. Within the atmospheric structure, search for, and if detected, study of the vertical structure of localized buoyancy waves, and the presence and properties of planetary waves. Study of the H 2SO 4 vapor absorbing layer in the atmosphere by variations in signal intensity and application of this information to tracing atmospheric motions. Scintillation effects caused by radio wave diffraction within the atmosphere can also provide information on small-scale atmospheric turbulence. Investigation of ionospheric structure from approximately 80 km to the ionopause (<600 km), allowing study of the interaction between solar wind plasma and the Venus atmosphere. Observation of forward-scattered surface echoes obliquely reflected from selected high-elevation targets with anomalous radar properties (such as Maxwell Montes). More generally, such bistatic radar measurements provide information on the roughness and density of the surface material on scales of centimeters to meters. Detection of gravity anomalies, thereby providing insight into the properties of the Venus crust and lithosphere. Measurement of the Doppler shift, propagation time, and frequency fluctuations along the interplanetary ray path, especially during periods of superior conjunction, thus enabling investigation of dynamical processes in the solar corona.

Häusler, B.; Pätzold, M.; Tyler, G. L.; Simpson, R. A.; Bird, M. K.; Dehant, V.; Barriot, J.-P.; Eidel, W.; Mattei, R.; Remus, S.; Selle, J.; Tellmann, S.; Imamura, T.

2006-11-01

161

The Atmosphere of Venus: Current Knowledge and Future Investigations  

NASA Astrophysics Data System (ADS)

As the Earth's nearest planetary neighbour, Venus has been studied by ground-based observers for centuries, and has been visited by more than 20 spacecraft. However, in the last decade and a half Venus research has been relatively neglected, despite the fact that a great many major questions about its atmosphere, surface and interior remain unanswered. Several of these questions relate to the unique position of Venus as the Earth's near twin, in terms of size, density and proximity to the Sun, which led early astronomers to expect an Earth-like environment on the planet, possibly one fit for human habitation, and perhaps even the seat of indigenous life. The picture which has emerged from missions to the planet is quite different, raising questions about the evolution and stability of terrestrial planet environments that are both intriguing and possibly of practical relevance to global change problems on the Earth. This chapter reviews the scientific issues, and goes on to describe two new missions to Venus, the European Venus Express and the Japanese Planet-C orbiters, which will take place in the next few years to address some of them in depth. Other questions will remain unanswered, and further missions will be required, including landing on Venus and sample return.

Titov, Dmitri V.; Svedhem, Hakan; Taylor, Fred W.

162

New measurements of Venus' dayside winds with CFHT/ESPaDOnS  

NASA Astrophysics Data System (ADS)

A renewed interest in measuring Venus' winds at cloud top level from the ground has emerged in the course of the Venus Express mission. In orbit since 2006, Venus Express characterizes the atmospheric circulation at 70 km through cloud tracking with combined VIRTIS-M and VMC observations. Our comparative study is based on observations from 2009 and 2011 obtained with the 3.60 m Canada- France-Hawaii telescope (CFHT) and the Visible Spectrograph ESPaDOnS. We measure the winds using Doppler shifted solar lines and compare with previous measurements (Venus Express, Galileo, VLT/UVES. Our main purpose is to provide direct wind measurements in the northern and southern hemispheres from visible Fraunhofer lines scattered at Venus' cloud tops. This will also contribute for cross validation of the cloud tracking method used in many orbiter-based measurements.

Machado, P.; Widemann, T.; Luz, D.; Peralta, J.; Rossi, L.

2012-09-01

163

First ever in situ observations of Venus' polar upper atmosphere density using the tracking data of the Venus Express Atmospheric Drag Experiment (VExADE)  

NASA Astrophysics Data System (ADS)

On its highly elliptical 24 h orbit around Venus, the Venus Express (VEX) spacecraft briefly reaches a periapsis altitude of nominally 250 km. Recently, however, dedicated and intense radio tracking campaigns have taken place in August 2008, October 2009, February and April 2010, for which the periapsis altitude was lowered to the 186-176 km altitude range in order to be able to probe the upper atmosphere of Venus above the North Pole for the first time ever in situ. As the spacecraft experiences atmospheric drag, its trajectory is measurably perturbed during the periapsis pass, allowing us to infer total atmospheric mass density at the periapsis altitude. A Precise Orbit Determination (POD) of the VEX motion is performed through an iterative least-squares fitting process to the Doppler tracking data, acquired by the VEX radioscience experiment (VeRa). The drag acceleration is modelled using an initial atmospheric density model (VTS3 model, Hedin, A.E., Niemann, H.B., Kasprzak, W.T., Seiff, A. [1983]. J. Geophys. Res. 88, 73-83). A scale factor of the drag acceleration is estimated for each periapsis pass, which scales Hedin's density model in order to best fit the radio tracking data. Reliable density scale factors have been obtained for 10 passes mainly from the second (October 2009) and third (April 2010) VExADE campaigns, which indicate a lower density by a factor of about 1.8 than Hedin's model predicts. These first ever in situ polar density measurements at solar minimum have allowed us to construct a diffusive equilibrium density model for Venus' thermosphere, constrained in the lower thermosphere primarily by SPICAV-SOIR measurements and above 175 km by the VExADE drag measurements (Müller-Wodarg et al., in preparation). The preliminary results of the VExADE campaigns show that it is possible to obtain with the POD technique reliable estimates of Venus' upper atmosphere densities at an altitude of around 175 km. Future VExADE campaigns will benefit from the planned further lowering of VEX pericenter altitude to below 170 km.

Rosenblatt, P.; Bruinsma, S. L.; Müller-Wodarg, I. C. F.; Häusler, B.; Svedhem, H.; Marty, J. C.

2012-02-01

164

Mars Express Science Results and Goals for the Extended Mission  

Microsoft Academic Search

The ESA Mars Express mission was successfully launched on 02 June 2003 from Baikonur, Kazakhstan, onboard a Russian Soyuz rocket with a Fregat upper stage. The mission comprises an orbiter spacecraft, which has been placed in a polar martian orbit, and the small Beagle-2 lander, due to land in Isidis Planitia but whose fate remains uncertain. In addition to global

A. F. Chicarro

2006-01-01

165

Beagle 2: the astrobiology lander on ESA's Mars Express mission  

Microsoft Academic Search

Due for launch in 2003 as part of the Mars Express mission, the primary goal of the Beagle 2 lander is the detection of extinct or extant life on Mars. Atmospheric studies, analysis of subsurface material and regime, and the first attempt at in-situ radiometric dating of rocks on another planet make Beagle 2 unique among planetary mission. The lander

M. R. Sims; C. T. Pillinger

2002-01-01

166

Thermosphere and Ionosphere of Venus.  

National Technical Information Service (NTIS)

Our knowledge of the upper atmosphere and ionosphere of Venus and its interaction with the solar wind has advanced dramatically over the last decade, largely due to the data obtained during the Pioneer Venus mission and to the theoretical work that was mo...

T. E. Cravens

1992-01-01

167

Venus lives  

Microsoft Academic Search

Observational evidence which supports the contention that Venus is a volcanically and tectonically active planet is discussed. It is argued that, although there are no observations to date that would prove that Venus has been volcanically active during the last decade, planetological studies presented evidence for youthful volcanic mountains on Venus: the surface of the northern quarter of Venus is

C. A. Wood; P. W. Francis

1988-01-01

168

Limb imaging of the Venus O2 visible nightglow with the Venus Monitoring Camera  

NASA Astrophysics Data System (ADS)

investigated the Venus O2 visible nightglow with imagery from the Venus Monitoring Camera on Venus Express. Drawing from data collected between April 2007 and January 2011, we study the global distribution of this emission, discovered in the late 1970s by the Venera 9 and 10 missions. The inferred limb-viewing intensities are on the order of 150 kR at the lower latitudes and seem to drop somewhat toward the poles. The emission is generally stable, although there are episodes when the intensities rise up to 500 kR. We compare a set of Venus Monitoring Camera observations with coincident measurements of the O2 nightglow at 1.27 µm made with the Visible and Infrared Thermal Imaging Spectrometer, also on Venus Express. From the evidence gathered in this and past works, we suggest a direct correlation between the instantaneous emissions from the two O2 nightglow systems. Possible implications regarding the uncertain origin of the atomic oxygen green line at 557.7 nm are noted.

GarcíA MuñOz, A.; Hueso, R.; SáNchez-Lavega, A.; Markiewicz, W. J.; Titov, D. V.; Witasse, O.; Opitz, A.

2013-06-01

169

Venus: an errant twin  

NASA Astrophysics Data System (ADS)

A examination of Venus written for the nonscientist is presented. The history of major discoveries about Venus is retold, outlining some of the great controversies surrounding them. All the exploratory missions to the planet are described, from American Mariner flights of the 1960s to recent Soviet flights. The resulting revelations about the volcanic eruptions on Venus and the disappearance of its ancient oceans are addressed. The reasons why Venus became a planet hostile to life are discussed, and the ways it might be engineered to become more hospitable to life are considered. Finally, the possibility that the earth might someday be pushed into a Venuslike 'runaway greenhouse effect' that would make it equally unhospitable to life is reviewed.

Burgess, E.

170

Investigation of the application of aerobot technology at Venus  

Microsoft Academic Search

Robotic aerovehicles, or aerobots, can perform long duration detailed studies of planetary surfaces and atmospheres in three dimensions. Here we explore specific abilities of an aerobot mission to Venus using two concept missions: the Balloon Experiment at Venus (BEV) and the Venus Flyer Robot (VFR). Oscillating between 40 and 60km altitude, the BEV is designed to collect atmospheric data over

M. S. Gilmore; G. C. Collins; L. S. Crumpler; J. A. Cutts; A. V. deCharon; J. W. Head; III; K. T. Nock; M. Parry; R. A. Yingst

2005-01-01

171

Venus Radar Mapper orbit accuracy analysis  

Microsoft Academic Search

Spacecraft orbital accuracies during the mapping phase of the Venus Radar Mapper Mission are the subject of this paper. The analysis presented describes the navigational strategy for the prime mission in support of mapping the planet Venus using a spacecraft deployed Synthetic Aperture Radar. Achievable orbital accuracies are shown to be limited by accuracy of interferometric data to be used.

S. N. Mohan; P. B. Esposito

1984-01-01

172

Nightside atomic oxygen and nitrogen densities deduced from Venus and Mars Express airglow observations  

NASA Astrophysics Data System (ADS)

Spectral observations of the O2 (1 delta g) infrared nightglow and of the ultraviolet nitric oxide bands have been obtained respectively with VIRTIS and SPICAV on board Venus Express. These observations were collected in the northern hemisphere using the tangent limb mode, where the altitude distribution of the airglow is accurately determined. The O2(1 delta g) emission results from three-body recombination of O atoms produced on the day side and transported to the night side by the global solar to antisolar circulation. It is variable in brightness and shows a peak between 95 and 100 km. The NO airglow is excited by N+O radiative recombination, with the N(4S) atoms produced by photodissociation of N2 and it shows a maximum intensity about 10- 15 km higher . We use the observed brightness and altitude of theses two emissions in conjunction with a chemical-diffusive model to determine the concentration of O and N atoms on Venus' night side and its variability. Typical O densities at low and mid-latitudes are about 1-5x1011 cm-3 at 100 km, while the N(4S) density is about 2 orders of magnitude smaller. These values will be compared with earlier models such as VIRA. It is shown that airglow observation is a valuable tool to remotely sense the distribution of these two constituents and improve atmospheric models. Similarly, SPICAM observations of the NO nightglow provide constraints on the [N]x[O] density product in the Martian atmosphere between 50 and 75 km, which constrain models of the night side composition in this region.

Gérard, J.-. C.; Saglam, A.; Cox, C.; Drossart, P.; Piccioni, G.; Bertaux, J.-L.

2007-08-01

173

Venus Express is a step toward the surface of the planet  

Microsoft Academic Search

The Venus atmosphere makes it extremely challenging to mimic the steps of the successful Mars Exploration Program, namely orbital reconnaissance, followed by targeted in situ landers, rovers and sample return. Thus, many fundamental questions about the Venus surface remain unanswered, the most important of which is composition. We must measure the composition of the crust to constrain the thermal, volatile

M. S. Gilmore

2005-01-01

174

Venus mapper resolution  

Microsoft Academic Search

NASA program managers for the Venus Radar Mapper (VRM) mission have decided to make improvements to the spacecraft's Synthetic Aperture Radar (SAR) system that will increase its mapping resolution by one and a half times over the original design. The changes, including a doubling of the system's range bandwidth, will add a total of about $5 million to a project

Tony Reichhardt

1984-01-01

175

Venus and Mars Obstacles in the Solar Wind  

NASA Astrophysics Data System (ADS)

Comparisons of the magnetosheaths of Venus and Mars contrast the relative simplicity of the Venus solar wind interaction and the ``Jekyll and Hyde" nature of the Mars interaction. Magnetometer observations from Mars Global Surveyor during the elliptical science phasing orbits and Pioneer Venus Orbiter in its normally elliptical orbit are compared, with various models used to compensate for the different near-polar periapsis of MGS and near-equator periapsis of PVO. Gasdynamic or MHD fluid models of flow around a conducting sphere provide a remarkably good desciption of the Venus case, and the Mars case when the strong Martian crustal magnetic anomalies are in the flow wake. In the case of Venus, large magnetosheath field fluctuations can be reliably tied to occurrence of a subsolar quasiparallel bow shock resulting from a small interplanetary field cone angle (angle between flow and field) upstream. At Mars one must also contend with such large fluctuations from the bow shock, but also from unstable solar wind proton distributions due to finite ion gyroradius effects, and from the complicated obstacle presented to the solar wind when the crustal magnetic anomalies are on the ram face or terminator. We attempt to distinguish between these factors at Mars, which are important for interpretation of the upcoming NOZOMI and Mars Express mission measurements. The results also provide more insights into a uniquely complex type of solar system solar wind interaction involving crustal fields akin to the Moon's, combined with a Venus-like ionospheric obstacle.

Luhmann, J. G.; Mitchell, D. L.; Acuna, M. H.; Russell, C. T.; Brecht, S. H.; Lyon, J. G.

2000-10-01

176

Pioneer Venus: Report of a Study by the Science Steering Group, June 1972.  

National Technical Information Service (NTIS)

The 1976/77 multiple probe mission of the Pioneer Venus spacecraft is discussed, along with the 1978 and 1980 missions. Various questions about Venus are answered; velocities and temperatures expected in the atmosphere, atmospheric chemistry, magnetic mea...

1974-01-01

177

Radar observation of Venus' terrestrial analogues using TecSAR X-band SAR  

NASA Astrophysics Data System (ADS)

Venus is shrouded in a dense CO2 atmosphere that prevents us from viewing the surface in visible light or with optronic sensors. Long wavelengths are required to 'see' through the dense atmosphere. In the early 1990s, the S-band synthetic aperture radar of the Magellan spacecraft acquired images of a variety of surface features on Venus, including morphologies attributed to wind processes. These include sand dunes, wind-sculpted hills (yardangs), and almost 6000 wind streaks. These aeolian landscapes were formed and shaped by near surface atmospheric circulation and local winds. These can serve as local markers, each providing an integrated wind direction. Since the Magellan mission, there were no missions to Venus until the Venus Express Mission of 2005 to examine the upper atmosphere. The future will probably include high-resolution SAR images of Venus. This poster will demonstrate high resolution SAR images in X-band from the TecSAR sensor launched by Israel in 2008. Observations of wind streaks, dunes and impact craters in desert areas will show the wealth of information that is extracted from high-res X-band data. Detailed images of Aurounga impact crater in Chad, Kelso dunes, California and Pisgah lava flow show immense detail of the morphologies associated with these features. These are compared with Magellan images of sites on Venus and SRL data in C and L-bands. The X-band provides extremely high resolution and resembles optical data much more than the longer wavelengths.

Blumberg, D. G.

2012-04-01

178

The characteristics of the O2 Herzberg II and Chamberlain bands observed with VIRTIS/Venus Express  

NASA Astrophysics Data System (ADS)

The oxygen Venus nightglow emissions in the visible spectral range have been known since the early observations from the Venera spacecraft. Recent observations with the VIRTIS instrument on board Venus Express allowed us to re-examine the Herzberg II system of O2 and to further study its vertical distribution, in particular the (0-?? with ?? = 7-13) bands. The present work describes the vertical profile of the observed bands and relative intensities from limb observation data. The wavelength-integrated intensities of the Herzberg II bands, with ?? = 7-11, are inferred from the recorded spectra. The resulting values lie in the range of 84-116 kR at the altitudes of maximum intensity, which are found to lie in the range of 93-98 km. Three bands of the Chamberlain system, centered at 560 nm, 605 nm, and 657 nm have been identified as well. Their emission peak is located at about 100 km, 4 km higher than the Herzberg II bands. For the first time, the O2 nightglow emissions were investigated simultaneously in the visible and in the IR spectral range, showing a good agreement between the peak position for the Herzberg II and the O(a?-X?g-) bands. An airglow model, proposed by Gérard et al. (Gérard, J.C., Soret, L., Migliorini, A., Piccioni, G. [2013]. Icarus.) starting from realistic O and CO2 vertical distributions derived from Venus-Express observations, allows reproduction of the observed profiles for the three O2 systems.

Migliorini, A.; Piccioni, G.; Gérard, J. C.; Soret, L.; Slanger, T. G.; Politi, R.; Snels, M.; Drossart, P.; Nuccilli, F.

2013-03-01

179

Orbital Express mission operations planning and resource management using ASPEN  

NASA Astrophysics Data System (ADS)

As satellite equipment and mission operations become more costly, the drive to keep working equipment running with less labor-power rises. Demonstrating the feasibility of autonomous satellite servicing was the main goal behind the Orbital Express (OE) mission. Like a tow-truck delivering gas to a car on the road, the "servicing" satellite of OE had to find the "client" from several kilometers away, connect directly to the client, and transfer fluid (or a battery) autonomously, while on earth-orbit. The mission met 100% of its success criteria, and proved that autonomous satellite servicing is now a reality for space operations. Planning the satellite mission operations for OE required the ability to create a plan which could be executed autonomously over variable conditions. As the constraints for execution could change weekly, daily, and even hourly, the tools used create the mission execution plans needed to be flexible and adaptable to many different kinds of changes. At the same time, the hard constraints of the plans needed to be maintained and satisfied. The Automated Scheduling and Planning Environment (ASPEN) tool, developed at the Jet Propulsion Laboratory, was used to create the schedule of events in each daily plan for the two satellites of the OE mission. This paper presents an introduction to the ASPEN tool, an overview of the constraints of the OE domain, the variable conditions that were presented within the mission, and the solution to operations that ASPEN provided. ASPEN has been used in several other domains, including research rovers, Deep Space Network scheduling research, and in flight operations for the NASA's Earth Observing One mission's EO1 satellite. Related work is discussed, as are the future of ASPEN and the future of autonomous satellite servicing.

Chouinard, Caroline; Knight, Russell; Jones, Grailing; Tran, Daniel

2008-05-01

180

Venus within ESA probe reach  

NASA Astrophysics Data System (ADS)

Venus Express mission controllers at the ESA Space Operations Centre (ESOC) in Darmstadt, Germany are making intensive preparations for orbit insertion. This comprises a series of telecommands, engine burns and manoeuvres designed to slow the spacecraft down from a velocity of 29000 km per hour relative to Venus, just before the first burn, to an entry velocity some 15% slower, allowing the probe to be captured into orbit around the planet. The spacecraft will have to ignite its main engine for 50 minutes in order to achieve deceleration and place itself into a highly elliptical orbit around the planet. Most of its 570 kg of onboard propellant will be used for this manoeuvre. The spacecraft’s solar arrays will be positioned so as to reduce the possibility of excessive mechanical load during engine ignition. Over the subsequent days, a series of additional burns will be done to lower the orbit apocentre and to control the pericentre. The aim is to end up in a 24-hour orbit around Venus early in May. The Venus orbit injection operations can be followed live at ESA establishments, with ESOC acting as focal point of interest (see attached programme). In all establishments, ESA specialists will be on hand for interviews. ESA TV will cover this event live from ESOC in Darmstadt. The live transmission will be carried free-to-air. For broadcasters, complete details of the various satellite feeds are listed at http://television.esa.int. The event will be covered on the web at venus.esa.int. The website will feature regular updates, including video coverage of the press conference and podcast from the control room at ESA’s Operations Centre. Media representatives wishing to follow the event at one of the ESA establishments listed below are requested to fill in the attached registration form and fax it back to the place of their choice. For further information, please contact: ESA Media Relations Division Tel : +33(0)1.53.69.7155 Fax: +33(0)1.53.69.7690 Venus Express Orbit Insertion - Tuesday 11 April 2006 ESA/ESOC, Robert Bosch Strasse, 5 - Darmstadt (Germany) PROGRAMME 07:30 - Doors open 08:45 - Start of local event, welcome addresses 09:10 - ESA TV live from Mission Control Room (MCR) starts 09:17 - Engine burn sequence starts 09:45 - Occultation of spacecraft by Venus starts 09:55 - Occultation ends 10:07 - Main engine burn ends 10:20 - Address by Jean-Jacques Dordain, ESA’s Director General, and other officials Break and buffet Interview opportunities 11:30-12:15 - Press Conference Jean-Jacques Dordain, Director General, ESA Prof. David Southwood, Director of Science, ESA Gaele Winters, Director of Operations and Infrastructure, ESA Manfred Warhaut, Flight Operations Director, ESA Håkan Svedhem, Venus Express Project Scientist, ESA Don McCoy, Venus Express Project Manager, ESA 13:15 - End of event at ESOC ACCREDITATION REQUEST FORM Venus Express Orbit Insertion - ESA/ESOC Darmstadt - 11 April 2006 First name:___________________ Surname:_____________________ Media:______________________________________________________ Address: ___________________________________________________ ____________________________________________________________ Tel:_______________________ Fax: ___________________________ Mobile :___________________ E-mail: ________________________ I will be attending the Venus Express Orbit Insertion event at the following site: [ ] Germany Location: ESA/ESOC Address: Robert Bosch Strasse 5, Darmstadt, Germany Opening hours: 07:30 - 13:00 Contact: Jocelyne Landeau-Constantin, Tel: +49.6151.902.696 - Fax: +49.6151.902.961 [ ] France Location: ESA HQ Address: 8/10, rue Mario Nikis - Paris 15, France Opening hours: 08:00 - 13:00 Contact: Anne-Marie Remondin - Tel: +33(0)1.53.69.7155 - fax: +33(0)1.53.69.7690 [ ] The Netherlands Location: Newton Room, ESA/ESTEC Address: Keplerlaan 1, Noordwijk, The Netherlands Opening hours: 08:30 - 12:30 Contact: Michel van Baal, tel. + 31 71 565 3006, fax + 31 71 565 5728 [ ] Italy Location: ESA/ESRIN Address: Via Galileo Galilei, Frascati (Rome), Italy Opening hours: 07:00 - 14:

2006-03-01

181

Atmospheric, Ionospheric, Surface and Radio Propagation Studies with the Radio Science Experiment VeRa onboard Venus Express  

NASA Astrophysics Data System (ADS)

The Venus Radio Science experiment (VeRa) onboard the proposed Venus Express Orbiter will make use of the spacecraft radio carrier signals at X/S-band and an ultrastable oscillator reference frequency source (USO, Allan deviation 10 -13 ) integrated into the onboard transponder system. VeRa will perform : radio sounding of the Venusian ionosphere from 80 km up to the ionopause (300km to 600 km), radio sounding of the neutral atmosphere from the cloud deck (35km to 40 km) to 100 km altitude, measurements of dielectric constant and roughness of the Venusian surface, studies of the propagation of radio waves in the inner solar system. We shall discuss the experimental methods (spacecraft occultation and bistatic radar) and conclude on the achievable accuracies and sensitivities. We shall indicate where improvements in comparison to the Pioneer Venus and Magellan observations can be expected and examine VeRa`s contribution to the understanding of plasmaphysical processes in the solar wind and planetary ionospheric environment. Effects of the solar coronal plasma and the gravitational field of the Sun on the observables (Doppler, group delay) will also be addressed.

Haeusler, B.; Paetzold, M.; Bird, M.; Treumann, R.; Simpson, R.; Hinson, D.

182

Small Scale Waves on Venus at High Latitudes  

NASA Astrophysics Data System (ADS)

On many occasions, the Venus Monitoring Camera (VMC) on Venus Express has observed several small scale waves or wave trains in high northern latitudes ( 70 to 75°) of Venus for the first time. Such waves were not detected earlier due to a combination of spatial resolution, observed region and duration. Wave trains with different characteristics have been seen at all four wavelengths used by the VMC (centered at 365, 513. 935 and 1010nm with 40, 50, 70 and 20 nm) in and are consistently in the same area on multiple consecutive orbits. Many are similar in appearance to ripples with wavelengths 5 to10 km with extents of some tens of km while others appear as thin straight lines, similar to the Circum Equatorial Belts (CEB) seen previously from Mariner 10 and Pioneer Venus missions at low latitudes. These are distinct from the fine scale transverse waves on the spiral bands on Venus which have been observed by both the VMC and the Visible Infrared Thermal Imaging Spectrometer (VIRTIS). In appearance and perhaps origins, these wave trains appear to be similar to gravity waves observed on Earth, particularly in the airglow images. Their detection on Venus confirms the existence of an atmospheric layer with a very stable lapse rate seen in the thermal structure data at an altitude of 65 to 67 km. The triggering mechanism for these waves could be horizontal or vertical wind shear. The contribution of these waves to momentum transport is not known, but likely is insignificant. However, this could be an observational limitation due to the combination of the eccentric orbit of Venus Express and the camera capabilities. This work has been made possible from a NASA Participating Scientist Grant NNG06GC68G and with the support provided by the VMC Team.

Limaye, Sanjay; Markiewicz, W. J.; Moissl, R.; Titov, D.

2008-09-01

183

On ion escape from Venus  

NASA Astrophysics Data System (ADS)

This doctoral thesis is about the solar wind influence on the atmosphere of the planet Venus. A numerical plasma simulation model was developed for the interaction between Venus and the solar wind to study the erosion of charged particles from the Venus upper atmosphere. The developed model is a hybrid simulation where ions are treated as particles and electrons are modelled as a fluid. The simulation was used to study the solar wind induced ion escape from Venus as observed by the European Space Agency's Venus Express and NASA's Pioneer Venus Orbiter spacecraft. Especially, observations made by the ASPERA-4 particle instrument onboard Venus Express were studied. The thesis consists of an introductory part and four peer-reviewed articles published in scientific journals. In the introduction Venus is presented as one of the terrestrial planets in the Solar System and the main findings of the work are discussed within the wider context of planetary physics. Venus is the closest neighbouring planet to the Earth and the most earthlike planet in its size and mass orbiting the Sun. Whereas the atmosphere of the Earth consists mainly of nitrogen and oxygen, Venus has a hot carbon dioxide atmosphere, which is dominated by the greenhouse effect. Venus has all of its water in the atmosphere, which is only a fraction of the Earth's total water supply. Since planets developed presumably in similar conditions in the young Solar System, why Venus and Earth became so different in many respects? One important feature of Venus is that the planet does not have an intrinsic magnetic field. This makes it possible for the solar wind, a continuous stream of charged particles from the Sun, to flow close to Venus and to pick up ions from the planet's upper atmosphere. The strong intrinsic magnetic field of the Earth dominates the terrestrial magnetosphere and deflects the solar wind flow far away from the atmosphere. The region around Venus where the planet's atmosphere interacts with the solar wind is called the plasma environment or the induced magnetosphere. Main findings of the work include new knowledge about the movement of escaping planetary ions in the Venusian induced magnetosphere. Further, the developed simulation model was used to study how the solar wind conditions affect the ion escape from Venus. Especially, the global three-dimensional structure of the Venusian particle and magnetic environment was studied. The results help to interpret spacecraft observations around the planet. Finally, several remaining questions were identified, which could potentially improve our knowledge of the Venus ion escape and guide the future development of planetary plasma simulations.

Jarvinen, Riku

2011-04-01

184

Unveiling Venus  

Microsoft Academic Search

As of this writing, the USSR's Venus-exploration probes have accomplished atmospheric analyses at different altitudes in the Venus atmosphere, pressure and temperature readings, lightning observations, wind-velocity measurements, close-up terrain imaging, in situ rock and soil analyses, seismic measurements, and radar terrain-imaging from orbit. While NASA's accomplishments are fewer, the Magellan Venus Radar Mapper will furnish a wealth of new information

Chris Bulloch

1989-01-01

185

The Infrared Limb Darkening of Venus  

Microsoft Academic Search

The observed infrared limb darkening of Venus in the 8- to 13-micron interval and over the observed range in tz, the cosine of the Venus zenith angle, can be expressed as t , where a  0.5, according to two independent sets of measurements. Three general categories of models of the atmosphere and clouds of Venus are here proposed to

James B. Pollack; Carl Sagan

1965-01-01

186

Dayside thermal structure of Venus' upper atmosphere characterized by a global model  

NASA Astrophysics Data System (ADS)

Observations of Venus' dayside thermal structure are being conducted through ground based observatories. These temperature measurements, along with those from several instruments onboard the current Venus Express mission, are augmenting the previous thermal structure data from past missions (e.g., Veneras', Pioneer Venus Orbiter, Pioneer Venus Probes). These recent ground-based and VEx observations reveal the Venus dayside lower thermosphere to be considerably warmer and dynamically important than previously understood. In this study, a three dimensional general circulation model, the Venus Thermospheric General Circulation Model (VTGCM), is used to provide dayside temperature predictions for comparison to these recent ground based observations. Such a comparison serves to identify and quantify the underlying thermal processes responsible for the observed dayside temperature structure. The VTGCM reproduces the dayside temperatures observed near 110 km at noon from 40°S to 40°N very well. In addition, the global winds generated by these warm dayside temperatures are shown to give rise to dayside upwelling (divergence) and nightside subsidence (convergence) resulting in nightside warming near the anti-solar point at ˜104 km. Corresponding nightside temperatures reach ˜198 K, in accord with averaged measurements. This agreement implies (1) it is important for GCMs to include the updated radiative heating and cooling rates presented in Roldán et al. (2000) and (2) the current VTS3 and VIRA empirical models are in-sufficient in representing the warm regions observed in the thermal structure of the dayside lower thermosphere (˜100 to 130 km) and need to be updated.

Brecht, A. S.; Bougher, S. W.

2012-08-01

187

Transgenic frogs expressing the highly fluorescent protein venus under the control of a strong mammalian promoter suitable for monitoring living cells.  

PubMed

To easily monitor living cells and organisms, we have created a transgenic Xenopus line expressing Venus, a brighter variant of yellow fluorescent protein, under the control of the CMV enhancer/chicken beta-actin (CAG) promoter. The established line exhibited high fluorescent intensity not only in most tissues of tadpoles to adult frogs but also in germ cells of both sexes, which enabled three-dimensional imaging of fluorescing organs from images of the serial slices of the transgenic animals. Furthermore, by using this transgenic line, we generated chimeric animals by brain implantation and importantly, we found that the brain grafts survived and expressed Venus in recipients after development, highlighting the boundary between fluorescent and nonfluorescent areas in live animals. Thus, Venus-expressing transgenic frogs, tadpoles, and embryos would facilitate their use in many applications, including the tracing of the fluorescent cells after tissue/organ transplantation. PMID:15778984

Sakamaki, Kazuhiro; Takagi, Chiyo; Yoshino, Jun; Yokota, Hideo; Nakamura, Sakiko; Kominami, Katsuya; Hyodo, Akiko; Takamune, Kazufumi; Yuge, Masahiro; Ueno, Naoto

2005-06-01

188

Pioneer Venus Polarimetry and Haze Optical Thickness.  

National Technical Information Service (NTIS)

The Pioneer Venus mission provided us with high-resolution measurements at four wavelengths of the linear polarization of sunlight reflected by the Venus atmosphere. These measurements span the complete phase angle range and cover a period of more than a ...

W. J. J. Knibbe W. M. F. Wauben L. D. Travis J. W. Hovenier

1992-01-01

189

X band model of Venus atmosphere permittivity  

Microsoft Academic Search

A model of Venus' atmosphere permittivity profile up to 300 km is developed in this paper for X band. The model includes both the real and imaginary parts of the atmospheric permittivity, derived using data sets inferred or directly measured from past exploration missions to Venus: the real part is obtained by calculating the total polarization of the mixture of

Xueyang Duan; Mahta Moghaddam; Daniel Wenkert; Rolando L. Jordan; Suzanne E. Smrekar

2010-01-01

190

Venus Transit 2004  

NASA Astrophysics Data System (ADS)

December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the astronomical unit, calculation of longitudes on the earth, and detection of Venus' atmosphere. The NASA Sun Earth Connection Education Forum in partnership with the Solar System Exploration Forum, DPS, and a number of NASA space missions is developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.

Mayo, L. A.; Odenwald, S. F.

2002-09-01

191

Venus Atmospheric Maneuverable Platform (VAMP)  

NASA Astrophysics Data System (ADS)

We have explored a possible new approach to Venus upper atmosphere exploration by applying Northrop Grumman (non-NASA) development programs to the challenges associated with Venus upper atmosphere science missions. Our concept is a low ballistic coefficient (<50 Pa), semi-buoyant aircraft that deploys prior to entering the Venus atmosphere, enters the atmosphere without an aeroshell, and provides a long-lived (months to years), maneuverable vehicle capable of carrying science payloads to explore the Venus upper atmosphere. In this presentation we report results from our ongoing study and plans for future analyses and prototyping. We discuss the overall mission architecture and concept of operations from launch through Venus arrival, orbit, entry, and atmospheric science operations. We present a strawman concept of VAMP, including ballistic coefficient, planform area, percent buoyancy, inflation gas, wing span, vehicle mass, power supply, propulsion, materials considerations, structural elements, subsystems, and packaging. The interaction between the VAMP vehicle and the supporting orbiter will also be discussed. In this context, we specifically focus upon four key factors impacting the design and performance of VAMP: 1. Feasibility of and options for the deployment of the vehicle in space 2. Entry into the Venus atmosphere, including descent profile, heat rate, total heat load, stagnation temperature, control, and entry into level flight 3. Characteristics of flight operations and performance in the Venus atmosphere: altitude range, latitude and longitude access, day/night performance, aircraft performance (aerodynamics, power required vs. power available, propulsion, speed, percent buoyancy), performance sensitivity to payload weight 4. Science payload accommodation, constraints, and opportunities We discuss interdependencies of the above factors and the manner in which the VAMP strawman’s characteristics affect the CONOPs and the science objectives. We show how these factors provide constraints as well as enable opportunities for novel long duration scientific studies of the Venus upper atmosphere that support VEXAG goals 2 and 3.

Shapiro Griffin, Kristen L.; Sokol, D.; Dailey, D.; Lee, G.; Polidan, R.

2013-10-01

192

Pioneer-Venus large probe infrared radiometer \\/LIR\\/ optical system  

Microsoft Academic Search

The LIR (large probe infrared radiometer) instrument has been developed for the NASA Ames Research Center for use in the 1978 Venus Atmospheric Probe Mission. The mission objectives are to determine the nature and composition of the clouds, the composition and structure of the atmosphere, and the atmospheric circulation pattern of the planet Venus. The LIR is a six-channel (3-50

F. G. Brown; J. Gilland; R. Hassig; R. W. Boese

1977-01-01

193

Optimizing Aerobot Exploration of Venus  

NASA Astrophysics Data System (ADS)

Venus Flyer Robot (VFR) is an aerobot; an autonomous balloon probe designed for remote exploration of Earth's sister planet in 2003. VFR's simple navigation and control system permits travel to virtually any location on Venus, but it can survive for only a limited duration in the harsh Venusian environment. To help address this limitation, we develop: (1) a global circulation model that captures the most important characteristics of the Venusian atmosphere; (2) a simple aerobot model that captures thermal restrictions faced by VFR at Venus; and (3) one exact and two heuristic algorithms that, using abstractions (1) and (2), construct routes making the best use of VFR's limited lifetime. We demonstrate this modeling by planning several small example missions and a prototypical mission that explores numerous interesting sites recently documented in the plane tary geology literature.

Ford, Kevin S.

1997-03-01

194

The VEGA missions  

Microsoft Academic Search

The flight plan, instrumentation and mission objectives of the USSR Vega 1 and 2 spacecraft, which will encounter both Venus and Halley's Comet, are detailed. Each probe will release descent probes into the Venus atmosphere during flyby at a 35,000 km distance. The probes will soft land by balloon descent. The main buses of each spacecraft will continue on to

P. Clark

1985-01-01

195

Pioneer Venus results - an overview  

Microsoft Academic Search

Data on the scientific results obtained during the first 120 days of the Pioneer Venus Orbiter mission are presented. Details of the composition and structure of the upper and lower atmosphere as well as of clouds, winds, net radioactive fluxes, solar-wind-ionosheath-atmosphere interactions and topographic information are given, noting that radio signals showed that atmospheric turbulence was not responsible for scintillations.

T. M. Donahue

1979-01-01

196

Solar Powered Flight on Venus.  

National Technical Information Service (NTIS)

Solar powered flight within the Venus environment from the surface to the upper atmosphere was evaluated. The objective was to see if a station-keeping mission was possible within this environment based on a solar power generating system. Due to the slow ...

A. Colozza G. Landis

2004-01-01

197

Near infrared imaging of the surface of Venus and implications for crustal composition  

NASA Astrophysics Data System (ADS)

Venus Express is an ESA spacecraft orbiting Venus since April 2006. The instrument VIRTIS acquires multispectral images in the range from 0.2 to 5 m wavelength. An analysis of VIRTIS images at the wavelengths of the atmospheric window at 1.02 m shows evidence for variation of surface emissivity on the southern hemisphere [Mueller et al. 2008]. Inferred surface emissivity is correlated to some extend with morphological units identified from radar images of the NASA/JPL Magellan mission [Tanaka et al. 1997]. Alpha and Phoebe Regios are highlands mostly composed of tessera terrain, which is defined as a region strongly deformed by compressive and extensional tectonism in at least two directions. In comparison to lowland plains and other less tectonized highlands, these regions generally emit less thermal radiation, which implies lower emissivity. A recent analysis of NIR data from the Galileo fly-by in 1990 finds, that highland regions on Venus on average have a lower emissivity than lowlands [Hashimoto et al. 2008]. As a significant part of Venus highlands in the area observed by Galileo is composed of tessera, this observation is consistent with the observation of Mueller et al. [2008]. In situ measurements by the Venera and Vega landers are at most places consistent with basaltic surface composition. The hypsometry of Venus is unimodal. Inferred lava viscosity of most volcanic features is low, consistent with basaltic composition. All these observations hint towards a crust mostly composed of basalt [Basilevsky et al 1997]. However, no landing site was on tessera terrain, tessera are hypsometrically elevated and the morphology is dominated by tectonic deformation. Among other arguments this leads to the hypothesis that tessera highlands crust is more abundant in feldspar and silica, comparable to lunar highlands or continents on Earth [Nikolaeva et al., 1992]. NIR mapping supports this hypothesis, although other interpretations of the NIR data can not be ruled out. Generation of felsic crust is unlikely under the current climatic and tectonic regime on Venus. The lunar highland crust is believed to be a remnant of an magma ocean [Taylor 1974]. Enrichment in silica as in the continental crust of Earth requires recycling of water into the mantle [Campbell and Taylor 1984]. The surface of Venus is extremely dry and Venus and crustal recycling by plate tectonics does not operate at present. Any crust with felsic bulk composition had to be created during the early history of the planet. In a stratigraphic analysis tessera terrain predates all units it is in contact with [Ivanov and Head 1996]. Tessera terrain is defined by an extensive history of tectonic deformation. Assuming that tessera highlands indeed represent less dense crustal blocks created early in the history of Venus, implications arise from their persistence on the surface of Venus regarding resurfacing mechanism, crustal recycling and thermal evolution. If tessera highlands are enriched in silica relative to basalt this implies existence of a primordial ocean on Venus [Hashimoto et al. 2008]. In either case Venus would even more closely resemble the Earth-Moon system than previously assumed, making Venus an excellent subject for general studies of earth-like planets. Basilevsky, A. T.,et al. (1997), The Resurfacing History of Venus, in Venus II, pp. 1047-1084. Hashimoto, et al. (2008), Galileo Near Infrared Mapping Spectrometer (NIMS) Data Suggests Felsic Highland Crust on Venus, JGR, in press. Ivanov, M. A., et al. (1996), Tessera terrain on Venus: A survey of the global distribution, characteristics, and relation to surrounding units from Magellan data, JGR, 101, 14,861-14,908. Mueller, N., et al. (2008), Venus surface thermal emission at one micrometer in VIRTIS imaging observations - evidence for variation of crust and mantle differentiation conditions, JGR , in press. Nikolaeva, O. V., et al. (1992), Evidence on the crustal dichotomy, pp. 129-139, Venus Geology, Geochemistry, and Geophysics - Research results from the USSR. Tanaka, K. L., et al. (1997), Phy

Müller, N.; Helbert, J.

2009-04-01

198

[Establishment of goat limbal stem cell strain expressing Venus fluorescent protein and construction of limbal epithelial sheets].  

PubMed

The integrity and transparency of cornea plays a key role in vision. Limbal Stem Cells (LSCs) are precursors of cornea, which are responsible for self-renewal and replenishing corneal epithelium. Though it is successful to cell replacement therapy for impairing ocular surface by Limbal Stem Cell Transplantation (LSCT), the mechanism of renew is unclear after LSCT. To real time follow-up the migration and differentiation of corneal transplanted epithelial cells after transplanting, we transfected venus (a fluorescent protein gene) into goat LSCs, selected with G418 and established a stable transfected cell line, named GLSC-V. These cells showed green fluorescence, and which could maintain for at least 3 months. GLSC-V also were positive for anti-P63 and anti-Integrinbeta1 antibody by immunofluorescent staining. We founded neither GLSC-V nor GLSCs expressed keratin3 (k3) and keratinl2 (k12). However, GLSC-V had higher levels in expression of p63, pcna and venus compared with GLSCs. Further, we cultivated the cells on denude amniotic membrane to construct tissue engineered fluorescent corneal epithelial sheets. Histology and HE staining showed that the constructed fluorescent corneal epithelial sheets consisted of 5-6 layers of epithelium. Only the lowest basal cells of fluorescent corneal epithelial sheets expressed P63 analyzed by immunofluorescence, but not superficial epithelial cells. These results showed that our constructed fluorescent corneal epithelial sheets were similar to the normal corneal epithelium in structure and morphology. This demonstrated that they could be transplanted for patents with corneal impair, also may provide a foundation for the study on the mechanisms of corneal epithelial cell regeneration after LSCT. PMID:21387825

Yin, Jiqing; Liu, Wenqiang; Liu, Chao; Zhao, Guimin; Zhang, Yihua; Liu, Weishuai; Hua, Jinlian; Dou, Zhongying; Lei, Anmin

2010-12-01

199

Electromagnetic waves observed on a flight over a Venus electrical storm  

NASA Astrophysics Data System (ADS)

The occurrence of electrical discharges in planetary atmospheres produces high temperatures and pressures enabling chemical reactions that are not possible under local thermodynamic equilibrium conditions. On Earth, electrical discharges in clouds produce nitric oxide. Similar abundances of nitric oxide exist in the Venus atmosphere, but the existence of extensive electrical activity in its substantive cloud system is not as firmly established. To determine the strength and occurrence rate of lightning, the Venus Express mission included dual magnetometers sampling at 128 Hz to detect the electromagnetic signals produced by lightning. We report herein evidence of the apparent overflight of electrical storms by the Venus Express spacecraft. These observations reveal two types of signals reaching the spacecraft: one in the ELF band that exhibits dispersion and travels along the magnetic field, and one in the ULF band that appears to travel vertically across the magnetic field from below.

Russell, C. T.; Leinweber, H.; Zhang, T. L.; Daniels, J. T. M.; Strangeway, R. J.; Wei, H.

2013-01-01

200

Meeting Venus  

NASA Astrophysics Data System (ADS)

On 2-3 June 2012, the University of Tromsoe hosted a conference about the cultural and scientific history of the transits of Venus. The conference took place in Tromsoe for two very specific reasons. First and foremost, the last transit of Venus of this century lent itself to be observed on the disc of the Midnight Sun in this part of Europe during the night of 5 to 6 June 2012. Second, several Venus transit expeditions in this region were central in the global enterprise of measuring the scale of the solar system in the eighteenth century. The site of the conference was the Nordnorsk Vitensenter (Science Centre of Northern Norway), which is located at the campus of the University of Tromsoe. After the conference, participants were invited to either stay in Tromsoe until the midnight of 5-6 June, or take part in a Venus transit voyage in Finnmark, during which the historical sites Vardoe, Hammerfest, and the North Cape were to be visited. The post-conference program culminated with the participants observing the transit of Venus in or near Tromsoe, Vardoe and even from a plane near Alta. These Proceedings contain a selection of the lectures delivered on 2-3 June 2012, and also a narrative description of the transit viewing from Tromsoe, Vardoe and Alta. The title of the book, Meeting Venus, refers the title of a play by the Hungarian film director, screenwriter and opera director Istvan Szabo (1938-). The autobiographical movie Meeting Venus (1991) directed by him is based on his experience directing Tannhauser at the Paris Opera in 1984. The movie brings the story of an imaginary international opera company that encounters a never ending series of difficulties and pitfalls that symbolise the challenges of any multicultural and international endeavour. As is evident from the many papers presented in this book, Meeting Venus not only contains the epic tales of the transits of the seventeenth, eighteenth and nineteenth centuries, it also covers the conference participants' encounter with "Venus on the Sun" in historical archives as well as face-to-face at several locations in the Troms and Finnmark counties.

Sterken, Christiaan; Aspaas, Per Pippin

2013-06-01

201

Mars Express spacecraft: design and development solutions for affordable planetary missions  

Microsoft Academic Search

The spacecraft designed to support the ESA Mars Express mission and its science payloads is customized around an existing avionics well suited to environmental and operational constraints of deep-space interplanetary missions. The reuse of the avionics initially developed for the Rosetta cometary program thanks to an adequate ESA cornerstone program budget paves the way for affordable planetary missions.The costs and

P. Moulinier; F. Faye; J. C. Lair; E. Maliet

2003-01-01

202

The Cassini Mission  

NASA Astrophysics Data System (ADS)

Here we describe the main results obtained at the date of the Cassini Mission. The Cassini Mission was launched in October 1997 on a Titan IV-Centaur rocket from Cape Canaveral. The Cassini spacecraft first executed two gravity- assist flybys of Venus, then one each of the Earth and Jupiter to be injected in the right orbit that brought the spacecraft at Saturn in June 2004, becoming a new satellite of Satellite of Saturn (1st of July 2004). With the use of the VVEJGA (Venus-Venus-Earth-Jupiter Gravity Assist) trajectory, it takes 6.7 years for the Cassini spacecraft to arrive at Saturn.

Coradini, A.

203

TheRadio Science Experiment VeRa onboard ESA's Venus Express (VEX) Spacecraft  

NASA Astrophysics Data System (ADS)

The VEX spacecraft was successfully injected into the Venus orbit on April 11, 2006. VeRa is an active radio sounding instrument which will measure atmospheric/ionospheric temperature and density profiles, sound with bistatic radar experiments the surface of the planet, will measure its gravity anomalies and investigate also the structure of the corona by analyzing radio carrier signals received on ground in the S- and X-frequency bands. The radio science instrument VeRa is equipped with an ultrastable oscillator (USO) which will be used especially for atmospheric sounding and bistatic radar experiments as frequency reference in the OneWay transmission mode. We will present the current status of the experiment, the results of the commissioning tests and first scientific results.

Haeusler, Bernd; Paetzold, M.; Bird, M. K.; Simpson, R. A.; Tyler, L. G.; Dehant, V.; Imamura, T.; Tellmann, S.; Mattei, R.

2006-09-01

204

Magellan paints a portrait of Venus  

NASA Astrophysics Data System (ADS)

A brief review is made of some of the findings of the Magellan mission to Venus. Examples of the high-resolution radar images produced by Magellan are shown and discussed. The objectives of the planned extension of the Magellan mission are addressed.

Kerr, R. A.; Tancredi, G.; Gallardo, T.

1991-03-01

205

Detector of low energy neutral atoms onboard Mars Express mission  

NASA Astrophysics Data System (ADS)

Neutral Particle Detector (NPD) developed for the ESA Mars Express mission is a compact low weight (650g) high efficiency sensor to image low energy neutral atoms (ENA) resulted from the solar wind interaction with the Martian exosphere. NPD provides measurements of the ENA differential flux over the energy range 100 eV - 10 keV resolving H and O with a coarse 5^o yen 30o angular resolution and total efficiency 1 - 50%. The sensor consists of two identical detectors each with a 9^o yen 90^o intrinsic field of view placed on a scanning platform which performs 180^o scans to cover a hemisphere. The measurement principle is based on surface interaction technique. ENAs incident on a start surface at a grazing angle of 15^o are reflected and cause secondary electron emission. The secondary electrons are transported to an MCP assembly, which gives the START signal. The reflected ENAs hit the stop surface and again produce the secondary electrons used to generate the STOP signal. The time-of-flight measurements give ENA velocity and are used to identify mass (H or O). Coincidence technique as well as properties of the START and STOP surface coating provide UV suppression to the level sufficient to achieve the required signal-to-noise ratio. The results of the flight model calibrations will be presented and analyzed.

Grigoriev, A.; Barabash, S.; Fedorov, A.; Wurz, P.; Grande, M.; Curtis, C.; Maggi, M.; Dierker, C.; Npd Team

2003-04-01

206

Scattering of Thermal Radiation by Droplets in Venus' Upper Atmosphere  

Microsoft Academic Search

The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express spacecraft has been providing a wealth of data on the Venus atmosphere since its arrival at Venus in 2006. Here, we present results from VIRTIS-IR measurements of the nightside limb of the planet, where we probe the atmosphere above the cloud tops at a range of altitudes. We

Remco de Kok; P. G. J. Irwin; G. Piccioni; P. Drossart

2009-01-01

207

Venus lives!  

Microsoft Academic Search

Comparison with the duration of major volcanic systems on Earth (75 - 80 m.y. for the Hawaiian-Emperor chain) and Mars (perhaps 1 b.y. for Olympus Mons) suggests that volcanism is likely to continue on Venus today if it existed 0.5 - 1.0 b.y. ago. Unfortunately, there is little hope of remotely detecting active volcanism because of the masking effects of

C. A. Wood; P. W. Francis

1988-01-01

208

Super-rotation simulated with the new LMD Venus General Circulation Model  

Microsoft Academic Search

Venus-Express is now in orbit around Venus, and soon will bring us new insights on Venus' atmosphere. In this context, we have developed at the Laboratoire de Météorologie Dynamique a new 3-dimensional General Circulation Model of Venus atmosphere, based on our experience of Earth, Mars and Titan models. The main feature of this new model is the infrared radiative transfer

S. Lebonnois; A. Crespin; F. Hourdin; V. Eymet; R. Fournier; J.-L. Dufresne

2006-01-01

209

Ionospheric photoelectrons: comparing Earth, Venus, Mars and Titan  

Microsoft Academic Search

Earth, Venus, Mars and Titan are all objects with significant atmospheres and ionospheres. Ionospheric studies at the Earth first revealed the presence of ionospheric photoelectrons, a product of the principal ionization process for the ionosphere, i.e. photoionization from solar EUV and X rays. Recent space missions with suitable instrumentation have also revealed similar photoelectrons at Venus, Mars and Titan. The

Andrew Coates; Anne Wellbrock; Sharon Tsang; Rudy Frahm; David Winningham; Stas Barabash; Rickard Lundin; Dave Young; Frank Crary

2010-01-01

210

Remote Raman - LIBS Geochemical Investigation under Venus Atmospheric Conditions  

Microsoft Academic Search

The extreme Venus surface temperature (740K) and atmospheric pressure (93 atm) creates a challenging environment for future lander missions. The scientific investigations capable of Venus geochemical observations must be completed within several hours of the landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of

S. M. Clegg; J. E. Barefield; R. C. Wiens; A. K. Misra; S. K. Sharma

2008-01-01

211

An AOTF-based spectrometer for the studies of Mars atmosphere for Mars Express ESA mission  

Microsoft Academic Search

The SPICAM Light optical package on the ESA Mars Express mission is dedicated to the nadir and limb observations in the UV between 118 nm and 320 nm, and has originally included an IR solar occultation channel, an inheritance of the IR part of the SPICAM solar occultation instrument for Mars 96. Because of severe mass constrains of the mission

O. Korablev; J.-L. Bertaux; A. Grigoriev; E. Dimarellis; Yu. Kalinnikov; A. Rodin; C. Muller; D. Fonteyn

2002-01-01

212

A radar tour of Venus  

NASA Astrophysics Data System (ADS)

The surface of Venus is briefly characterized in a summary of results obtained by the Soviet Venera 15 and 16 8-cm synthetic-aperture radars, IR radiometers, and radar altimeters. A series of radar images, mainly from Kotelnikov et al. (1984), are presented and discussed, and the descent vehicles to be released by the two Vega spacecraft as they pass Venus in June 1985 on their way to an encounter with Halley's comet are described. Plans for the missions Phobos (two spacecraft to orbit Mars, rendezvous with Phobos and Deimos, release small instrumented landers, and perform mass spectrometry of vapors released by laser pulses directed at the satellite surfaces, beginning in 1988), a lunar-orbiter mission for 1989-1990, and Vesta (a not-yet-approved 1991 mission comprising a French probe to the asteroid 4 Vesta and perhaps 53 Kalypso and 453 Tea and a Soviet spacecraft to release a kite-supported Venus-atmosphere probe before flying on to an unknown destination) are considered.

Beatty, J. K.

1985-06-01

213

Greenhouse effects on Venus  

Microsoft Academic Search

Calculations that used Pioneer-Venus measurements of atmosphere composition, temperature profiles, and radiative heating predicted Venus' surface temperature `very precisely,' says the Ames Research Center. The calculations predict not only Venus' surface temperature but agree with temperatures measured at various altitudes above the surface by the four Pioneer Venus atmosphere probe craft.Using Pioneer-Venus spacecraft data, a research team has virtually proved

Peter M. Bell

1981-01-01

214

Vénus version Express  

NASA Astrophysics Data System (ADS)

En avril 2006, Vénus a "capturé" un objet d'un genre particulier: une sonde robotique européenne, baptisée Venus Express et destinée à scruter cette planète sous tous les angles. Bilan de cette mission 5 ans après le lancement de la sonde, dont 4 d'observations vénusiennes.

Nazé, Yaël

2010-04-01

215

Spacecraft for Flight in the Atmosphere of Venus.  

National Technical Information Service (NTIS)

Possible configurations of space vehicles which would be delivered to Venus by rocket system in order to autonomously carry out flights in an automatic (and possibly piloted) mode are considered with respect to mission and flight altitude. Base (high alti...

G. M. Moskalenko

1980-01-01

216

Hot Flow Anomalies at Venus  

NASA Astrophysics Data System (ADS)

We present a multi-instrument study of a Hot Flow Anomaly (HFA) observed by the Venus Express spacecraft in the Venutian foreshock, expanding on an initial study by Slavin et al [2009] that employed magnetometer observations of an HFA-like event during the flyby of NASA's Messenger spacecraft. Whilst the Messenger events were indicative of an HFA, they were unable to demonstrate the unambiguous signatures of plasma heating or deflection due to the paucity of data. We examine the complex internal structure of a Venutian HFA on the 22nd of March 2008, incorporating both Venus Express magnetometer and ASPERA plasma observations to demonstrate the presence of plasma heating within one such event. Centered on an interplanetary discontinuity and bounded by shock, the properties of this event are consistent with those of HFA's observed at other planets within the Solar System. Finally, we present a discussion of the implications of an HFA on the planet Venus.

Collinson, G. A.; Sibeck, D. G.; Masters, A.; Shane, N.; Slavin, J. A.; Coates, A. J.; Zhang, T.; Boardsen, S. A.; Moore, T. E.; Barabash, S.

2011-12-01

217

Venus Highland Anomalous Reflectivity  

NASA Astrophysics Data System (ADS)

Maxwell Montes was one of several unusually bright areas identified from early Venus radar backscatter observations. Pioneer Venus' orbiting radar associated low emissivity with the bright areas and established a correlation between reflectivity and altitude. Magellan, using an oblique bistatic geometry, showed that the bright surface dielectric constant was not only large but also imaginary -- i.e., the material was conducting, at least near Cleopatra Patera (Pettengill et al., Science, 272, 1996). Venus Express (VEX) repeated Magellan's bistatic observations over Maxwell, using the more conventional circular polarization carried by most spacecraft. Although VEX signal-to-noise ratio was lower than Magellan's, echoes were sufficiently strong to verify the Magellan conclusions near Cleopatra (see J. Geophys. Res., 114, E00B41, doi:10.1029/2008JE003156). Only about 40% of the surface at Cleopatra scatters specularly, opening the Fresnel (specular) interpretation model to question. Elsewhere in Maxwell, the specular percentage may be even lower. Nonetheless, the echo polarization is reversed throughout Maxwell, a result that is consistent with large dielectric constants and difficult to explain without resorting qualitatively (if not quantitatively) to specular models. VEX was scheduled to explore other high altitude regions when its S-Band (13-cm wavelength) radio system failed in late 2006, so further probing of high altitude targets awaits arrival of a new spacecraft.

Simpson, Richard A.; Tyler, G. L.; Häusler, B.; Mattei, R.; Patzold, M.

2009-09-01

218

The thermosphere and ionosphere of Venus  

NASA Astrophysics Data System (ADS)

Our knowledge of the upper atmosphere and ionosphere of Venus and its interaction with the solar wind has advanced dramatically over the last decade, largely due to the data obtained during the Pioneer Venus mission and to the theoretical work that was motivated by this data. Most of this information was obtained during the period 1978 through 1981, when the periapsis of the Pioneer Venus Orbiter (PVO) was still in the measurable atmosphere. However, solar gravitational perturbations will again lower the PVO periapsis into the upper atmosphere in September 1992, prior to the destruction of the spacecraft toward the end of this year. The physics and chemistry of the thermosphere and ionosphere of Venus are reviewed.

Cravens, T. E.

1992-12-01

219

Venusian ion populations and bow shock as seen by the ASPERA-4 ion instrument on Venus Express  

NASA Astrophysics Data System (ADS)

Introduction We examine ion populations at Venus. Previous models use magnetic crossing points to derive the bow shock position. The current work uses data from the ASPERA-4 (Analyser of Space Plasmas and Energetic Atoms) [1] instrument to measure ion populations and derive a bow shock position at Venus. Instrumentation The ASPERA-4 instrument flies onboard Venus Express (VEX) and is comprised of five different detectors (Barabash et al 2006 [1]). A neutral particle detector and analyser, an electron spectrometer and the Ion Mass Analyser (IMA) (ref). This paper uses the IMA instrument for all its data and an explanation of the specifications is required. The instrument is a top hat electrostatic analyser; it runs through voltages to scan look angles and also acceptance energies. In one look direction it scans through 96 different energy values before changing to the next. A full scan of all look directions and energies takes 192 seconds. Data Collection All data is weighed dependant upon its probability of the spacecraft measuring at a particular point and when fitted produces a value of 1.24 RV, somewhat closer distance for the sub solar point than previous authors - see figure 1. We separate the data according to slow or fast solar wind and not the similarities and differences in the results derived. The inbound and outbound bow shock crossings were taken by inspection of 106 orbits between November 2006 and February 2007. Any orbits where the crossing point was not clear or with data missing were ignored. The occupational probability is found from orbital mechanics. By setting up a grid and deriving the amount of time it takes to cross each square the probability as a whole can then be determined. Ion distribution plots Two dimensional maps of the ions are produced and the bow shock model overplotted to verify its accuracy, as shown in figure 3. The test of the bow shock is to place it upon real data and examine the fit. To do this ion distribution plots are created and have the bow shock model placed upon them. The maps are shown in fig 8 and comprise 6 months of data from VEX in 2007. The count rates of all spectra of every orbit were stored and binned into a grid system. Each box in the grid being averaged from all values placed into it. The results were then smoothed and the maps created for individual species and plot types. Fig 3 shows maps for hydrogen ions in the x-y plane and in cylindrical coordinates signed with y. This plot is the same as a standard cylindrical plot but the r value is positive if y is positive and negative if y is negative. Effect of Coronal mass Ejections The HI imager on STEREO is able to image Coronal mass Ejections (CME) in the inner Solar System. In a recent paper, Roullard et al 2008 [2] have considered a CME observed to impact Venus, and used in situ measurements to examine the response of the magnetosphere. The plots in figure4 show the measured ion response to this and an earlier CME. We will examine the ion signatures in detail. Acknowledgements We acknowledge the contributions of the entire Aspera 4 team: S. Barabash, R. Lundin, H. Andersson, K. Brinkfeld, A. Grigoriev, H. Gunell, M. Holmström, M. Yamauchi, K. Asamura, P. Bochsler, P. Wurz, R. Cerulli-Irelli, A. Mura, A. Milillo, M. Maggi, S. Orsini, A. J. Coates, D. R. Linder, D. O. Kataria, C. C. Curtis, K. C. Hsieh, B. R. Sandel, R. A. Frahm, J. R. Sharber, J. D. Winningham, M. Grande, E. Kallio, H. Koskinen, P. Riihelä, W. Schmidt, T. Säles, J. U. Kozyra,N. Krupp, J. Woch,.S. Livi, J. G., Luhmann, S. McKenna-Lawlor, E. C. Roelof, D. J. Williams, J.-A. Sauvaud, A. Fedorov, and J.-J. Thocaven. References [1] S. Barabash, R. Lundin, H. Andersson, K. Brinkfeld, A. Grigoriev, H. Gunell, M. Holmström, M. Yamauchi, K. Asamura, P. Bochsler, P. Wurz, R. Cerulli-Irelli, A. Mura, A. Milillo, M. Maggi, S. Orsini, A. J. Coates, D. R. Linder, D. O. Kataria, C. C. Curtis, K. C. Hsieh, B. R. Sandel, R. A. Frahm, J. R. Sharber, J. D. Winningham, M. Grande, E. Kallio, H. Koskinen, P. Riihelä, W. Schmidt, T. Säles, J. U. Kozyra,N. Krupp

Grande, M.; Whittaker, I.; Guymer, G.; Barabash, S.

2008-09-01

220

Aerobraking techniques for planetary missions  

Microsoft Academic Search

Aerobraking techniques are applied to trajectory design for the VOIR (Venus Orbiting Imaging Radar) mission to enhance overall mission performance. The approach can be used for other planetary missions such as a Titan orbiter or a Mars sample return to earth. The orientation of the elliptical insertion orbit must be chosen in such a way that the combined effects of

C. C. H. Tang; J. H. Kwok

1981-01-01

221

New measurements of Venus winds with ground-based Doppler velocimetry at CFHT  

NASA Astrophysics Data System (ADS)

Since Venus Express spacecraft operations started in 2006, an ongoing effort has been made to coordinate its operations with observations from the ground using various techniques and spectral domains (Lellouch and Witasse, 2008). We present an analysis of Venus Doppler winds at cloud tops based on observations made at the Canada France Hawaii 3.6-m telescope (CFHT) with the ESPaDOnS visible spectrograph. These observations consisted of high-resolution spectra of Fraunhofer lines in the visible range (0.37-1.05 ?m) to measure the winds at cloud tops using the Doppler shift of solar radiation scattered by cloud top particles in the observer's direction (Widemann et al., 2007, 2008). The observations were made during 19-20 February 2011 and were coordinated with Visual Monitoring Camera (VMC) observations by Venus Express. The complete optical spectrum was collected over 40 spectral orders at each point with 2-5 seconds exposures, at a resolution of about 80000. The observations included various points of the dayside hemisphere at a phase angle of 67°, between +10° and -60° latitude, in steps of 10° , and from +70° to -12° longitude relative to sub-Earth meridian in steps of 12°. The Doppler shift measured in scattered solar light on Venus dayside results from two instantaneous motions: (1) a motion between the Sun and Venus upper cloud particles; (2) a motion between the observer and Venus clouds. The measured Doppler shift, which results from these two terms combined, varies with the planetocentric longitude and latitude and is minimum at meridian ?N = ?Sun - ?Earth where the two components subtract to each other for a pure zonal regime. Due to the need for maintaining a stable velocity reference during the course of acquisition using high resolution spectroscopy, we measure relative Doppler shifts to ?N. The main purpose of our work is to provide variable wind measurements with respect to the background atmosphere, complementary to simultaneous measurements made with the VMC camera onboard the Venus Express. We will present first results from this work, comparing with previous results by the CFHT/ESPaDOnS and VLT-UVES spectrographs (Machado et al., 2012), with Galileo fly-by measurements and with VEx nominal mission observations (Peralta et al., 2007, Luz et al., 2011). Acknowledgements: The authors acknowledge support from FCT through projects PTDC/CTE-AST/110702/2009 and PEst-OE/FIS/UI2751/2011. PM and TW also acknowledge support from the Observatoire de Paris. Lellouch, E., and Witasse, O., A coordinated campaign of Venus ground-based observations and Venus Express measurements, Planetary and Space Science 56 (2008) 1317-1319. Luz, D., et al., Venus's polar vortex reveals precessing circulation, Science 332 (2011) 577-580. Machado, P., Luz, D. Widemann, T., Lellouch, E., Witasse, O, Characterizing the atmospheric dynamics of Venus from ground-based Doppler velocimetry, Icarus, submitted. Peralta J., R. Hueso, A. Sánchez-Lavega, A reanalysis of Venus winds at two cloud levels from Galileo SSI images, Icarus 190 (2007) 469-477. Widemann, T., Lellouch, E., Donati, J.-F., 2008, Venus Doppler winds at Cloud Tops Observed with ESPaDOnS at CFHT, Planetary and Space Science, 56, 1320-1334.

Machado, P.; Widemann, T.; Luz, D.; Peralta, J.; Berry, D. L.

2012-04-01

222

High Temperature Mechanisms for Venus Exploration  

NASA Astrophysics Data System (ADS)

Future Venus missions, including New Frontiers Venus In-Situ Explorer and three Flagship Missions - Venus Geophysical Network, Venus Mobile Explorer and Venus Surface Sample Return all focus on searching for evidence of past climate change both on the surface and in the atmospheric composition as well as in the interior dynamics of the planet. In order to achieve these goals and objectives, many key technologies need to be developed for the Venus extreme environment. These key technologies include sample acquisition systems and other high-temperature mechanisms and mobility systems capable of extended operation when directly exposed to the Venus surface or lower atmosphere environment. Honeybee Robotics has developed two types of high temperature motors, the materials and components in both motors were selected based on the requirement to survive temperatures above a minimum of 460° C, at earth atmosphere. The prototype Switched Reluctance Motor (SRM) has been operated non-continuously for over 20 hours at Venus-like conditions (460° C temperature, mostly CO2 gas environment) and it remains functional. A drilling system, actuated by two SRMs was tested in Venus-like conditions, 460° C temperature and mostly CO2 gas environment, for more than 15 hours. The drill successfully completed three tests by drilling into chalk up to 6 inches deep in each test. A first generation Brushless DC (BLDC) Motor and high temperature resolver were also tested and the feasibility of the designs was demonstrated by the extended operation of both devices under Venus-like condition. Further development of the BLDC motor and resolver continues and these devices will, ultimately, be integrated into the development of a high temperature sample acquisition scoop and high temperature joint (awarded SBIR Phase II in October, 2007). Both the SR and BLDC motors will undergo extensive testing at Venus temperature and pressure (TRL6) and are expected to be mission ready before the next New Frontiers AO release. Scalable high temperature motor, resolver and bearing developments allow for creation of long lasting sample acquisition systems, booms, robot arms and even mobility systems that operate outside of an environment-controlled landed platform on the surface of Venus. The SR and BLDC motors are no longer expected to limit the life of Venus surface operations. With the accompanying high temperature bearing and other mechanisms development, surface operations will be limited only by available power. Therefore, the motor and resolver's capability to survive for hours (and potentially longer) in the environment is a major benefit to future Venus science missions and they also allow time for communication ground loops to optimize sample target selection and the possibility for acquiring multiple samples from the surface. The extreme temperature motors, resolver and other high temperature mechanisms therefore revolutionize the exploration of Venus.

Ji, Jerri; Narine, Roop; Kumar, Nishant; Singh, Sase; Gorevan, Steven

223

Pioneers' Venus - More than fire and brimstone  

Microsoft Academic Search

Results from NASA's Pioneer Venus space mission are presented and studied. Pioneer radar equipment has uncovered the profile of a large rift extending east-west 1,400 km and exhibiting up to 7 km of relief between its floor and the surrounding hills. In addition, an area known as Maxwell seems to be 8 km higher than the adjacent Great Northern Plateau,

J. K. Beatty

1979-01-01

224

And back to Venus yet again  

Microsoft Academic Search

\\u000a The final missions in the Soviet Venera series were launched in June 1983. Having achieved most of their objectives with the\\u000a Venera landers, these two spacecraft were outfitted with large radar antennas replacing the entry system and sent to Venus\\u000a as orbital radar mappers.

Wesley T. Huntress; Mikhail Ya. Marov

225

Approach and challenges to science and mission planning for the European orbiter Mars Express  

Microsoft Academic Search

The paper focuses on the end-to-end science operations for the first and only European Mars mission to-date, describing the approaches to science and mission planning and the challenges imposed by the operations constraints. It includes the activities of the instrument and science planning teams to plan and process the collected data. The Mars Express spacecraft has been in orbit around

Erhard Rabenau; Michel Denis; Nicolas Altobelli

2012-01-01

226

Comparison of accelerated ion populations observed upstream of the bow shocks at Venus and Mars  

Microsoft Academic Search

Foreshock ions are compared between Venus and Mars at energies of 0.6~20 keV using the same ion instrument, the Ion Mass Analyser, on board both Venus Express and Mars Express. Venus Express often observes accelerated protons (2~6 times the solar wind energy) that travel away from the Venus bow shock when the spacecraft location is magnetically connected to the bow

M. Yamauchi; Y. Futaana; A. Fedorov; R. A. Frahm; J. D. Winningham; E. Dubinin; R. Lundin; S. Barabash; M. Holmström; C. Mazelle; J.-A. Sauvaud; T. L. Zhang; W. Baumjohann; A. J. Coates; M. Fraenz

2011-01-01

227

Long-term Behaviour Of Venus Winds At Cloud Level From Virtis/vex Observations  

NASA Astrophysics Data System (ADS)

The Venus Express (VEX) mission has been in orbit to Venus for more than three years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 ?m) map the opacity of the lower cloud deck at 48 km. Here we present an analysis of the overall dynamics of Venus’ atmosphere at both levels using observations that cover a large fraction of the VIRTIS dataset. We will present our latest results concerning the zonal winds, the overall stability in the lower cloud deck motions and the variability in the upper cloud. Meridional winds are also observed in the upper and lower cloud in the UV and IR images obtained with VIRTIS. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present more irregular, variable and less intense motions in the meridional direction. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

Hueso, Ricardo; Peralta, J.; Sánchez-Lavega, A.; Pérez-Hoyos, S.; Piccioni, G.; Drossart, P.

2009-09-01

228

Venus Mesospheric Water Vapour From VIRTIS-H VEX Dayside Measurements  

NASA Astrophysics Data System (ADS)

The Venus-Express mission works in orbit around Venus since April 11th 2006. VIRTIS-H is a high resolution (1-3 nm) IR channel of the VIRTIS mapping spectrometer. Venus nadir dayside spectra measured with VIRTIS-H have been used to derive simultaneously the altitude of the cloud tops and water abundance in the mesosphere. A line-by-line multiple scattering code has been used to fit the CO2 bands at 2.48 micron and H2O bands at 2.56 micron. Clouds have been simulated with "mode 2" particles of 75 percent H2SO4 and exponential vertical profile in the mesosphere with the scale height of 4 km. Highest quality data has been selected from 8 orbits with local times from 10 to 15 h, and a special attention has been given to the regions near the local noon. We obtained an average cloud top altitude of 75 +/-1 km for low latitudes regions, equator ward of 30 degrees. Results for higher latitude are under examination. Water vapour abundance in low latitudes regions is found to be about 1 ppm at 75 km, with weak variations in the selected orbits and up to 2 -3 ppm in the others, besides with no indication of enhancement observed in 80s from Pioneer Venus observations. Our measurements of cloud top altitude and H2O abundance agree well with other VEX observations: VIRTIS-M and SPICAV, respectively.

Cottini, V.; Ignatiev, N.; Grassi, D.; Piccioni, G.; Drossart, P.

2008-12-01

229

Study and Implementation of the End-to-End Data Pipeline for the Virtis Imaging Spectrometer Onbaord Venus Express: "From Science Operations Planning to Data Archiving and Higher Lever Processing"  

NASA Astrophysics Data System (ADS)

This PhD Thesis describes the activities performed during the Research Program undertaken for two years at the Istituto Nazionale di AstroFisica in Rome, Italy, as active member of the VIRTIS Technical and Scientific Team, and one additional year at the European Space Astronomy Center in Madrid, Spain, as member of the Mars Express Science Ground Segment. This document will show a study of all sections of the Science Ground Segment of the Venus Express mission, from the planning of the scientific operations, to the generation, calibration and archiving of the science data, including the production of valuable high level products. We will present and discuss here the end-to-end diagram of the ground segment from the technical and scientific point of view, in order to describe the overall flow of information: from the original scientific requests of the principal investigator and interdisciplinary teams, up to the spacecraft, and down again for the analysis of the measurements and interpretation of the scientific results. These scientific results drive to new and more elaborated scientific requests, which are used as feedback to the planning cycle, closing the circle. Special attention is given here to describe the implementation and development of the data pipeline for the VIRTIS instrument onboard Venus Express. During the research program, both the raw data generation pipeline and the data calibration pipeline were developed and automated in order to produce the final raw and calibrated data products from the input telemetry of the instrument. The final raw and calibrated products presented in this work are currently being used by the VIRTIS Science team for data analysis and are distributed to the whole scientific community via the Planetary Science Archive. More than 20,000 raw data files and 10,000 calibrated products have already been generated after almost 4 years of mission. In the final part of the Thesis, we will also present some high level data processing methods developed for the Mapping channel of the VIRTIS instrument. These methods have been implemented for the generation of high level global maps of measured radiance over the whole planet, which can then be used for the understanding of the global dynamics and morphology of the Venusian atmosphere. This method is currently being used to compare different emissions probing at different altitudes from the low cloud layers up to the upper mesosphere, by using the averaged projected values of radiance observed by the instrument, such as the near infrared windows at 1.7 ?m and 2.3?m, the thermal region at 3.8?m and 5?m plus the analysis of particular emissions in the night and day side of the planet. This research has been undertaken under guidance and supervision of Giuseppe Piccioni, VIRTIS co-Principal Investigator, with support of the entire VIRTIS technical and scientific team, in particular of the Archiving team in Paris (LESIA-Meudon). The work has also been done in close collaboration with the Science and Mission Operations Centres in Madrid and Darmstadt (European Space Agency), the EGSE software developer (Techno Systems), the manufacturer of the VIRTIS instrument (Galileo Avionica) and the developer of the VIRTIS onboard software (DLR Berlin). The outcome of the technical and scientific work presented in this thesis is currently being used by the VIRTIS team to continue the investigations on the Venusian atmosphere and plan new scientific observations to improve the overall knowledge of the solar system. At the end of this document we show some of the many technical and scientific contributions, which have already been published in several international journals and conferences, and some articles of the European Space Agency used for public outreach.

Cardesín Moinelo, Alejandro

2010-04-01

230

Spatial and Temporal distribution of CO_{2} 4.3-mu m NLTE Emission from nadir VIRTIS-H/Venus Express observations  

NASA Astrophysics Data System (ADS)

Non-Local Thermodynamic Equilibrium (non-LTE) emissions are known to play a key role in the radiative heating and cooling of the Venus mesosphere and lower thermosphere (Dickinson, JAS, 1973; Roldan et al., Icarus, 2000). In the case of the Venusian atmosphere, CO2 vibrational-rotational emissions at 4.3 ?m and 2.7 ?m were predicted to give intense emissions, and since they are originated between 80 and 150 km, their observation might give information on the atmospheric parameters at those altitudes, depending on sensitivity and spectral resolution. The VIRTIS spectrometer on board Venus Express allows for the first time the systematic sounding of these bands in the Venus atmosphere, both in nadir and limb observing geometries. The limb data by VIRTIS has been recently studied by our team (Gilli et al., JGR, 2009; López-Valverde et al., 2010 submitted; Gilli et al., 2010 submitted), focusing on its vertical distribution and the validation of non-LTE models, but an exhaustive study of nadir observations has not been presented so far, except for the detection of gravity waves by García et al. (2008; 2009). In this work, we have used the nadir observations to study the horizontal distribution of the CO2 non-LTE emissions at 4.3 ?m, mainly originated at altitudes about ~110 km. The analyzed dataset comprises the whole nadir measurements with VIRTIS-H (the highest spectral resolution channel) obtained up to September 2009, covering nearly 900 days of observations and more than 140,000 spectra. Similarly to the case of limb data, it was found that the nadir radiance depends not only on the Solar Zenith Angle, but also on the Emission Angle, as predicted by our non-LTE model. After careful radiance averages, the small dispersion found in the mean emission of this band suggests that the Venus lower thermosphere is more stable than expected, with scarce episodes of significant variation during the studied period. Since the spectral resolution of VIRTIS-H allows separating different CO2 isotopic and hot bands, this dataset implies a valuable test for non-LTE models. Therefore, a revision of some key rate coefficients for collisional relaxation of CO2 vibrational energy levels is also carried out, by means of a systematic comparison between radiance ratios measured by VIRTIS-H and the ones obtained with our non-LTE radiative transfer model. Conclusions will be briefly discussed at the meeting.

Peralta, Javier; Ángel López-Valverde, Miguel; Gilli, Gabriella; Drossart, Pierre; Piccioni, Giuseppe

2010-05-01

231

Mission Impact of Cyber Events: Scenarios and Ontology to Express the Relationships between Cyber Assets, Missions, and Users.  

National Technical Information Service (NTIS)

Awareness of the dependencies between cyber assets, missions and users is critical to assessing the mission impact of cyber attacks and maintaining continuity of business operations. However, there is no systematic method for defining the complex mapping ...

A. D'Amico J. Goodall L. Buchanan P. Walczak

2009-01-01

232

Venus atmospheric platform options revisited  

NASA Astrophysics Data System (ADS)

Various balloon systems intended as scientific platforms to float in the atmosphere of Venus at altitudes between about 35 and 65 km are briefly reviewed. Previous predictions of the altitude oscillations of balloons filled with helium gas and water vapor are largely confirmed through numerical simulation and analysis. The need for refined thermal modelling is emphasised. Several novel technical concepts are introduced. It is concluded that phase change balloons would be more suitable than non-condensing super pressure gas balloons when repeated altitude excursions are a mission requirement.

Dorrington, G. E.

2010-08-01

233

MARS ADVANCED RADAR FOR SUBSURFACE AND IONOSPHERE SOUNDING (MARSIS) ON MARS EXPRESS MISSION  

Microsoft Academic Search

According to the Mars Express mission (scheduled for launch in 2003), the MARSIS primary scientific objective is to map the distribution of water, both liquid and solid, in the upper portions of the crust of Mars. Detection of such reservoirs of water will address key issues in the hydrologic, geologic, climatic and possible biologic evolution of Mars. Moreover three secondary

G. Picardi; D. Biccari; R. Seu; A. Gurnett; F. Provvedi; O. Bombaci; E. Zampolini

234

Beagle 2: A proposed exobiology lander for ESA's 2003 Mars Express mission  

Microsoft Academic Search

The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on

M. R. Sims; C. T. Pillinger; I. P. Wright; J. Dowson; S. Whitehead; A. Wells; J. E. Spragg; G. Fraser; L. Richter; H. Hamacher; A. Johnstone; N. P. Meredith; C. de la Nougerede; B. Hancock; R. Turner; S. Peskett; A. Brack; J. Hobbs; M. Newns; A. Senior; M. Humphries; H. U. Keller; N. Thomas; J. S. Lingard; J. C. Underwood; N. M. Sale; M. F. Neal; G. Klingelhofer; T. C. Ng

1999-01-01

235

Current Sheets and Substroms in Venus' Magnetotail  

NASA Astrophysics Data System (ADS)

We investigate 2 years of Venus Express FGM data when the spacecraft is crossing Venus' magnetotail. Using only data when the IMF is within ± 20° of the nominal Parker spiral ~ 37° and little variation of the field before and after the tail crossing, we obtain a quiet-time magnetic field profile along the orbit of the spacecraft. There is an Earth-like tail field in the region less then 3 RV downstream from Venus and the current sheet is in the XYVSO-plane, with an estimated current density of 3 nA/m2. We also investigate two cases, one for a quiet tail and one for an acitive tail, using both FGM and ASPERA data. Increased but constant pressure of the solar wind is shown to increase the esitmated cross- tail current. Most importantly, strongly varying solar wind magnetic field is shown to lead to observations that can be interpreted as reconnection in Venus' magnetotail.

Volwerk, M.; Delva, M.; Futaana, Y.; Vörös, Z.; Zhang, T.; Baumjohann, W.; Barabash, S.

2008-12-01

236

Inner solar system sample return missions using solar electric propulsion  

Microsoft Academic Search

This study evaluated the effects of solar electric propulsion (SEP) and PowerSail solar array technology on four sample return missions. These missions, to the Moon, Mars, Mercury, and Venus, were compared against previous Jet Propulsion Laboratory (JPL) studies. Compared to these baselines, PowerSail\\/SEP missions in general had longer trip times, though the Venus mission was of similar duration. Costs for

Ryan D. McDaniel; Swati Mohan; Jaime Juarez

2003-01-01

237

Quantification of middle and lower cloud variability and mesoscale dynamics from Venus Express\\/VIRTIS observations at 1.74 ?m  

Microsoft Academic Search

We present an analysis of VIRTIS-M-IR observations of 1.74?m emission from the nightside of Venus. The 1.74?m window in the near infrared spectrum of Venus is an ideal proxy for investigating the evolution of middle and lower cloud deck opacity of Venus because it exhibits good signal to noise due to its brightness, good contrast between bright and dark regions,

Kevin McGouldrick; Thomas W. Momary; Kevin H. Baines; David H. Grinspoon

238

Venus - The mystery continues  

NASA Astrophysics Data System (ADS)

Topics and discussion at the International Conference on the Venus Environment in Nov. 1981, dealing with data from the Pioneer Venus orbiter, five Pioneer probes, and four Venera spacecraft, are examined. The orbital radar maps have revealed an absence of oceanic ridges, of subduction trenches, and the presence of a topography similar to earth's. The possibility of active volcanoes at Beta Reggio, Aphrodite Terra, and Maxwell Montes is suggested by the similar sizes of the earth and Venus, the heights of some of the surface topography, satellite-detected gravitational anomalies, radar images that look like volcanoes, and the clustering of lightning patches over suspected volcanic areas. Finally, the presence of an enhanced deuterium concentration in the Venus atmosphere has been taken as evidence that a hydrogen migration away from Venus from dissociated water occurred in Venus' geologic past.

Beatty, J. K.

1982-02-01

239

Venus Exploration using Piloted Flybys and Telepresence  

NASA Astrophysics Data System (ADS)

This paper investigates near-term, low-cost human expeditions to Venus using gravity assisted trajectories and telepresence. In this mission design, a crewed spacecraft is injected onto a near minimum-energy transfer to Venus, and upon arrival is targeted to perform a polar flyby manoeuvre which transforms its outbound trajectory into a heliocentric orbit that maintains close proximity to the planet for an extended period of time. From this vantage point, astronauts can utilize real-time surface communications to remotely operate a series of robotic Venusian explorers. At the conclusion of the mission, a second polar flyby is used to re-inject the spacecraft onto its original trajectory, which returns the crewed vehicle to Earth exactly two years after launch. Employing such gravity-assisted trajectories, an entire round-trip piloted flight to Venus can be accomplished using a single low-energy injection burn leaving Earth, with only minute (<1500 m/s velocity change) adjustments required subsequently. The proposed mission design can be accomplished with either dedicated spacecraft and Evolved Expendable Launch Vehicle (EELV)-class boosters, or alternatively, with combinations of spacecraft and launch systems planned for NASA's current exploration systems architecture. It is concluded that the mission design proposed herein represents a simple, safe, and cost-effective method of exploring one of the most compelling worlds in our solar system, while simultaneously allowing humankind to extend its reach further into space.

Bonin, G.; Kaya, T.

240

Venus: Geochemical conclusions from the Magellan data  

NASA Astrophysics Data System (ADS)

Though the Magellan mission was not designed to collect geochemical or petrological information, it has done so nonetheless. Since the time of the Pioneer Venus mission it has been known that high-altitude (greater than 2.5-5 km) mountainous areas on Venus exhibit anomalously low radiothermal emissivity (e less than 0.6). Magellan has greatly refined and extended these observations. The low emissivity requires surface material in the uplands to have a mineralogical composition that gives it a high bulk dielectric constant, greater than 20. The dielectric constant of dry terrestrial volcanic rocks seldom exceeds 7. The high-dielectric character of high-altitude surface material cannot be a primary property of the local volcanic rock, because there is no reason why rock having the required special mineralogy would erupt only at high altitudes. Therefore it is a secondary property; the primary Venus rock has reacted with the atmosphere to form a mineralogically different surface layer, and the secondary minerals formed are controlled by the ambient temperature, which decreases with altitude on Venus. A further investigation of venusian mineralogy is presented.

Wood, J. A.

1992-12-01

241

Induced magnetosphere and its outer boundary at Venus  

Microsoft Academic Search

The induced magnetosphere at Venus consists of regions near the planet and its wake for which the magnetic pressure dominates all other pressure contributions. Initial Venus Express measurements indicate a well-defined outer boundary, the magnetopause, of the induced magnetosphere. This magnetopause acts as an obstacle to deflect the solar wind. Across this boundary, the magnetic field exhibits abrupt directional changes

T. L. Zhang; M. Delva; W. Baumjohann; M. Volwerk; C. T. Russell; H. Y. Wei; C. Wang; M. Balikhin; S. Barabash; H.-U. Auster; K. Kudela

2008-01-01

242

The exosphere of Venus - Analysis of the Lyman alpha data furnished by Venera 9 and 10  

Microsoft Academic Search

The exosphere of Venus observed with a Lyman-alpha photometer carried on Venera 9 and 10 space probes is examined. Previous information on this exosphere, mission profile and instruments, the intensity measurements, the dayside and nightside exospheres, and dark and bright disks are discussed. The Venus exosphere appears to be strongly asymmetric with an exobase temperature Te = 500 K plus

M. Marcelin

1979-01-01

243

The 2004 Transit of Venus as a Space Science Education Opportunity  

Microsoft Academic Search

We will present some of the programs and activities that NASA and its missions are preparing in order to support public and K12 education in space science and astronomy using the 2004 transit of Venus as a focal event. The upcoming transit of Venus on June 8 offers a unique opportunity to educate students and the general public about the

S. Odenwald; L. Mayo; R. Vondrak; J. Thieman; I. Hawkins; G. Schultz

2003-01-01

244

Remote Raman - Laser Induced Breakdown Spectroscopy (LIBS) Geochemical Investigation under Venus Atmospheric Conditions  

Microsoft Academic Search

The extreme Venus surface temperatures (~740 K) and atmospheric pressures (~93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical

Sanuel M Clegg; James E Barefield; Seth D Humphries; Roger C Wiens; D. T. Vaniman; S. K. Sharma; A. K. Misra; M. D. Dyar; S. E. Smrekar

2010-01-01

245

Remote Laser Induced Breakdown Spectroscopy (LIBS) Geochemical Investigation under Venus Atmospheric Conditions  

Microsoft Academic Search

The extreme Venus surface temperature (740 K) and atmospheric pressure (93 atm) creates a challenging environment for future lander missions. Scientific investigations capable of Venus geochemical observations must be completed within several hours of landing before the lander is overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing geochemical

S. M. Clegg; J. E. Barefield; S. Humphries; R. C. Wiens; D. Vaniman; M. D. Dyar; J. M. Tucker; S. K. Sharma; A. K. Misra

2009-01-01

246

South-polar features on Venus similar to those near the north pole  

Microsoft Academic Search

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright `dipole' feature surrounded by a cold `collar' at its north pole. The polar dipole is a `double-eye' feature at the centre of a vast vortex that rotates

G. Piccioni; P. Drossart; A. Sanchez-Lavega; R. Hueso; F. W. Taylor; C. F. Wilson; D. Grassi; L. Zasova; M. Moriconi; A. Adriani; S. Lebonnois; A. Coradini; B. Bézard; F. Angrilli; G. Arnold; K. H. Baines; G. Bellucci; J. Benkhoff; J. P. Bibring; A. Blanco; M. I. Blecka; R. W. Carlson; A. di Lellis; T. Encrenaz; S. Erard; S. Fonti; V. Formisano; T. Fouchet; R. Garcia; R. Haus; J. Helbert; N. I. Ignatiev; P. G. J. Irwin; Y. Langevin; M. A. Lopez-Valverde; D. Luz; L. Marinangeli; V. Orofino; A. V. Rodin; M. C. Roos-Serote; B. Saggin; D. M. Stam; D. Titov; G. Visconti; M. Zambelli; Eleonora Ammannito; Alessandra Barbis; Rainer Berlin; Carlo Bettanini; Angelo Boccaccini; Guillaume Bonnello; Marc Bouye; Fabrizio Capaccioni; Alejandro Cardesin Moinelo; Francesco Carraro; Giovanni Cherubini; Massimo Cosi; Michele Dami; Maurizio de Nino; Davide Del Vento; Marco di Giampietro; Alessandro Donati; Olivier Dupuis; Sylvie Espinasse; Anna Fabbri; Agnes Fave; Iacopo Ficai Veltroni; Gianrico Filacchione; Katia Garceran; Yamina Ghomchi; Maurizio Giustini; Brigitte Gondet; Yann Hello; Florence Henry; Stefan Hofer; Gerard Huntzinger; Juergen Kachlicki; René Knoll; Kouach Driss; Alessandro Mazzoni; Riccardo Melchiorri; Giuseppe Mondello; Francesco Monti; Christian Neumann; Fabrizio Nuccilli; Jerome Parisot; Claudio Pasqui; Stefano Perferi; Gisbert Peter; Alain Piacentino; Carlo Pompei; Jean-Michel Reess; Jean-Pierre Rivet; Antonio Romano; Natalie Russ; Massimo Santoni; Adelmo Scarpelli; Alain Soufflot; Douchane Stefanovitch; Enrico Suetta; Fabio Tarchi; Nazzareno Tonetti; Federico Tosi; Bernd Ulmer

2007-01-01

247

The abundance and vertical distribution of the unknown ultraviolet absorber in the venusian atmosphere from analysis of Venus Monitoring Camera images  

NASA Astrophysics Data System (ADS)

Observations of Venus using the ultraviolet filter of the Venus Monitoring Camera (VMC) on ESA's Venus Express Spacecraft (VEX) provide the best opportunity for study of the spatial and temporal distribution of the venusian unknown ultraviolet absorber since the Pioneer Venus (PV) mission. We compare the results of two sets of 125 radiative transfer models of the upper atmosphere of Venus to each pixel in a subset of VMC UV channel images. We use a quantitative best fit criterion based upon the notion that the distribution of the unknown absorber should be independent of the illumination and observing geometry. We use the product of the cosines of the incidence and emission angles and search for absorber distributions that are uncorrelated with this geometric parameter, finding that two models can describe the vertical distribution of the unknown absorber. One model is a well-mixed vertical profile above a pressure level of roughly 120 mb (˜63 km). This is consistent with the altitude of photochemical formation of sulfuric acid. The second model describes it as a thin layer of pure UV absorber at a pressure level roughly around 24 mb (˜71 km) and this altitude is consistent with the top of upper cloud deck. We find that the average abundance of unknown absorber in the equatorial region is 0.21 ± 0.04 optical depth and it decreases in the polar region to 0.08 ± 0.05 optical depth at 365 nm.

Molaverdikhani, Karan; McGouldrick, Kevin; Esposito, Larry W.

2012-02-01

248

Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 Measurements  

NASA Astrophysics Data System (ADS)

We discuss the detection and evolution of a complex series of transient and quasi-static solar-wind structures in the days following the well-known comet 2P/Encke tail disconnection event in April 2007. The evolution of transient solar-wind structures ranging in size from <105 km to >106 km was characterised using one-minute time resolution observation of Interplanetary Scintillation (IPS) made using the European Incoherent SCATter (EISCAT) radar system. Simultaneously, the global structure and evolution of these features was characterised by the Heliospheric Imagers (HI) on the Solar TERrestrial RElations Observatory (STEREO) spacecraft, placing the IPS observations in context. Of particular interest was the observation of one transient in the slow wind, apparently being swept up and entrained by a Stream Interaction Region (SIR). The SIR itself was later detected in-situ at Venus by the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express (VEX) spacecraft. The availability of such diverse data sources over a range of different time resolutions enables us to develop a global picture of these complex events that would not have been possible if these instruments were used in isolation. We suggest that the range of solar-wind transients discussed here may be the interplanetary counterparts of transient structures previously reported from coronagraph observations and are likely to correspond to transient magnetic structures reported in in-situ measurements in interplanetary space. The results reported here also provide the first indication of heliocentric distances at which transients become entrained.

Dorrian, G. D.; Breen, A. R.; Davies, J. A.; Rouillard, A. P.; Fallows, R. A.; Whittaker, I. C.; Brown, D. S.; Harrison, R. A.; Davis, C. J.; Grande, M.

2010-08-01

249

Ballistic trajectory options for manned Mars Missions  

Microsoft Academic Search

Mars Mission profile options and mission requirements data are presented for earth-Mars opposition and conjunction class round-trip flyby and stopover mission opportunities. The opposition-class flyby and sprint mission uses direct transfer trajectories to and on return from Mars. The opposition-class stopover mission employs the gravitational field of Venus to accelerate the space vehicle on either the outbound or inbound leg

Archie C. Young

1990-01-01

250

Venus mapping delayed by Magellan problem  

Microsoft Academic Search

The start of full-scale radar mapping of Venus by NASA's Magellan spacecraft has been delayed until at least September 15 while a task force of mission personnel investigates the cause of two communication losses with the spacecraft during its first week in orbit.The task force, headed by Frank McKinney of the Martin-Marietta spacecraft operations division, convened August 28 at the

Steven Cole

1990-01-01

251

Data from Venus  

NASA Website

On Dec. 14, 1962, NASA's Mariner 2 spacecraft sailed close to the shrouded planet Venus, marking the first time any spacecraft had ever successfully made a close-up study of another planet. It flew by Venus as planned at a range of 34,762 km ...

252

Gravity anomalies on Venus  

Microsoft Academic Search

Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable

W. L. Sjogren; R. J. Phillips; P. W. Birkeland; R. N. Wimberly

1980-01-01

253

Future exploration of Venus  

Microsoft Academic Search

The present state of knowledge concerning the planet Venus is examined. It is pointed out that Venus, even with our present data, remains enigmatic and contradictory. A summary is given of seven major areas in which further studies are needed. The rewards of such studies would be related to an emergence of basic principles and processes which shape the origin

L. D. Friedman; J. L. Lewis

1975-01-01

254

Venus on the Verge  

NASA Astrophysics Data System (ADS)

Venus’s descent into hellish heat must have been caused by its proximity to the Sun. The story of how Venus lost its water becomes: too much sunlight caused a runaway greenhouse effect, any water evaporated, and the hydrogen escaped into space.

Zahnle, K. J.; Abe, Y.; Abe-Ouchi, A.; Sleep, N. H.

2012-06-01

255

Venus Transit 2004  

Microsoft Academic Search

December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus

L. A. Mayo; S. F. Odenwald

2002-01-01

256

Ice Caps on Venus.  

National Technical Information Service (NTIS)

The Venus data obtained by the Mariner 5 and Venera 4 probes are interpreted as evidence for giant polar ice caps which hold the water which must have come out of the volcanos with the observed CO2 on the assumption that the earth and Venus are of similar...

W. F. Libby

1968-01-01

257

Venus Upper Atmosphere Structure  

Microsoft Academic Search

From analysis of the orbiter atmospheric drag (OAD) data obtained from the orbital decay of the Pioneer Venus orbiter from December 9, 1978, to August 7, 1979, atmospheric densities have been determined and tabulated near 16øN latitude between 140 and 190 km for all times of day. Maximum daytime densities on Venus are approximately 8 x 10 -13 g cm

G. M. Keating; J. Y. Nicholson; L. R. Lake

1980-01-01

258

Extreme Space Weather at Venus and Mars: What We Know and Don't Know (Yet) (Invited)  

NASA Astrophysics Data System (ADS)

The atmospheres of our unmagnetized planetary neighbors, Venus and Mars, experience extreme space weather unfiltered by a sometimes protective planetary field. While there are standard ionosphere reactions to the XUV photon enhancements associated with major flares, the effects of particles and fields are not so terrestrial-like and can last several days following the events on the Sun. Unfortunately detailed information about these responses at Venus and Mars are very limited, in part by the fact that the instruments to make some of the needed observations are either absent or inadequate on missions designed for other purposes, while others are compromised by the disturbed conditions themselves. In addition, the connections of planetary responses with the solar/interplanetary causes is often difficult to establish with available heliospheric monitors. This presentation summarizes the current state of our understanding based on the existing observations during two major event periods: The October- November 2003 period, and the December 2006 period when Venus Express and/or Mars Express were in orbit. We also consider what was learned from the solar cycle-long PVO mission, and the potential for improving our state of knowledge during the upcoming solar maximum with VEX, MEX and MAVEN.

Luhmann, J. G.; McEnulty, T.; Ulusen, D.; Brain, D. A.; Delory, G. T.; Ma, Y.; Jian, L.; Russell, C. T.; Zhang, T.; Futaana, Y.; Dubinin, E.; Fedorov, A.; Jakosky, B. M.

2010-12-01

259

The Planetary Fourier Spectrometer (PFS) onboard the European Mars Express mission  

Microsoft Academic Search

The Planetary Fourier Spectrometer (PFS) for the Mars Express mission is an infrared spectrometer optimised for atmospheric studies. This instrument has a short wave (SW) channel that covers the spectral range from 1700 to 8200.0cm-1 (1.2–5.5?m) and a long-wave (LW) channel that covers 250–1700cm-1 (5.5–45?m). Both channels have a uniform spectral resolution of 1.3cm-1. The instrument field of view FOV

V. Formisanoa; F. Angrilli; G. Arnold; S. Atreya; G. Bianchini; D. Biondi; A. Blanco; M. I. Blecka; A. Coradini; L. Colangeli; A. Ekonomov; F. Esposito; S. Fonti; M. Giuranna; D. Grassi; V. Gnedykh; A. Grigoriev; G. Hansen; H. Hirsh; I. Khatuntsev; A. Kiselev; N. Ignatiev; A. Jurewicz; E. Lellouch; J. Lopez Moreno; A. Marten; A. Mattana; A. Maturilli; E. Mencarelli; M. Michalska; V. Moroz; B. Moshkin; F. Nespoli; Y. Nikolsky; R. Orfei; P. Orleanski; V. Orofino; E. Palomba; D. Patsaev; G. Piccioni; M. Rataj; R. Rodrigo; J. Rodriguez; M. Rossi; B. Saggin; D. Titov; L. Zasova

2005-01-01

260

Methods for the analysis of data from the Planetary Fourier Spectrometer on the Mars Express Mission  

Microsoft Academic Search

This work presents an algorithm for the scientific analysis of individual calibrated measurements from the Planetary Fourier spectrometer (PFS).The instrument, included in the scientific payload of the ESA Mars Express mission to Mars, acquires spectra in the range between 250 and 8200cm?1, with a sampling step of ?1cm?1 and an effective resolution of ?2cm?1. The observed radiance depends on several

Davide Grassi; N. I. Ignatiev; L. V. Zasova; A. Maturilli; V. Formisano; G. A. Bianchini; M. Giuranna

2005-01-01

261

Exploring the Planets: Venus  

NSDL National Science Digital Library

This site contains most of the up-to-date information known about the planet Venus, including mean distance from Sun, length of year, rotation period, mean orbital velocity, inclination of axis, average temperature (day and night), and diameter. Many discoveries about Venus have been made using Earth-based radio telescopes, however the images of Venus in this exhibit were collected by the Magellan spacecraft. Magellan used radar to produce the first high-resolution global map of Venus. Since Venus has no water erosion and little wind, volcanic eruptions are a major force reshaping the landscape. Geologic forces at work beneath the crust create mountains, rifts, and patterns of fractures, while the sluggish winds sculpt the surface in subtler ways but many mysteries remain. This site includes numerous images of the planet.

262

Evolution of Venus: Current knowledge and future prospects  

NASA Astrophysics Data System (ADS)

Venus is commonly thought to have experienced a transition, early in its history, from a wet, more Earth-like environment to its currently highly desiccated state. A more recent global transition is indicated by the sparse, randomly distributed and relatively pristine crater population, which implies a rapid decrease in volcanic resurfacing rate between 300 and 1000 Myr ago. The accompanying precipitous decline in outgassing rate would have caused large climate changes and globally synchronous plains deformation. These two transitions may have been causally related, as the loss of atmospheric water through evaporation, photodissociation and H escape caused the transition from plate tectonics to single plate behavior, and the cessation of subducting hydrated sediments caused the desiccation of the mantle and consequent loss of an asthenosphere. New data from Venus Express can help test these ideas by refining the timescale for water loss, constraining current outgassing rates, and improving models of climate, cloud formation and atmospheric dynamics, thus improving the sophistication of evolutionary climate models. I will discuss these efforts and review relevant plans for future missions.

Grinspoon, David

263

Radar characteristics of small craters - Implications for Venus  

NASA Astrophysics Data System (ADS)

Shuttle radar images (SIR-A) of volcanic and impact craters were examined to assess their appearance on radar images. Radar characteristics were determined for (1) nine maarlikie craters in the Pinacate volcanic field, Sonora, Mexico; (2) the caldera of Cerro Volcan Quemado, in the Bolivian Andes; (3) Talemzane impact crater, Algeria; and (4) Al Umchaimin, a possible impact structure in Iraq. SIR-A images were compared with conventional photographs and with results from field studies. Consideration was then given to radar images available for Venus, or anticipated from the Magellan mission. Of the criteria ordinarily used to identify impact craters, some can be assessed with radar images and others cannot be used; planimetric form, expressed as circularity, and ejecta-block distribution can be assessed on radar images, but rim and floor elevations relative to the surrounding plain and disposition of rim strata are difficult or impossible to determine. It is concluded that it will be difficult to separate small impact craters from small volcanic craters on Venus using radar images and is suggested that it will be necessary to understand the geological setting of the areas containing the craters in order to determine their origin.

Greeley, R.; Christensen, P. R.; McHone, J. F.

1987-01-01

264

Pluto express: Advanced technologies enable lower cost missions to the outer Solar System and beyond  

NASA Astrophysics Data System (ADS)

Missions to Pluto and the outer Solar System are typically driven by factors which tend to increase cost, such as: long life, high radiation exposure, a large power source, high ?V requirements, difficult telecommunications links, low solar illumination at the destination, and demanding science measurements. Advanced technology is a central part of responding to such challenges in a manner which permits the cost of development and operations to be an order of magnitude less than for prior outer planet missions. Managing the process of technology planning and advanced development versus the associated cost and mission risk is a formidable challenge. Outer Solar System/Europa/Pluto/Solar Probe development activities are leveraging the latest products from the industry, government lab and academia technology pipeline in the areas of software, low power integrated microelectronics, low mass, high efficiency radioisotope power if used, and telecommunications. This paper summarizes the current technology development plan, which is tightly coupled to the New Millennium Program (NMP) Deep Space 1 technology validation flight. Specific detail will be presented about advanced microelectronics technology. This technology will also be shown in the context of an on-going technology roadmap that extends beyond the Pluto Express mission. Other details focus on new technologies available for low cost mission operations, and the processes required to best develop and utilize these technologies. The development goal is to create an integrated flight and ground system with the functional simplicity necessary to achieve high reliability, operability, and a low total mission cost. The development process leverages the JPL Flight System Testbed and commercial off-the-shelf (COTS) products. A university partnership provides additional development support and is leading to a partnership for operations. Software technologies for spacecraft self-commanding and self-monitoring play a key role in meeting an operations vision called Beacon Monitoring. This approach is expected to decrease operations cost significantly by reducing the amount of routine interaction with the spacecraft. The experience gathered may be valuable to Earth orbiting missions, the Mars Exploration Program, and Mission to Planet Earth.

Staehle, Robert L.; Alkalai, Leon J.; Wyatt, E. Jay; Dohoney, John

1997-01-01

265

HIGH-RESOLUTION SATELLITE IMAGING OF THE 2004 TRANSIT OF VENUS AND ASYMMETRIES IN THE CYTHEREAN ATMOSPHERE  

SciTech Connect

This paper presents the only space-borne optical-imaging observations of the 2004 June 8 transit of Venus, the first such transit visible from Earth since AD 1882. The high-resolution, high-cadence satellite images we arranged from NASA's Transition Region and Coronal Explorer (TRACE) reveal the onset of visibility of Venus's atmosphere and give further information about the black-drop effect, whose causes we previously demonstrated from TRACE observations of a transit of Mercury. The atmosphere is gradually revealed before second contact and after third contact, resulting from the changing depth of atmospheric layers refracting the photospheric surface into the observer's direction. We use Venus Express observations to relate the atmospheric arcs seen during the transit to the atmospheric structure of Venus. Finally, we relate the transit images to current and future exoplanet observations, providing a sort of ground truth showing an analog in our solar system to effects observable only with light curves in other solar systems with the Kepler and CoRoT missions and ground-based exoplanet-transit observations.

Pasachoff, Jay M. [Williams College-Hopkins Observatory, 33 Lab Campus Drive, Williamstown, MA 01267 (United States); Schneider, Glenn [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Widemann, Thomas [Observatoire de Paris-LESIA, 92190 Meudon (France)

2011-04-15

266

Hinode Views the Transit of Venus  

NASA Video Gallery

On June 5, 2012, Hinode captured this stunning view of the transit of Venus -- the last instance of this rare phenomenon until 2117. Hinode is a joint JAXA/NASA mission to study the connections of the sun's surface magnetism, primarily in and around sunspots. NASA's Marshall Space Flight Center in Huntsville, Ala., manages Hinode science operations and oversaw development of the scientific instrumentation provided for the mission by NASA, and industry. The Smithsonian Astrophysical Observatory in Cambridge, Mass., is the lead U.S. investigator for the X-ray Telescope. (JAXA/NASA/SAO)

Sydney B

2012-06-08

267

Hinode Views the 2012 Venus Transit  

NASA Video Gallery

On June 5, 2012, Hinode captured these stunning views of the transit of Venus -- the last instance of this rare phenomenon until 2117. Hinode is a joint JAXA/NASA mission to study the connections of the sun's surface magnetism, primarily in and around sunspots. NASA's Marshall Space Flight Center in Huntsville, Ala., manages Hinode science operations and oversaw development of the scientific instrumentation provided for the mission by NASA, and industry. The Smithsonian Astrophysical Observatory in Cambridge, Mass., is the lead U.S. investigator for the X-ray Telescope. (JAXA/NASA/SAO)

Sydney B

2012-06-06

268

The induced magnetotails of Mars and Venus: A tale of two tails (Invited)  

NASA Astrophysics Data System (ADS)

Venus and Mars occupy a similar region in the broad spectrum of plasma interactions with solar system bodies. The magnetospheres at both objects are induced, formed by the interaction of supersonic solar wind plasma at roughly 1 AU with highly conducting ionospheres. The magnetic field carried by incident solar wind plasma 'drapes' around the atmospheric obstacle on the day side of each planet, and forms an induced two-lobed magnetotail on the night side. The global configuration of the two magnetotails can be highly variable, determined by the constantly changing upstream conditions. Magnetotail plasma is dominated by atmospheric ions at both planets - these processes are believed to have significantly altered the atmospheres, climate, and even surface evolution at both. Yet these two magnetotails are not entirely similar. Mars is substantially smaller than Venus and orbits at double the heliocentric distance. These differences influence the importance of ion gyromotion in the magnetotails, the amount of mass loading of the solar wind plasma flow, and the upstream conditions encountered at each object. Mars also possesses strong crustal magnetic fields which significantly complicate the magnetotail structure and plasma processes close to the planet. In this presentation we will provide an overview of the global structure, variability, and active plasma processes in the magnetotails of both Venus and Mars, placing them in context with other solar system bodies. We will then focus on recent results from the Mars Global Surveyor, Mars Express, and Venus Express spacecraft missions, as well as recent results obtained from global plasma simulations for both bodies. We will identify outstanding questions and measurements for the future.

Brain, D. A.; Halekas, J. S.; Eastwood, J. P.

2010-12-01

269

Comparing Earth and Venus  

NASA Astrophysics Data System (ADS)

For obvious reasons the atmosphere of Venus has received much less attention in the natural sciences than the atmosphere of Earth. The same is true for numerical modeling efforts concerning the two atmospheres. The circulation of Venus' atmosphere can be described by the same set of basic equations valid for the other planetary atmospheres: the Navier-Stokes equations describing the temporal evolution of momentum plus equations of continuity and the conservation of thermodynamic energy (see Chap. 5). These equations are discretized in the so-called dynamical cores of numerical models, and it is not surprising that Venus models, in general, use dynamical cores originally built for Earth modeling (see Chap. 6). Parameterizations needed in complex planetary models to describe subgrid-scale processes are more difficult to exchange because parameters may differ considerably among planets. Nevertheless, many parameterizations used in Venus models are based on developments made for other planets.

Schmidt, Hauke

270

Astrobiology and Venus exploration  

NASA Astrophysics Data System (ADS)

For hundreds of years prior to the space age, Venus was considered among the most likely homes for extraterrestrial life. Since planetary exploration began, Venus has not been considered a promising target for Astrobiological exploration. However, Venus should be central to such an exploration program for several reasons. At present Venus is the only other Earth-sized terrestrial planet that we know of, and certainly the only one we will have the opportunity to explore in the foreseeable future. Understanding the divergence of Earth and Venus is central to understanding the limits of habitability in the inner regions of habitable zones around solar-type stars. Thus Venus presents us with a unique opportunity for putting the bulk properties, evolution and ongoing geochemical processes of Earth in a wider context. Many geological and meteorological processes otherwise active only on Earth at present are currently active on Venus. Active volcanism most likely affects the climate and chemical equilibrium state of the atmosphere and surface, and maintains the global cloud cover. Further, if we think beyond the specifics of a particular chemical system required to build complexity and heredity, we can ask what general properties a planet must possess in order to be considered a possible candidate for life. The answers might include an atmosphere with signs of flagrant chemical disequilibrium and active, internally driven cycling of volatile elements between the surface, atmosphere and interior. At present, the two planets we know of which possess these characteristics are Earth and Venus. Venus almost surely once had warm, habitable oceans. The evaporation of these oceans, and subsequent escape of hydrogen, most likely resulted in an oxygenated atmosphere. The duration of this phase is poorly understood, but during this time the terrestrial planets were not isolated. Rather, due to frequent impact transport, they represented a continuous environment for early microbial life. Life, once established in the early oceans of Venus, may have migrated to the clouds which, on present day Venus, may represent a habitable niche. Though highly acidic, this aqueous environment enjoys moderate temperatures, surroundings far from chemical equilibrium, and potentially useful radiation fluxes. Observations of unusual chemistry in the clouds, and particle populations that are not well characterized, suggest that this environment must be explored much more fully before biology can be ruled out. A sulfur-based metabolism for cloud-based life on Venus has recently been proposed (Schulze-Makuch et al., 2004). While speculative, these arguments, along with the discovery of terrestrial extremophile organisms that point toward the plausibility of survival in the Venusian clouds, establish the credibility of astrobiological exploration of Venus. Arguments for the possible existence of life on Mars or Europa are, by convention and repetition, seen as more mainstream than arguments for life elsewhere, but their logical status is similar to plausibility arguments for life on Venus. With the launch of COROT in 2006 and Kepler in 2008 the demographics of Earth-sized planets in our galaxy should finally become known. Future plans for a Terrestrial Planet Finder or Darwin-type space-based spectrograph should provide the capability of studying the atmospheric composition and other properties of terrestrial planets. One of the prime rationales for building such instruments is the possibility of identifying habitable planets or providing more generalized observational constraints on the habitable zones of stellar systems. Given the prevalence of CO2 dominated atmospheres in our own solar system, it is quite likely that a large fraction of these will be Venus-like in composition and evolutionary history. We will be observing these planets at random times in their evolution. In analogy with our own solar system, it is just as likely that we will find representatives of early Venus and early Earth type planets from the first 2 billion years of their evolution as i

Grinspoon, David H.; Bullock, Mark A.

271

The planet Venus  

Microsoft Academic Search

Astronomical observations and space probe explorations of Venus are discussed. The use of ultraviolet photography and radioastronomy to determine the period of rotation of the Venusian atmosphere (4 days) and the planetary surface (243 days) is described. Studies of the Venusian atmosphere conducted by the U.S. Mariner program and the Soviet Venera probes are considered. The launch of the Pioneer-Venus-Orbiter

C. Boyer; A. Cazenave

1977-01-01

272

Venus Transit Observer  

NSDL National Science Digital Library

This Java applet shows the location in the sky of the Sun and Venus for any given location on Earth. The date and time can be set for past and future years, and the program indicates the rise, set, azimuth, and elevation for both celestial bodies. Details about Venus also include elongation from the Sun, distance from the Earth, and past and future transits across the Sun as seen from Earth (date, time, and year).

Giesen, Juergen

273

Mercury, Venus, and Earth!  

NSDL National Science Digital Library

You will compare and contrast Mercury, Venus, and Earth. While looking at these different websites, use the information to fill in your handout of a column chart and on the back answer the questions you are asked on here. First view this website and record on your chart the distance from the sun Mercury,Venus, and Earth are. Now, learn about Mercury! What is the surface ...

Bschiffer

2009-10-21

274

Stratospheric balloon BIRBA 2 mission: effects of cosmic radiations on gene expression of human cells  

NASA Astrophysics Data System (ADS)

In space living organisms, including cells, are affected by two new environmental conditions: microgravity and cosmic radiations. In order to evaluate the effects of cosmoc radiation on the gene expression we exposed human cell lines to high quote cosmic radiation during stratospheric balloon trans-mediterranean flights (BIRBA2, mission 2002). To this purpose HUVEC (endotelial human cells) and purified human T lymphocytes, were used. After a 22 h flight the cells lines were examinated by the cDNA microarrays method, proved to be very sensible and accurate. A panel of genes candidate to be defined modulated by cosmic radiation has been isolated.

Galleri, Grazia; Camboni, Maria Gavina; Negri, Rodolfo; de Sanctis, Veronica; Costanzo, Giovanna; Meloni, Maria Antonia; Pipia, Proto; Cotronei, Vittorio; Cogoli, Augusto

2003-08-01

275

Initial PVO evidence of electron depletion signatures downstream of Venus  

Microsoft Academic Search

This first analysis of Pioneer Venus Orbiter (PVO) plasma analyzer electron measurements obtained in early 1992 during teh PVO entry phase of the mission indicates the presence downstream from the terminator of a depletion or 'bite out' of energetic ionosheath electrons similar to that observed on Mariner 10. There is more than one possible explanation for this energetic electron depletion.

D. S. Intriligator; R. E. Hartle; H. Perez-de-Tejada; G. L. Siscoe

1993-01-01

276

Initial PVO evidence of electron depletion signatures downstream of Venus  

Microsoft Academic Search

This first analysis of Pioneer Venus Orbiter (PVO) plasma analyzer electron measurements obtained in early 1992 during the PVO entry phase of the mission indicates the presence downstream from the terminator of a depletion or “bite out” of energetic ionosheath electrons similar to that observed on Mariner 10. There is more than one possible explanation for this energetic electron depletion.

D. S. Intriligator; R. E. Hartle; H. Perez-de-Tejada; G. L. Siscoe

1993-01-01

277

Images and topographic relief at the north pole of Venus  

Microsoft Academic Search

The analysis of unique coverage of the north pole of Venus using a subset of 13 images from a total of about 775 synthetic aperture radar orbits during cycle 1 of the Magellan mission is reported. Images at 13 distinctly different azimuths are reported that range over 360 deg in longitude and that show the topographic relief at vastly different

Franz W. Leberl; Kelly E. Maurice; John K. Thomas; Craig E. Leff; Stephen D. Wall

1992-01-01

278

Design And Operation of the Pioneer Venus Orbiter Ultraviolet Spectrometer  

Microsoft Academic Search

The University of Colorado's Ultraviolet Spectrometer instrument carried on the Pioneer Venus Orbiter spacecraft is a 125 mm f\\/5 Ebert-Fastie design with a 250-mm Cassegrainian telescope. The instrument has extensive logic to control the grating motor drive and to adapt the basic spectrometer to the constraints and opportunities of the mission. Success has been achieved in reconciling the confficting requirements

A. I. F. Stewart

1980-01-01

279

Venus lower atmospheric composition - Preliminary results from Pioneer Venus  

Microsoft Academic Search

Initial examination of data from the neutral mass spectrometer on the Pioneer Venus sounder probe indicates that the abundances of argon-36, argon-38, and neon-20 in the Venus atmosphere are much higher than those of the corresponding gases in Earth's atmosphere, although the abundance of radiogenic argon-40 is apparently similar for both planets. The lower atmosphere of Venus includes significant concentrations

J. H. Hoffman; M. B. McElroy; T. M. Donahue; M. Kolpin; R. R. Hodges

1979-01-01

280

Characterizing the Venus atmospheric dynamics from ground-based Doppler velocimetry  

NASA Astrophysics Data System (ADS)

We present an analysis of observations of Venus made with the UVES instrument (Ultraviolet and Visual Echelle Spectrograph) at ESO's Very Large Telescope (VLT). The observations were carried out in May and June 2007 with the aim of characterizing the zonal wind flow in the atmosphere of Venus during the nominal mission phase of Venus Express. Doppler velocimetry measurements are based on solar Fraunhofer lines in the visible, probing the cloud tops velocity close to 65 km altitude. The narrow slit width of the UVES instrument, combined with the large apparent angular size of the planet, allows to simultaneously achieve high spectral resolving power and high spatial resolution. The observations were made at a central wavelength of 580 nm with the UVES red arm and at 437 and 860 nm in dichroic mode, using both the blue and red arms. In one observation block the field has been derotated in order to align the 0.3-arcsec aperture perpendicularly to Venus's rotation axis, while in other observations it was aligned parallel to it. In each case, spatial information, respectively in the East-West and in the North-South direction, is preserved in the spectra in the direction perpendicular to dispersion, allowing to spatially resolve relative variations in atmospheric rotation. We estimate both the relative variations of the atmospheric rotation with latitude and the hemispheric asymmetry of the zonal wind between 35S and 35N. The absolute magnitude of the zonal winds at latitudes of 23S, 13S and 2S has also been determined. [P. Machado acknowledges support from Fundação para a Ciência e a Tecnologia, grant SFRH-BD-66473-2009.

Machado, Pedro; Luz, David; Widemann, Thomas; Lellouch, Emmanuel; Witasse, Olivier; Bertaux, Jean-Loup

2010-05-01

281

Astrobiology and Venus Exploration  

NASA Astrophysics Data System (ADS)

Venus has not traditionally been considered a promising target for Astrobiological exploration. We propose that Venus should be central to such an exploration program for several reasons. 1) Putting Earth life in context: Venus is the only other Earth-sized terrestrial planet that we know of, and certainly the only one we will have the opportunity to explore in the foreseeable future. Many geological and meteorological processes otherwise active only on Earth at present are currently active on Venus. For example, active volcanism is most likely responsible for maintaining the global cloud cover (Bullock and Grinspoon, 2001). Understanding the divergence of Earth and Venus is central to understanding the limits of habitability in the inner regions of habitable zones around solar-type stars. Thus Venus presents us with a unique opportunity for putting the bulk properties, evolution and ongoing geochemical processes of Earth in a wider context. 2) The possibility of extant life: Venus almost surely once had warm oceans. The evaporation of these oceans, and subsequent escape of hydrogen, most likely resulted in an oxygenated atmosphere. The duration of this phase is poorly understood, but during this time the terrestrial planets were not isolated. Rather, due to frequent impact transport, they represented a continuous environment for early microbial life. Life, once established in the early oceans of Venus, may have migrated to the clouds which, on present day Venus, may represent a habitable niche. Though highly acidic, this aqueous environment enjoys moderate temperatures, surroundings far from chemical equilibrium, and potentially useful radiation fluxes. Observations of unusual chemistry in the clouds, and particle populations that are not well characterized, suggest that this environment must be explored much more fully before biology can be ruled out. A sulfur-based metabolism for cloud-based life on Venus has recently been proposed (Schulze-Makuch et al., 2004). While speculative, these arguments, along with the discovery of terrestrial extremophile organisms that might survive in the Venusian clouds, establish the credibility of astrobiological exploration of Venus. Arguments for the possible existence of life on Mars or Europa are, by convention and repetition, seen as more mainstream than arguments for life elsewhere, but their logical status is no different from the plausibility arguments for life on Venus. 3) Rare planetary properties of astrobiological interest: All of our ideas about extraterrestrial biochemistry are, of necessity, extrapolations from the single example of life which we have been able to study. Our planetary exploration, with an increasing focus on Astrobiology, is designed to 'follow the water'. This is a reasonable strategy but it is based, at best, on an educated guess about life's universals. If we think beyond the specifics of a particular chemical system required to build complexity and heredity, we can ask what general properties a planet must possess in order to be considered a possible candidate for life. The answers might include an atmosphere with signs of flagrant chemical disequilibrium and active, internally driven cycling of volatile elements between the surface, atmosphere and interior. At present, the two planets we know of which possess these characteristics are Earth and Venus. Bullock, M.A. and D.H. Grinspoon (2001) Icarus, 150, 19-37 Schulze-Makuch, D.H. Grinspoon., O. Abbas, L.N. Irwin and M. Bullock. (2004) . Astrobiology, 4, 11-18.

Grinspoon, D. H.; Bullock, M. A.

2005-12-01

282

Sox10-Venus mice: a new tool for real-time labeling of neural crest lineage cells and oligodendrocytes  

PubMed Central

Background While several mouse strains have recently been developed for tracing neural crest or oligodendrocyte lineages, each strain has inherent limitations. The connection between human SOX10 mutations and neural crest cell pathogenesis led us to focus on the Sox10 gene, which is critical for neural crest development. We generated Sox10-Venus BAC transgenic mice to monitor Sox10 expression in both normal development and in pathological processes. Results Tissue fluorescence distinguished neural crest progeny cells and oligodendrocytes in the Sox10-Venus mouse embryo. Immunohistochemical analysis confirmed that Venus expression was restricted to cells expressing endogenous Sox10. Time-lapse imaging of various tissues in Sox10-Venus mice demonstrated that Venus expression could be visualized at the single-cell level in vivo due to the intense, focused Venus fluorescence. In the adult Sox10-Venus mouse, several types of mature and immature oligodendrocytes along with Schwann cells were clearly labeled with Venus, both before and after spinal cord injury. Conclusions In the newly-developed Sox10-Venus transgenic mouse, Venus fluorescence faithfully mirrors endogenous Sox10 expression and allows for in vivo imaging of live cells at the single-cell level. This Sox10-Venus mouse will thus be a useful tool for studying neural crest cells or oligodendrocytes, both in development and in pathological processes.

2010-01-01

283

The Planet Venus  

NASA Astrophysics Data System (ADS)

This book is not so much for the space scientist looking for background material for research as it is for one interested in the history of planetary exploration. The first half (˜100 pps) is devoted to studies of Venus before the space age, starting at several hundred years BC. It is obvious from the multitude of detailed descriptions of observers' accounts that considerable library research went into this section. While sometimes tedious, this chronology of Venus research is punctuated with amusing facts. While many may know about the Velikovsky theory of the cometary origin of the planet, few may know that Lowell drew pictures of Cytherian canals similar to the canals of Mars or that Frederick the Great of Prussia proposed to name the (once suspected) satellite of Venus D'Alembert, after the mathematician. An equally amusing appendix shows the ups and downs of the rotation period of this planet with the invisible surface. Much attention is focused on early telescope observations, the ashen light, and transits of Venus. At the end of this half, one appreciates that Venus has played a fairly important role in history in the areas of religion, science, and technology.

Luhmann, Janet

284

Perspectives of the bistatic radar and occultation studying of the Venus atmosphere and surface  

NASA Astrophysics Data System (ADS)

Studying the physical properties of Venus surface and subsurface structures is an important direction in the space research. The first aim of this contribution is to present some results of reanalysis of the bistatic radar and occultation experiments provided using Venera-9, 10 and 15, 16 satellites. Comparison is made with Magellan and Venus Express bistatic radar missions. Bistatic radio images of the Venus surface is compared with monostatic radio images obtained by the Soviet and USA orbiters. The second aim consists in introducing new methods for investigation of the layered structure of the Venus atmosphere and measuring parameters of Venus surface and subsurface structures using the bistatic radar technology. The first bistatic radar measurements with spatial resolution ~ 10-20 km have been carried out during autumn of 1975 year in the five Venus equatorial regions using the Venera-9 and 10 satellites. Small roughness and, in general, plain character of relief in the investigated regions have been revealed. In 1983, the satellites Venera 15 and 16 have carried out new bistatic radar experiments with spatial resolution in the interval 5 - 10 km. New information on the large-scale topography and roughness of small-scale relief has been obtained in Northern polar areas of the planet. Some features have been detected. 1. The significant variations of the reflectivity ~ 2-4 times were found in the first region. The second area of reflectivity magnitude was far below (by three - four times) the previously measured values in the equatorial regions of Venus. These significant reflectivity variations may be related to changes in the conductivity of the ground. 2. Extremely small values roughness with rms of slopes ~ 0.20 were recorded in the northern area. 3. Both the bending angle and the reflection coefficient were determined in the experiment from the measured frequency difference between the direct and the reflected signals as a function of time, using the orbital data. New methods developed by analysis of the experimental data obtained using high-stability radio fields of the Earth's navigational satellites are introduced. For investigations of the layered structures of the Venus atmosphere a new eikonal acceleration/intensity technique is proposed. This technique allows: (1) one frequency high-precision measuring the total absorption of radio waves in the atmosphere; (2) estimating vertical gradients of the refractivity, and determining the height, slope, and horizontal displacement of the atmospheric and ionospheric layers; (3) a criterion is introduced for identification of the internal waves in the Venus atmosphere. To obtain the information on the planetary subsurface structure up to depth 1 km it is necessary to use radio waves in the Low Frequency (LF), Medium Frequency (MF), or High Frequency (HF) bands with wavelength from 1 m up 300 m. The depth of radio sounding is proportional to the wavelength, the intensity of the radio-emission source, and depends on the conductivity of the ground. The bistatic subsurface remote sensing of the planet can be achieved using powerful Earth based transmitters, and/or sporadic radio emission of the Sun and other space radio sources. The work was partly supported by Program 22 of Presidium of Russian Academy of Sciences.

Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Yakovlev, Oleg

2013-04-01

285

Prospective spacecraft for venus research: Venera-D design  

NASA Astrophysics Data System (ADS)

A new phase of Venus research has started in Russia; the Federal Space Program includes the Venera-D design with the launch of the spacecraft scheduled for 2016. The mission comprises an orbiter, a descent vehicle, and balloon probes. The balloon probes will be placed at different altitudes in the cloud layer and under the clouds, where they are intended to last for a long time in the atmosphere of Venus. The successful implementation of the design will allow solving of quite a number of scientific tasks for comparative planetology.

Vorontsov, V. A.; Lokhmatova, M. G.; Martynov, M. B.; Pichkhadze, K. M.; Simonov, A. V.; Khartov, V. V.; Zasova, L. V.; Zelenyi, L. M.; Korablev, O. I.

2011-12-01

286

Beagle 2: a proposed exobiology lander for ESA's 2003 Mars Express mission  

NASA Astrophysics Data System (ADS)

The proposed Beagle 2 lander for ESA's 2003 Mars Express mission will be described. The aim of Beagle 2 will be to search for organic material on and below the surface of Mars in addition to a study of the inorganic chemistry and mineralogy of the landing site. The lander will utilize a small rover equipped with a mechanical and grinder to obtained samples from below the surface, under rocks, and inside rocks. Samples will be returned to the lander for analysis. Analysis performed by Beagle 2 will include examination of samples with an optical microscope and APX and Mossbauer Spectrometers as well as a search for organics and a measurement of their isotopic composition. The lander systems design as well as the experiment configuration will be described.

Sims, Mark R.; Pillinger, C. T.; Wright, I. P.; Cole, Richard E.; Whitehead, S.; Wells, Alan A.; Wittmann, K.; Richter, L.; Kochan, H.; Hamacher, H.; Johnstone, A.; Rees, K.; Turner, R. F.; Peskett, S.; Brack, A.; Hobbs, J.; Berthoud, L.; Durrant, R.; Higgins, J.; Turner, R.; Windsor, J.; Keller, Horst U.; Rosenbauer, H.; Thomas, Nicolas; Lingard, J. S.; Underwood, J. C.; Neukum, Gerhard

1998-07-01

287

Beagle 2: a proposed exobiology lander for ESA's 2003 Mars express mission  

NASA Astrophysics Data System (ADS)

The aim of the proposed Beagle 2 small lander for ESA's 2003 Mars Express mission is to search for organic material on and below the surface of Mars and to study the inorganic chemistry and mineralogy of the landing site. The lander will have a total mass of 60kg including entry, descent, and landing system. Experiments will be deployed on the surface using a robotic arm. It will use a mechanical mole and grinder to obtain samples from below the surface, under rocks, and inside rocks. Sample analysis by a mass spectrometer will include isotopic analysis. An optical microscope, an X- ray spectrometer and a Mossbauer spectrometer will conduct in-situ rock studies.

Sims, M. R.; Pillinger, C. T.; Wright, I. P.; Dowson, J.; Whitehead, S.; Wells, A.; Spragg, J. E.; Fraser, G.; Richter, L.; Hamacher, H.; Johnstone, A.; Meredith, N. P.; de La Nougerede, C.; Hancock, B.; Turner, R.; Peskett, S.; Brack, A.; Hobbs, J.; Newns, M.; Senior, A.; Humphries, M.; Keller, H. U.; Thomas, N.; Lingard, J. S.; Underwood, J. C.; Sale, N. M.; Neal, M. F.; Klingelhofer, G.; Ng, T. C.

1999-01-01

288

Dynamics of the Venus atmosphere from a Fouriertransform analysis  

Microsoft Academic Search

The radiance escaping from the Venus deep atmosphere into space at 1.74 mu m, one of the atmospheric window, is modulated by the opacity of the lower clouds at about 47 km and it can be effectively used to probe the layer at this altitude. We have used the VIRTIS (Visible and InfraRed Thermal Imaging Spectrometer) instrument onboard the Venus-Express

O. Lanciano; G. Piccioni; R. Hueso; A. Sánchez-Lavega; J. Peralta

2011-01-01

289

V-Gram. A Newsletter for Persons Interested in the Exploration of Venus, No. 8, 24 March 1986.  

National Technical Information Service (NTIS)

The status of the Magellan (MGN) Project (formerly the Venus Radar Mapper Project) is outlined and the impact of the Challenger accident on the planned mission launch date and use of residual Galileo hardware is discussed. The responsibilities and planned...

W. W. James

1986-01-01

290

Gravity anomalies on Venus  

NASA Astrophysics Data System (ADS)

Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.

Sjogren, W. L.; Phillips, R. J.; Birkeland, P. W.; Wimberly, R. N.

1980-12-01

291

The terraforming of Venus  

NASA Astrophysics Data System (ADS)

Methods are considered for the 'terraforming' modification of Venusian environmental conditions. It is noted that Venus cannot be terraformed by microbiological means alone, and that the massive importation of such materials as H2 from various regions of the solar system will have to be instituted; recent impact erosion research on atmospheres appears to preclude this as an option. More fundamentally, a decrease in the axial rotation period of Venus will be mandatory. Taking all factors into account, a project duration of 16,500 years, begining in 2500 AD, is envisioned. Human colonization could not begin before 19,000 AD.

Fogg, M. J.

1987-12-01

292

Ice caps on venus?  

PubMed

The data on Venus obtained by Mariner V and Venera 4 are interpreted as evidence of giant polar ice caps holding the water that must have come out of the volcanoes with the observed carbon dioxide, on the assumption that Earth and Venus are of similar composition and volcanic history. The measurements by Venera 4 of the equatorial surface temperature indicate that the microwave readings were high, so that the polar ice caps may be allowed to exist in the face of the 10-centimeter readings of polar temperature. Life seems to be distinctly possible at the edges of the ice sheets. PMID:17775046

Libby, W F

1968-03-01

293

The galileo venus encounter.  

PubMed

The Galileo spacecraft passed Venus on its way to Jupiter on 10 February 1990, less than 4 months after launch from Earth aboard the shuttle Atlantis. Because Galileo's instruments were selected for broad-based planetary exploration, the spacecraft was able to obtain a wide range of measurements during the Venus encounter. Together with ground-based observations conducted during the encounter, these observations have yielded more accurate information about the planet's plasma environment, cloud patterns, and the possible existence of lightning. PMID:17784091

Johnson, T V; Yeates, C M; Young, R; Dunne, J

1991-09-27

294

Magellan - Initial analysis of Venus surface modification  

NASA Astrophysics Data System (ADS)

Images of the Venus surface provided by the Magellan mission make it possible to see the fine-scale features diagnostic of weathering, erosion, and deposition. These include ejecta deposits extending up to 1000 km to the west of several impact craters, windblown deposits, features containing both obstacles and a source of particulate material, and evidence for degradation by atmosphere-surface interactions and mass movements. Initial Magellan observations pertaining to the nature, rate, and history of surficial processes are analyzed. Emphasis is placed on radar imaging, but results from radiometry and altimetry observations are also discussed.

Arvidson, R. E.; Baker, V. R.; Elachi, C.; Saunders, R. S.; Wood, J. A.

1991-04-01

295

Tectonic connections to interior processes on Venus  

NASA Astrophysics Data System (ADS)

The ultimate goal of geophysical/geological exploration of Venus is to relate the present tectonic (and volcanic) state of the lithosphere to interior processes, particularly mantle convection, operating both now and in the past. The Magellan mission has provided a spectacular view of the surface, and upcoming gravity measurements, particularly if the Magellan orbit is circularized, will provide significant constraints on the state of the interior. This extended abstract focuses on several controversial issues regarding venusian tectonics and its relationship to geodynamic mechanisms in the planet's interior. The origin of highlands, coronae diapir structures, and trenches and subduction are discussed.

Phillips, R. J.

1992-12-01

296

Future magnetic missions, Potential and Reality  

NASA Astrophysics Data System (ADS)

The observation and study of planetary magnetism has seen a tremendous expansion with the recent exploration of magnetic fields associated with Mars, the Moon, 433 Eros, Titan, Europa, Io, Ganymede, Jupiter, Saturn and the Earth. Presently MESSENGER is on its way to Mercury to attempt to solve the enigma posed by the Hermean field discovered by Mariner 10 and the JUNO mission will provide a detailed mapping of the Jovian magnetic field to unprecedented accuracy to explore the mysteries of planet formation. Missions like ARES are being proposed to carry out close-in observations of the intense magnetic anomalies at Mars and attempt to establish their true spatial scale and possible composition. At Earth the SWARM mission will provide the best ever survey of the geomagnetic field and its temporal evolution using a constellation of three satellites while Venus Express will continue the exploration of the induced Venusian magnetosphere. This talk will review the status and objectives of planned and recently launched missions that will carry out magnetic field measurements in the immediate vicinity of several solar system bodies in the near future.

Acuna, M. H.

2006-05-01

297

Venus transit 2004: An international education program  

NASA Astrophysics Data System (ADS)

December 6th, 1882 was the last transit of the planet Venus across the disk of the sun. It was heralded as an event of immense interest and importance to the astronomical community as well as the public at large. There have been only six such occurrences since Galileo first trained his telescope on the heavens in 1609 and on Venus in 1610 where he concluded that Venus had phases like the moon and appeared to get larger and smaller over time. Many historians consider this the final nail in the coffin of the Ptolemaic, Earth centered solar system. In addition, each transit has provided unique opportunities for discovery such as measurement and refinement of the detection of Venus' atmosphere, calculation of longitudes, and calculation of the astronomical unit (and therefore the scale of the solar system). The NASA Sun Earth Connection Education Forum (SECEF) in partnership with the Solar System Exploration (SSE) and Structure and Evolution of the Universe (SEU) Forums, AAS Division for Planetary Sciences (DPS), and a number of NASA space missions and science centers are developing plans for an international education program centered around the June 8, 2004 Venus transit. The transit will be visible in its entirety from Europe and partially from the East Coast of the United States. We will use a series of robotic observatories including the Telescopes In Education (TIE) network distributed in latitude to provide observations of the transit that will allow middle and high school students to calculate the A.U. through application of parallax. We will compare the terrestrial planets in terms of the evolutionary processes that define their magnetic fields, their widely differing interactions with the solar wind, and the implications this has for life on Earth and elsewhere in the universe. We will also use Venus transit as a probe of episodes in American history (e.g. 1769: revolutionary era, 1882: post civil war era, and 2004: modern era). Museums and planetariums in the US and Europe will offer real time viewing of the transit and conduct educational programs through professional development seminars, public lectures, and planetarium shows. We are interested in soliciting advice from the research community to coordinate professional research interests with this program.

Mayo, L.; Odenwald, S.

2003-04-01

298

Venus Mobile Explorer with RPS for active cooling: A feasibility study  

Microsoft Academic Search

This paper presents the findings from a study to evaluate the feasibility of a radioisotope power system (RPS) combined with active cooling to enable a long-duration venus surface mission. On-board power with active cooling technology featured prominently in both. the national research council's decadal survey and in the 2006 NASA solar system exploration roadmap as mission enabling for the exploration

Stephanie D. Leifer; Jacklyn R. Green; Tibor S. Balint; Ram Manvi

2009-01-01

299

Structure and parameters of the Venus atmosphere according to Venera probe data  

Microsoft Academic Search

Direct temperatures and pressure measurements, carried out for the first time on the entry probe of the Venera 4 mission in 1967, laid the foundation for systematic studies of the structure and parameters of the atmosphere of Venus. Measurements made during the Venera 4 - 12 missions cover the altitude range from 62 km to the surface of the planet

V. S. Avduevskii; M. Ia. Marov; Iu. N. Kulikov; V. P. Shari; A. Ia. Gorbachevskii; G. R. Uspenskii; Z. P. Cheremukhina

1983-01-01

300

Design Reference Mission Set for RPS Enabled Missions in Support of NASA's SSE Roadmap  

Microsoft Academic Search

NASA's 2006 Solar System Exploration (SSE) Strategic Roadmap identified a set of small, medium and large missions, to address exploration targets, set out by the National Research Council (NRC) in the SSE Decadal Survey. Large size Flagship class missions are proposed to target Europa, Titan \\/ Enceladus, Venus, and the Neptune system. Under the current candidate architectures, all of these

Tibor S. Balint

2007-01-01

301

The ionosphere of Venus  

Microsoft Academic Search

The Venus dayside ionosphere model includes both photochemistry and vertical diffusion. Basic neutral atmosphere and temperature structure were obtained from models by Dickinson and Ridley. A comprehensive study of ion chemistry and diffusion processes used approximations for ion and electron temperature structures. The model accurately reproduces the location of electron density peaks and shows that large mixing ratios of He

D. M. Butler

1975-01-01

302

Aeolian processes on Venus  

Microsoft Academic Search

In this pre-Magellan review of aeolian processes on Venus we show that the average rate of resurfacing is less than 2 to 4 km\\/Ga, based on the impact crater size frequency distribution derived from Venera observations, reasonable values of the impact flux, and the assumption of steady state conditions between crater production and obliteration. Viscous relaxation of crater topography, burial

Ronald Greeley; Raymond E. Arvidson

1990-01-01

303

Is Venus alive?  

Microsoft Academic Search

Apart from the earth, the near environment of only one other planet, Venus, has been the subject of sustained in situ investigations from space. Owing to the similarity in the physical characteristics of the two bodies, this is most appropriate in that it provides the opportunity to test the credo that through comparative analysis, planetary exploration holds the promise for

Harry A. Taylor Jr.

1986-01-01

304

The Prodigal Sister - Venus  

NASA Astrophysics Data System (ADS)

If you think Venus is a hellhole now, be thankful you weren't there 500 million years ago. Those were the days, many planetary scientists believe, of apocalypse on our sister world: Volcanoes wracked the land, while greenhouse gases broiled the air. Is this the Earth's fate, too?

Barlow, Nadine G.

1995-09-01

305

The Prodigal Sister - Venus  

Microsoft Academic Search

If you think Venus is a hellhole now, be thankful you weren't there 500 million years ago. Those were the days, many planetary scientists believe, of apocalypse on our sister world: Volcanoes wracked the land, while greenhouse gases broiled the air. Is this the Earth's fate, too?

Nadine G. Barlow

1995-01-01

306

Mercury and Venus  

NSDL National Science Digital Library

Students explore Mercury and Venus, the first and second planets nearest the Sun. They learn about the planets' characteristics, including their differences from Earth. Students also learn how engineers are involved in the study of planets by designing equipment and spacecraft to go where it is too dangerous for humans.

Integrated Teaching And Learning Program

307

Venus Atmospheric Dynamics  

Microsoft Academic Search

Over the last four decades, we have learned much about the atmosphere of Venus and its circulation through earth-based, spacecraft orbiters and entry probes and even balloons. However, our understanding of the processes maintaining the atmospheric circulation of the atmosphere is poor. We have discovered every where we have measured, the atmosphere moves in the same direction as the underlying

S. S. Limaye

2004-01-01

308

Lithospheric failure on Venus  

Microsoft Academic Search

We develop a predictive model which has the ability to explain a postulated style of episodic plate tectonics on Venus, through the periodic occurrence of lithospheric subduction events. Present-day incipient subduction zones are associated with the existence of arcuate trenches on the Venusian lithosphere. These trenches resemble terrestrial subduction zones, and occur at the rim of coronae, uplift features thought

A. C. Fowler; S. B. G. O'Brien

2003-01-01

309

Windblown dust on Venus  

Microsoft Academic Search

The threshold frictional velocity necessary to initiate grain movement on the Venus surface is 1 to 2 cm\\/s. Particles smaller than 30 or 40 microns in effective diameter will also be so moved and suspended at the threshold of movement. Theoretical arguments and Venera 8 Doppler measurements suggest marginally that dust should not be raised at the Venera 8 landing

Carl Sagan

1975-01-01

310

Transit of Venus  

NSDL National Science Digital Library

The Transit of Venus is similar to a solar eclipse, where -- from the perspective on Earth -- Venus passes in front of the Sun. This event does not happen very often. In fact, no one alive today has experienced this phenomenon, which will take place on June 8 and will be visible for most of Europe, Asia, and Africa.First, the Armagh Planetarium created a great, expansive informational site all about the Transit of Venus (1). Users can find basic facts, observing information, histories of past transits, and much more. Next, the European Southern Observatory presents the VT-2004 project's aim to gain knowledge and encourage public interest in the event (2). Users can observe Venus's progression towards the transit with the daily images from April 17, 2004 to present news updates. Educators can discover transit-related activities and educational materials. The third site, created by NASA, discusses the details of the Sun-Earth Connection Education Forum and San Francisco's Exploratorium's live webcast of the Transit (3). The site supplies enjoyable, educational materials for students, educators, museums, scientists, and amateur astronomers. The next site, also created by NASA, provides an introduction to the Venus Transits that will take place June 2004 and 2012 (4). Visitors can find helpful figures and text about the geographic visibility of the events. The site offers an observer's handbook as well as a discussion about the predictions of the event. Next, Professor Backhaus presents a project where schools, amateur astronomers, and universities will collaborate to gather transit data and learn about observing (5). Users can discover the six parts of the project as well as learn how to participate in the worldwide endeavor. The sixth site also discusses a Venus Transit project (6). Endorsed by the Astronomical Association of Zurich, this project's goals are to process data collected by amateur astronomers by different observation methods, to act as a data exchange center, and to determine the astronomical unit. Next, the Exploratorium furnishes general information about the Transit, its history, how viewers observe it, what it looks like, and why it is an important event (7). Users can find out about the live webcast that will begin on June 7, 2004 from Athens, Greece. Educators can find student activities developed to integrate discussions into the classroom. Lastly, Willie Koorts, an employee at the South African Astronomical Observatory, recounts the observations of scientists in Africa of the last transit of Venus (8). The site contains many historical photographs along with informational diagrams and figures.

311

Aerobraking at Venus: A science and technology enabler  

NASA Astrophysics Data System (ADS)

Venus remains one of the great unexplored planets in our solar system, with key questions remaining on the evolution of its atmosphere and climate, its volatile cycles, and the thermal and magmatic evolution of its surface. One potential approach toward answering these questions is to fly a reconnaissance mission that uses a multi-mode radar in a near-circular, low-altitude orbit of ?400 km and 60-70° inclination. This type of mission profile results in a total mission delta-V of ?4.4 km/s. Aerobraking could provide a significant portion, potentially up to half, of this energy transfer, thereby permitting more mass to be allocated to the spacecraft and science payload or facilitating the use of smaller, cheaper launch vehicles.Aerobraking at Venus also provides additional science benefits through the measurement of upper atmospheric density (recovered from accelerometer data) and temperature values, especially near the terminator where temperature changes are abrupt and constant pressure levels drop dramatically in altitude from day to night.Scientifically rich, Venus is also an ideal location for implementing aerobraking techniques. Its thick lower atmosphere and slow planet rotation result in relatively more predictable atmospheric densities than Mars. The upper atmosphere (aerobraking altitudes) of Venus has a density variation of 8% compared to Mars' 30% variability. In general, most aerobraking missions try to minimize the duration of the aerobraking phase to keep costs down. These short phases have limited margin to account for contingencies. It is the stable and predictive nature of Venus' atmosphere that provides safer aerobraking opportunities.The nature of aerobraking at Venus provides ideal opportunities to demonstrate aerobraking enhancements and techniques yet to be used at Mars, such as flying a temperature corridor (versus a heat-rate corridor) and using a thermal-response surface algorithm and autonomous aerobraking, shifting many daily ground activities to onboard the spacecraft. A defined aerobraking temperature corridor, based on spacecraft component maximum temperatures, can be employed on a spacecraft specifically designed for aerobraking, and will predict subsequent aerobraking orbits and prescribe apoapsis propulsive maneuvers to maintain the spacecraft within its specified temperature limits. A spacecraft specifically designed for aerobraking in the Venus environment can provide a cost-effective platform for achieving these expanded science and technology goals.This paper discusses the scientific merits of a low-altitude, near-circular orbit at Venus, highlights the differences in aerobraking at Venus versus Mars, and presents design data using a flight system specifically designed for an aerobraking mission at Venus. Using aerobraking to achieve a low altitude orbit at Venus may pave the way for various technology demonstrations, such as autonomous aerobraking techniques and/or new science measurements like a multi-mode, synthetic aperture radar capable of altimetry and radiometry with performance that is significantly more capable than Magellan.

Hibbard, Kenneth; Glaze, Lori; Prince, Jill

2012-04-01

312

The surface of Venus  

NASA Astrophysics Data System (ADS)

Venus is a planet that is similar to Earth in terms of some important planetary parameters (size, mass, position in the solar system, presence of atmosphere) and different in terms of other, equally important ones (absence of an intrinsic magnetic field, large atmospheric mass, carbon dioxide composition of the atmosphere, lack of water, very high surface pressure and temperature). The surface morphology of Venus is dominated by the signatures of basaltic volcanism and tectonic deformation. Other geological processes such as impact cratering, aeolian activity and gravity-driven down-slope mass movement, although active on the planet, are certainly of subordinate significance. Venusian volcanism resulted in the formation of vast regional plains, occupying most of the planet's surface, and in the building of numerous volcanic edifices. Venusian tectonic deformation was both compressional and extensional. Scales and, periodically, rates of Venusian volcanism and tectonism were comparable to those on Earth. But Venus shows no evidence of the global plate-tectonic style so dominant in the geology of Earth. The morphological record seen in the Magellan radar images of Venus extends back into geological history not earlier than about 0.5-1 billion years. It is represented by a sequence of units from highly tectonized tessera and densely fractured plains, whose compositional nature is unclear, through moderately deformed basaltic lava plains, and then to only locally deformed basaltic plains and edifices. In the beginning of the time period during which this sequence formed, the rates of volcanic and tectonic activity were significantly higher than in the subsequent time extending to the present. This change in volcanic and tectonic activity may correspond to a change in the convection style in the mantle of Venus.

Basilevsky, Alexander T.; Head, James W.

2003-10-01

313

Storms On Venus: Lightning-induced Chemistry And Predicted Products  

NASA Astrophysics Data System (ADS)

Observations by many spacecraft that have visited Venus over the last 40 years appear to confirm the presence of lightning storms in the Venus atmosphere. Recent observations by Venus Express indicate that lightning frequency and power is similar to that on Earth. While storms are occurring, energy deposition by lightning into Venus atmospheric constituents will immediately dissociate molecules into atoms, ions and plasma from the high temperatures in the lightning column (>30,000 K) and the associated shock waves and heating, after which these atom and ion fragments will recombine during cooldown to form new sets of molecules. Lightning will re-sort the atoms of C,O,S,N,H to create highly energetic new products. Spark and discharge experiments in the literature suggest that lightning effects on the main atmospheric molecules CO2, N2, SO2, H2SO4 and H2O will yield new molecules such as mixed carbon oxides (CnOm), mixed sulfur oxides (SnOm), oxygen (O2), elemental sulfur (Sn), nitrogen oxides (NO, N2O, NO2, NO3), sulfuric acid clusters (HnSmOx-.aHnSmOx e.g. HSO4-.mH2SO4), polysulfur oxides, carbon soot, and also halogen oxides from HCl or HF and other exotic species. Many of these molecular species may be detectable by instruments onboard Venus Express. We explore the diversity of new products likely created in the storm clouds on Venus.

Delitsky, M. L.; Baines, K. H.

2012-10-01

314

Venus Surface Sample Return: A Weighty High-Pressure Challenge  

NASA Astrophysics Data System (ADS)

A mission to return a sample to Earth from the surface of Venus faces a multitude of multidisciplinary challenges. In addition to the complications inherent in any sample return mission, Venus presents the additional difficulties of a deep gravity well essentially equivalent to Earth's and a hot-house atmosphere which generates extremes of high temperature, density, and pressure unmatched at any other known surface in the solar system. The Jet Propulsion Laboratory of the California Institute of Technology recently conducted a study to develop an architecture for such a mission; a major goal of this study was to identify technology developments which would need to be pursued in order to make such a mission feasible at a cost much less than estimated in previous. The final design of this mission is years away but the study results presented here show our current mission architecture as it applies to a particular mission opportunity, give a summary of the engineering and science trades which were made in the process of developing it, and identify the main technology development efforts needed.

Sweetser, Ted; Cameron, Jonathon; Chen, Gun-Shing; Cutts, Jim; Gershman, Bob; Gilmore, Martha S.; Hall, Jeffrey L.; Kerzhanovich, Viktor; McRonald, Angus; Nilsen, Erik

1999-01-01

315

Super-alloy, AMTEC cells for the pluto/express mission  

NASA Astrophysics Data System (ADS)

A number of design changes for improving the performance of super-alloy AMTEC cells, and options of integrating them to General Purpose Heat Source (GPHS) modules in the configuration proposed by Advanced Modular Power Systems were investigated, for satisfying the electric power requirements for the Pluto/Express mission. A power system consisting of 6 fresh-fuel GPHS modules and 48, 7-tube super-alloy cells connected electrically in 4 parallel strings would weight 28.75 kg and provide 174 We at EOM, at an efficiency of 13.2%. The cells' BASE brazes and evaporator temperatures would be below 1059 K and 971 K, respectively. A power system consisting of 5 fresh-fuel GPHS modules and 4 parallel strings of 8, 9-tube cells each would deliver 156 We at EOM and weight only 24.53 kg. In this system, the AMTEC cells would also operate at low BASE brazes and evaporator temperatures (1071 K and 995 K, respectively).

El-Genk, Mohamed S.; Tournier, Jean-Michel; James, Ralph; Mayberry, Clay

1999-01-01

316

Magellan unveils Venus  

SciTech Connect

Images obtained after an eight month Venusian year, during which the radar mapper Magellan surveyed nearly all of Venus, are described. It is observed that, instead of rigid plates moving as on earth, Venus appears covered with plumes of hot upwellings that dome out over hundreds or thousands of kilometers, feeding a continuous volcanic resurfacing of the planet. Although the Venusian surface is changing relatively rapidly by vulcanism and tectonic processes, the Magellan images make it clear that erosion is very slow. It is seen that some of the lava flows are highly fluid, etching narrow channels for hundreds of kilometers through the crust. Magellan also revealed some peculiarly Venusian formations, the tesserated areas where ridges and faults crosshatch the region into large blocks.

Lerner, E.J.

1991-07-01

317

Hypsometric features of Venus  

NASA Astrophysics Data System (ADS)

The surface of Venus is characterized hypsometrically and compared with those of the other terrestrial planets and the moon. The hypsometric map constructed by the U.S. Geological Survey (1981) is used to determine the areas and average heights of 22 regions; the results are presented in a table and a relief map based on 5-deg trapezia; and the proportions occupied by mountains, hilly regions, and lowlands are found to be 7.4, 54.8, and 37.9 percent, respectively. The distribution of plains on Venus, Mars, Mercury, and the moon is found to show a distinct similarity (with a predominance in the northern hemispheres) to the distribution of continents on earth.

Rodionova, Zh. F.

1984-10-01

318

Orogenic belts on Venus  

NASA Astrophysics Data System (ADS)

Recent radar observations of Venus show evidence for three types of deformational features in the linear mountain belts of Ishtar Terra: linear ridges and troughs oriented parallel to the strike of the mountains and interpreted to be anticlines and synclines; broad low arches similar to mare-ridge-type features seen on the Moon and interpreted to represent low-angle thrusting and buckling; and linear discontinuities that cut across the strike of the ridges and troughs and are interpreted to represent strike-slip movement. On the basis of the localized concentration of these features, their orientations and patterns of distribution, and their association with linear mountainous topography, we conclude that they mark the location of concentrated horizontal compressional deformation and that Akna and Freyja Montes represent erogenic belts on Venus.

Crumpler, L. S.; Head, James W.; Campbell, Donald B.

1986-12-01

319

Near infrared imaging of the surface of Venus and implications for crustal composition  

Microsoft Academic Search

Venus Express is an ESA spacecraft orbiting Venus since April 2006. The instrument VIRTIS acquires multispectral images in the range from 0.2 to 5 m wavelength. An analysis of VIRTIS images at the wavelengths of the atmospheric window at 1.02 m shows evidence for variation of surface emissivity on the southern hemisphere [Mueller et al. 2008]. Inferred surface emissivity is

N. Müller; J. Helbert

2009-01-01

320

Schistosoma mansoni: Structural and biochemical characterization of two distinct Venus Kinase Receptors  

Microsoft Academic Search

Venus Kinase Receptors (VKRs) are atypical transmembrane proteins composed of an extracellular Venus FlyTrap module linked through a single helix to a tyrosine kinase domain similar to that of insulin receptors. This structure was first described in Schistosoma mansoni, then in a selected range of invertebrates, including many insects. The preferential expression of VKRs in larvae and gonads suggested their

Nadege Gouignard; Mathieu Vanderstraete; Katia Cailliau; Arlette Lescuyer; Edith Browaeys; Colette Dissous

321

Correlations between cloud thickness and sub-cloud water abundance on Venus  

Microsoft Academic Search

Past spacecraft observations of Venus have found considerable spatial and temporal variations of water vapour abundance above the clouds. Previous searches for variability below the clouds at 30–45 km altitude found no large scale latitudinal gradients, but lacked the spatial resolution to detect smaller scale variations. Here we interpret results from the VIRTIS imaging spectrometer on Venus Express, remotely sounding

Constantine C. C. Tsang; Colin F. Wilson; Joanna K. Barstow; Patrick G. J. Irwin; Fredric W. Taylor; Kevin McGouldrick; Giuseppe Piccioni; Pierre Drossart; Håkan Svedhem

2010-01-01

322

Correlations between cloud thickness and sub-cloud water abundance on Venus  

Microsoft Academic Search

Past spacecraft observations of Venus have found considerable spatial and temporal variations of water vapour abundance above the clouds. Previous searches for variability below the clouds at 30-45 km altitude found no large scale latitudinal gradients, but lacked the spatial resolution to detect smaller scale variations. Here we interpret results from the VIRTIS imaging spectrometer on Venus Express, remotely sounding

Constantine C. C. Tsang; Colin F. Wilson; Joanna K. Barstow; Patrick G. J. Irwin; Fredric W. Taylor; Kevin McGouldrick; Giuseppe Piccioni; Pierre Drossart; Håkan Svedhem

2010-01-01

323

Venus: dead or alive?  

PubMed

In situ nightside electric field observations from the Pioneer Venus Orbiter have been interpreted as evidence of extensive lightning in the lower atmosphere of Venus. The scenario, including proposed evidence of clustering of lightning over surface highland regions, has encouraged the acceptance of currently active volcanic output as part of several investigations of the dynamics and chemistry of the atmosphere and the geology of the planet. However, the correlation between the 100-hertz electric field events attributed to lightning and nightside ionization troughs resulting from the interaction of the solar wind with the ionosphere indicates that the noise results from locally generated plasma instabilities and not from any behavior of the lower atmosphere. Furthermore, analysis of the spatial distribution of the noise shows that it is not clustered over highland topography, but rather occurs at random throughout the latitude and longitude regions sampled by the orbiter during the first 5 years of operation, from 1978 to 1984. Thus the electric field observations do not identify lightning and do not provide a basis for inferring the presence of currently active volcanic output. In the absence of known evidence to the contrary, it appears that Venus is no longer active. PMID:17778949

Taylor, H A; Cloutier, P A

1986-11-28

324

Venus nightside ionospheric holes  

NASA Astrophysics Data System (ADS)

Pioneer Venus Orbiter (PVO) measured the ionosphere and atmosphere of Venus for 13 years 10 months yielding a rich data set of archived data from a complement of instruments. One particularly striking feature seen was the occurrence of deep localized nightside ionization depletions commonly called holes. A number of theories have been put forth to explain their observed characteristics, but there is still no consensus on their source. A possibly related phenomenon in the Venus nightside ionosphere is the occurrence of "disappearing" or severely disturbed ionospheres characterized by deep, widespread plasma depletions in almost the entire nightside. This paper reexamines the holes and "disappearing ionospheres" and other characteristics of the nightside ionosphere during solar maximum using a more extensive database than earlier studies. The hole locations, occurrences, and dependencies on solar wind dynamic pressure (Psw) are analyzed, and a comparison is made with earlier studies. It is shown that there is no Psw threshold for holes to occur and at Psw values greater than ˜9 nPa, hole occurrence decreases while the occurrence of severely disturbed orbits increases, suggesting that holes may evolve into severely disturbed orbits. Other characteristics of the nightside are shown to be influenced by solar wind pressure to varying degrees; for example, the density integrated along the orbit path below the ionopause, and the median density at low altitudes exhibit strong inverse correlation with Psw, while the peak density is nearly independent of Psw.

Hoegy, Walter R.; Grebowsky, Joseph M.

2010-12-01

325

Ballistic trajectory options for manned Mars Missions  

NASA Astrophysics Data System (ADS)

Mars Mission profile options and mission requirements data are presented for earth-Mars opposition and conjunction class round-trip flyby and stopover mission opportunities. The opposition-class flyby and sprint mission uses direct transfer trajectories to and on return from Mars. The opposition-class stopover mission employs the gravitational field of Venus to accelerate the space vehicle on either the outbound or inbound leg in order to reduce the propulsion requirement associated with the opposition-class mission. The conjunction-class mission minimizes propulsion requirements by optimizing the stopover time at Mars. Representative interplanetary space vehicle systems are sized to compare and show sensitivity of the initial mass required in low earth orbit to one mission profile option and mission opportunity to another.

Young, Archie C.

326

Radiative Energy Balance in the Venus Atmosphere  

NASA Astrophysics Data System (ADS)

This chapter reviews the observations of the radiative fluxes inside and outside the Venusian atmosphere, along with the available data about the planetary energy balance and the distribution of sources and sinks of radiative energy. We also briefly address the role of the radiation on the atmospheric temperature structure, global circulation, thermodynamics, climate and evolution of Venus and compare the main features of radiative balance on the terrestrial planets. We describe the physics of the greenhouse effect as it applies to the evolution of the Venusian climate, concluding with a summary of outstanding open issues. The article is to a great extent based on the paper by Titov et al. [2007] expanded byincluding recent results from the Venus Express observations relevant to the topic.

Titov, Dmitrij V.; Piccioni, Giuseppe; Drossart, Pierre; Markiewicz, Wojciech J.

327

Mars Express - ESA sets ambitious goals for the first European mission to Mars  

NASA Astrophysics Data System (ADS)

Mars has always fascinated human beings. No other planet has been visited so many times by spacecraft. And still, it has not been easy to unveil its secrets. Martian mysteries seem to have increased in quantity and complexity with every mission. When the first spacecraft were sent - the Mariner series in 1960s - the public was expecting an Earth ‘twin’, a green, inhabited planet full of oceans. Mariner shattered this dream by showing a barren surface. This was followed by the Viking probes which searched for life unsuccessfully in 1976. Mars appeared dry, cold and uninhabited: the Earth’s opposite. Now, two decades later, modern spacecraft have changed that view, but they have also returned more questions. Current data show that Mars was probably much warmer in the past. Scientists now think that Mars had oceans, so it could have been a suitable place for life in the past. “We do not know what happened to the planet in the past. Which process turned Mars into the dry, cold world we see today?” says Agustin Chicarro, ESA’s Mars Express project scientist. “With Mars Express, we will find out. Above all, we aim to obtain a complete global view of the planet - its history, its geology, how it has evolved. Real planetology!” Mars Express will reach the Red Planet by the end of December 2003, after a trip of just over six months. Six days before injection into its final orbit, Mars Express will eject the lander, Beagle 2, named after the ship on which Charles Darwin found inspiration to formulate his theory of evolution. The Mars Express orbiter will observe the planet and its atmosphere from a near-polar orbit, and will remain in operation for at least a whole Martian year (687 Earth days). Beagle 2 will land in an equatorial region that was probably flooded in the past, and where traces of life may have been preserved. The Mars Express orbiter carries seven advanced experiments, in addition to the Beagle 2 lander. The orbiter’s instruments have been built by group of scientific institutes from all over Europe, plus Russia, the United States, Japan and China. These instruments are a subsurface sounding radar; a high-resolution camera, several surface and atmospheric spectrometers, a plasma analyzer and a radio science experiment. The high-resolution camera will image the entire planet in full colour, in 3D, at a resolution of up to 2 metres in selected areas. One of the spectrometers will map the mineral composition of the surface with great accuracy. The missing water Data from some of the instruments will be key to finding out what happened with the water which was apparently so abundant in the past. For instance, the radar altimeter will search for subsurface water and ice, down to a depth of a few kilometres. Scientists expect to find a layer of ice or permafrost, and to measure its thickness. Other observations with the spectrometers will determine the amount of water remaining in the atmosphere. They will also tell whether there is a still a full ‘water cycle’ on Mars, for example how water is deposited in the poles and how it evaporates, depending on the seasons. "These data will determine how much water there is left. We have clear evidence for the presence of water in the past, we have seen dry river beds and sedimentary layers, and there is also evidence for water on present-day Mars. But we do not know how much water there is. Mars Express will tell us,” says Chicarro. The search for life The instruments on board Beagle 2 will investigate the geology and the climate of the landing site. But, above all, it will look for signs of life. Contrary to the Viking missions, Mars Express will search for evidence for both present and past life. Scientists are now more aware that a few biological experiments are not enough to search for life - they will combine many different types of tests to help discard contradictory results. To ‘sniff’ out direct evidence of past or present biological activity, Beagle 2’s ‘nose’ is a gas analysis package. This will determine whether carbonate mineral

2003-05-01

328

Design and operation of the Pioneer Venus Orbiter ultraviolet spectrometer  

Microsoft Academic Search

The University of Colorado's ultraviolet spectrometer instrument carried on the Pioneer Venus Orbiter spacecraft is a 125-mm f\\/5 Ebert-Fastie design with a 250-mm Cassegrain telescope. The instrument has extensive logic to control the grating motor drive and to adapt the basic spectrometer to the constraints and opportunities of the mission. Success has been achieved in reconciling the conflicting requirements of

A. I. F. Stewart

1980-01-01

329

Why Venus has No Moon  

Microsoft Academic Search

Venus does not have a moon. We argue that this is at least as surprising as the presence of Earth's moon and more surprising than the absence of a substantial moon for Mercury or Mars. We do not know if Venus ever had a moon. The accepted explanation for Earth's moon is a giant impact with an impactor on the

Alex Alemi; D. Stevenson

2006-01-01

330

Crustal deformation: Earth VS Venus  

Microsoft Academic Search

It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate

D. L. Turcotte

1989-01-01

331

Venus: Interaction with Solar Wind  

NASA Astrophysics Data System (ADS)

The solar wind interaction with VENUS provides the archetypal interaction of a flowing magnetized PLASMA with a PLANETARY IONOSPHERE. Mars interacts with the solar wind in much the same way as does Venus, while the rotating plasma in the Saturnian magnetosphere is believed to interact similarly with its moon, Titan (see SATURN: MAGNETOSPHERE INTERACTION WITH TITAN). The interaction of the Jovian ...

Russell, C.; Luhmann, J.; Murdin, P.

2002-07-01

332

Electrical memory in Venus flytrap  

Microsoft Academic Search

Electrical signaling, memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we developed a new method for direct measurements of the

Alexander G. Volkov; Holly Carrell; Andrew Baldwin; Vladislav S. Markin

2009-01-01

333

Is Venus a living planet?  

Microsoft Academic Search

Stimulated by electric field and atmospheric results from the Pioneer Venus Orbiter (PVO) a perception has evolved that Venus may recently have been very active geologically, with massive explosive volcanoes generating extensive atmospheric lightning and dramatic changes in the SO2 content in the atmosphere. The authors find no basis in the PVO results for inferring either the presence of lightning

H. A. Taylor; P. A. Cloutier

1990-01-01

334

A radar tour of Venus  

Microsoft Academic Search

The surface of Venus is briefly characterized in a summary of results obtained by the Soviet Venera 15 and 16 8-cm synthetic-aperture radars, IR radiometers, and radar altimeters. A series of radar images, mainly from Kotelnikov et al. (1984), are presented and discussed, and the descent vehicles to be released by the two Vega spacecraft as they pass Venus in

J. K. Beatty

1985-01-01

335

Optimizing Aerobot Exploration of Venus.  

National Technical Information Service (NTIS)

Venus Flyer Robot (VFR) is an aerobot; an autonomous balloon probe designed for remote exploration of Earth's sister planet in 2003. VFR's simple navigation and control system permits travel to virtually any location on Venus, but it can survive for only ...

K. S. Ford

1997-01-01

336

Optimizing Aerobot Exploration of Venus  

Microsoft Academic Search

Venus Flyer Robot (VFR) is an aerobot; an autonomous balloon probe designed for remote exploration of Earth's sister planet in 2003. VFR's simple navigation and control system permits travel to virtually any location on Venus, but it can survive for only a limited duration in the harsh Venusian environment. To help address this limitation, we develop: (1) a global circulation

Kevin S. Ford

1997-01-01

337

Sulfur dioxide observations above Venus' clouds by means of solar occultation in the infrared  

NASA Astrophysics Data System (ADS)

The experiment SOIR (Solar Occultation in the Infra-Red) - a part of the Venus Express mission - is performed for study of gaseous and aerosol vertical structure in Venus' mesosphere. The instrument of SOIR is an acousto-optical (AO) echelle spectrometer that operates at wavelengths 2.2-4.3 µm with high spectral resolution (?/??=30000). The spectrometer is capable to detect important minor gaseous constituents such as CO, SO2 , HCl, HF, H2 O and HDO at altitudes 65-110 km. Here we report results from some occultation sessions with observation of 4 µm SO2 band at latitudes 69o -88o N and 23o -30o N. It's the first time of SO2 vertical distribution retrieval above Venus' clouds by means of solar occultation. Since sulfur dioxide spectrum of transmission is measured on a background of abundant CO2 band, it is impossible to retrieve any separate SO2 line for observing and fitting. This fact forces us to do modeling of combined spectrum (CO2 *SO2 ) and to perform fitting with appropriate mixing ratio of SO2 by comparison between the combined model and a measured spectrum (point-by-point). As result, just a few points of a SO2 vertical profile can be detected clearly (0.1 ppm at high latitudes and 1 ppm at low latitudes at the altitude about 70 km). All the rest points provide upper limit of the gas' mixing ratio (0.05 ppm at 75 km and higher).

Belyaev, Denis; Korablev, Oleg; Fedorova, Anna; Bertaux, Jean-Loup; Vandaele, Ann-Carine; Neefs, Eddy; Mahieux, Arnaud; Wilquet, Valerie

338

Solar and inner heliospheric conditions during an unusual Venus polar brightening  

NASA Astrophysics Data System (ADS)

Space weather events are very well known on the Sun-Earth system. During solar activity maximum the main sources for space weather events are eruptive solar drivers such as, flares and coronal mass ejections. During solar minimum when these phenomena are less present, high speed streams, emanating from coronal holes, play a major role in the variability of space weather. The main manifestations of these forcing in the Earth system are magnetic storms and substorms. Space weather is not exclusive of the Sun-Earth system. All the solar system objects inside the heliosphere respond to solar variability. Different bodies react in distinct ways to this variability depending on their dynamical position, magnetic field intensity, atmospheric structure and composition. The influence of solar magnetic variability on Earth's climate is an important research topic intending to estimate the natural contributions to climate change. The solar influence on the lower atmospheric regions has been observed on different atmospheric parameters in different time scales, but a plausible mechanism to explain these observations remains unclear. Here we present a case that a changing in the global appearance of the Venus upper cloud deck could be related with the January 2007 inner heliospheric conditions. Using an unprecedented set of space and ground based observations of the inner Solar System (Sun, Venus, Earth and inner heliosphere) we observed a strong coupling between a CME, two high speed streams and the Venusian magnetosphere and upper atmosphere. On January 2007, the inner heliosphere structure was dominated by the presence of two coronal holes, separated by approximately 180 degrees. They extended from the Sun's South Pole equatorward and persisted during several solar rotations. Emanating from these coronal holes, corotating high speed streams were detected near Earth by the ACE, SOHO and STEREO spacecrafts during January 2007. The interaction of these high speed streams with Earth's magnetosphere triggered High-Intensity, Long-Duration, Continuous AE Activity (HILDCAA) events, which are characterized by an intense AE index lasting for more than 2 days. Due to solar rotation and to the relative position of Earth and Venus, these high speed streams interacted previously with Venus. On January 8, a Coronal Mass Ejection (CME) was observed on the solar corona, probably related to the off-limb active region 10938. This CME was released in the direction of Venus. The CME was observed by SOHO's LASCO C2/C3 and STEREO SECCHI COR1A- B/2A-B and HI1A. Based on these observations and propagation models we predicted the arrival date of the CME on Venus between January 11 -12. Instruments on board Venus Express, around planet Venus, detected changes in the plasma parameters that could be related to the CME passage and a change in the upper atmosphere conditions. ASPERA-4 observed an increase in the magnetosheath temperature and density of the ions and electrons on January 12. In the same time window, Venus Monitoring Camera observed a catastrophic change in its upper cloud deck appearance. Brightener clouds appeared on January 12 in the South Pole and expanded to lower latitudes, changing the global atmospheric appearance till January 13. Curiously the comet McNaught, crossed northward the ecliptic plane on January and it was imaged by STEREO HI1A - HI1B and SOHO LASCO C3 during its southward descending from January 11 to 18. Although the comet McNaught was present in the inner heliosphere, it is not likely that particles from the comet tail reached the Venus orbit and contributed to the observed changes in the venusian atmosphere. But we don't rule out the possibility that particles from the comet reached Venus. These observations show how the solar variability can drive changes on the cloud coverage on Venusian atmosphere driven by the space weather conditions in the inner heliosphere. With the expected increase of the solar activity throughout the ascending phase of solar cycle, Venus Express and STEREO missions can investigate furthermore the

Antunes Vieira, Luis Eduardo; Russo, Pedro; Dal Lago, Alisson; Manoel, Nuno; Titov, Dmitri

339

Pioneer Venus large probe neutral mass spectrometer  

Microsoft Academic Search

The deuterium hydrogen abundance ratio in the Venus atmosphere was measured while the inlets to the Pioneer Venus large probe mass spectrometer were coated with sulfuric acid from Venus' clouds. The ratio is (1.6 + or - 0.2) x 10 to the minus two power. It was found that the 100 fold enrichment of deuterium means that Venus outgassed at

J. Hoffman

1982-01-01

340

Hydroxyl airglow on Venus in comparison with Earth  

NASA Astrophysics Data System (ADS)

Hydroxyl nightglow is intensively studied in the Earth atmosphere, due to its coupling to the ozone cycle. Recently, it was detected for the first time also in the Venus atmosphere, thanks to the VIRTIS-Venus Express observations. The main ? ?=1, 2 emissions in the infrared spectral range, centred, respectively, at 2.81 and 1.46 ?m (which correspond to the (1-0) and (2-0) transitions, respectively), were observed in limb geometry ( Piccioni et al., 2008) with a mean emission rate of 880±90 and 100±40 kR (1R=10 6 photon cm -2 s -1 (4 ?ster) -1), respectively, integrated along the line of sight. In this investigation, the Bates-Nicolet chemical reaction is reported to be the most probable mechanism for OH production on Venus, as in the case of Earth, but HO 2 and O may still be not negligible as mechanism of production for OH, differently than Earth. The nightglow emission from OH provides a method to quantify O 3, HO 2, H and O, and to infer the mechanism of transport of the key species involved in the production. Very recently, an ozone layer was detected in the upper atmosphere of Venus by the SPICAV (Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus) instrument onboard Venus Express ( Montmessin et al., 2009); this discovery enhances the importance of ozone to the OH production in the upper atmosphere of Venus through the Bates-Nicolet mechanism. On Venus, OH airglow is observed only in the night side and no evidence has been found whether a similar emission exists also in the day side. On Mars it is expected to exist both on the day and night sides of the planet, because of the presence of ozone, though OH airglow has not yet been detected. In this paper, we review and compare the OH nightglow on Venus and Earth. The case of Mars is also briefly discussed for the sake of completeness. Similarities from a chemical and a dynamical point of view are listed, though visible OH emissions on Earth and IR OH emissions on Venus are compared.

Migliorini, A.; Piccioni, G.; Cardesín Moinelo, A.; Drossart, P.

2011-08-01

341

Mars Simulation Chamber 1 - preparation for Mars Express and future Mars missions  

NASA Astrophysics Data System (ADS)

We have installed at ESTEC and instrumented a Mars Simulation Chamber (MSC), in order to answer a range of questions on the subject of the apparent absence of organic compounds on Mars. We shall investigate: A. The effects of the changes of the Martian atmosphere over the history of Mars. B. The effect of UV irradiation on organic molecules embedded in the soil. C. The effect of oxidation on organic molecules embedded in the soil. D. The effect of thermal cycling on the surface. E. A combination of the above mentioned parameters. Techniques to be used include gas analysis, environmental sensors, HPLC, spectroscopy and other analytical techniques. We shall also assess the sensitivity of instruments for the detection of minerals and organic compounds of exobiological relevance in Martian analogue soils (mixed under controlled conditions with traces of these organics). The results concerning the simulation of complex organics on Mars, as well as lander instrument chamber simulations will be included in a database to serve for the interpretation of Beagle 2 data and other future Mars missions. The results of the experiments can also provide constraints for the observations from orbit, such as spectroscopy of minerals, measurements of the water cycle, frost and subsurface water, the CO2 cycle, and the landing site selection. In summary, the experiments have as a main goal to simulate various processes on organics, such as the effects of UV radiation, diffusion, and temperature, as a function of their depth in the soil. The specific organics will be embedded in either porous or compact Martian soil analogues or quartz beads. In this presentation we will concentrate on the preparation for Mars Express.

Ehrenfreund, P.; ten Kate, I. L.; Ruiterkamp, R.; Botta, O.; Lehmann, B.; Boudin, N.; Foing, B. H.

2003-04-01

342

Ion escape from Venus using statistical distribution functions  

NASA Astrophysics Data System (ADS)

We use more than three years of data from the ASPERA-4 instrument onboard Venus Express to compile statistical distribution functions of ion flux in and around induced magnetosphere of Venus. We present samples of statistical distribution functions, as well average flux patterns in the near Venus space based on the statistical distribution functions. The statistical distribution functions allows for a compensation of biased sampling regarding both position and angular coverage of the instrument. Protons and heavy ions (mass/charge > 16) are the major ion species escaping from Venus. The escape is due to acceleration of planetary ions by energy transfer from the solar wind. The ion escape appears to exclusively take place in the induced magnetotail region and no heavy ions are present in the magnetosheath. Protons of solar wind origin are travelling around the planet and penetrating the tail, resulting in a mix of planetary and solar wind protons inside the induced magnetosphere boundary. The escape rates of ions inside the tail agree with results from recent published studies, where other analysis methods have been used. We also compare our results for Venus with a recent study of ion escape from Mars, where the same analysis method has been applied to data from the ASPERA-3 instrument on Mars Express. Both Mars and Venus are unmagnetized planets and are expected to interact similarly with the solar wind. On Mars the heavy ions are seen escaping in both the magnetosheath and tail regions as opposed to Venus where escape only takes place inside the tail. A possible explanation is that the magnetosphere of Mars is smaller compared to the ion gyroradius, making it easier for the ions to pass through the induced magnetosphere boundary. On both planets the escape rates of heavy ions in the tail are constant with increasing tail distance, verifying that the ions are leaving the planet in this region.

Nordstrom, T.; Stenberg, G.; Nilsson, H.; Barabash, S.; Futaana, Y.

2012-04-01

343

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

NASA Astrophysics Data System (ADS)

We 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 ?m 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.

Peralta, J.; Luz, D.; Berry, D. L.; Tsang, C. C. C.; Sánchez-Lavega, A.; Hueso, R.; Piccioni, G.; Drossart, P.

2012-08-01

344

Horizontal and Vertical Distribution of SO2 in the Venus Clouds From SPICAV UV spectrometer.  

NASA Astrophysics Data System (ADS)

The two bands of UV absorption of SO2 at 180-220 and 280-300 nm may be used to detect SO2 in the upper atmosphere of Venus. On board Venus Express mission, the UV spectrometer (118 - 320 nm, resolution 1.5 nm) of SPICAV is dedicated to nadir viewing, limb viewing and vertical profiling by stellar and solar occultation. In the solar occultation mode, SO2 is seen up to 100 km with a mixing ratio of about 1 ppmv, a puzzling result since it should be photo-dissociated at this altitude. In the stellar occultation mode which is performed at night, SO2 is also seen up to 100 km, possibly resulting from the evaporation of H2SO4 cloud droplets. In nadir orientation, SPICAV UV analyzes 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 day side with implications for cloud structure, and atmospheric dynamics. The abundance of SO2 and its scale height are determined by comparison of the measured albedo spectrum with the output of a radiative transfer code, yielding horizontal distributions. Results obtained from the various modes of observation will be compared.

Bertaux, J.; Bertaux, E.; Montmessin, F.

2008-12-01

345

Modeling the distribution of H2O and HDO in the upper atmosphere of Venus  

NASA Astrophysics Data System (ADS)

The chemical and dynamical processes in the upper atmosphere of Venus are poorly known. Recently obtained vertical profiles of trace species from the Venus Express mission, such as HCl, H2O, and HDO, provide new information to constrain these processes. Here, we simulate these profiles, using the model we have developed and described in a related paper by Yung et al. (2008), with special emphasis on the modeling of H2O and HDO. A new mechanism, the photo-induced isotopic fractionation effect (PHIFE) of H2O and HCl, is incorporated into our model. The observed enhancement of HDO could be attributed to (1) preferential destruction of H2O relative to HDO via PHIFE and (2) escape of hydrogen that enhances the abundance of D and hence its parent molecule HDO. Over a wide range of the sensitivity of the results to the changes of the two mechanisms, we find that the observed profiles of HDO and H2O profiles cannot be explained satisfactorily by current knowledge of chemical and dynamical processes in this region of the atmosphere. Several conjectures to tackle the problems are discussed.

Liang, Mao-Chang; Yung, Yuk L.

2009-02-01

346

Escape of volatiles from Venus  

NASA Astrophysics Data System (ADS)

A model for describing the loss of atmosphere in Venus in the geologic time is presented. The amount of volatiles degassed from Venus in 4.6 Ga is in the order of 286.9 Terrestrial Atmospheric Masses (TAM) (1 TAM = 5.28x1018 kg). If the drag of the solar wind acted since the birth of Venus, 4.6 Ga ago, a minimum limit of the amount of atmosphere lost by the planet is 6.76 TAM. The current atmosphere of Venus has 88.44 TAM of mass. The sum of the lost and the current atmosphere is 95.2 TAM. This result is 191.7 TAM smaller than the estimation of the mass degassed in all the history of Venus. Then we have a deficit of 191.7 TAM of volatiles on Venus. It is well known that the surface of Venus is geologically young (? 500 Ma) In all this period the model predicts that Venus lost, by the solar wind, only 0.08 TAM of atmosphere. From this we can assume that the deficit of volatiles is due to events that occur before that time or perhaps at that time. It is possible to speculate that the resurfacing of Venus, the massive loss of volatiles, and a change from prograde to retrograde rotation of the planet occur at the same time and could be produced by a gigantic impact with a planetary-size body. In this catastrophic event the angular momentum of the planet could change from the original (possibly prograde) to the current one, all the surface of Venus could be melt producing a resurfacing and the water and part of the CO2 in the atmosphere could be ejected to space.

Durand-Manterola, H. J.

347

Variations of sulphur dioxide at the cloud top of Venus's dynamic atmosphere  

NASA Astrophysics Data System (ADS)

Sulphur dioxide is a million times more abundant in the atmosphere of Venus than that of Earth, possibly as a result of volcanism on Venus within the past billion years. A tenfold decrease in sulphur dioxide column density above Venus's clouds measured by the Pioneer Venus spacecraft during the 1970s and 1980s has been interpreted as decline following an episode of volcanogenic upwelling from the lower atmosphere. Here we report that the sulphur dioxide column density above Venus's clouds decreased by an order of magnitude between 2007 and 2012 using ultraviolet spectrometer data from the SPICAV instrument onboard the Venus Express spacecraft. This decline is similar to observations during the 1980s. We also report strong latitudinal and temporal variability in sulphur dioxide column density that is consistent with supply fluctuations from the lower atmosphere. We suggest that episodic sulphur dioxide injections to the cloud tops may be caused either by periods of increased buoyancy of volcanic plumes, or, in the absence of active volcanism, by long-period oscillations of the general atmospheric circulation. The 30-year observational record from Pioneer Venus and Venus Express confirms that episodic injections of sulphur dioxide above the clouds recur on decadal timescales, suggesting a more variable atmosphere than expected.

Marcq, Emmanuel; Bertaux, Jean-Loup; Montmessin, Franck; Belyaev, Denis

2013-01-01

348

Venus glory and the unknown uv absorber  

NASA Astrophysics Data System (ADS)

We report on the first observation of a complete glory on top of the Venus clouds captured with the Venus Monitoring Camera (VMC) when the Sun was almost directly behind the Venus Express space-craft. The wavelengths dependence of the position of the glory is consistent with clouds being composed of spherical droplets of sulphuric acid with radius of 1.2 micron, the so called mode-2 particles. The ratio of backscattering (zero phase angle) to maximum intensity of the glory as well the slope of the observed intensity at larger phase angles cannot be explained by the sulphuric acid droplets alone suggesting a need of an additional component.We investigated several possibilities and argue that one good explanation is that the acid droplets nucleate on small inner cores composed of iron chloride. Iron chloride is one candidate for the so-called unknown absorber in the ultraviolet wavelengths range. An alternate explanation could be that the sulphuric acid droplets are coated with a thin layer of sulphur.

Markiewicz, Wojciech; Almeida, Miguel; Limaye, Sanjay; Ignatiev, Nikolay; Petrova, Elena; Shalygina, Oksana; Titov, Dmitrij

2012-07-01

349

Venus glory and the unknown uv absorber  

NASA Astrophysics Data System (ADS)

We report on the first observation of a complete glory on top of the Venus clouds captured with the Venus Monitoring Camera (VMC) when the Sun was almost directly behind the Venus Express space-craft. The wavelengths dependence of the position of the glory is consistent with clouds being composed of spherical droplets of sulphuric acid with radius of 1.2 micron, the so called mode-2 particles. The ratio of backscattering (zero phase angle) to maximum intensity of the glory as well the slope of the observed intensity at larger phase angles cannot be explained by the sulphuric acid droplets alone suggesting a need of an additional component. We investigated several possibilities and argue that one good explanation is that the acid droplets nucleate on small inner cores composed of iron chloride. Iron chloride is one candidate for the so-called unknown absorber in the ultraviolet wavelengths range. An alternate explanation could be that the sulphuric acid droplets are coated with a thin layer of sulphur.

Markiewicz, W. J.; Petrova, E.; Shalygina, O.; Almeida, M.; Titov, D. V.; Limaye, S. S.; Ignatiev, N.

2012-04-01

350

Impact Craters: Source of Sand-Sized Fines on Venus?  

NASA Astrophysics Data System (ADS)

The Magellan mission detected the presence of wind streaks and dune fields on Venus (Greeley, et al., 1992, J. Geophys. Res. 97, 13,319). However, these aeolian deposits are not abundant, suggesting that the fine-grained materials of which they are composed do not occur in great quantities on Venus. The source of this material is unclear; weathering in the terrestrial sense does not occur on Venus, so the release of resistant mineral grains by differential weathering is probably unimportant. Impact cratering, which produces large quantities of small (< 1 cm diameter) ejecta particles, may be the dominant source of sand-sized fines on Venus. The volume of such material produced by impact cratering on Venus may be estimated by using the results of fitting a model of the formation of the parabolic deposits that occur around approximately 50 Venusian craters (Vervack and Melosh, 1992, Geophys. Res. Lett. 19, 525). The results yield a relation for the mean particle diameter of impact ejecta as a function of the crater rim radius and range from the crater center (Schaller and Melosh, 1994, LPSC XXV, 1199). Integration of this function over (a) range and (b) the total crater distribution on Venus (approximately Ncum = 9.1 x 10(-5) rc({-) 2} for rc > 15 km [Schaber, et al., 1992, J. Geophys. Res. 97, 13,257]), yields a relation for the total volume of ejecta between the size d and sqrt {2}d: V({d,sqrt {2}d}) = 1.7 x 10({) -4} d(0.377) , where d is in cm and V is in km(3) . For particles in the sand-size range (60 to 2000 mu m), we estimate a total volume produced by impact cratering of 3.5 x 10(4) km(3) . The largest observed dune field on Venus, Fortuna-Meshkenet, covers 17,000 km(2) . Assuming the average dune height is 200 m, Fortuna-Meshkenet has a volume of 3.4 x 10(3) km(3) , a factor of 10 smaller. It thus appears that impact cratering may dominate the production of sand-sized material on Venus.

Schaller, C. J.

1996-09-01

351

Venus lower atmospheric composition: preliminary results from pioneer venus.  

PubMed

Initial examination of data from the neutral mass spectrometer on the Pioneer Venus sounder probe indicates that the abundances of argon-36, argon-38, and neon-20 in the Venus atmosphere are much higher than those of the corresponding gases in Earth's atmosphere, although the abundance of radiogenic argon-40 is apparently similar for both planets. The lower atmosphere of Venus includes significant concentrations of various gaseous sulfur compounds. The inlet leak to the mass spectrometer was temporarily blocked by an apparently liquid component of the Venus clouds during passage through the dense cloud layer. Analysis of gases released during the evaporation of the droplets shows the presence of water vapor to some compound or compounds of sulfur. PMID:17833003

Hoffman, J H; Hodges, R R; McElroy, M B; Donahue, T M; Kolpin, M

1979-02-23

352

Transits Of Venus: 1639, 1761, 1769, 1874, 1882, 2004, And 2012  

NASA Astrophysics Data System (ADS)

Transits of Venus are exceedingly rare predictable astronomical events, with only six having been observed since Jeremiah Horrox corrected Johannes Kepler's Rudolphine Tables and observed the transit of 1639. Edmond Halley's 1716 method of finding the size and scale of the Solar System and thus of the Universe led to hundreds of 18th-century and 19th-century transit-of-Venus expeditions for each event. I discuss the history and importance of the transit observations, and how spacecraft observations of the 1999 transit of Mercury, repeated at the 2003 and 2006 transits, led to the solution of the black-drop effect problem that had prevented Halley's method from reaching its desired accuracy and thus solution of the noble problem of astronomy to find the size and scale of the solar system. Other spacecraft observations of the 2004 transit of Venus have led to an analysis of how Venus's atmosphere becomes visible for about 25 minutes before second contact and after third contact, and links with prior historical claims, mostly invalid, to have discovered Venus's atmosphere at transits. Total-solar-irradiance spacecraft observations at the 2004 Venus transit link to exoplanet discoveries with NASA's aptly named Kepler Mission and ESA's CoRoT. I further link previous transit observations to planned observations for the June 5/6, 2012, Venus transit and the May 9, 2016, Mercury transit, together providing a historical basis for 22nd-century astronomers preparing to observe the December 10, 2117, Venus transit. My observations at the 2004 and 2012 transits of Venus were and will be supported in large part by grants from the Committee for Research and Exploration of the National Geographic Society. My solar observations were supported in part by NASA grant NNG04GK44G for work with the TRACE spacecraft and NASA Marshall grant NNX10AK47A and planetary work supported in part by NNX08AO50G from NASA Planetary Astronomy.

Pasachoff, Jay M.

2012-01-01

353

Pioneer Venus gas chromatography of the lower atmosphere of Venus  

Microsoft Academic Search

A gas chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, Nâ, Oâ, Ar, CO, HâO, SOâ, and COâ were measured, and upper limits set for Hâ, COS, HâS, CHâ, Kr, NâO, CâHâ, CâHâ, and CâHâ. Simulation studies have provided indirect evidence for sulfuric acid--like droplets and support

V. I. Oyama; G. C. Carle; F. Woeller; J. B. Pollack; R. T. Reynolds; R. A. Craig

1980-01-01

354

So2 vertical profile on Venus  

NASA Astrophysics Data System (ADS)

Introduction The distribution of SO2 below the clouds of Venus is an unsettled matter because various entry probes and earth observed values show big differences for the same altitude levels. A new analysis of the SO2 vertical profile with a 'best of' data set [1] is compared to the Vega 1 and Vega 2 results. For the analysis of the SO2 vertical profile two models have been formulated. While one model considers the fast decrease of SO2 with descending altitude and starts with 0 ppmV at the surface, the other model starts with 25 ppmV, as indicated by Vega 1. Although there is a lack of information on the lowest 10 kms of the atmosphere, an analysis should be done to understand the geological evolution and a possible activity on Venus. Vertical Profiles The two models produce two different vertical profiles and with those it was possible to calculate the mass of SO2 in the whole lower atmosphere. It is important to note that SO2 nearly disappears at 69 km height [1,3] while 99,6% of the whole mass is still contained in the lower atmosphere. The difference in the results is based on the different surface values, which have been used. The first model stands in good agreement with the Vega mission data and the second model can be used as an upper limit of SO2 in the atmosphere. The results yield a good estimation of how much SO2 is existent and give new discussion points about volcanic activity on Venus and a possible still unknown SO2 destroying mechanism. References [1] Bertaux, J. et al. (1996) JGR, 101, 12709-12745. [2] de Bergh, C. et al. (2006) Planetary and Space Sci., 54, 1389-1397. [3] Esposito L.W. et al., (1997) Venus II : Geology, Geophysics, Atmosphere, and Solar Wind Environment. Edited by Stephen W. Bougher, D.M. Hunten, and R.J. Philips. Tucson, AZ : University of Arizona Press, 415-458

Duricic, Alen; Leitner, Johannes; Firneis, Maria G.

2010-05-01

355

Definition and archiving of ground-based observations in support of space missions  

NASA Astrophysics Data System (ADS)

This science case was developed by the WG3&5 to induce and optimize the follow- up of space missions or to monitor a probe entry, in order to provide support in the case of failure, and help achieve science objectives. The space mission data need to be complemented by ground-based and space-borne observations that can help interpret the space mission return. Such coordinated observations were performed at the time of the Huygens descent in Titan's atmosphere and led to a JGR special issue publication (2006, in press). We should gather and archive all such observations to support space missions already existing or to come. For this we would need to get the space mission data from Cassini-Huygens (both images and spectra), Venus Express, Mars Express and future missions (to Europa and Mercury for instance) and complete them with ground-based observations (spectra, images, radio data, radar,...) of Titan, Venus, Mars, Europa, Mercury with the HST, ISO, etc, as well as amateur observations, if possible, taken from 1990 on. This applies to cometary, moon and planet surfaces/subsurfaces composition- structure. This would help among other with the target selections (comets, moons) and landing sites for SMART-1 (on the Moon). There are specific needs for stereoscopic images of the Moon and other objects. Our study will assist in optimizing the Rosetta mission return. For Mercury we need to observe from the ground at the time of the Bepi-Colombo mission to cross-calibrate the mission data. There are many examples of success from this additional input, as for instance with Cassini-Huygens (DWE- Channel C), Galileo, etc. For Titan there is a requirement for RADAR measurements of the whole surface during the extended Cassini mission. Also, assist with the interpretation of high-resolution DISR images in terms of surface activity and surface-atmosphere interactions This involves in some cases techniques possible only from the Earth such as the VLBI 1 radio-tracking of a space mission with probe signal during entry or landing and a radar search for solid and liquid extents on moon surfaces. We need to assure extended temporal monitoring to study diurnal or seasonal effects and complete planetary objects' lightcurves and derive insights on the evolution of their surface properties 2

Coustenis, A.; Europlanet Wg3&5

356

Simulation of Venus polar vortices with the non-hydrostatic general circulation model  

NASA Astrophysics Data System (ADS)

The dynamics of Venus atmosphere in the polar regions presents a challenge for general circulation models. Numerous images and hyperspectral data from Venus Express mission shows that above 60 degrees latitude atmospheric motion is substantially different from that of the tropical and extratropical atmosphere. In particular, extended polar hoods composed presumably of fine haze particles, as well as polar vortices revealing mesoscale wave perturbations with variable zonal wavenumbers, imply the significance of vertical motion in these circulation elements. On these scales, however, hydrostatic balance commonly used in the general circulation models is no longer valid, and vertical forces have to be taken into account to obtain correct wind field. We present the first non-hydrostatic general circulation model of the Venus atmosphere based on the full set of gas dynamics equations. The model uses uniform grid with the resolution of 1.2 degrees in horizontal and 200 m in the vertical direction. Thermal forcing is simulated by means of relaxation approximation with specified thermal profile and time scale. The model takes advantage of hybrid calculations on graphical processors using CUDA technology in order to increase performance. Simulations show that vorticity is concentrated at high latitudes within planetary scale, off-axis vortices, precessing with a period of 30 to 40 days. The scale and position of these vortices coincides with polar hoods observed in the UV images. The regions characterized with high vorticity are surrounded by series of small vortices which may be caused by shear instability of the zonal flow. Vertical velocity component implies that in the central part of high vorticity areas atmospheric flow is downwelling and perturbed by mesoscale waves with zonal wavenumbers 1-4, resembling observed wave structures in the polar vortices. Simulations also show the existence of areas with strong vertical flow, concentrated in spiral branches extending from low latitude to the circumpolar vortex. Qualitatively this pattern suggest that the dynamics of the polar Venus atmosphere resembles that of terrestrial hurricanes, but is characterized with preferentially poleward and downwelling motions.

Rodin, Alexander V.; Mingalev, Oleg; Orlov, Konstantin

2012-07-01

357

Solar wind alpha particle capture at Mars and Venus  

NASA Astrophysics Data System (ADS)

Helium is detected in the atmospheres of both Mars and Venus. It is believed that radioactive decay of uranium and thorium in the interior of the planets' is not sufficient to account for the abundance of helium observed. Alpha particles in the solar wind are suggested to be an additional source of helium, especially at Mars. Recent hybrid simulations show that as much as 30We use ion data from the ASPERA-3 and ASPERA-4 instruments on Mars and Venus Express to estimate how efficient solar wind alpha particles are captured in the atmospheres of the two planets.

Stenberg, Gabriella; Barabash, Stas; Nilsson, Hans; Fedorov, A.; Brain, David; André, Mats

358

Recent hotspot volcanism on Venus from VIRTIS emissivity data.  

PubMed

The questions of whether Venus is geologically active and how the planet has resurfaced over the past billion years have major implications for interior dynamics and climate change. Nine "hotspots"--areas analogous to Hawaii, with volcanism, broad topographic rises, and large positive gravity anomalies suggesting mantle plumes at depth--have been identified as possibly active. This study used variations in the thermal emissivity of the surface observed by the Visible and Infrared Thermal Imaging Spectrometer on the European Space Agency's Venus Express spacecraft to identify compositional differences in lava flows at three hotspots. The anomalies are interpreted as a lack of surface weathering. We estimate the flows to be younger than 2.5 million years and probably much younger, about 250,000 years or less, indicating that Venus is actively resurfacing. PMID:20378775

Smrekar, Suzanne E; Stofan, Ellen R; Mueller, Nils; Treiman, Allan; Elkins-Tanton, Linda; Helbert, Joern; Piccioni, Giuseppe; Drossart, Pierre

2010-04-08

359

Scattering of Thermal Radiation by Droplets in Venus' Upper Atmosphere  

NASA Astrophysics Data System (ADS)

The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on the Venus Express spacecraft has been providing a wealth of data on the Venus atmosphere since its arrival at Venus in 2006. Here, we present results from VIRTIS-IR measurements of the nightside limb of the planet, where we probe the atmosphere above the cloud tops at a range of altitudes. We find that the measurements are dominated by thermal radiation from the lower atmosphere that is scattered into the line of sight by cloud or haze particles. This is even true at 5 micron, the longest wavelength observed by VIRTIS. A limb scattering model is used to analyse the data and put constraints on particle size and vertical distribution of the cloud/haze particles up to an altitude of 90 km.

de Kok, Remco; Irwin, P. G. J.; Piccioni, G.; Drossart, P.; VIRTIS/Venus Express Team

2009-09-01

360

Imaging of Mercury and Venus from a flyby  

USGS Publications Warehouse

This paper describes the results of study of an imaging experiment planned for the 1973 Mariner Venus/Mercury flyby mission. Scientific objectives, mission constraints, analysis of alternative systems, and the rationale for final choice are presented. Severe financial constraints ruled out the best technical alternative for flyby imaging, a film/readout system, or even significant re-design of previous Mariner vidicon camera/tape recorder systems. The final selection was a vidicon camera quite similar to that used for Mariner Mars 1971, but with the capability of real time transmission during the Venus and Mercury flybys. Real time data return became possible through dramatic increase in the communications bandwidth at only modest sacrifice in the quality of the returned pictures. Two identical long focal length cameras (1500 mm) were selected and it will be possible to return several thousand pictures from both planets at resolutions ranging from equivalent to Earthbased to tenths of a kilometer at encounter. Systematic high resolution ultraviolet photography of Venus is planned after encounter in an attempt to understand the nature of the mysterious ultraviolet markings and their apparent 4- to 5-day rotation period. Full disk coverage in mosaics will produce pictures of both planets similar in quality to Earthbased telescopic pictures of the Moon. The increase of resolution, more than three orders of magnitude, will yield an exciting first look at two planets whose closeup appearance is unknown. ?? 1971.

Murray, B. C.; Belton, M. J. S.; Edward, Danielson, G.; Davies, M. E.; Kuiper, G. P.; O'Leary, B. T.; Suomi, V. E.; Trask, N. J.

1971-01-01

361

Image and spectral image compression for four experiments on the ROSETTA and Mars Express missions of ESA  

NASA Astrophysics Data System (ADS)

The output rates of imaging scientific experiments on planetary missions far exceed the few 10 kbits/s provided by X or Ka band downlink. This severely restricts the duration and frequency of observations. Space applications present specific constraints for compression methods: space qualified ROM and fast RAM chips have limited capacity and large power requirements. Real time compression is therefore preferable (no large local data buffer) but requires a large processing throughput. Wavelet compression provides a fast and efficient method for lossy data compression, when combined with tree- coding algorithms such as that of Said and Pearlman. We have developed such an algorithm for four instruments on ROSETTA (ESA cometary rendez-vous mission) and Mars Express (ESA Mars Orbiter and Lander mission), building on the experience from two experiments on CASSINI and MARS 96 for which lossless compression was implemented. Modern Digital Signal Processors using a pipeline architecture provide the required high computing capability. The Said-Pearlman tree-coding algorithm has been optimized for speed and code size by reducing branching and bit manipulation, which are very costly in terms of processor cycles. Written in C with a few assembly language modules, the implementation on a DSP of this new version of the Said-Pearlman algorithm provides a processing capability of 500 kdata/s (imaging), which is adequate for our applications. Compression ratios of at least 10 can be achieved with acceptable data quality.

Langevin, Yves; Forni, O.

2000-12-01

362

The spatial distribution of coronae on Venus  

NASA Astrophysics Data System (ADS)

Coronae on Venus are large, generally circular surface features that have distinctive tectonic, volcanic, and topographic expressions. They range in diameter from less than 200 km to at least 1000 km. Data from the Magellan spacecraft have now allowed complete global mapping of the spatial distribution of coronae on the planet. Unlike impact craters, which show a random (i.e., Poisson) spatial distribution, the distribution of coronae appears to be nonrandom. We investigate the distribution here in detail, and explore its implications in terms of mantle convection and surface modification processes.

Squyres, S. W.; Schubert, G.; Bindschadler, D. L.; Janes, D. M.; Moersch, J. E.; Moore, W.; Olson, P.; Ratcliff, J. T.; Stofan, E. R.; Turcotte, D. L.

1992-12-01

363

Radio occultation measurements of turbulence in the Venus atmosphere by Pioneer Venus  

Microsoft Academic Search

As in the cases of Mariner 5 and 10 and Venera 9, the Pioneer Venus radio occultation measurements of Venus show an upper region of turbulence located in the vicinity of 60 km. Estimates of the deduced intensity of turbulence are consistent with the upper bound obtained earlier from the complementary Pioneer Venus probe measurements. Comparison with the Pioneer Venus

Richard Woo; J. W. Armstrong; Akira Ishimaru

1980-01-01

364

The Pioneer Venus Orbiter: 11 years of data. A laboratory for atmospheres seminar talk  

Microsoft Academic Search

The Pioneer Venus Orbiter has been in operation since orbit insertion on December 4, 1978. For the past 11 years, it has been acquiring data in the salient features of the planet, its atmosphere, ionosphere, and interaction with the solar wind. A few of the results of this mission are summarized and their contribution to our general understanding of the

W. T. Kasprzak

1990-01-01

365

Venus Transit and the Search for New Worlds (Webcast)  

NSDL National Science Digital Library

This webcast features a panel of NASA scientists and engineers discussing the future of extrasolar planet research and the science behind a rare astronomical event: Venus crossing the Sunâs disk for about seven hours on June 8, 2004, an event not seen since 1882. The transit demonstrates a key technique being used to detect planets orbiting stars outside our Solar System. Just as Venus temporarily dimmed the light of the Sun when it crossed in front of it, a distant planet may cross in front of and block the light of its parent star. Several planned missions will hunt for such extrasolar planets as part of NASA's Origins program, which seeks to answer the following questions: Where did we come from? Are we alone?

2004-03-19

366

Oxygen Chemistry and Airglow in Venus' Atmosphere  

NASA Astrophysics Data System (ADS)

Airglow in a planetary atmosphere is diagnostic of the combined effects of transport, both vertical and horizontal, and chemistry. Airglow emission on the night side in the OH(3-2, 2-1, 2-0, and 1-0), O2(c-X and a-X), and NO(C-A) bands has been reported in the past two years based on observations by VIRTIS on Venus Express [1,2,3]. Previous observations had also identified airglow emission in the O2(a-X) band on the day side [4]. Vertical profiles from limb observations indicate the OH and O2 nightglow emissions are typically most intense at 95-100 km altitude [1,5] while the NO nightglow emission is most intense at about 110 km altitude [2]. All of these airglow emissions are directly or indirectly connected to the atomic oxygen abundance at these altitudes and vertical profiles of the O2(a-X) nightglow emission as observed by VIRTIS on Venus Express have been used to infer the atomic oxygen profile [6]. The expected connections among these day and night side airglow emissions based on photochemical modelling will be discussed along with their implications for oxygen chemistry in the 90-110 km altitude range in Venus' atmosphere. This work was partially supported by the Australian Research Council. [1] Piccioni et al, A&A 483, L29, 2008 [2] García Muñoz et al, PNAS 106, 985, 2009 [3] García Muñoz et al, JGR, in revision, 2009 [4] Connes et al, ApJ 233, L29, 1979 [5] Piccioni et al, JGR 114, E00B38, 2009 [6] Gérard et al, GRL 35, L02207, 2008

Mills, Franklin P.; Garcia Munoz, A.; Yung, Y. L.; Allen, M.; Piccioni, G.; Drossart, P.

2009-09-01

367

Venus project : experimentation at ENEA's pilot site.  

National Technical Information Service (NTIS)

The document describes the ENEA's (Italian Agency for New Technologies, Energy and the Environment) experience in the Venus Project (Esprit III ). Venus is an advanced visual interface based on icon representation that permits to end-user to inquiry datab...

M. L. Bargellini F. Fontana C. Bucci F. Ferrara P. A. Sottile

1996-01-01

368

Why Venus has No Moon  

NASA Astrophysics Data System (ADS)

Venus does not have a moon. We argue that this is at least as surprising as the presence of Earth's moon and more surprising than the absence of a substantial moon for Mercury or Mars. We do not know if Venus ever had a moon. The accepted explanation for Earth's moon is a giant impact with an impactor on the order of one Mars mass. Given current theories of solar system formation, it is unlikely that Venus would have avoided such a large collision. Simulations suggest that most large collisions create a disk from which a moon forms. Moreover, the natural outcome is one where the sense of orbital motion and planetary spin are the same, leading to outward tidal evolution. Despite the smaller sphere of influence of Venus relative to Earth, and the larger solar tidal influence, only very large moons or very dissipative tides allow such a moon to escape. The alternative of inward evolution and coalescence cannot be explained without a second large impact that provides an angular momentum impulse of the opposite sense. A two large collision hypothesis is presented, and argued for. Since tidal evolution is primarily symmetric with respect to relative mean motion, the moon created by the first giant impact returns to Venus on roughly the same timescale as the time between giant impacts, 10^7 years. This hypothesis also allows Venus to eventually evolve to the current slow retrograde rotation state, an outcome that is otherwise difficult to explain quantitatively, notwithstanding the accepted current balance between solar thermal and solid body tides. The two giant impact hypothesis may have isotopic and possibly compositional consequences for Venus but the coalescence is unlikely to have left a clear geophysical or geological trace. We have not identified a clear observational test of this model.

Alemi, Alex; Stevenson, D.

2006-09-01

369

The Mariner 10 Venus encounter - A review  

Microsoft Academic Search

A brief description is given of the Mariner 10 spacecraft, its complement of scientific instruments, and its encounter with Venus. It is noted that the geometry of the Venus encounter was dictated entirely by the necessity to use Venus' gravitational field to deflect the flight path toward Mercury. Results discussed include observations of plasma and magnetic-field perturbations several hundreds of

J. A. Dunne

1975-01-01

370

Biologically Closed Electrical Circuits in Venus Flytrap  

Microsoft Academic Search

The Venus flytrap (Dionaea muscipula Ellis) is a marvel of plant electrical, mechanical, and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical

Alexander G. Volkov; Holly Carrell; Vladislav S. Markin

2009-01-01

371

Plasma Waves in the Magnetosheath of Venus.  

National Technical Information Service (NTIS)

Research supported by this grant is divided into three basic topics of investigation. These are: (1) Plasma waves in the Venus magnetosheath, (2) Plasma waves in the Venus foreshock and solar wind, (3) plasma waves in the Venus nightside ionosphere and io...

R. J. Strangeway

1996-01-01

372

Mercury and Venus Section: Star-spots of Venus  

NASA Astrophysics Data System (ADS)

According to his compatriot Forest Ray Moulton, Edward Emerson Barnard at times saw small white spots dotted like stars about the apparent surface of Venus. Thinking they 'might be the lofty summits of snow-clad mountains, reaching above the level of the denser clouds,' he attempted to use them to determine the rotation period of the planet. Moulton, who cites no source for this story, tells us, 'he never found it possible to follow such spots long enough to throw any light' on the matter. Today the rotation of Venus is known, and the myth of a mountainous planet dispelled. But the phenomenon itself is beyond doubt; as Henry McEwen, the first Director of the Mercury and Venus Section, noted in 1950, 'points of light... have been seen by most of the 'classic' observers and several moderns, myself included.'

Baum, R. M.

1999-06-01

373

Surface of Venus: Possible sulfides  

NASA Astrophysics Data System (ADS)

The surface reflectivity of Venus at radar wavelengths of 17 cm varies from very ‘bright’ areas, such as the Maxwell Montes and other elevated regions like Terra Aphrodite, to the darkest regions, which are located in low-lying valleys. Radar altimeter data received from the instrument aboard the Pioneer Venus Orbiter are showing good correlations between brightness and surface elevations, but the indications are that the bright regions are too bright to be explained by radar reflections from dry terrestrial-type rocks. The dielectric constant (K) of rocks that radar reflect as the elevated regions of Venus' surface must be high, probably on the order K=9 or more. On Venus bright areas have K between 11 and 20, presenting difficulties in the interpretation of the surface materials. In a study by G.H. Pettengill, P.G. Ford, and S. Nozette (Science, Aug. 13, 1982), the high-reflectivity regions of Venus are interpreted as being due possibly to the presence of free metal or, more likely, to pyrite (FeS2), one of the few minerals with sufficiently high conductivity (1-105 mho/m).

Bell, Peter M.

374

Electrical memory in Venus flytrap.  

PubMed

Electrical signaling, memory and rapid closure of the carnivorous plant Dionaea muscipula Ellis (Venus flytrap) have been attracting the attention of researchers since the XIX century. The electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf in 0.3 s without mechanical stimulation of trigger hairs. Here we developed a new method for direct measurements of the exact electrical charge utilized by the D. muscipula Ellis to facilitate the trap closing and investigated electrical short memory in the Venus flytrap. As soon as the 8 microC charge for a small trap or a 9 microC charge for a large trap is transmitted between a lobe and midrib from the external capacitor, the trap starts to close at room temperature. At temperatures 28-36 degrees C a smaller electrical charge of 4.1 microC is required to close the trap of the D. muscipula. The cumulative character of electrical stimuli points to the existence of short-term electrical memory in the Venus flytrap. We also found sensory memory in the Venus flytrap. When one sustained mechanical stimulus was applied to only one trigger hair, the trap closed in a few seconds. PMID:19356999

Volkov, Alexander G; Carrell, Holly; Baldwin, Andrew; Markin, Vladislav S

2009-03-20

375

Variability of CO, OCS And H2O Below The Clouds of Venus From VIRTIS-HNight-side Spectra  

NASA Astrophysics Data System (ADS)

The VIRTIS imaging spectrometer has provided numerous spectra of Venus since the beginning of the Venus Express mission in April 2006. The high resolution of the H-channel (R 2000) enables the investigation of the composition below the clouds using the thermal emission from the night side of the planet, since several absorption of minor components (CO, OCS, H2O, HDO, SO2, HF) are located in the 2.3 µm transparency window of CO2. Using a radiative transfer computer model, we were able to derive constraints on the vertical profiles of CO, OCS and H2O in the 30-40 km altitude range up to areas unreacheable with Earth-based instruments (0° - 60°S). Our findings extend the latitudinal trends already noticed from both space (Collard et al., 1993, using Galileo/NIMS) and Earth (Marcq et al. 2005,2006, using IRTF/SpeX): an increase of CO towards high latitudes (30 ± 10 % between 60°S and 0°), a correlated decrease of OCS in the same region and a constant abundance of 28 ± 4 ppmv at 35 km for H2O. The latitudinal variations of CO are in good agreement with the VIRTIS-M observations from Tsang et al. (private communication). The quantitative interpretation of CO and OCS variations in terms of global-scale vertical circulation is in progress, using circulation models such as Yung et al's (private communication) in 2D and Lebonnois et al.'s (38th DPS meeting, #19.04) in 3D, thus helping in precising the understanding of both dynamics and chemistry in the deep atmopshere of Venus. This work has been funded by the CNES space agency.

Marcq, Emmanuel; Bezard, B.; Drossart, P.; Piccioni, G.; VIRTIS Team

2007-10-01

376

A teardrop-shaped ionosphere at Venus in tenuous solar wind  

NASA Astrophysics Data System (ADS)

A very tenuous solar wind regime, following a series of large coronal mass ejections, impacted Venus during early August, 2010. STEREO-B downstream from Venus observed that the solar wind density at Earth orbit dropped to ˜0.1#/cm3 and persisted at this value over 1 day. A similar low value was observed at Earth in 1999 and has attracted comprehensive attention (Lazarus, A.J., 2000. Solar physics: the day the solar wind almost disappeared. Science 287, 2172-2173.), especially its consequences on Earth's ionosphere and magnetosphere (Lockwood, M., 2001. Astronomy: the day the solar wind nearly died. Nature 409, 677-679.). We now have an opportunity to examine the response of Venus' ionosphere to such a tenuous solar wind. After Venus Express spacecraft entered the ionosphere near the terminator, it continuously sampled O+ dominated planetary plasma on the nightside till it left the optical shadow region when Venus Express was located at 2 RV (Venus' Radii) to the Venus center and 1.1 RV to the Sun-Venus line. Moreover, the O+ speed was lower than the gravitational escape speed. We interpret this low-speed O+ as a constituent of the extended nightside ionosphere as a consequence of long-duration (18 h) tenuous solar wind, because the very low dynamic pressure enhances the source and reduces the sink of the nightside ionosphere. Though the full extent of the nightside ionosphere is not known due to the limitation of spacecraft's trajectory, our results suggest that the global configuration of Venus' ionosphere could resemble a teardrop-shaped cometary ionosphere.

Wei, Y.; Fraenz, M.; Dubinin, E.; Coates, A. J.; Zhang, T. L.; Wan, W.; Feng, L.; Angsmann, A.; Opitz, A.; Woch, J.; Barabash, S.; Lundin, R.

2012-12-01

377

Radio occultation experiment of the Venus atmosphere and ionosphere with the Venus orbiter Akatsuki  

NASA Astrophysics Data System (ADS)

The Radio Science experiment (RS) in the Akatsuki mission of JAXA aims to determine the vertical structure of the Venus atmosphere, thereby complementing the imaging observations by onboard instruments. The physical quantities to be retrieved are the vertical distributions of the atmospheric temperature, the electron density, the H2SO4 vapor density, and small-scale density fluctuations. The uniqueness of Akatsuki RS as compared to the previous radio occultation experiments at Venus is that low latitudes can be probed many times thanks to the near-equatorial orbit. Systematic sampling in the equatorial region provides an opportunity to observe the propagation of planetary-scale waves that might contribute to the maintenance of the super-rotation via eddy momentum transport. Covering the subsolar region is essential to the understanding of cloud dynamics. Frequent sampling in the subsolar electron density also helps the understanding of ionosphere dynamics. Another unique feature of Akatsuki RS is quasi-simultaneous observations with multi-band cameras dedicated to meteorological study; the locations probed by RS are observed by the cameras a short time before or after the occultations. An ultra-stable oscillator provides a stable reference frequency which is needed to generate the X-band downlink signal used for RS.

Imamura, T.; Toda, T.; Tomiki, A.; Hirahara, D.; Hayashiyama, T.; Mochizuki, N.; Yamamoto, Z.-I.; Abe, T.; Iwata, T.; Noda, H.; Futaana, Y.; Ando, H.; Häusler, B.; Pätzold, M.; Nabatov, A.

2011-06-01

378

Wave granulation in the Venus' atmosphere  

NASA Astrophysics Data System (ADS)

In unique venusian planetary system the solid body rotates very slowly and the detached massive atmosphere very rapidly. However both together orbit Sun and their characteristic orbital frequency -1/ 0.62 year - places them in the regular row of planets assigning them characteristic only for Venus wave produced granulation with a granule size ?R/6 [1& others]. Remind other bodies in the row with their granule sizes inversely proportional to their orbital frequencies: solar photosphere ?R/60, Mercury ?R/16, Venus ?R/6, Earth ?R/4, Mars ?R/2, asteroids ?R/1 (R-a body radius). Three planets have atmospheres with wave granulations having sizes equal to their lithospheric granules. But Venus, unlike Earth and Mars, has the detached atmosphere that can be considered as a separate body with its own orbital frequency around the center of the Venus' system. According to the correlation between an orbital frequency and a wave granule size the venusian wave granule will be ?R/338 (a scale can be Earth: orbital frequency 1/ 1year, granule size ?R/4 or Sun: frequency 1/1month, granule size ?R/60). So, ?R/338 = 57 km. This theoretical size is rather close to that observed by Galileo SC through a violet filter "the filamentary dark features. . . are here revealed to be composed of several dark nodules, like beads on a string, each about 60 miles across" (PIA00072). Actually all Venus' disc seen from a distance ~1.7mln.miles is peppered with these fine features seen on a limit of resolution. So, the Venus' atmosphere has two main frequencies in the solar system with corresponding wave granulations: around Sun 1/225 days (granule ?R/6) and around Venus 1/ 4 days (granule ?R/338). As was done for the Moon, Phobos, Titan and other icy satellites of Saturn [2, 3, 4 & others] one can apply the wave modulation technique also for the atmosphere of Venus. The lower frequency modulates the higher one by dividing and multiplying it thus getting two side frequencies and corresponding them wave granule sizes. (1/338 : 1/6)?R = ?R/56.3 = 342 km. (1/338 x 1/6)?R = ?R/2028 = 9.5 km. The larger granules as well arranged network were seen in the near IR Galileo image PIA00073 (several miles below the visible cloud tops). The smaller granules, hopefully, will be detected by the Venus Express cameras. So, the wave planetology applying wave methods to solid planetary bodies and to surrounding them gaseous envelopes shows their structural unity. This understanding may help to analyze and predict very complex behavior of atmospheric sells at Earth (anticyclones up to 5000 km across or ?R/4), other planets and Titan. Long time ago known the solar supergranules about 30000 km across were never fully understood. The comparative wave planetology placing them together with wave features of planets and satellites throws light on their origin and behavior and thus expands into an area of the solar physics. In this respect it is interesting to note that rather typical for Sun radio emission in 1 meter diapason also was never properly explained. But applying modulation of the solar photosphere frequency 1/ 1month by the Galaxy frequency 1/ 200 000 000 y. one can obtain such short waves [5]. Radio emissions of planets of the solar system also can be related to this modulation by Galaxy rotation [5]. References: [1] Kochemasov G.G. (1992) Comparison of blob tectonics (Venus) and pair tectonics (Earth) // LPS XXIII, Houston, LPI, pt. 2, 703-704; [2] Kochemasov G.G. (2000) Orbiting frequency modulation in Solar system and its imprint in shapes and structures of celestial bodies // Vernadsky-Brown microsymposium 32 on Comparative planetology, Oct. 9-11, 2000, Moscow, Russia, Abstracs, 88-89; [3] Kochemasov G.G. (2000) Titan: frequency modulation of warping waves // Geophys. Res. Abstr., v. 2, (CD-ROM); [4] Kochemasov G.G. (2005) Cassini' lessons: square craters, shoulderto- shoulder even-size aligned and in grids craters having wave interference nature must be taken out of an impact craters statistics to make it real // Vernadsky-Brown

Kochemasov, G.

2007-08-01

379

Wave granulation in the Venus' atmosphere  

NASA Astrophysics Data System (ADS)

In unique venusian planetary system the solid body rotates very slowly and the detached massive atmosphere very rapidly. However both together orbit Sun and their characteristic orbital frequency -1/ 0.62 year - places them in the regular row of planets assigning them characteristic only for Venus wave produced granulation with a granule size ?R/6 [1& others]. Remind other bodies in the row with their granule sizes inversely proportional to their orbital frequencies: solar photosphere ?R/60, Mercury ?R/16, Venus ?R/6, Earth ?R/4, Mars ?R/2, asteroids ?R/1 (R-a body radius). Three planets have atmospheres with wave granulations having sizes equal to their lithospheric granules. But Venus, unlike Earth and Mars, has the detached atmosphere that can be considered as a separate body with its own orbital frequency around the center of the Venus' system. According to the correlation between an orbital frequency and a wave granule size the venusian wave granule will be ?R/338 (a scale can be Earth: orbital frequency 1/ 1year, granule size ?R/4 or Sun: frequency 1/1month, granule size ?R/60). So, ?R/338 = 57 km. This theoretical size is rather close to that observed by Galileo SC through a violet filter "the filamentary dark features. . . are here revealed to be composed of several dark nodules, like beads on a string, each about 60 miles across" (PIA00072). Actually all Venus' disc seen from a distance ?1.7mln.miles is peppered with these fine features seen on a limit of resolution. So, the Venus' atmosphere has two main frequencies in the solar system with corresponding wave granulations: around Sun 1/225 days (granule ?R/6) and around Venus 1/ 4 days (granule ?R/338). As was done for the Moon, Phobos, Titan and other icy satellites of Saturn [2, 3, 4 & others] one can apply the wave modulation technique also for the atmosphere of Venus. The lower frequency modulates the higher one by dividing and multiplying it thus getting two side frequencies and corresponding them wave granule sizes. (1/338 : 1/6)?R = ?R/56.3 = 342 km. (1/338 x 1/6)?R = ?R/2028 = 9.5 km. The larger granules as well arranged network were seen in the near IR Galileo image PIA00073 (several miles below the visible cloud tops). The smaller granules, hopefully, will be detected by the Venus Express cameras. So, the wave planetology applying wave methods to solid planetary bodies and to surrounding them gaseous envelopes shows their structural unity. This understanding may help to analyze and predict very complex behavior of atmospheric sells at Earth (anticyclones up to 5000 km across or ?R/4), other planets and Titan. Long time ago known the solar supergranules about 30000 km across were never fully understood. The comparative wave planetology placing them together with wave features of planets and satellites throws light on their origin and behavior and thus expands into an area of the solar physics. In this respect it is interesting to note that rather typical for Sun radio emission in 1 meter diapason also was never properly explained. But applying modulation of the solar photosphere frequency 1/ 1month by the Galaxy frequency 1/ 200 000 000 y. one can obtain such short waves [5]. Radio emissions of planets of the solar system also can be related to this modulation by Galaxy rotation [5]. References: [1] Kochemasov G.G. (1992) Comparison of blob tectonics (Venus) and pair tectonics (Earth) // LPS XXIII, Houston, LPI, pt. 2, 703-704; [2] Kochemasov G.G. (2000) Orbiting frequency modulation in Solar system and its imprint in shapes and structures of celestial bodies // Vernadsky-Brown microsymposium 32 on Comparative planetology, Oct. 9-11, 2000, Moscow, Russia, Abstracs, 88-89; [3] Kochemasov G.G. (2000) Titan: frequency modulation of warping waves // Geophys. Res. Abstr., v. 2, (CD-ROM); [4] Kochemasov G.G. (2005) Cassini' lessons: square craters, shoulderto- shoulder even-size aligned and in grids craters having wave interference nature must be taken out of an impact craters statistics to make it real // Vernadsky-Brown

Kochemasov, G.

2007-08-01

380

Virtis: An Imaging Spectrometer for the Rosetta Mission  

NASA Astrophysics Data System (ADS)

The VIRTIS (Visual IR Thermal Imaging Spectrometer) experiment has been one of the most successful experiments built in Europe for Planetary Exploration. VIRTIS, developed in cooperation among Italy, France and Germany, has been already selected as a key experiment for 3 planetary missions: the ESA-Rosetta and Venus Express and NASA-Dawn. VIRTIS on board Rosetta and Venus Express are already producing high quality data: as far as Rosetta is concerned, the Earth-Moon system has been successfully observed during the Earth Swing-By manouver (March 2005) and furthermore, VIRTIS will collect data when Rosetta flies by Mars in February 2007 at a distance of about 200 kilometres from the planet. Data from the Rosetta mission will result in a comparison using the same combination of sophisticated experiments of targets that are poorly differentiated and are representative of the composition of different environment of the primordial solar system. Comets and asteroids, in fact, are in close relationship with the planetesimals, which formed from the solar nebula 4.6 billion years ago. The Rosetta mission payload is designed to obtain this information combining in situ analysis of comet material, obtained by the small lander Philae, and by a long lasting and detailed remote sensing of the comet, obtained by instrument on board the orbiting Spacecraft. The combination of remote sensing and in situ measurements will increase the scientific return of the mission. In fact, the “ in situ” measurements will provide “ground-truth” for the remote sensing information, and, in turn, the locally collected data will be interpreted in the appropriate context provided by the remote sensing investigation. VIRTIS is part of the scientific payload of the Rosetta Orbiter and will detect and characterise the evolution of specific signatures such as the typical spectral bands of minerals and molecules arising from surface components and from materials dispersed in the coma. The identification of spectral features is a primary goal of the Rosetta mission as it will allow identification of the nature of the main constituent of the comets. Moreover, the surface thermal evolution during comet approach to sun will be also studied.

Coradini, A.; Capaccioni, F.; Drossart, P.; Arnold, G.; Ammannito, E.; Angrilli, F.; Barucci, A.; Bellucci, G.; Benkhoff, J.; Bianchini, G.; Bibring, J. P.; Blecka, M.; Bockelee-Morvan, D.; Capria, M. T.; Carlson, R.; Carsenty, U.; Cerroni, P.; Colangeli, L.; Combes, M.; Combi, M.; Crovisier, J.; De Sanctis, M. C.; Encrenaz, E. T.; Erard, S.; Federico, C.; Filacchione, G.; Fink, U.; Fonti, S.; Formisano, V.; Ip, W. H.; Jaumann, R.; Kuehrt, E.; Langevin, Y.; Magni, G.; McCord, T.; Mennella, V.; Mottola, S.; Neukum, G.; Palumbo, P.; Piccioni, G.; Rauer, H.; Saggin, B.; Schmitt, B.; Tiphene, D.; Tozzi, G.

2007-02-01

381

Biologically closed electrical circuits in venus flytrap.  

PubMed

The Venus flytrap (Dionaea muscipula Ellis) is a marvel of plant electrical, mechanical, and biochemical engineering. The rapid closure of the Venus flytrap upper leaf in about 0.1 s is one of the fastest movements in the plant kingdom. We found earlier that the electrical stimulus between a midrib and a lobe closes the Venus flytrap upper leaf without mechanical stimulation of trigger hairs. The Venus flytrap can accumulate small subthreshold charges and, when the threshold value is reached, the trap closes. Here, we investigated the electrical properties of the upper leaf of the Venus flytrap and proposed the equivalent electrical circuit in agreement with the experimental data. PMID:19211696

Volkov, Alexander G; Carrell, Holly; Markin, Vladislav S

2009-02-11

382

Visible and near-infrared nightglow of molecular oxygen in the atmosphere of Venus  

Microsoft Academic Search

The Herzberg II system of O2 has been a known feature of Venus' nightglow since the Venera 9 and 10 orbiters detected its c(0)–X(v?) progression more than 3 decades ago. We search for its emission at 400 nm–700 nm in spectra obtained with the VIRTIS instrument on Venus Express. Despite the weakness of the signal, integration over a few hours

A. García Muñoz; F. P. Mills; T. G. Slanger; G. Piccioni; P. Drossart

2009-01-01

383

Dynamical Structure of Venus' Middle Atmosphere Constrained by Direct Wind Measurements  

Microsoft Academic Search

Dynamical study of Venus' mesosphere from Venus Express will largely rely on temperature measurements, cloud motion tracking and the structure of non-LTE O2 and CO2 emissions. However, direct wind measurements can only be provided using high spectral resolution (105-107) ground-based facilities measuring Doppler shifts in CO and isotopic 13CO rotational millimeter lines (95-115 km), solar Fraunhofer (67 km) and CO2

Thomas Widemann; E. Lellouch; D. Luz; R. Moreno

2006-01-01

384

Mission Interstellaire (Interstellar Mission).  

National Technical Information Service (NTIS)

The technology required for an unmanned spacecraft to reach the nearest star in less than a century is examined. The average mission velocity must be at least 0.043c, implying a specific impulse of at least 100,000s. The only types of propulsion which can...

M. Boyer

1984-01-01

385

Stability of the Venus ionopause  

SciTech Connect

One of the previously proposed mechanisms for the formation of magnetic ropes in the Venus ionosphere -breakup of the ionopause as a result of the development of the Kelvin-Helmholtz instability - is analyzed. Because the plasma flow in the transitional region is axisymmetric disturbances greater than 50 km in size (characteristic size of the magnetic ropes near the ionopause) are stable for zenith angles 0 less than or equal to 10/sup 0/. It was found that existing data, obtained on the American Pioneer-Venus space probe, also apparently indicate that the ionopause is stable for low dynamic solar-wind pressure.

Krymskii, A.M.

1987-11-01

386

Largest impact craters on Venus  

NASA Astrophysics Data System (ADS)

High-resolution radar images from the Magellan spacecraft have allowed us to perform a detailed study on 25 large impact craters on Venus with diameters from 70 to 280 km. The dimension of these large craters is comparable with the characteristic thickness of the venusian lithosphere and the atmospheric scale height. Some physical parameters for the largest impact craters on Venus (LICV), such as depth, ring/diameter ratio, and range of ballistic ejecta deposits, have been obtained from the SAR images and the altimetry dataset produced by MIT. Data related to each of these parameters is discussed.

Ivanov, B. A.; Weitz, C. M.; Basilevsky, A. T.

1992-12-01

387

Photochemical Modelling of Venus Clouds Using Pioneer Venus Data.  

National Technical Information Service (NTIS)

In order to understand the evolution of water on Venus, we must know the hydrogen escape flux as a function of the tropospheric water abundance. We have studied the connection between total stratospheric hydrogen and exobase hydrogen available to non-ther...

M. B. Mcelroy

1985-01-01

388

Pancakelike domes on Venus  

NASA Astrophysics Data System (ADS)

The shape of seven large domes on the plains of Venus, with volumes between 100 and 1000 cu km, is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the SAR images agree well with the theoretical similarity solution for a newtonian fluid, but not with the shape calculated for a rigid-plastic rheology, nor with that for a static model with a strong skin. As a viscous current spreads, it generates an isotropic strain rate tensor whose magnitude is independent of radius. Such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes. The stress induced by the flow in the plains material below is obtained, and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot, and lies between 1014 and 1017 Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 - 690 C in dry rhyolitic magmas. These temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite. These results show that the development of the domes can be understood using simple fluid dynamical ideas, and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

McKenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

1992-12-01

389

Mantle Plumes on Venus Revisited.  

National Technical Information Service (NTIS)

The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120...

W. S. Kiefer

1992-01-01

390

Venus atmospheric platform options revisited  

Microsoft Academic Search

Various balloon systems intended as scientific platforms to float in the atmosphere of Venus at altitudes between about 35 and 65km are briefly reviewed. Previous predictions of the altitude oscillations of balloons filled with helium gas and water vapor are largely confirmed through numerical simulation and analysis. The need for refined thermal modelling is emphasised. Several novel technical concepts are

G. E. Dorrington

2010-01-01

391

Venus atmospheric platform options revisited  

Microsoft Academic Search

Various balloon systems intended as scientific platforms to float in the atmosphere of Venus at altitudes between about 35 and 65 km are briefly reviewed. Previous predictions of the altitude oscillations of balloons filled with helium gas and water vapor are largely confirmed through numerical simulation and analysis. The need for refined thermal modelling is emphasised. Several novel technical concepts

G. E. Dorrington

2010-01-01

392

Oscillation of Venus' upper atmosphere  

Microsoft Academic Search

Little is known about the variability of Venus' upper atmosphere. We report discovery of a large (~ +\\/-30-50%) 9-day period density oscillation, derived from radar tracking of the Magellan spacecraft from 15 Sept 92 - 24 May 93. The densities correspond to 164-184 km altitude, 11°N latitude, and cover all local times. The wave is presumed to propagate upward from

J. M. Forbes; A. Konopliv

2007-01-01

393

Oscillation of Venus' upper atmosphere  

Microsoft Academic Search

Little is known about the variability of Venus' upper atmosphere. We report discovery of a large (? ±30–50%) 9-day period density oscillation, derived from radar tracking of the Magellan spacecraft from 15 Sept 92 – 24 May 93. The densities correspond to 164–184 km altitude, 11°N latitude, and cover all local times. The wave is presumed to propagate upward from

J. M. Forbes; A. Konopliv

2007-01-01

394

How the Venus flytrap snaps  

Microsoft Academic Search

The rapid closure of the Venus flytrap (Dionaea muscipula) leaf in about 100ms is one of the fastest movements in the plant kingdom. This led Darwin to describe the plant as ``one of the most wonderful in the world''. The trap closure is initiated by the mechanical stimulation of trigger hairs. Previous studies have focused on the biochemical response of

Yoël Forterre; Jan M. Skotheim; Jacques Dumais; L. Mahadevan

2005-01-01

395

USGS Magellan stereomapping of Venus  

Microsoft Academic Search

Introduction: The Magellan spacecraft went into Venus orbit in 1990 and by 1992 had made three complete cycles of polar orbits, each cycle covering the full range of longitudes. During this time the spacecraft obtained synthetic aperture radar (SAR) images of >96% of the planet at a resolution of 75 m\\/pixel [1]. Images taken with a decreased look angle from

E. Howington-Kraus; R. L. Kirk; D. Galuszka; B. L. Redding

2006-01-01

396

ISS Update: Transit of Venus  

NASA Video Gallery

ISS Update commentator Brandi Dean interviews Mario Runco, NASA astronaut, about Venus's transit across the sun on June 5, 2012. Questions? Ask us on Twitter @NASA_Johnson and include the hashtag #askStation. For the latest news about the space station, visit http://www.nasa.gov/station.

John Kossum

2012-06-06

397

Venus: Lower Atmosphere Not Measured  

Microsoft Academic Search

The common ranges of pressure and temperature of the atmosphere of Venus measured last October establish the connection between the Soviet Venera 4 altitude scale and the United States Mariner V radial scale. But if the Venera 4 measurements extended to the surface, as claimed, this comparison implies a radius of the planet which is about 25 kilometers greater than

Von R. Eshleman; Gunnar Fjeldbo; John D. Anderson; Arvydas Kliore; Rolf B. Dyce

1968-01-01

398

Venus lower atmosphere heat balance  

Microsoft Academic Search

Pioneer Venus observations of temperatures and radiative fluxes are examined in an attempt to understand the thermal balance of the lower atmosphere. If all observations are correct and the probe sites are typical of the planet, the second law of thermodynamics requires that the bulk of the lower atmosphere heating must come from a source other than direct sunlight or

A. P. Ingersoll; J. B. Pechmann

1980-01-01

399

Venus Lower Atmosphere Heat Balance  

Microsoft Academic Search

Pioneer Venus observations of temperatures and radiative fluxes are examined in an attempt to understand the thermal balance of the lower atmosphere. If all observations are correct and the probe sites are typical of the planet, the second law of thermodynamics requires that the bulk of the lower atmosphere heating must come from a source other than direct sunlight or

Andrew P. Ingersoll; Judith B. Pechmann

1980-01-01

400

The Venus Tablet and Refraction  

Microsoft Academic Search

It is shown that the refraction near the horizon is introducing an additional bias into the Venus Tablet of Ammisaduqa, which is able to influence the interpretation of the data. We then discuss the attempts to link certain solar eclipses to the birth of Shamshi-Adad and conclude that a record of a single solar eclipse without description of details and\\/or

V. G. Gurzadyan

2003-01-01

401

Loss of oxygen from Venus  

NASA Astrophysics Data System (ADS)

Ionization of thermal and nonthermal oxygen atoms above the plasmapause on Venus supplies an escape flux for O averaging 6 x 10 to the 6th atoms/sq cm-sec. Hydrogen and oxygen atoms escape with stoichiometry characteristic of water. It is argued that escape of H is controlled by the oxidation state of the atmosphere, regulated by escape of O.

McElroy, M. B.; Prather, M. J.; Rodriguez, J. M.

1982-06-01

402

Coronae of Parga Chasma, Venus  

Microsoft Academic Search

Parga Chasma is a 10,000 km long fracture and trough system in the southern hemisphere of Venus. In this study, we analyze coronae in the Parga region, addressing the relationship between corona and rift formation, the relationship of volcanism to rifting and coronae, and the overall evolution of the rift system. Our observations are compared with various models, with the

P. Martin; E. R. Stofan; L. S. Glaze; S. Smrekar

2007-01-01

403

Episodic Plate Tectonics on Venus.  

National Technical Information Service (NTIS)

Studies of impact craters on Venus from the Magellan images have placed important constraints on surface volcanism. Some 840 impact craters have been identified with diameters ranging from 2 to 280 km. Correlations of this impact flux with craters on the ...

D. Turcotte

1992-01-01

404

Geophysical models of Western Aphrodite-Niobe region: Venus  

NASA Astrophysics Data System (ADS)

The new topography and gravitational field data for Venus expressed in spherical harmonics of degree and order up to 50 allow us to analyze the crust-mantle boundary relief and stress state of the Venusian lithosphere. In these models, we consider models in which convection is confined beneath a thick, buoyant lithosphere. We divide the convection regime into an upper mantle and lower mantle component. The lateral scales are smaller than on Earth. In these models, relative to Earth, convection is reflected in higher order terms of the gravitational field. On Venus geoid height and topography are highly correlated, although the topography appears to be largely compensated. We hypothesize that Venus topography for those wavelengths that correlate well with the geoid is partly compensated at the crust-mantle boundary, while for the others compensation may be distributed over the whole mantle. In turn the strong sensitivity of the stresses to parameters of the models of the external layers of Venus together with geological mapping allows us to begin investigations of the tectonics and geodynamics of the planet. For stress calculations we use a new technique of space- and time-dependent Green's response functions using Venus models with rheologically stratified lithosphere and mantle and a ductile lower crust. In the basic model of