Exploration Of Venus

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Venus Express is a European Space Agency mission to Earth's nearest planetary neighbour. On 9th November 2005 it was launched from the Baikonour Cosmodrome in Kazakhstan aboard a Russian Soyuz-Fregat launcher. It was constructed using the Mars Express design (ESA's successful Mars orbiter). This made it cheaper and quicker to build than is usual for planetary probes. Venus Express will enter Venus orbit on 11th April 2006.

The latest update from ESA is reproduced below:

Venus within ESA probe reach

An artist's impression of the first firing test of the Venus Express spacecraft main engine,

being performed in space during the night of 16/17 February 2006. The burn started at

01:27 CET and lasted about three seconds.

Credits: ESA

31 March 2006

PR 12-2006. After its five-month, 400-million-kilometre journey inside our Solar System following its lift-off on 9 November 2005, ESA’s Venus Express spacecraft will finally arrive on 11 April at its destination: planet Venus.

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 spacecraft 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.

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 Space Operations Centre.

Source: ESA - News

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ESA’s Venus Express to reach final destination

Venus Express will make unprecedented studies of the largely unkown phenomena taking place in the Venusian atmosphere. Its suit of instruments will also dig into the interaction between the solar wind and the planetary environment. Finally, the mission will gather glimpses about the planet's surface, so dense that it is striclty coupled with the atmosphere.

Credits: ESA - AOES Medialab

7 April 2006
ESA INFO 02-2006. It was on 9 November last year that ESA's Venus Express spacecraft lifted off from the desert of Kazakhstan onboard a Soyuz-Fregat rocket. Now, after having travelled 400 million kilometres in only about five months, the spacecraft is about to reach its final destination. The rendezvous is due to take place on 11 April.


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.

Timeline of major VOI events (some times subject to change)


Artist's impression of the Venus Express orbit insertion, to take place on 11 April 2006. In this phase of the mission, the most challenging since launch, the spacecraft's main engine will have to burn for about 50 minutes, to reduce its speed with respect to Venus so that the spacecraft can be captured by the planet's gravitation.

Credits: ESA - AOES Medialab

4 April, spacecraft 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.


Artist's impression of the Venus Express orbit insertion burn (the firing of its engine to slow down enough to be captured by the gravity of Venus and enter orbit).

Credits: ESA - AOES Medialab

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 visible from Earth. This is known as its ‘occultation’ period. The spacecraft will re-emerge from behind Venus’s disc some ten minutes later. So, even with the low gain antenna’s signal, it will only be visible during the first half of the burn and the last six minutes. Receiving the spacecraft signal after the occultation period will be the first positive sign of successful orbit insertion.

11 April, h 11:13 (CEST), re-establish communication with Earth. At the end of the burn, Venus Express still has to perform a few automatic operations. These re-orient the solar panels towards the sun and one of the high gain antennas (the smaller High Gain Antenna 2) towards Earth. If everything goes as expected, at 11:13 the spacecraft should be able to establish its first communication link with ESA’s Cebreros ground station near Madrid. Over the next few hours, it will send much-awaited information about its state of health. Information about its actual trajectory will be available from ESOC’s flight dynamics team around 12:30 (CEST).

12 to 13 April 2006, full reactivation starts. During the 24 hours following orbital capture, time will be devoted to reactivating all spacecraft functions, including all internal monitoring capacity. By the morning of the 13th, the larger ‘High Gain Antenna 1, hitherto unused, will be oriented and fed by the transmitter to communicate with Earth. The two high gain antennas, located on different sides of the spacecraft, will be used alternately during the mission, to avoid exposure to the sun of critical equipment on the outside.


Reaching final orbit


This artist's impression shows the trajectory of ESA's Venus Express to its final destination, planet Venus. In the first week of March 2006, the spacecraft crossed the path of the planet around the Sun. The trajectory took it inside the orbit of Venus to ‘anticipate’ the celestial motion of the planet and finally to catch up with it on 11 April 2006. Once at Venus, the spacecraft will have travelled 400 million kilometres. The injection into orbit will put the spacecraft into a first, elongated orbit lasting about 9 days. On 7 May 2006, after a series of manoeuvres and 16 ever smaller loops around the planet, Venus Express will reach its final operational orbit, lasting 24 hours.

Credits: ESA - C.Carreau

A series of further manoeuvres and many more days will be required to settle Venus Express into its final orbit. The preliminary nine-day orbit is elliptical, ranging from 350 000 kilometres at its furthest point from the planet (apocentre) to less than 400 kilometres at its closest (pericentre).

During this period, Venus Express will also have to perform seven burns (two with the main engine, five with its banks of thrusters) to gradually reduce the apocentre of the following orbits. Final orbit will be reached on 7 May after 16 loops around the planet. It will be a polar orbit, ranging from 66 000 to 250 kilometres from Venus and with a pericentre located at above latitude 80°North.

On 22 April, Venus Express will start its in-orbit commissioning phase. Its instruments will be switched on one by one for detailed checking until 13 May, then operated all together or in groups. This allows simultaneous observation of phenomena to be tested, to be ready for the nominal science phase beginning on 4 June.


Observations in capture orbit


This artist's impression shows Venus Express over the 'double-eye' atmospheric vortex at the planet's North pole. In fact two enormous atmospheric vortices, with very complex shapes and behaviour, rotate vertically over both poles of Venus, recycling the atmosphere downwards. The vortex at the North pole, the only one previously studied in some detail, completes a full rotation in only three days. Venus Express' observations will help understand how the stormy atmospheric circulation on Venus work.

The preliminary nine-day polar orbit will be a great opportunity to perform scientific observations. These will proceed only if other critical operations of the spacecraft do not take priority, and in any case not before 30 hours after VOI. The first opportunity to gather scientific data will be on 12-13 April.

During this preliminary orbit phase, the complete disc of Venus will be fully visible for the spacecraft’s imaging instruments, an opportunity that will not occur during the nominal mission, when the range of distances from the planet will be smaller. Such observations will mainly cover the southern hemisphere, which was inadequately studied on previous missions.

In particular, the geometry of the capture orbit makes it possible to observe the dynamics of the Venusian atmosphere continuously and thoroughly from a greater distance, over a duration even longer than the full rotation cycle of the atmosphere at the cloud tops (the still-unexplained four-day ‘super rotation’). Indeed, atmospheric study is one of the mission’s prime goals.

For instance, from distances greater than 200 000 kilometres, the visible/near-infrared mapping spectrometer (VIRTIS) will be able to take snapshots of the entire planetary disc and atmosphere. During the nominal science phase, images of the atmosphere will need to be built up in mosaics.

The analyser of space plasma and energetic atoms (ASPERA) will have an unprecedented opportunity to study from great distances the unperturbed solar wind and to gather data on the atmospheric escape processes on a planet which has no magnetic protection.

In the capture orbit, all the instruments (except the VeRA radio science experiment and PFS spectrometer) may perform observations for a few hours a day on selected dates.


…and plenty of science to come


Venus is a planet with no intrinsic magnetic field and so, differently from Earth, it has no shield to protect it from the continuous attack of the capricious and violent solar wind. ESA's Venus Express will study how much of the atmosphere of the planet escaped under the bombardment of the solar wind and how much it combined with the surface material.

Credits: ESA - C.Carreau

Venus Express is designed to carry out scientific observations over two Venusian days, corresponding to 486 Earth days. The mission could be extended to double the nominal duration.

Notwithstanding the intense previous exploration (Venus is the third most visited celestial body in our solar system after the Moon and Mars), a plethora of mysteries still surround this planet. Venus Express’s unique instruments for planetary investigation are tailored to taking advantage of clues from previous missions and investigating the planet’s oddities with unprecedented precision.

The instruments onboard, the spacecraft’s ‘eyes’, include a combination of spectrometers (the PFS planetary fourier spectrometer and the SpicaV/SOIR ultraviolet and infrared atmospheric spectrometer), spectro-imagers (VIRTIS ultraviolet /visible/near-infrared mapping spectrometer) and imagers (VMC Venus monitoring Camera).


Through the Venus Radio Science Experiment on board Venus Express - using the powerful radio link bewteen the spacecraft and Earth - scientists will investigate the conditions of the ionosphere of the planet (upper atmospheric layer), and study the local conditions of the solar wind. The experiment will also allow the study of the physical properties of mid atmospheric layers and the roughness and electrical properties of the surface.

Credits: ESA - AOES Medialab

They are extremely sensitive in a wide range of electromagnetic wavelengths from ultraviolet to infrared and will allow detailed study of the Venusian atmosphere and its interaction with the surface. Also onboard are the MAG magnetometer, the ASPERA analyser of space plasma & energetic atoms and the VeRA radio science experiment, to study all interaction between the atmosphere and the ever-blowing solar wind.

Venus Express will take advantage, for the first time ever, of the so-called ‘infrared windows’, which are narrow atmospheric bands in the infrared part of the spectrum. Through these, precious information about the lower layers of the atmosphere and even the surface can be gathered.

The Venus Express mission will help find answers to several unsolved questions. How does the complex atmospheric dynamics and cloud system work? What causes the fast “super-rotation” of the atmosphere at the cloud top? And what is the origin of the double vortex at the north pole?

Venus Express will also investigate the processes that determine the chemistry of the noxious Venusian atmosphere, which can be as hot as 500°C at the surface and is mainly composed of carbon dioxide, with clouds of sulphuric acid drops. It will study what role the greatest greenhouse effect in the solar system plays in the overall evolution of the Venusian climate. It will also help us to ascertain whether Venus provides a possible preview of a future Earth.

Lastly, through combined analysis of the dense atmosphere and surface, Venus Express will help us to understand the planet’s geology and ascertain there are signs of present volcanic or seismic activity.


“Venus Express to ground control”


The Cebreros Deep Space 35m antenna.

Credits: ESA

During the course of the nominal mission, Venus Express will communicate with Earth via ESA’s Cebreros ground station near Madrid. ESA’s New Norcia station in Australia will be used to support the VeRA radio science experiment.

Source: ESA - News

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Venus Express main engine burn starts

11 April 2006
At 09:17 CEST today (07:17 GMT), Venus Express started its main engine burn. The burn, to last 50 minutes, will slow down the spacecraft and allow the capture into orbit around Venus. The main engine burn started a few minutes after the firing of the spacecraft thrusters, to make sure the propellant settles in the feed lines to the main engine.

This thrust is aimed at reducing the initial velocity of 29 000 kilometres per hour (in relation to Venus) by 15 percent, to allow capture by the planet’s gravity. Thanks to this burn, Venus Express will settle into its preliminary, elongated nine-day orbit.
Only the spacecraft low-gain antenna, carrying a feeble but instantly recognisable signal, is transmitting throughout all VOI manoeuvres. This allows 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.

During the burn, at 09:45 CEST, Venus Express will disappear behind the planet and will not be visible from Earth. This is known as its ‘occultation’ period, in which the only signal coming from the spacecraft – the carrier signal from the low gain antenna - will become unavailable for ten minutes.

Source: ESA - News

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Venus Express main engine burn ended

11 April 2006
Ground controllers at ESA’s European Spacecraft Operations Centre (ESOC) confirmed the end of the Venus Express main engine burn at 10:07 (CEST) today (08:07 GMT).

A few more automatic operations should now follow to reorient the spacecraft towards the Sun (so-called ‘sun acquisition mode’) and then have one of the spacecraft’s high gain antennas (the HGA 2) oriented towards Earth, ready to establish the first communication link with ground control.

Source: ESA - News

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Venus Express 'talks' to Earth

Venus Express communicates with Earth

11 April 2006
At 11:12 CEST Venus Express re-established communication with Earth for the first time after the start of the orbit insertion manoeuvres.

After the end of the main engine burn, Venus Express still had to perform a few automatic operations. These included re-orienting the solar panels towards the Sun and one of its high gain antennas (the smaller High Gain Antenna 2) towards Earth.
It is through this antenna that the spacecraft established the first communication link with Earth and started to send back information about its health status. The spacecraft data are sent to ESA’s European Spacecraft Operations Centre (ESOC) via ESA’s Cebreros ground station near Madrid. The data downlink lasts for a few hours.

Information about Venus Express’ actual trajectory will be available from ESOC’s flight dynamics team around 12:30 CEST.

Source: ESA - News Edited April 11, 2006 by Waspie_Dwarf

[Waspie_Dwarf]

Europe scores new planetary success: Venus Express enters orbit around the Hothouse Planet

Artist's impression of the Venus Express orbit insertion on 11 April 2006. In this phase of the mission, the most challenging since launch, the spacecraft's main engine burns for about 50 minutes, to reduce its speed with respect to Venus to allow the the spacecraft to be captured by the planet's gravitation.

Credits: ESA - AOES Medialab

11 April 2006
ESA PR 13-2006. This morning, at the end of a 153-day and 400-million km cruise into the inner Solar System beginning with its launch on 9 November 2005, ESA’s Venus Express space probe fired its main engine at 09:17 CEST for a 50-minute burn, which brought it into orbit around Venus.

With this firing, the probe reduced its relative velocity toward the planet from 29,000 to about 25,000 km/h and was captured by its gravity field. This orbit insertion manoeuvre was a complete success.
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 kilometres. 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


The Venus Express mission mainly focusses on studying the peculiar atmosphere of Venus, with a precision never achieved before. In doing so, it will make the first ever use of the so called 'infrared windows', which are narrow bands in the atmospheric spectrum, discovered in the 1980s thanks to ground observations. Looking through these 'windows' Venus Express will be able to gather precious information about the lower layers of the atmosphere and even the surface.

Credits: ESA - AOES Medialab

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.

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


ESA can now add Venus to its range of Solar System studies

Credits: ESA

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


This image is an artistic interpretation of a possible volcano on Venus. In fact, from previous missions to the planet, Venus appears to be among the most geologically active planets in the solar system. Venus Express is able to detect gaseous markers in the lower layers of the atmosphere and variations in its temperature, possible signs of volcanic activity. Local variations in atmospheric temperature and pressure may also indicate the presence of seismic activity.

Credits: ESA - AOES Medialab

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 multiple wavelengths to characterise the atmospheric dynamics.


Venus is a planet with no intrinsic magnetic field and so, differently from Earth, it has no shield to protect it from the continuous attack of the capricious and violent solar wind. ESA's Venus Express will study how much of the atmosphere of the planet escaped under the bombardment of the solar wind and how much it combined with the surface material.

Credits: ESA - C. Carreau

On the outer edge of the atmosphere, the Aspera instrument and a magnetometer will investigate the interaction with the solar wind and plasma it generates in an open environment without the protection of a magnetosphere like the one we have around Earth.

The VMC wide-angle multi-channel camera will provide imagery in four wavelengths, including one of the 'infrared windows' which will make imaging of the surface possible through the cloud layer. It will provide global images and will assist in the identification of phenomena detected by the other instruments.

Source: ESA - News

[Bella-Angelique]

I would like to see some Venus dome pictures.

[Waspie_Dwarf]

I would like to see some Venus dome pictures.

The domes seem to be volcanic in origin. This image is a radar image made by the US Magellan probe:

Venus Express will concentrate on on the atmosphere of Venus but will also be able to take infrared images of the surface. This will be the first time that the surface of venus has been seen directly.

[Waspie_Dwarf]

Venus Express’ initial orbit matches expectations

Venus Express flight control team

11 April 2006
At about 13:30 CEST ground controllers at ESA’s European Spacecraft Operations Centre (ESOC) confirmed that the geometry of the initial orbit of Venus Express is matching expectations.

The ground team were able to confirm this by analysing the data that the spacecraft has been sending down to Earth after the first communication link was established at 11:12 CEST today.
ESA’s Cebreros ground station sent the spacecraft High-Gain antenna (HGA 2) receiver a sequence of tones. The time needed for the spacecraft to receive and then mirror these tones back to Earth, together with the precise measurements of the radio signal frequency change, provides point-by-point positioning and velocity of the spacecraft, and hence its trajectory.

The capture orbit is a long ellipse ranging from 350 000 kilometres at its furthest point from the planet (the apocentre) to less than 400 kilometres at its closest (the pericentre, which is almost over the planet’s North pole). The spacecraft will take nine days to travel this orbit, during which a few slots for preliminary scientific observations will be available.

A series of further engine and thrusters burns will then be needed to gradually reduce the apocentre during the following 16 orbital loops around the planet.

The final polar 24-hour orbit will be reached on 7 May 2006, and will range from 66 000 to 250 kilometres above Venus.

A period of commissioning for the spacecraft and its instruments will then precede the official start of Venus Express scientific operations on 4 June this year.

Source: ESA - News

[Waspie_Dwarf]

Unexpected detail in first-ever Venus south pole images

Composite, false-colour view of Venus south pole captured by VIRTIS 12 April 2006 onboard Venus Express.

Credits: ESA/INAF-IASF, Rome, Italy, and Observatoire de Paris, France

13 April 2006
ESA's Venus Express has returned the first-ever images of the hothouse planet’s south pole from a distance of 206 452 kilometres, showing surprisingly clear structures and unexpected detail. The images were taken 12 April during the spacecraft’s initial capture orbit after successful arrival on 11 April 2006.

Engineers have lost no time in switching on several of the instruments and yesterday the VMC (Venus Monitoring Camera) and VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) imaged, for the first time in space history, the southern hemisphere of Venus as the spacecraft passed below the planet in an elliptical arc.
Scientists are especially intrigued by the dark vortex shown almost directly over the south pole, a previously suspected but until now unconfirmed structure that corresponds to a similar cloud structure over the north pole. “Just one day after arrival, we are already experiencing the hot, dynamic environment of Venus,” said Dr Hakan Svedhem, Venus Express project scientist. “We will see much more detail at an unprecedented level as we get over 100 times better resolution as we get closer to Venus, and we expect to see these spiral structures evolve very quickly.”

The initial, low-quality images were taken from an extreme distance of 206 452 kms from the planet, yet caught scientists’ attention, particularly with the surprisingly clear structures and unexpected details shown in the VIRTIS spectrometer images.

The false-colour VIRTIS composite image shows Venus’s day side at left and night side at right, and corresponds to a scale of 50 kms per pixel.

The day half is itself a composite of images taken via wavelength filters and chiefly shows sunlight reflected from the tops of clouds, down to a height of about 65 km above the planet’s surface.


Dynamic spiral cloud structures

The more spectacular night half, shown in reddish false colour, was taken via an IR filter at a wavelength of 1.7 microns, and chiefly shows dynamic spiral cloud structures in the lower atmosphere, around 55 km altitude. The darker regions correspond to thicker cloud cover, while the brighter regions correspond to thinner cloud cover, allowing hot thermal radiation from lower down to be imaged.


False-colour view imaged in ultraviolet of Venus south pole captured by VMC 12 April 2006 onboard Venus Express.

Credits: ESA/MPS, Katlenburg-Lindau, Germany

The smaller VMC image shows Venus at a scale of 150 kms per pixel and is also shown in false colour. It was recorded in ultraviolet.
Venus Express fired its main engine to enter Venus orbit on 11 April 2006 and is now in the first 9-day capture orbit taking it to apocentre (maximum height) at 350 000 kilometres below the south pole. It will swing back up to pass pericentre (minimum height) at an altitude of 250 kilometres over the planet’s north pole.


Towards the 24-hour final orbit

In the first capture orbit, Venus Express will have 5 additional opportunities for gathering data until reaching pericentre. These observations represent a great opportunity because, at apocentre, the full disc of Venus is fully visible for the spacecraft’s imagers. Such opportunities will not occur again during the nominal mission, starting on 4 June 2006, when the range of distances from the planet will be much smaller.


View imaged in ultraviolet of Venus south pole captured by VMC 12 April 2006 onboard Venus Express.

In addition to VMC and VIRTIS, the spacecraft’s MAG (Venus Express Magnetometer) has been switched on for initial verification and is operating nominally. Together with the ASPERA (Analyser of Space Plasma and Energetic Atoms), the two instruments are expected to gather information about the unperturbed solar wind and the atmospheric escape processes on Venus, a planet with no magnetic protection.

A series of further engine and thruster burns are planned to gradually reduce the apocentre during the following 16 orbital loops around the planet and the spacecraft is due to attain its final 24-hour polar orbit on 7 May, ranging from 66 000 to 250 kilometres above Venus.

Source: ESA - News

[Bella-Angelique]

The domes seem to be volcanic in origin.

Thanks. The domes are the most interesting visual of Venus to me. I am glad the new probe is getting a lot of nice new Venus pics.

[Waspie_Dwarf]

Thanks. The domes are the most interesting visual of Venus to me. I am glad the new probe is getting a lot of nice new Venus pics.

Glad to be of service.

[Waspie_Dwarf]

Venus Express has reached final orbit

Venus Express will make unprecedented studies of the largely unkown phenomena taking place in the Venusian atmosphere. Its suit of instruments will also dig into the interaction between the solar wind and the planetary environment. Finally, the mission will gather glimpses about the planet's surface, striclty coupled with the dense atmosphere.

Credits: ESA - AOES Medialab

9 May 2006
Less than one month after insertion into orbit, and after sixteen loops around the planet Venus, ESA’s Venus Express spacecraft has reached its final operational orbit on 7 May 2006.

Already at 21:49 CEST on 6th May, when the spacecraft communicated to Earth through ESA’s ground station at New Norcia (Australia), the Venus Express ground control team at ESA’s European Spacecraft Operations Centre (ESOC) in Darmstadt (Germany) received advanced confirmation that final orbit was to be successfully achieved about 18 hours later.
Launched on 9 November 2005, Venus Express arrived to destination on 11 April 2006, after a five-month interplanetary journey to the inner solar system. The initial orbit – or ‘capture orbit’ – was an ellipse ranging from 330 000 kilometres at its furthest point from Venus surface (apocentre) to less than 400 kilometres at its closest (pericentre).


This artist's impression shows the trajectory of ESA's Venus Express to its final destination, planet Venus. In the first week of March 2006, the spacecraft crossed the path of the planet around the Sun. The trajectory took it inside the orbit of Venus to ‘anticipate’ the celestial motion of the planet and finally to catch up with it on 11 April 2006. Once at Venus, the spacecraft will have travelled 400 million kilometres. The injection into orbit will put the spacecraft into a first, elongated orbit lasting about 9 days. On 7 May 2006, after a series of manoeuvres and 16 ever smaller loops around the planet, Venus Express will reach its final operational orbit, lasting 24 hours.

Credits: ESA - C. Carreau

As of the 9-day capture orbit, Venus Express had to perform a series of further manoeuvres to gradually reduce the apocentre and the pericentre altitudes over the planet. This was achieved by means of the spacecraft main engine – which had to be fired twice during this period (on 20 and 23 April 2006) - and through the banks of Venus Express’ thrusters – ignited five times (on 15, 26 and 30 April, 3 and 6 May 2006).

"Firing at apocentre allows the spacecraft to control the altitude of the next pericentre, while firing at the pericentre controls the altitude of the following apocentre," says Andrea Accomazzo, Spacecraft Operations Manager at ESOC. "It is through this series of operations that we reached the final orbit last Sunday, about one orbital revolution after the last ‘pericentre change manoeuvre’ on Saturday 6 May".


Venus Express entered its target orbit at apocentre on 7 May 2006 at 15:31 (CEST), when the spacecraft was at 151 million kilometres from Earth. Now the spacecraft is running on an ellipse substantially closer to the planet than during the initial orbit. The orbit now ranges between 66 000 and 250 kilometres over the Venus and it is polar. The pericentre is located almost above the North pole (80º North latitude), and it takes 24 hours for the spacecraft to travel around the planet.


This artist's impression shows Venus Express focussing on studying the peculiar atmosphere of Venus, with a precision never achieved before. In doing so, the mission will make the first ever use of the so called 'infrared windows', which are narrow bands in the atmospheric spectrum, discovered in the 1980s thanks to ground observations. Looking through these 'windows' Venus Express will be able to gather precious information about the lower layers of the atmosphere and even the surface.

Credits: ESA - AOES Medialab

"This is the orbit designed to perform the best possible observations of Venus, given the scientific objectives of the mission. These include global observations of the Venusian atmosphere, of the surface characteristics and of the interaction of the planetary environment with the solar wind," says Håkan Svedhem, Venus Express Project Scientist. "It allows detailed high resolution observations near pericentre and the North Pole, and it lets us study the very little explored region around the South Pole for long durations at a medium scale," he concluded.

Until beginning of June, Venus Express will continue its ‘orbit commissioning phase’, started on 22 April this year. "The spacecraft instruments are now being switched on one by one for detailed checking, which we will continue until mid May. Then we will operate them all together or in groups" said Don McCoy, Venus Express Project Manager. "This allows simultaneous observations of phenomena to be tested, to be ready when Venus Express’ nominal science phase begins on 4 June 2006," he concluded.

Source: ESA - News

[Waspie_Dwarf]

Double vortex at Venus South Pole unveiled!

This video is composed by six sequences of images (in false colour) taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft between 12 and 19 April 2006, during the first orbit, or ‘capture orbit’, around the planet.
The sequences (taken at 5 microns) were obtained during six different time slots and at different distances from Venus:

• 12 April: from 210 000 kilometres
• 13 April: from 280 000 kilometres
• 14 April: from 315 000 kilometres
• 16 April: from 315 000 kilometres
• 17 April: from 270 000 kilometres
• 19 April: from 190 000 kilometres

The planet’s globe, imaged at different angles, was mapped onto an electronic mock-up of Venus, so to have the South Pole always plotted at the centre of each single image.
Around the South pole it is possible to see a peculiar double-eye vortex structure, never clearly seen by any other Venusian mission before. The movie shows the rotation and the shape variation of the double vortex over time. It is also possible to see the rotation of the ‘terminator’, the line separating the day side – visible in yellow - from the night side.

The images also show the presence of a collar of cold air around the vortex structure (dark blue), possibly due to the recycling of cold air downwards.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA


27 June 2006
ESA’s Venus Express data undoubtedly confirm for the first time the presence of a huge 'double-eye' atmospheric vortex at the planet's south pole. This striking result comes from analysis of the data gathered by the spacecraft during the first orbit around the planet.

On 11 April this year, Venus Express was captured into a first elongated orbit around Venus, which lasted 9 days, and ranged between 350 000 and 400 kilometres from Venus' surface. This orbit represented for the Venus Express scientists a unique opportunity to observe the planet from large distances. This made it possible to obtain first clues about the Venusian atmospheric dynamics on a global scale, before the spacecraft got closer and started observing the planet in greater detail.

This composite image shows six infrared views of Venus as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft between 12 and 19 April 2006, during the first orbit, or ‘capture orbit’, around the planet.
The images (taken at 5 microns) were obtained at six different time slots and at different distances from Venus (top left: 12 April, from 210 000 kilometres; centre left: 13 April, from 280 000 kilometres; bottom left: 14 April, from 315 000 kilometres; top right: 16 April, from 315 000 kilometres; centre right: 17 April, from 270 000 kilometres; bottom right: 19 April, from 190 000 kilometres), while the spacecraft moved along a long ellipse around the planet. The separate images can be downloaded here [COB_01.TIF, COB_02.TIF, COB_03.TIF, COB_0.TIF, COB_05.TIF, COB_06.TIF].

The infrared radiation coming from Venus was converted in this reddish colour scheme. Thermal radiation comes from the lower atmosphere, (just above the cloud top, located at about 60 kilometres altitude). Solar radiation reflected by the upper atmospheric layers (roughly between 60 and 80 kilometres altitude) and thermal radiation from the layers below contribute to the brightest part of the image.

The south polar vortex structure is visible from different view points close to the centre of the images, mostly in the dark side.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

During this first orbit – called the 'capture orbit' – some of the Venus Express instruments were used to perform the first observations at different distances from Venus, for a few hours per time on six different slots between 12 and 19 April 2006.
Amazing infrared, visible and ultraviolet images of the Venusian globe already reveal several atmospheric features of great interest. The most striking of these is a huge, double-eye atmospheric vortex over the south pole, not dissimilar from the equivalent structure present at the north pole – the only one previously studied in some detail.

These two images of Venus’s south pole were taken by NASA’s Mariner 10 (during a Venus fly-by on its way to Mercury) and Pioneer Venus missions during the early 1970s and 1980s, respectively. The images provided the first glimpses about a stormy atmospheric behaviour at the south pole of the planet.

Credits: NASA

Only glimpses of the stormy atmospheric behaviour at the south pole were obtained by previous missions (Pioneer Venus and Mariner 10), but such a double-eye structure was never clearly seen before now.

High velocity winds are known to spin westwards around the planet, and to take only four days to complete a rotation. This 'super-rotation', combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole. But why two vortexes?

These six different infrared images (in false colour) were taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft between 12 and 19 April 2006, during the first orbit, or ‘capture orbit’, around the planet.
The images (taken at 5 microns) were obtained at six different time slots and different distances from Venus (top left: 12 April, from 210 000 kilometres; top centre: 13 April, from 280 000 kilometres; top right: 14 April, from 315 000 kilometres; bottom left:16 April, from 315 000 kilometres; bottom centre: 17 April, from 270 000 kilometres; bottom right: 19 April, from 190 000 kilometres), while the spacecraft moved along a long ellipse around the planet. The separate images can be downloaded here [ COB_01_geo.TIF, COB_02_geo.TIF, COB_03_geo.TIF, COB_04_geo.TIF, COB_05_geo.TIF, COB_06_geo.TIF].

The planet’s globe, imaged at different angles, was mapped onto an electronic mock-up of Venus, so to have the south pole always plotted at the centre of each single image.

Around the south pole it is possible to see a peculiar double-eye vortex structure, never clearly seen by any other mission to Venus before. The sequence shows the rotation and variation of the double vortex over time. It is also possible to see the rotation of the ‘terminator’, the line separating the day side – visible in yellow - from the night side.

The images also show the presence of a collar of cold air around the vortex structure (dark blue), possibly due to the recycling of cold air downwards.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

"We still know very little about the mechanisms by which the super-rotation and the polar vortexes are linked," said Håkan Svedhem, ESA’s Venus Express Project Scientist. "Also, we are still not able to explain why the global atmospheric circulation of the planet results in a double and not single vortex formation at the poles. However the mission is just at the beginning and it's doing fine; we expect this and many other long-standing mysteries to be addressed and possibly solved by Venus Express," he added. Atmospheric vortexes are very complex structures that are very difficult to model, even on Earth.

Thanks to these first pictures, it has also been possible to observe the presence of a collar of cold air around the vortex structure, possibly due to the recycling of cold air downwards.

This visible/ultraviolet image of Venus (380 nanometres) was taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft on 19 April 2006, during the first orbit (capture orbit) around the planet, from a distance of about 190 000 kilometres.
In the day side (blue part) it is possible to see interesting atmospheric stripe-like structures. Spotted for the first time by Mariner 10 in the 1970s, they may be due to the presence of dust and aerosols in the atmosphere, but their true nature is still unexplained.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Views of the southern hemisphere of Venus in visible and ultraviolet light show interesting atmospheric stripe-like structures. Spotted for the first time by Mariner 10 in the 1970s, they may be due to the presence of dust and aerosols in the atmosphere, but their true nature is still unexplained. "Venus Express has the tools to investigate these structures in detail," added Svedhem. "Studies have already begun to dig into the properties of the complex wind fields on Venus, to understand the atmospheric dynamics on local and global scales."

Venus Express also made use for the first time ever from orbit of the so-called 'infrared windows' present in the atmosphere of Venus – if observed at certain wavelengths, it is possible to detect thermal radiation leaking from the deepest atmospheric layers, revealing what lies beneath the dense cloud curtain situated at about 60 kilometres altitude.

This sequence of images was taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express spacecraft between 12 and 19 April 2006, during the first orbit (capture orbit) around the planet.
The images were obtained at six different time slots and different distances from the planet (top left: 12 April, from 210 000 kilometres; top centre: 13 April, from 280 000 kilometres; top right: 14 April, from 315 000 kilometres; bottom left:16 April, from 315 000 kilometres; bottom centre: 17 April, from 270 000 kilometres; bottom right: 19 April, from 190 000 kilometres), while the spacecraft moved along a long ellipse around Venus. The separate images can be downloaded here [ VOI_1_12_04_2006_b, VOI_2_13_04_2006_b, VOI_3_14_04_2006_b, VOI_4_16_04_2006_b, VOI_5_17_04_2006_b, VOI_6_19_04_2006].

Each image is the composite of the day side of Venus (left, in blue, taken in visible light at 380 nanometres) and the night side (right, in a red colour scheme, taken in infrared light at 1.7 microns).

The visible part shows solar radiation reflected by the atmosphere. The infrared part shows complex cloud structures, revealed by the thermal radiation coming up from different atmospheric depths. Venus Express can resolve these structures by use (for the first time from orbit) of the so so-called ‘infrared windows’ present in the atmosphere of Venus. In fact, if observed at certain wavelengths, it is possible to detect thermal radiation leaking from the deepest atmospheric layers, revealing what lies beneath the dense cloud curtain situated at about 60 kilometres altitude.

In the colour scheme of the presented infrared images, the brighter the colour, the more radiation comes up from the lower layers.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The first infrared images making use of the ‘windows’ show complex cloud structures, all revealed by the thermal radiation coming up from different atmospheric depths. In the colour scheme shown in the image at right, the brighter the colour (that is, the more radiation comes up from the lower layers), the less cloudy is the observed area.

During capture orbit, preliminary data about the chemical composition of the atmosphere were also retrieved. Venus’ atmosphere is mainly composed of carbon dioxide (CO2). The incoming solar radiation dissociates this molecule into carbon monoxide (CO) and oxygen in the upper atmospheric layers. In fact, Venus Express has already spotted the presence of an oxygen (O2) airglow high in the atmosphere. However, Venus Express has revealed the presence of carbon monoxide as low as the cloud-layer top.

Scientists will continue the data analysis and retrieval to understand the phenomenon, which is very important to clarify the complex chemical processes and cycles at work in the atmosphere of Venus under the influence of solar radiation.

This false colour image of planet Venus was taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 19 April 2006, during the first orbit, or ‘capture orbit’, around the planet.
From a distance of about 190 000 kilometres, it was already possible to see the complex atmosphere that surrounds the planet.

Credits: ESA/MPS, Katlenburg-Lindau, Germany

Since 7 May 2006 Venus Express has been circling the planet in its final 24-hour orbit, ranging between 66 000 and 250 kilometres from Venus - therefore at much closer distances with respect to the capture orbit. Venus Express scientists are now analysing the new data coming in, which already show what seems to be exciting new features. “We have never seen Venus in such great detail so far. We are eagerly waiting for these new data to be available,” concluded Svedhem.

Source: ESA - Venus Express

[Waspie_Dwarf]

Flying over the cloudy world – science updates from Venus Express

This false-colour movie was built with ultraviolet images taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 22 May 2006. The spacecraft was flying over the northern hemisphere approaching the planet, over distances ranging between about 39 100 and 22 600 kilometres from the surface.
The images were taken at 365 nanometres, starting respectively 03:30 and 01:45 hours before reaching the pericentre (point of closest approach of the spacecraft to Venus). The complex atmosphere that surrounds the planet is clearly visible.

The true-colour (grey-scale) version of this movie can be downloaded here.

Credits: ESA/MPS, Katlenburg-Lindau, Germany


12 July 2006
On 20 April 2006, after its first 9-day, elongated orbit around Venus, ESA’s Venus Express started to get closer to the planet, until it reached its final 24-hour long orbit on 7 May. During this time, and up to today, the spacecraft has been working relentlessly: the new data coming in are already providing first glimpses on planetary features never seen before.

If taking the first ever clear images of the double-eye vortex at Venus’ south pole - imaged by Venus Express during its very first orbit - was already a first in the history of planetary exploration and a very pleasant surprise for the scientists, nobody could expect that the vortex had a structure even more complicated than possibly foreseen.
Infrared images taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board the spacecraft not only provided the first clear view of the vortex, but also gave a much closer insight into it when Venus Express flew over the south pole at the end of May this year.

This triple image provides a close-up view of the double-eyed vortex at Venus south pole, as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express. The images were taken on 29 May 2006, from a distance of about 64 000 kilometres from the planet. All the separate images can be downloaded here:
- South polar_vortex close up_1_b.gif
- South polar_vortex close up_1_b.tif
- South polar_vortex close up_3_b.tif
- South polar_vortex close up_2_b.tif

The vortex is imaged at different infrared wavelengths, corresponding to different atmospheric depths. The left image (taken at 5.05 microns) correspond to an atmospheric altitude of about 59 kilometres, just about the Venusian cloud deck. The central image (taken at 4.65 microns) corresponds to an atmospheric altitude of about 60 kilometres. The right image (taken at 4.08 microns) corresponds to an altitude of about 65 kilometres, just in the upper clouds. The images were taken with a 20º inclination with respect to vertical pointing.

The brighter the colour, the more radiation is reaching out from the hot layers below. The brightest spot correspond to the centre of the vortex, where radiation from the deeper layers become clearly visible , like looking through a hole.

The dark circular structures surrounding the brighter area belong to the big vortex structure (bottom of the images) - as large as a big portion of Europe (2500 kilometres across) - and are part of the planet atmospheric super-rotation. The left image also clearly shows a complex structure, where many more small structures are visible.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

VIRTIS is an instrument that can operate at different wavelengths. Each infrared wavelength provides a view of the Venusian atmosphere at a different altitude, like a 'cross-section'. "When we looked at this gigantic vortex at different depths, we realised how much its shape is varying over altitude," said Pierre Drossart, VIRTIS co-Principal Investigator, from the Observatoire de Paris, France. "It is like if we were looking at different structures, rather than a single one. And the new data we have just started gathering and analysing reveal even stronger differences".

This movie, built with infrared images taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express, provides a close-up view of the double-eyed vortex at Venus south pole. The images (ranging from 4.5 to 5.1 microns) were taken on 29 May 2006, from a distance of about 64 000 kilometres from the planet.
Thanks to the use of different wavelengths, VIRTIS probed the atmosphere at different depths, ranging from 70 kilometres to about 60 kilometres altitude. It is interesting to see how the images contrast and the details increase while approaching the 60 kilometres altitude.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The reason why the morphology of the vortex varies so extensively along a 'vertical' line is still unexplained. "This is why we are organizing a campaign to observe the south polar vortex, fully dedicated to solve this unexpected puzzle," said Giuseppe Piccioni, VIRTIS co-Principal Investigator. "First we want to understand how the structure is organized - actually, with VIRTIS we are building a true 3D view of the vortex. Then we hope to be able to better understand what are the driving forces that shape it".

Tracking clouds and winds

While Venus Express was flying over the planet, many other details from the thick atmosphere have also started to emerge. Both the Venus Monitoring Camera (VMC) and the VIRTIS instruments started to monitor the cloud system and to track its complex dynamics, while the SpicaV/SOIR spectrometers started retrieving information on the atmospheric chemistry and temperature.

Ultraviolet images from the VMC camera show the complex morphology of the cloud deck, characterised by very thin, low-contrast stripe-features, possibly due to the presence of strong winds that produce elongated structures. Set of periodic 'wave' patterns in the clouds, possibly due to the local variation of temperature and pressure, or to a kind of tidal forces in action at Venus, can also be seen.

This mosaic is composed of ultraviolet images taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 24 April 2006, when the spacecraft was flying over the northern hemisphere, at distances ranging between 7505 and 1570 kilometres over the surface.
The original images (taken at a wavelength of 365 nanometres) were projected on geographical coordinates. While flying over the cloud deck at high speed (from left to right), Venus Express got closer to the deck itself and obtained ever more detailed images (see right-hand side).

The sequence allows a first qualitative analysis of the cloud structures. Low-contrast stripe-features are visible, possibly due to the presence of strong winds that produce elongated structures. Set of periodic ‘wave’ patterns in the clouds, possibly due to the local variation of temperature and pressure, or to a kind of tidal forces in action at Venus, can also be seen.

The mysterious ‘UV absorbers’, ultraviolet markings on the cloud top, are visible as darker features in this mosaic. They are so called because they absorb almost half of the solar energy received by the planet. The mysterious substance that causes this absorption still represents a true puzzle for the scientists.

Differently from Earth and other planets, Venus absorbs only the ultraviolet radiation coming from the sun, while it scatters most of the rest of the solar radiation. This is the reason why Venus appears so bright in the sky (high ‘albedo’).

Credits: ESA/MPS, Katlenburg-Lindau, Germany

One of the most important confirmations from the first set of data being analysed by the scientists is the detection of the so called 'UV absorbers'- ultraviolet markings on the cloud top, also visible as darker features in the VMC mosaic image. They are so called because they absorb almost half of the solar energy received by the planet. The mysterious substance that causes this absorption still represents a true puzzle for the scientists.

"Understanding what is the origin of these ultraviolet markings and what makes their absorbing power so high is one of the major objectives of Venus Express," said Wojciech J. Markiewicz, VMC Principal Investigator, from the Max Planck Institute for Solar System Research in Lindau, Germany. "We now have confirmation that we can actually see them, so we can start working to understand what their source is. Because of their amazing absorbing power, they are very important to understand the overall radiative and thermal balance of the planet, and also the atmospheric dynamics".

This spectacular night image is an infrared view taken at 1.7 microns, as seen by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express on 12 April 2006, during the first orbit around the planet (capture orbit).
The image, covering an area situated between 20º and 90 º south, show clouds being clearly pushed by winds. Using a set of images of the same area acquired at different times, it is possible to make a direct measurement of the wind speed.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Tracking cloud motion and starting to characterise the wind speed is an exercise that the Venus Express scientists have already started. A spectacular night view of the mid to low atmospheric layers over low latitudes (between 20º and 90 º south) by VIRTIS, show clouds being clearly pushed by winds.

"We can now make a first qualitative assessment of the wind fields and circulation, which is comfortably matching with previous measurement from the Galileo mission over the north pole," continued Giuseppe Piccioni. "We are now collecting more data from different atmospheric depths, to be able to provide the first precise numbers, possibly in the near future".

These infrared images were taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express on 25 April 2006, while the spacecraft was flying over low planetary latitudes (between 15º and 60º south).
The two images on the left panel (taken at 2.3 and 1.7 microns, respectively) show a fine atmospheric structure below the Venusian cloud deck, at about 35 and 20 kilometres altitude, respectively.

The right panel is the result of the projection on geographical coordinates of the second image of the left panel. The images at the top where taken from a distance of about 6000 kilometres from the surface, allowing VIRTIS to generate the high resolution details visible at the top of the panel. While Venus Express continued flying over the planet it got farer from the surface – up to 20 000 kilometres distance – allowing VIRTIS to obtain a wider view, but in lower resolution.

Stripe-like features are visible at the bottom of all images. They could be indicative of a wave-like atmospheric motion (due to tidal forces?), but their nature is still unexplained. The separate images can be downloaded here: [Cloud_tracking_infrared_b_H.tif, Cloud_tracking_infrared_c_H.tif, Wind_tracking_b_H.tif]

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

"We are also collecting the first information on the minor chemical components of the atmosphere, such as carbon monoxide," added Pierre Drossart. "With VIRTIS we can see in the atmosphere of the southern hemisphere deeper than any other previous mission, and we started gathering data on the yet unknown chemistry of the lower atmospheric layers, to build a global picture. Studying the variation of minor chemical compounds over different latitudes and depths is also a very useful tracer for the atmospheric global motion."

Surprise at the atmospheric 'top'

This ultraviolet image of the Venus southern hemisphere was taken by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express spacecraft on 15 May 2006, when the spacecraft was flying at about 66500 kilometres distance from the planet.
In this image (taken at 365 nanometres) the South Pole is near the terminator, just above the centre of the image. The complex atmosphere that surrounds the planet is clearly visible. Near the pole we see spiralling clouds surrounding the polar vortex, away from the pole we see cloud features of the upper cloud deck at approximately 70 kilometres altitude.

Credits: ESA/MPS, Katlenburg-Lindau, Germany

When looking at the higher atmospheric layers with Venus Express, the scientists were taken once more by surprise. It is in fact know that the Venusian cloud deck is about 20 kilometres thick and it extends up to about 65 kilometres altitude over the planet. The first 'stellar occultation' measurements ever done at the Venus thanks to the SpicaV spectrometer, revealed that on the night side the cloud deck actually extends up to 90 kilometres altitude in the form of a fully opaque haze, and then continues as a more transparent haze up to 105 kilometres.

Stellar occultation is a technique that allows to determine the composition of a planet's atmosphere by looking at the 'sunset' of a pointed star through the atmosphere itself. "On Earth the atmosphere becomes perfectly clear already above 20 kilometres altitude," said Jean-Loup Bertaux, SpicaV/SOIR Principal Investigator, from the Service d'Aéronomie of CNRS, France.

"We were truly amazed to see how unexpectedly higher the haze at Venus can get. Actually, on Earth as well as on Venus, at around 20 kilometres it is sometimes possible to see droplets of sulphuric acid. On Earth they come from volcanic eruptions. It makes us wonder if on Venus, where differently from Earth the droplets form very thick clouds, their origin is volcanic too."

The haze phenomenon may be due to water condensation in ice crystals on the night side, but it is too early to rule out other explanations. "Now we need to gather and study more data to understand this phenomenon in the high atmosphere - an area that, before SpicaV, was still virtually unexplored," he concluded.

Bertaux also expressed his satisfaction for the atmospheric detection of 'heavy water' - a molecule similar to water but with higher mass – thanks to the SOIR spectrometer. "The detection of heavy water in the atmosphere of a planet, and its percentage with respect to normal water, is very important to understand how much water was present on the planet in the past, and how much of it escaped," added Bertaux.

"The amount of water vapour present today in the atmosphere of Venus would be enough to cover the planet with a 3-centimetre deep liquid layer. If we find out that heavy water – a trace of the original water – is massively present in the top atmospheric layers where it can more easily escape, than the amount of water in the past may have well corresponded to a layer up to a few hundred metres deep," Bertaux concluded.

These two plots where built with data retrieved from ASPERA, the Analyzer of Space Plasma and Energetic Atoms on board ESA’s Venus Express, on 30 May 2006, when the spacecraft was flying through different domains of the interaction region between Venus and the solar wind.
The X axis of the plots provides the different position at which the ions (charged atoms) hit the ASPERA detectors. The Y axis provides the energy of the detected ions. The white lines correspond to different ion masses.

The left plot shows the heated solar wind (protons and ‘alfa-particles’) which just passed the Venus bow shock (the region in space separating the unperturbed solar wind from the area where the solar wind interacts with the planetary environment). The right plot shows massive escape of the planetary oxygen ions detected inside the solar wind void which results from the interaction with Venus.

Credits: ESA/ASPERA/Swedish Institute of Space Physics (Kiruna)

Studying the atmospheric escape process at Venus is actually one of the major objective of another Venus Express instrument – ASPERA (Analyzer of Space Plasma and Energetic Atoms). The instrument already detected the massive escape of oxygen and tracked trajectories of other planetary ions such as singly-charged helium.

"This early detection confirms the strong interaction between the solar environment and the atmosphere of Venus - a planet without a planetary magnetic field to protect it from the incoming solar wind," said Stanislav Barabash, ASPERA Principal Investigator, from the Swedish Institute of Space Physics in Kiruna, Sweden. "The study of this interaction will provide important clues on the complex set of mechanisms by which atmospheric gases get lost in space, and on the influence that this may have had on Venus’ climate over geological time scales", he concluded.

The status of the spacecraft

During the course of its mission, Venus Express communicates with Earth by means of its two high gain antennas, located on two different sides of the spacecraft. Routinely, Venus Express will downlink scientific data for about eight hours once a day, when the spacecraft is around its furthest point from the planet (apocentre) along its 24-hour orbit.

Credits: ESA - AOES Medialab

On 4 July 2006 Venus Express passed an important exam. An ESA board declared the conclusion of the spacecraft in-orbit commissioning phase and declared that the spacecraft has met the requisites to officially enter the operational phase of its scientific mission.

The Venus commissioning phase, started on 7 May when Venus Express reached its final 24-hour orbit around the planet, and concluded on 4 June this year, is a series of operations aimed at validating the performance of the spacecraft and its systems in the Venus environment, of the scientific instruments, and of all ground systems and operations.

The spacecraft and instruments are showing an overall good performance. However, one of the instruments on board - the Planetary Fourier Spectrometer (PFS) – showed a malfunctioning, that could not be fixed yet in the series of attempts performed so far in space. The PFS scanner - the mirror needed by the instrument for pointing - is currently blocked in a close position, preventing the instrument spectrometer from 'seeing' its targets.

The commissioning review board endorsed a series of activities and further in-orbit tests to be conducted in the next months, as well as a series of independent investigations to examine the origin of the problem. In the meantime, other instruments will cover some of the PFS objectives.

PFS is designed to measure the chemical composition and temperature of the atmosphere of Venus. It is also able to measure surface temperature, and so search for signs of volcanic activity.

Source: ESA - Venus Express

[Waspie_Dwarf]

Complex meteorology at Venus

The false-colour view is the composite of three infrared images acquired by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA's Venus Express on 22 July 2006, at a time interval of about 30 minutes from each other and from a distance of about 65 000 kilometres over the planet's surface. Venus was in the night side.
The image, taken at a wavelength of 1.7-micrometre, shows the thermal radiation emitted from about 15-20 kilometres altitude. The brighter the colour (towards white), the more radiation comes from the surface, so the less cloudy the region in the line of sight between the view and the spacecraft is.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

13 October 2006
On 20 April 2006, after its first 9-day, elongated orbit around Venus, ESA’s Venus Express In its relentless probing of Venus's atmosphere, ESA's Venus Express keeps revealing new details of the Venusian cloud system. Meteorology at Venus is a complex matter, scientists say.

New night-side infrared images gathered by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) in July 2006, clearly show new details of a complex cloud system.
The first (false colour) view - the composite of three infrared images acquired by VIRTIS, was taken on 22 July when the spacecraft was flying around the apocentre of its orbit (point of maximum distance from the planet surface) at about 65 000 kilometres altitude. Venus was in the night side.

Using its capability to observe at 1.7-micrometre wavelenght, VIRTIS could probe at about 15-20 kilometres altitude, below the thick cloud deck situated at about 60 kilometres from the surface. The thermal radiation coming from the oven-hot surface of Venus is represented by the intensity of the colours: the brighter the colour (towards white), the more radiation comes from the surface, so the less cloudy the region in the line of sight between the view and the spacecraft is.

The edge of the images, taken at a time interval of about 30 minutes from each other, do not precisely match. This is due to the fact that clouds on Venus move very rapidly and constantly vary their shape. Venus’s atmosphere is certainly the most dynamic among the terrestrial planets that have one, taking only four days to completely rotate around the planet.

"Clouds at Venus present repetitive patterns and recurrent features, but they are very variable in position both on short and long time scales," said Giuseppe Piccioni who, with Pierre Drossart, is the instrument co-Principal Investigator. "This makes meteorology a very complex matter for this planet."

Since the thermal radiation from the surface of Venus is in practice modulated by the presence of the clouds, taking the negative of the image it is possible to see directly the clouds structure on the night side, and so study its morphology and dynamics.

This picture of the Venusian atmosphere is the 'negative' of a night-side infrared image acquired by the VIRTIS instrument on board ESA's Venus Express on 29 July 2006, from a distance of about 65 000 kilometres from the surface.
At the centre of the image, taken at 2.3-micrometre wavelength, it is possible to see a large cloud extending toward the bottom-right part of the view. The cloud is about 2000 kilometres long and 500 kilometres wide. It presents the peculiar elongated shape of clouds at Venus, which is due to high-speed winds.

The very cloudy region visible at the top-right of the image is situated beyond 60º South latitude, and represents the transition to the region where the atmosphere is dominated by the effects of the powerful South double polar vortex.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

This was done for this other night-side image, acquired by VIRTIS on 29 July around apocentre from a distance of about 65 000 kilometres from the surface.

The 2.3-micrometre wavelength used for this image brought the 'view' again down below the cloud deck. The large cloud visible in the centre of the image and extending toward the bottom-right part is about 2000 kilometres long and 500 kilometres wide.

This cloud presents the familiar and peculiar shape of clouds at Venus. They are usually elongated due to the very high-speed winds – reaching up the formidable velocity of 360 kilometres per hour and being caused by the 'super-rotation' of the atmosphere.

The very cloudy region visible at the top-right of the image is situated beyond 60º South latitude, and represents the transition to the region where the atmosphere is dominated by the effects of the powerful South double polar vortex.

Source: ESA - Venus Express

[Waspie_Dwarf]

Happy birthday, Venus Express!

This night-side, false-colour image was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express on 23 September 2006, when the spacecraft was flying at about 60 000 kilometres over the planet around the point of furthest distance from the surface (apocentre). It was taken at 1.7-micrometre wavelength, and shows an area close to the South pole (out of the field of view beyond the top left of the image).

The bright big spot on the left of the image corresponds to an area where the cloud deck is thinner. Such regions, similar to large holes, allow the thermal radiation from below the clouds layer to increase significantly with respect to the surrounding areas, and make it possible to probe very deep in the atmosphere with a limited attenuation from the clouds.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

9 November 2006
One year after its launch on 9 November 2005 and a few months into its science phase, ESA's Venus Express keeps working well and continues to gather lots of data about the hot and noxious atmosphere of the planet. Newly released images show additional details of the thick cloud deck that surrounds Venus.

It was 11 April 2006 when, after a delicate manoeuvre, Venus Express entered into orbit around Venus, and started a series of gradually smaller loops around the planet to reach its 24-hour science orbit (spanning between 66 000 over the South pole and 250 kilometres over the North pole) on 7 May 2006.

This artist's impression shows Venus Express focussing on studying the peculiar atmosphere of Venus, with a precision never achieved before. In doing so, the mission will make the first ever use of the so called 'infrared windows', which are narrow bands in the atmospheric spectrum, discovered in the 1980s thanks to ground observations. Looking through these 'windows' Venus Express will be able to gather precious information about the lower layers of the atmosphere and even the surface.

Credits: ESA - AOES Medialab

"From that time onwards this unique spacecraft, equipped with the most advanced instruments ever used for atmospheric investigations at Venus, has started gathering views and information on the thick atmosphere, its cloud system and its dynamics – during experiment tests in the beginning, and on a nominal basis after 4 June 2006," said Håkan Svedhem, Venus Express Project Scientist.

From the very first images of the approaching planet and from the South Pole views obtained on 12 April - the first of this area taken in the infrared in the history of Venus’ exploration - scientists immediately obtained novel glimpses about an extraordinarily complex weather system.

This is ruled by huge and still largely unexplained forces at work in the atmosphere, causing hurricane-force winds and generating the amazing double-eyed vortices over both poles.

This movie, built with infrared images taken by the Ultraviolet/Visible/Near-Infrared spectrometer (VIRTIS) on board ESA’s Venus Express, provides a close-up view of the double-eyed vortex at Venus south pole. The images (ranging from 4.5 to 5.1 microns) were taken on 29 May 2006, from a distance of about 64 000 kilometres from the planet.

Thanks to the use of different wavelengths, VIRTIS probed the atmosphere at different depths, ranging from 70 kilometres to about 60 kilometres altitude. It is interesting to see how the images contrast and the details increase while approaching the 60 kilometres altitude.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

It was indeed this European spacecraft to entirely reveal for the first time the double vortex over the planet's South pole, with its 3D structure so much differentiated over different altitudes and similarly shaped (but mirrored) to that present over the North pole.

Newly released images, obtained in July and September 2006 by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express, show new details of the cloud structure. This thick layer of clouds, located around 60 kilometres altitude over the surface, blocks part of the thermal radiation coming from below.

However, VIRTIS is designed to catch the only radiation that can pass through the lower atmopshere and the cloud deck, making use of the so called 'infrared windows'. Through these 'windows', thermal (infrared) radiation at specific wavelengths can cross the lower atmosphere and escape towards space. By doing so, it carries information about the lower atmospheric layers and the surface that VIRTIS can collect from orbit.

The first, false-colour night-side image (see top of the article), was taken at a 1.7-micrometre wavelength on 23 September 2006, when the spacecraft was flying at about 60 000 kilometres over the planet around the point of furthest distance from the surface (apocentre). It shows an area close to the South pole (out of the field of view beyond the top left of the image).

"The bright big spot on the left of the image corresponds to an area where the cloud deck is thinner," said Giuseppe Piccioni, VIRTIS co-Principal Investigator. "Such regions, similar to large holes, allow the thermal radiation from below the clouds layer to increase significantly with respect to the surrounding areas, and make it possible to probe very deep in the atmosphere with a limited attenuation from the clouds."

The atmospheric layers below the cloud deck, and the fact that they are blocking almost all thermal radiation coming from the surface, are the main responsible for the tremendous green-house effect at work on the planet – the most powerful found in the Solar System. It maintains the surface temperature as high as 450°C!

This night-side image of the southern hemisphere of Venus was taken by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) on board Venus Express on 29 July 2006, from a distance of about 64 000 kilometres over the surface (around the orbit apocentre), at a wavelength of 1.7 micrometres. The South pole is visible on the top left of the image.

This image provides a remarkable example of a wave structure, running from the bottom to the top-right, each ‘wave’ extending about 150 kilometres. This peculiar cloud feature is often seen at a latitude of about 55º South.

The picture also shows a part of the polar vortex (top left). Regions of thinner clouds are also present in this image. They are visible as bright spots (top left corner), as they allow more thermal radiation to escape towards deep space from the hotter regions below.

The region between the black stripe around the pole and the wave structure contains the so called ‘cold collar’, a region in which the temperature of the clouds is lower than that of the surrounding area.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The second, night-side image of the southern hemisphere was taken by VIRTIS on 29 July 2006 from a distance of about 64 000 kilometres over the surface (around the orbit apocentre) at a wavelength of 1.7 micrometres. The South pole is visible on the top left of the image.

This image provides a remarkable example of a wave structure, running from the bottom to the top-right, each 'wave' extending about 150 kilometres. This peculiar cloud feature is often seen at a latitude of about 55º South.

"Despite the fact that the cloud structure is very variable and dynamic at Venus, recurrent patterns and structures tend to appear in the same locations," said Pierre Drossart, VIRTIS co-Principal Investigator. "They are mostly visible in the infrared, sometimes very easily, some other times less. When they are very faint and hidden, we need to play with the intensity of the images."

The picture also shows a part of the polar vortex (top left). Regions of thinner clouds are present also in this image. They are visible as bright spots (top left corner), as they allow more thermal radiation to escape towards deep space from the hotter regions below.

The region between the black stripe around the pole and the wave structure contains the so called 'cold collar', a region in which the temperature of the clouds is lower than that of the surrounding area. Similar cold-collar structures are present at both poles. The cold collar over the South pole cannot be clearly seen in this image (1.7 micrometre wavelenght), but it was was imaged by VIRTIS at 5 micrometres in April 2006.


In the meantime, VIRTIS and the other instruments on board Venus Express keep observing the mysterious atmosphere of Venus. Well done so far and…happy anniversary, Venus Express!

Source: ESA - Venus Express

[Waspie_Dwarf]

Vesper Could Explore Earth's Fiery Twin

Earth has a twin sister, and she's gone bad.

The planet Venus is almost the same size as Earth, so it has been called Earth's twin. It's only about 30 percent closer to the sun than Earth, and at the dawn of the space age, scientists thought its cloudy atmosphere might hide a steamy jungle planet teeming with life. However, when the first American and Russian space probes visited Venus in the 1960s, it became clear that something had gone terribly wrong with the planet's ability to support life.


Image above: This is a Hubble Space Telescope ultraviolet-light image of the planet Venus, taken on January 24 1995, when Venus was at a distance of 70.6 million miles (113.6 million kilometers) from Earth. At ultraviolet wavelengths cloud patterns become distinctive. In particular, a horizontal "Y"-shaped cloud feature is visible near the equator. This global feature might indicate atmospheric waves, similar to high and low pressure cells on Earth. From previous missions, astronomers know that such features travel east to west along with the Venus' prevailing winds, to make a complete circuit around the planet in four days. False color has been used enhance cloud features.
Credit: NASA

The spacecraft revealed Venus as a searing desert, its waterless surface crushed under a thick atmosphere almost 100 times the pressure of Earth's. The clouds that shroud the planet contain droplets of deadly sulfuric acid, not life-sustaining water. The surface temperature hovers around 800 degrees Fahrenheit, hot enough to melt lead. All known forms of life would be broiled alive.

Yet, both Venus and Earth may have had had similar climates shortly after they formed. "The big mystery Vesper will help answer is how these two similar worlds ended up with such different outcomes," said Gordon Chin, Principal Investigator for the proposed mission at NASA's Goddard Space Flight Center, Greenbelt, Md.

Vesper, the Latin name for "Evening Star" or Venus, is a proposed NASA Discovery-class mission that would increase our knowledge of what the planet's atmosphere is made of and how it changes. Understanding the atmosphere of Venus will help scientists learn how a world that might have been a tropical Eden became instead a close approximation of Hell.


Image above: The volcano Maat Mons is displayed in this computer generated three-dimensional perspective of the surface of Venus. Radar data is combined with radar altimetry from NASA's Magellan mission to develop a three-dimensional map of the surface. The viewpoint is located 634 kilometers (393 miles) north of Maat Mons at an elevation of 3 kilometers (2 miles) above the terrain. Lava flows extend for hundreds of kilometers across the fractured plains shown in the foreground, to the base of Maat Mons. The vertical scale in this perspective has been exaggerated 10 times. Simulated color and a digital elevation map developed by the U.S. Geological Survey are used to enhance small-scale structure.
Print-resolution copy (1 meg jpg image)
Credit: NASA/JPL

The Vesper proposal was among approximately two dozen submitted in response to NASA's Discovery Program 2006 Announcement of Opportunity in April. NASA selected three new mission proposals for concept studies, including Vesper. As a new mission, the Vesper team will receive $1.2 million to conduct further study of the concept. If selected for continuation beyond the concept phase, Vesper must complete its mission, including archiving and analyzing data, for less than $425 million.

If approved, Vesper would observe Venus for two days. They are Venus days, which are 243 Earth days long. Venus rotates so slowly that its day is longer than its year (which lasts 224.7 Earth days).

The many mysteries Vesper will investigate include:

How the atmosphere evolved from a supposed Earthlike beginning to its current, unimaginably hostile state. Understanding what happened can provide insight to climate change on Earth.

Although the surface hardly rotates, the cloud tops swirl around the planet at over 200 miles per hour. This is called "superrotation," and scientists want to understand what drives it.

Vortices of spinning clouds resembling twin hurricanes, side by side, exist at each pole. Scientists want to understand how and why they form, and whether they produce unusual chemical reactions, similar to the polar vortices on Earth that set up conditions which allow the ozone holes to form.

Vesper will also investigate whether long-term changes in atmospheric sulfur dioxide compounds are evidence of active volcanoes on Venus.

The planet's atmosphere is mostly carbon dioxide (CO2), which should get broken down by sunlight into carbon monoxide (CO) and oxygen. That's not happening, at least not on a large scale, or scientists would have seen it by now. There must be some as yet unknown chemistry stabilizing the atmosphere.


Image right: A preliminary drawing of the proposed Vesper spacecraft.
Credit: NASA

Vesper will complement past and current missions to Venus like the European Space Agency's Venus Express. That mission arrived at Venus on April 11, 2006, and will explore the planet for two Venus days, or 486 Earth days. Vesper could enter Venus orbit in March 2015. By observing the planet's atmosphere at different times, scientists can get a more complete record of how the atmosphere is changing.

Goddard will manage the Vesper project if it is approved. NASA may select one or more investigations to continue into a development effort after detailed review of the concept studies. Decisions about which mission concepts are further developed are expected next year.

Bill Steigerwald
NASA Goddard Space Flight Center

Source: NASA - Goddard Spaceflight Centre - News

[Waspie_Dwarf]

Hot stuff on Venus! Venus Express sees right down to the hell-hot surface

The temperature maps of the Venusian surface shown in this image were built thanks to direct measurements obtained by Venus Express’ VIRTIS instruments (left), compared with surface temperature predictions based on the Magellan topographic data obtained in the early 1990s (right).

VIRTIS, the Visible and Infrared Thermal Imaging Spectrometer on board ESA’s Venus Express, gathered the data combined into this mosaic on 10 August 2006, during a single orbit (orbit 112). The spacecraft was flying over the Themis and Phoebe Regiones in the southern hemisphere of Venus. Themis Regio is a highland plateau located on the 270º East meridian and at about 37º South latitude. In the future, combining data from many orbits will significantly improve the quality and the spatial resolution of the surface images.

This is a region that has experienced strong volcanic activity in the past, and possibly still does today. A series of interconnecting large coronae is running through the highland. Coronae are circular to elongate features, which are surrounded by multiple concentric ridges. These features are thought to be forming by hot spots in the Venusian crust. The coronae in Themis Regio are building a chain of volcanoes and faults called Parga Chasma, which runs from northwest to southeast, and eventually connect Parga with Atla Regio (not covered in the inage). The Phoebe Regio is a highland region of Venus (such regions are called 'tesserae'), where most of the Soviet Venera probes landed.

Large highland regions are clearly visible, as well as single volcanic structures such the Mielikki Mons, in the centre of the mosaic. On the south-eastern part of the mosaic VIRTIS covered a region for which Magellan maps are not available.

The surface-temperature measurements were performed using the atmospheric windows located in the near infrared at 1.02, 1.10, and 1.18 microns, respectively. The radiation coming from the surface is affected by the thick cloud layer, so a ‘de-clouding’ algorithm had to be applied.

The non-labelled version of this image is available by clicking here.

Credits: ESA/VIRTIS-VenusX Team

14 December 2006
Thanks to ESA’s Venus Express data, scientists obtained the first large-area temperature maps of the southern hemisphere of the inhospitable, lead-melting surface of Venus.

The new data may help with searching and identifying ‘hot spots’ on the surface, considered to be possible signs of active volcanism on the planet.

The results, presented today at the American Geophysical Union (AGU) assembly in San Francisco, USA, were obtained thanks to VIRTIS, the Visible and Infrared Thermal Imaging Spectrometer on board Venus Express.

To obtain this fundamental information about the surface temperature, VIRTIS made use of the so-called infrared spectral 'windows’ present in the Venusian atmosphere. Through these ‘windows’ thermal radiation at specific wavelengths can leak from the deepest atmospheric layers, pass through the dense cloud curtain situated at about 60 kilometres altitude, and then escape to space, where it can be detected by instruments like VIRTIS. In this way VIRTIS succeeded in looking through the thick carbon dioxide curtain surrounding Venus and detected the heat directly emitted by the hot rocks on the ground.


"We are very excited about these results, as they represent a very important item in the list of Venus Express' and VIRTIS' scientific objectives at Venus", says Giuseppe Piccioni, one of the Principal Investigators of the VIRTIS experiment, from the Istituto di Astrofisica Spaziale e Fisica Cosmica in Rome, Italy.

Venus Express is making unprecedented studies of the largely unkown phenomena taking place in the Venusian atmosphere. Its suit of instruments is also digging into the interaction between the solar wind and the planetary environment. Finally, the mission is also gathering glimpses about the planet's surface, striclty coupled with the dense atmosphere.

Credits: ESA - AOES Medialab

The measurements, made in August 2006 over the Themis and Phoebe Regions in the southern hemisphere of Venus, reveal temperature variations of 30 degrees between lowlands and mountain tops, correlating well with existing topographical radar data from previous missions. The Themis Region is a highland plateau located at 270º East longitude and at about 37º South latitude. It is a region that has experienced strong volcanic activity, at least in the geologic past.

On Venus there are no day and night variations of the surface temperature. The heat is globally 'trapped' under the carbon-dioxide atmosphere, with pressure 90 times higher than on Earth. Instead, the main temperature variation is due to topography. Just like on Earth, mountain tops are colder, whereas the lowlands are warmer. The 'only' difference is that on Venus 'cold' means 447º Celsius, while 'warm' means 477º Celsius. Such high temperatures are caused by the strongest greenhouse effect found in the Solar System.

"The VIRTIS results represent a major step forward in our attempt to identify specific surface features on the surface of Venus", said Jörn Helbert from the German Aerospace Center's (DLR) Institute of Planetary Research in Berlin, Germany, and a member of the VIRTIS team. "By 'peeling' off the atmospheric layers from the VIRTIS data, we can finally measure the surface temperature," Helbert added.


Eventually, the VIRTIS team hopes to identify 'hot spots' on the surface of Venus, possibly stemming from active volcanoes. In the Solar System, besides Earth, active volcanoes have been observed only on Io, a satellite of Jupiter, on Neptune's satellite Triton, and on Saturn's moon Enceladus (in the form of the so-called 'cryo-volcanism'). Venus is the most likely planet to host other active volcanoes.

On this radar-map of Venus, built with data that NASA’s Magellan gathered in the early 1990s, the areas that were over-flown by Venus Express on 10 August 2006 are indicated by the named features. The VIRTIS instrument on board retrieved unprecedented information about the surface temperature, and so provided the first ever large-scale temperature map of the Southern hemisphere of Venus.

The non-labelled version of this image is available by clicking here.

Credits: NASA/Magellan

In order to achieve this, the Venus Express scientists started comparing the maps of the Venusian topography obtained by NASA’s Magellan orbiter in the early 1990s with the data gathered by VIRTIS. The Magellan topography maps allow for a rough prediction of the surface temperature, too. Comparing these predictions with the measurements made by VIRTIS allows searching for hot spots that show even higher temperatures than the oven-hot surface, possibly indicative of active volcanism.

This direct interdependence between temperature and topography will enable scientists to derive new topography maps of the Venusian surface from temperature measurements. This will help in complementing the Magellan maps.

"Actually, when comparing our temperature map with topographical data from Magellan, we are not only obtaining quite a good agreement, but we can even fill gaps that the Magellan and Venera 15 radar data sets left open", concluded Pierre Drossart, the other Principal Investigator of the VIRTIS experiment, from the Observatoire de Paris Meudon, France.


Note

Even though Venus is the brightest planet in the night sky other than Earth's moon, and it is the closest planet to Earth, it is extremely difficult to obtain detailed information about its surface from Earth. Even if some evidence of surface thermal emission has been obtained from ground-based telescopes working in the near-infrared since 1990, the spatial resolution of such observations remain very limited.

Venus Express is instead making use of the 'infrared windows', known to scientists from the middle of the 1980s. In 1990, during the flyby of Venus, NASA's Galileo spacecraft on its way to Jupiter made a first attempt to make use of these 'windows'.

Source: ESA - News

[Waspie_Dwarf]

Tracking alien turbulences with Venus Express

3 April 2007

This image is a composite of four different views of the Venusian cloud system. The images were acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from distances of about 65 000 kilometres (top left), 60 000 kilometres (top right), 53 000 kilometres (bottom left), 37 000 kilometres (bottom right) from the planet’s surface.

The images, showing a complex cloud system, were taken on the night-side of Venus (04:00 local time), at a wavelength of 1.7 micron that allows viewing the deep atmospheric layers.

The grey-scale of the images is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA


New images and data from ESA’s mission to Venus provide new insights into the turbulent and noxious atmosphere of Earth’s sister planet. What causes violent winds and turbulences? Is the surface topography playing a role in the complex global dynamics of the atmosphere? Venus Express is on the case.

Venus’ atmosphere represents a true puzzle for scientists. Winds are so powerful and fast that they circumnavigate the planet in only four Earth days – the atmospheric ‘super-rotation’ – while the planet itself is very slow in comparison, taking 243 Earth days to perform one full rotation around its axis.

At the poles things get really complicated with huge double-eyed vortices providing a truly dramatic view. In addition, a layer of dense clouds covers the whole planet as a thick curtain, preventing observers using conventional optical means from seeing what lies beneath.

This image of the Venusian south polar region was acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from a distance of about 65 000 kilometres from the planet’s surface.

The image, showing a complex cloud system, was taken on the night-side of Venus (04:00 local time), at a wavelength of 1.7 micron that allows viewing the deep atmospheric layers. The field of view covers an area located at approximately 20 degrees west longitude (diagonal top left to bottom right), spanning from the equator (at the horizon on the right) to 60 degrees southern latitude (top left corner of the image).

The grey-scale of the image is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.

The Alpha Regio area is at the bottom left of the image. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 kilometres high. It is not yet clear if atmospheric turbulences may be induced by the rough topography below the clouds.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Venus Express is on the contrary capable of looking through the atmosphere at different depths, by probing it at different infrared wavelengths. The Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board is continuing its systematic investigation of Venus’ atmospheric layers to solve the riddle of the causes for such turbulent and stormy atmosphere.

The images presented with this article focus on Venusian atmospheric turbulences and cloud features, whose shape and size vary with planetary latitudes. At the equator, clouds are irregular and assume a peculiar ‘bubble’-shape. At mid latitudes they are more regular and streaky, running almost parallel to the direction of the super rotation with speed reaching more than 400 kilometres per hour. Going higher up in latitude, in the polar region, the clouds end up in entering a vortex shape.

This image of the Venusian south polar region was acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from a distance of about 60 000 kilometres from the planet’s surface.

The image, taken on the night-side of Venus at a wavelength of 1.7 micron, shows waves structure (faint light vertical streaks at the lower left part of the dark band in the centre-left side of the image) and a highly turbulent region (bottom left).

The Alpha Regio area is at the bottom left of the image. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 kilometres high. It is not yet clear if atmospheric turbulences may be induced by the rough topography below the clouds.

The grey-scale of the image is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

With its multi-wavelength eyes, VIRTIS can observe the atmosphere and the cloud layers not only at different depths, but also both in the day- and night-side of the planet – a characteristic that allows an overall assessment of the ‘environmental’ causes that can be at the origin of such an atmospheric complexity.

At the equator, the extremely violent winds of the super-rotation are in constant ‘battle’ with other kinds of local turbulences, or ‘regional’ winds, creating very complex cloud structures.

This image of the Venusian south polar region was acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from a distance of about 53 000 kilometres from the planet’s surface.

The image, taken on the night-side of Venus at a wavelength of 1.7 micron, shows waves structure (faint light vertical streaks at the lower left part of the dark band in the centre-left side of the image) and a highly turbulent region (bottom left).

The Alpha Regio area is at the bottom left of the image. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 kilometres high. It is not yet clear if atmospheric turbulences may be induced by the rough topography below the clouds.

The grey-scale of the image is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

One type of regional wind is due to the strong flux of radiation from the Sun reaching the atmosphere of the planet on the day-side. This flux heats up the atmosphere creating convective cells, where masses of warm air move upwards and generate local turbulence and winds.

On the night-side there is obviously no flux from the Sun, but the clouds’ shape and the wind dynamics are somehow similar to that we see on the day-side. So, scientists are currently trying to understand if there is any mechanism other than ‘convection’ responsible for the equatorial turbulences, both on the day- and night-side of Venus.

This image of the near-equatorial region of Venus was acquired on 24 September 2006 by the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board ESA’s Venus Express, from a distance of about 37 000 kilometres from the planet’s surface.

The image, taken on the night-side of Venus at a wavelength of 1.7 micron, provides a close-up view of a highly turbulent region, with irregular and warped clouds, which is common at these low latitudes. This is different from what happens at higher latitudes (pole-ward) where clouds are generally streaky and more regularly shaped.

The gray ‘bubble’ slightly below the centre of the image is located at about 27 degrees southern latitude and 7 degrees western longitude, and has a diameter of about 300 kilometres.

The Alpha Regio area is at the bottom left of the image. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 kilometres high. It is not yet clear if atmospheric turbulences may be induced by the rough topography below the clouds.

The grey-scale of the image is such that black means more transparency, therefore less clouds, while white means more opacity, therefore more cloud concentration.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

For instance, VIRTIS imaged clouds over Alpha Regio, an area close to the equator. This area is characterised by a series of troughs, ridges, and faults that are oriented in many directions, with surface features that can be up to 4 kilometres high. There might be a connection between the surface topography and the local atmospheric turbulence which is observed in this area. This and other hypotheses are being investigated by the Venus Express science teams using data from several instruments.

Actually, the Venusian topography may play an important role also in the global atmospheric dynamics. Understanding this surface-atmosphere connection is one of the major objectives of Venus Express - something to be verified in the whole course of the mission.

Source: ESA - Venus Express

[Waspie_Dwarf]

One year at Venus, and going strong

11 April 2007

This false-colour view was obtained on 26 August 2006 by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard ESA's Venus Express, at a distance of 65 000 kilometres from Venus' surface, from the south. The horizon seen at the bottom-right in both panels is about Venus' equator. The top left of the images is located at about 60 degrees south latitude; the images centre is at 130 degrees west longitude.

Both panels show the oxygen airglow in the night-side atmosphere of Venus, fully detectable only at specific infrared wavelengths. The images are built by a combination of colours: the airglow is blue, corresponding to 1.27 micrometres; yellow corresponds to 1.7 micrometres, and its modulation is due to the different cloud thickness in different areas.

On the right panel the airglow appears in atmospheric structures similar to 'clouds'. In the left image a slightly different colour scale has been used to emphasize the brightening of the limb (side view of the atmosphere) due to the airglow itself.

The fluorescence of the airglow is produced when oxygen atoms, 'migrating' from the day-side to the night-side of the atmosphere of Venus under the push of the so-called sub-solar and anti-solar atmospheric circulation, recombine into molecular oxygen (or 'O2') emitting light.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA


One year has passed since 11 April 2006, when Venus Express, Europes first mission to Venus and the only spacecraft now in orbit around the planet, reached its destination. Since then, this advanced probe, born to explore one of the most mysterious planetary bodies in the Solar System, has been revealing planetary details never caught before.

Intensively visited by several Russian and American probes from the 60s to the early 90s, Venus has always represented a puzzling target for scientists worldwide to observe. Venus Express, designed and built in record time by ESA, was conceived with the purpose of studying Venus - unvisited since 1994 - in the most comprehensive and systematic way ever, to provide a long-due tribute to a planet so interesting, yet cryptic.

Using state-of-the-art instrumentation, Venus Express is approaching the study of Venus on a global scale. The space probe is collecting information about Venus' noxious and restless atmosphere (including its clouds and high-speed winds, as seen from this video obtained with the VMC camera on board) and its interaction with the solar wind and the interplanetary environment. Last but not least, it is looking for signs of surface activity, such as active volcanism.

"During one year of observations, we have already collected huge amount of data, which is exactly what we need to decode the secrets of an atmosphere as complex as that of Venus," said Håkan Svedhem, Venus Express Project Scientist at ESA. "Analysing it is an extreme effort for all science teams, but it is definitively paying back in terms of results."

The first ever, terrific global views of the double-eyed vortex at Venus' south pole, the first sets of 3D data about the structure and the dynamics of the sulphuric-acid clouds surrounding the planet in a thick curtain, temperature maps of the surface and the atmosphere at different altitudes, are only a few of the results obtained so far.

"Continuing at today's rate, and on the basis of what we were able to see so far, there is no doubt that Venus Express will eventually allow a better global understanding of this planet," continued Svedhem. "Not only will planetary science in general benefit from this, but also understanding Venus - its climate and atmospheric dynamics - will provide a better comprehension of the mechanisms that drive long-term climate evolution on our own Earth."


The night-glowing 'lantern' of Venus

New infrared data is now available about Venus' oxygen airglow - a phenomenon detectable on the night-side that makes the planet glow like a 'space lantern'.

"The oxygen airglow was first discovered thanks to ground observations, and also observed by other missions to Venus such as the Russian Venera spacecraft and the US Pioneer Venus orbiter," said Pierre Drossart, co-Principal Investigator on Venus Express' VIRTIS instrument. "However, the global and detailed view we are getting thanks to Venus Express is truly unprecedented."

The fluorescence of the airglow is produced when oxygen atoms present in the atmosphere ‘recombine’ into molecular oxygen (or 'O2') emitting light. Where does the oxygen come from?

This grey-scale image was taken on 3 June 2006 by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard ESA's Venus Express, at a distance of 68 000 kilometres from the planet's surface.

The image shows the oxygen airglow in the night-side of Venus, appearing as the bright features similar to ‘clouds’ visible at the bottom of the image, and also visible as the white ring surrounding the planet's disk (limb). The oxygen airglow is fully detectable only at specific infrared wavelengths. This image was obtained at 1.27 micrometres.

The fluorescence of the airglow is produced when oxygen atoms, 'migrating' from the day-side to the night-side of the atmosphere of Venus under the push of the so-called sub-solar and anti-solar atmospheric circulation, recombine into molecular oxygen (or 'O2') emitting light.

The view was obtained from south, with the south pole at the top of the image. The lower horizon is at about 20 degrees South latitude, while the image centre is at 60 degrees East longitude (coinciding with midnight local time).

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

"The oxygen in the atmosphere of Venus is a very rare element," continued Drossart. At high altitudes in the atmosphere, on the day-side of Venus, the strong flux of ultraviolet radiation coming from the Sun 'breaks' the molecules of carbon dioxide ('CO2') present in large quantity in the atmosphere, liberating oxygen atoms. "These atoms are then transported by the so-called 'sub-solar' and 'anti-solar' atmospheric circulation towards the night side of the planet. Here the atoms migrate from the high atmosphere to a lower layer, called 'mesosphere', where they recombine into O2. By doing this, they emit light at specific wavelengths that can be observed through remote sensing from Earth and with Venus Express," added Drossart.

The detection of the airglow, and the capability to follow its evolution in time, is extremely important for several reasons.

"First, we can use the distribution and motion of these fluorescent O2 'clouds' to understand how the atmospheric layers below move and behave," said Giuseppe Piccioni, the other co-Principal Investigator on VIRTIS. "In this sense, the O2 airglow is a real 'tracer' of the atmospheric dynamics on Venus."

"Second, the analysis of this phenomenon will provide new clues on how its global atmospheric chemistry works – a very challenging task indeed, and still an open field of research," continued Piccioni. "By calculating the speed at which this chemical 'recombination' takes place, we might be able - in the future - to understand if there are mechanisms that favour, or catalyze, this recombination, and learn more about the production and recombination of the other chemical species in the Venusian atmosphere."

"Third, the observation of the oxygen airglow also allows to a better understanding of the global 'energetic' exchange between Venus's mesosphere - at upper boundary of which the airglow is situated, with Venus' thermosphere, an even higher layer directly influenced by the Sun."

This image provides a schematic view of the oxygen airglow production in the atmosphere of Venus.

At high altitudes in the atmosphere, on the day-side of Venus, the strong flux of ultraviolet radiation coming from the Sun 'breaks' the molecules of carbon dioxide ('CO2') present in large quantity in the atmosphere, liberating oxygen atoms. These atoms are then transported by the so-called 'sub-solar' and ‘anti-solar' atmospheric circulation towards the night side of the planet. Here the atoms migrate from the high atmosphere to a lower layer, called ‘mesosphere’, where they recombine into O2. By doing this, they emit light at specific infrared wavelengths.

The images used to produce the sketch were obtained by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard ESA's Venus Express, and provide a view of the southern hemisphere of the planet.

The left image was obtained at visible wavelengths (400 nanometres) on 19 April 2006, along the capture orbit around Venus.

The right image is a composite of three VIRTIS observations performed on 22 July 2006. Because of this particular viewing geometry, the oxygen airglow appears on the right-hand side of the image (night-side equatorial region) as an area of brightness increase.

Credits: R. Hueso, Grupo de Ciencias Planetarias, Univ. del País Vasco, Spain

Notes

The mechanism for the production of the airglow was described in 1979 by P.Connes, after its emission was discovered through ground-based observations.

Venus Express was launched on 9 November 2005 from the Baikonur cosmodrome in Kazakhstan on board a Starsem Soyuz-Fregat rocket. It reached Venus about five months later, on 11 April 2006, when a delicate manoeuvre injected it into orbit around the planet. After a period of commissioning the spacecraft and the instruments, Venus Express started its nominal science operations on 4 July 2006.

Source: ESA - News Edited May 8, 2007 by Waspie_Dwarf

[Waspie_Dwarf]

Venus and Pleiades unite for celebration!

11 April 2007

Venus and the constellation Pleiades are converging for a close encounter.

Credits: Michel Hersen

Venus Express, Europe’s first mission to Venus, has now successfully orbited our closest neighbour 355 times during the past year. Coincidentally on its first anniversary on 11 April, Venus and the constellation Pleiades are very close in the sky, for your viewing pleasure.

The celestial spectacle is clearly visible with the naked eye – provided that there are no clouds to cover it. Venus and Pleiades can be seen drawing closer together in the western sky; after sunset and before midnight. The planet and the star cluster will be close enough to fit behind an upturned thumb held at arm's length.

Although the time of closest approach as seen from Earth is during the early morning hours of April 12, it will not be visible then since Venus sets at midnight. Given that there is currently no moon in the evening hours, the uncommon occurrence will be even more obvious.

In the foreground, Venus Express, which will study the Venusian atmosphere. Venus is like Earth's twin in someways and unlike in many others.

Credits: ESA/Medialab

Venus and the Pleiades form a peculiar couple. Venus is extravagantly bright surrounded by a thick atmosphere reflecting 70 percent of all received light. The Pleiades however are dim and slight, since the young and not yet completely formed cluster is 400 light years away. These opposite characteristics offer a pretty view for star-gazers as well as photographers and astronomers.

Thanks to its intense reflection, Venus is the brightest planet within the solar system making it fairly easy to distinguish the ensemble as it outshines all stars and planets in the evening sky.

Take a look and raise a toast to Venus Express’ first anniversary!.

Source: ESA - Space Science

[Waspie_Dwarf]

Venus Express’ infrared camera goes filming

7 May 2007

VIRTIS composite video of Venus’ south polar vortex.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

An exciting new series of videos from ESA’s Venus Express has been capturing atmospheric details of day and night areas simultaneously, at different altitudes.

The south pole of the planet and its gigantic double vortex has been pictured as never before.

The south pole of Venus and the double-eyed storm permanently rule atmospheric phenomena in that area of the planet. They are key to understanding the global atmospheric dynamics on Venus and will contribute to a better comprehension of the global meteorology of the planet.

In the search for all possible clues on how to solve the global atmospheric ‘puzzle’, the team of scientists behind the Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) on board Venus Express, have tried something new – starting from the south pole.

They started by focusing on this target from the advantageous position of the orbit apocentre (the furthest distance of the spacecraft from the planet). This allows the instrument to keep the target in the field of view for longer than in other portions of the orbit, where the spacecraft travels faster. In this favourable position, scientists made efficient use of the multi-wavelength capability of VIRTIS.

By using wavelengths longer than 3 microns in the thermal infrared range, VIRTIS can obtain a combined view of the day and night sides simultaneously. This is more convenient since at shorter wavelengths, the difference between the thermal radiation emitted on the day and night sides is too high to observe both regions simultaneously without ‘blinding’ some channels of the camera.

“It is comparable to looking at bright, sun-illuminated snow and at a dark sky without having to change your glasses,” said Giuseppe Piccioni, VIRTIS co-Principal Investigator. “In addition, within this observation process, not only can we look at the dark and lit sides of the south pole at the same time, but we can also look into the atmosphere at different depths. What we are building is the most complete 3D data set of the Venusian atmosphere to date.”

VIRTIS edge-enhanced video of the south polar vortex.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The VIRTIS videos of the south polar vortex presented here are the result of combined observations at two different wavelengths (3.8 and 1.7 microns, respectively) used at the same time. The various images were taken over five orbits, during a time-span of about 8 hours per orbit.

The 3.8-micron channel was chosen because of its compatibility (in exposure time) with the 1.7-micron observations, as well as for its capability to provide information about the cloud deck at about 65 kilometres altitude over the planet. The 1.7-micron wavelength was chosen to probe the atmosphere below the clouds when looking at the night side.

It is clearly possible to see that the morphology of the vortex changes a lot during the 8-hour observation session and from one orbit to the next (one Venus Express orbit is 24 hours long).

It is interesting to note that due to ‘bad weather conditions’, by the time of the observations, the videos do not show the maximum achievable image contrast. In fact, the visibility of the polar structure was somewhat reduced by the local increase of the upper atmospheric haze.

“If the weather permits, by extending the time span of our future observations, we may have the chance to obtain even clearer and more detailed views of the polar vortex,” added Piccioni.

“With video sequences of this kind, combining all the pieces of information together, we can study the dynamics and the evolution of the vortex both in the short and the long term,” said Pierre Drossart, the other co-Principal Investigator on VIRTIS. “What we want to understand is the overall 3D thermal structure of the vortex, especially the vertical variation of the horizontal winds.”

The next step will be the correlation of this data and data collected in the next sessions, with fluid dynamics computer models. This will eventually help the scientists create the best possible atmospheric model of Venus to date.

Source: ESA - News

[Waspie_Dwarf]

Ground - based observatories join forces with Venus Express

23 May 2007

Thanks to ESA's Venus Express, scientists have been revealing new and crucial details about our closest planetary neighbour.

A coordinated ground-based observation campaign will now contribute to the growing body of information on the nature of Venus’s atmosphere and will help put the spacecraft’s observations in a broader context.

Between 23 May and 9 June, tens of scientists, working at a dozen telescopes and observatories spread all over the world, will examine Venus from the ground and perform measurements, some of which are not feasible for Venus Express.

Credits: ESA - C. Carreau


Data from Venus Express, which has been revealing new and crucial details about our closest planetary neighbour, will now be augmented by synoptic data from a coordinated ground-based observation campaign.

This campaign will contribute to the growing body of information on the nature of Venus’s atmosphere and will help put the spacecraft’s observations into a broader context.

Between 23 May and 9 June, scientists working at a dozen telescopes and observatories spread all over the world will examine Venus from the ground and perform measurements, some of which are not feasible for Venus Express.

In the foreground, Venus Express, which is studying the Venusian atmosphere. Venus is like Earth's twin in someways and unlike in many others.

Credits: ESA/Medialab

By applying different techniques and performing measurements at wavelengths that are not within the capabilities of the spacecraft, scientists intend to complement the existing dataset and obtain simultaneous measurements and cross-validation of the spacecraft’s observations.

Thus the ground-based observations - radio, submillimetre, infrared and visible - are very useful for interpretation of Venus Express results.

The main focus of the ground-based observations is on measurements of the atmosphere above Venus’ cloud tops. This will complement Venus Express’ capability to study the cloud layer in high detail and the lower atmospheric altitudes, down to the surface.

Spectroscopy at visible, infrared and submillimetre wavelengths from ground-based observatories will enable direct measurements of the wind and unearth fresh data about the mesosphere and the thermosphere, two atmospheric layers situated above Venus’ cloud deck.

This directly complements Venus Express, which determines wind characteristics by tracking motions of the clouds and studies the distribution of gaseous species and temperatures in Venus’ upper atmosphere.

Following on Venus Express’ investigations, the ground-based observations will perform studies of Venus’ oxygen airglow emission – a phenomenon detectable on the night-side that makes the planet glow – and study the composition of the mesosphere and the deep atmosphere.

The timeframe of the ground-based campaign, which extends from 23 May to 9 June, was chosen for different reasons. The most important reason is the fact that Venus is close to its maximum elongation, that is its maximum angular distance from the Sun as seen from Earth, during this period. This is a favourable position for observations of both its day and night sides from Earth.

The time window also encompasses the Venus flyby of NASA’s Messenger on 6 June at 1:10 CEST, en route to its final destination, Mercury. For one day, Messenger’s observations of Venus will also complement those from Venus Express and ground.


Who is involved?

The telescopes involved in the Venus ground-based observation campaign are:

• CFHT: Canada-France-Hawaii Telescope, Hawaii
• OHP: Observatoire de Haute Provence, France
• VLT: Very large Telescope, Chile
• Observatoire du Pic du Midi, Telescope Bernard Lyot (TBL), France
• IRAM: Institut de Radio-Astronomie Millimetrique, Spain
• IRAM PdB: Institut de Radio-Astronomie Millimetrique: antennae at Plateau de Bures, France
• JCMT: James Clerk Maxwell Telescope, Hawaii
• Nobeyama: Radio Observatory, Japan
• HHT: Heinrich Hertz Submillimeter Telescope Observatory, Arizona, USA
• Kitt Peak National Observatory, Arizona, USA
• IRTF: Infrared facility, Hawaii
• AAT: Anglo-Australian Telescope, Siding Spring Mountain in north-western New South Wales, UK
• Keck telescope (Hawaii)

Ground - based campaigns for previous missions

The Very Large Telescope (VLT) at Cerro Paranal is ESO's premier site for observations in the visible and infrared. All four unit telescopes of 8.2-metre diameter are individually in operation.

Credits: The European Space Agency and the European Southern Observatory

“Previous examples demonstrate the importance of connecting space-borne observations with the synoptic coverage provided by continued ground-based programmes,” said Emmanuel Lellouch, Venus Express Supporting Investigator and coordinator of the ground-based observation campaign.

One of the recent ground-based observation campaigns in support of a scientific mission was conducted during the Huygens probe’s descent and landing on Titan on 14 January 2005. As Huygens parachuted to the surface of Titan, a battery of radio and optical telescopes around the world were watching and listening.

The observations brought in new information on the atmosphere and surface properties of Saturn’s largest moon. They also provided information about the probe’s drift in the winds and thus helped to reconstruct the descent trajectory and the coordinates of the landing site.

Other supporting ground-based observations were successfully performed for other scientific missions such as ESA’s SMART-1 which flew to the Moon and NASA’s Deep Impact which flew to comet 9P/Tempel 1.

There are also a large number of amateur astronomers watching Venus regularly, obtaining excellent images to complement data from observatories. During the current campaign, Venus is particularly bright and thus easily observable, even with small telescopes – for amateurs’ viewing pleasure.


For more information

Emmanuel Lellouch, VEX Supporting investigator, Observatoire de Paris, France
Email: Emmanuel.Lellouch@obspm.fr

Olivier Witasse, ESA Venus Express Deputy Project Scientist
Email: Olivier.Witasse@esa.int

Source: ESA - News

[Waspie_Dwarf]

Venus Express and MESSENGER to look at Venus in tandem

4 June 2007

In the foreground, Venus Express, which is studying the Venusian atmosphere. Venus is like Earth's twin in someways and unlike in many others.

Credits: ESA/Medialab

On 6 June this year, scientists all around the world will be watching with eager eyes as not one but two spacecraft observe Venus simultaneously.

ESA’s Venus Express, in orbit around Venus since 11 April 2006, will be joined for a few hours by NASA’s MESSENGER (MErcury Surface Space ENvironment GEochemistry and Ranging mission), flying by Venus while on its way to Mercury.

Earth-based observatories and telescopes in orbit around Earth will also be watching. Looking at Venus together, spacecraft and ground observatories will obtain a unique set of data each, so many different ‘eyes’ will observe the same regions and phenomena during the same time frame.

This event, coordinated from both sides of the Atlantic, might help us learn some things about Venus that may otherwise be out of reach. Scientists believe that direct and two-point measurements of some planetary phenomena have great potential to offer new science.

On Earth, international teams of ESA’s Venus Express and NASA’s MESSENGER mission are coordinating the observations of Venus as MESSENGER makes its closest approach to Venus during its second fly – by of the planet. This time around, MESSENGER will be in a better condition with respect to its first fly-by, when the planet was behind the Sun, barring all communication with Earth. It will also be a great opportunity for MESSENGER to test its instruments before it reaches its destination.

Geometry and timing of closest approach

ESA’s Venus Express, in orbit around Venus since 11 April 2006, will be joined for a few hours by NASA’s MESSENGER spacecraft, flying by Venus while on its way to Mercury.

Earth-based observatories and telescopes in orbit around Earth will also be watching. Looking at Venus together, spacecraft and ground observatories will obtain a unique set of data each, so many different ‘eyes’ will observe the same regions and phenomena during the same time frame.

Credits: NASA/APL

At the time of closest approach, MESSENGER will be flying over Venus at an altitude of approximately 337 kilometres. Maximum vicinity will be reached at 01:08 CEST on 6 June, above the Venusian coordinates 12.25° South and 165° East.

At this time, Venus Express will be behind Venus, but it will look at the same regions observed by MESSENGER before and after the fly-by. This will allow the scientists to compare data of the same areas obtained by the two spacecraft within only a short difference in time from each other.


Science in tandem

Venus Express and MESSENGER together will carry out observations of Venus’ cloud deck, plasma environment, atmosphere and its oxygen airglow and surface.

At closest approach, MESSENGER will perform direct sounding measurements of Venus’ cloud deck with its laser altimeter instrument (MLA). These will complement the data about the clouds obtained by Venus Express at visible, ultraviolet and infrared wavelengths.

The two spacecraft will also be gathering information about the dynamics of Venus’ atmosphere. In this task, they will be joined by a telescope at the Observatoire de Haute-Provence in France which will also be taking measurements of Venusian winds. This fly-by campaign will also include complementary observations of the oxygen airglow. This is a phenomenon detectable on the night-side and on the dayside and makes the planet glow like a ‘space lantern’.

At the same time, on Earth, the IRTF facility in Hawaii will observe the same phenomenon in the infrared, along with the Apache Point Observatory (APO) (working at visible wavelengths) and the W. M. Keck observatory in Hawaii. The study of the Venusian plasma environment will greatly benefit from the presence of two spacecraft around Venus.

Plasma - a gas of charged particles diffused in space and strongly influenced by solar activity - is a very complex state of matter. Its has a very low density but its scale of distribution around planets is huge. Hence the possibility of a multipoint observation campaign at Venus is a unique asset that helps understand the plasma behaviour around this planet.

The advantage of multipoint plasma measurements has largely been demonstrated by the constellation of Cluster spacecraft studying the plasma environment around Earth and by the Cassini-Huygens and Galileo spacecraft at Jupiter, during the Cassini-Huygens flyby of the Jovian system in late 2000.

After about 30 hours after closest approach, MESSENGER will have concluded its observation campaign of Venus, ready for its next and final target: Mercury. During the fly-by, instruments on Venus Express will be operated so as to maximize the synergy between the two spacecraft.

ESA’s Venus Express, in orbit around Venus since 11 April 2006, will be joined for a few hours by NASA’s MESSENGER spacecraft, flying by Venus while on its way to Mercury.

Earth-based observatories and telescopes in orbit around Earth will also be watching. Looking at Venus together, spacecraft and ground observatories will obtain a unique set of data each, so many different ‘eyes’ will observe the same regions and phenomena during the same time frame.

Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Meanwhile, Venus Express will continue its unprecedented study of this intriguing planet, ready for its next discoveries.

As you read this, Venus is still bright in the evening sky.


Notes:

Venus Express, ESA’s first mission to Venus was launched on 9 November 2005 and reached the planet on 11 April 2006.

NASA’s MESSENGER, launched on 3 August 2004, will fly by Venus for a second time on 6 June 2007 on its way to Mercury. It is expected to reach its destination in March 2011.


For more information:

Håkan Svedhem, ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int

Sean Solomon, NASA Principal Investigator for the MESSENGER mission
Email: Scs @ dtm.ciw.edu

Olivier Witasse, ESA Venus Express deputy Project Scientist
Email: Olivier.Witasse @ esa.int

Source: ESA - News

More on the MESSENGER Venus fly-by and other news on the mission can be found in this thread.

[Waspie_Dwarf]

Venusian rendezvous results: chapter one

13 July 2007

As NASA’s MESSENGER departed from planet Venus on 5 June 2007 to continue its journey towards Mercury, its Wide Angle Camera captured a sequence of 50 images (480-nm wavelength filter) showing the planet disappearing in the distance. At the start of the sequence MESSENGER was 60 688 kilometres from the planet, by the end it was at 89 310 kilometres. Initially, images were acquired at a rate of one of every 20 minutes and then, as Venus shrank, the timing interval was increased to 60 minutes.

As well as allowing a joint observation campaign of the planet with ESA’s Venus Express, the Venus flyby provided the MESSENGER mission operations team an opportunity to complete successfully a full test of the complicated series of spacecraft motions required to build up high-resolution image mosaics at Mercury.

Mariner 10 imaged only one hemisphere of Mercury in 1974-75. During the upcoming flyby, in January 2008, the MESSENGER instruments will photograph and make measurements of half of the hemisphere viewed by Mariner 10 and half of the hemisphere never before imaged by spacecraft. MESSENGER will capture the rest of the planet in subsequent flybys in October 2008 and September 2009. In March 2011 MESSENGER will be inserted into orbit about Mercury, allowing detailed observations of the planet for a full Earth year.

Credits: NASA/APL

ESA’s Venus Express and NASA’s MESSENGER booked an appointment at Venus late in the evening of 5 June, to look at the oddities of this mysterious planet in tandem for a few hours. Just a few weeks on, scientists from both teams are ready to present a first set of images.

This unique opportunity to make multi-point observations of the Venusian atmosphere was possible thanks to the MESSENGER (MErcury Surface, Space ENvironment, Geochemistry, and Ranging) swingby of Venus – a key step during its long journey to Mercury - while Venus Express was already orbiting the planet in the course of its mission.

The two spacecraft carry sets of instruments employing different observation techniques which complement each other. The data collected at Venus are now being analysed by teams on both sides of the Atlantic and, as can be appreciated in the first images presented here, already hints at the potential of the results to come.

The particular orbital geometry of Venus Express when MESSENGER skimmed past Venus on 5 June meant that the two spacecraft were not at the same location (with respect to the surface of the planet) at the exact same time.

This grey-scale image, obtained by the VIRTIS instrument on board ESA’s Venus Express, shows the atmospheric region of Venus over flown by NASA’s MESSENGER on 5 June 2007. The region of MESSENGER’s closest approach is in the night side (marked by a circle).

VIRTIS obtained this image at 2.3 microns from about 35 000 kilometres from the planet, on the night side. This wavelength makes it possible to probe the atmosphere down to about 30 kilometres from the surface. Much of the contrast in this image is due to the structure of the lower clouds.

The bright areas correspond to radiation coming from the lower atmospheric layers, indicating that the clouds are less thick in those areas. At the 2.3 micron wavelength it is possible to study not only the morphology of the cloud layers, but also its chemical composition (carbon monoxide, water, sulphur-dioxide, etc).

A not annotated version of this image and one indicating the planetary latitude can be downloaded here [ VI410_01_23_no_layers.gif, VI410_01_23.gif]

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

MESSENGER made its closest approach at a distance of about 338 km from the planet over the planetary coordinates 12.25° South and 165° East, on the night side of the planet. Meanwhile, Venus Express was behind the horizon, almost right above the South Pole, at about 35 000 km from Venus.

So how could they make true joint observations of the same regions and phenomena? Scientists came up with a highly creative solution.


Two hunters for the same cloud

The scientists used a computer simulation based on real atmospheric data about Venus obtained from previous ground and space observations. Knowing the speed of the local winds, which depend both on the altitude and the latitude, they were able to predict where a particular set of clouds would be at a given point in time.

For their observation, the Venus Express scientists selected a cloud that – moving west by about 90° longitude every day - was visible to Venus Express and would be in view of MESSENGER 12 hours later, at the time of its closest approach. The same cloud became visible again for Venus Express 12 hours after MESSENGER’s closest approach, this time on the night-side.

The images in this panel were obtained by the VIRTIS imaging spectrometer on board Venus Express on 5 and 6 June 2007, before and after MESSENGER’s closest approach to the planet. The panels provide a night-side view of the same region flown over and imaged by MESSENGER (top row) and the same cloud observed by MESSENGER (bottom row).

The images where obtained at 1.7 micron, revealing atmospheric details down to 50 kilometres altitude from the surface.

Two stills from this images composite can be downloaded here [VI0410_00_prj_17.tif, VI0411_03_prj_17.tif]


Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

The VIRTIS imaging spectrometer on board Venus Express probed this cloud (top row of this image composite) at several wavelengths. These observations provided a view of the cloud at about 45-50 km altitude (bottom row) from the planet. The clouds above the point of closest approach can be seen in the top row.

The Mercury Laser Altimeter (MLA) instrument on board MESSENGER probed the same cloud structure at 50-75 km from the surface, like VIRTIS.

Such an observation – a typical example of atmospheric structure at Venus – with cross-sections obtained at different altitudes and with different instruments, is a unique opportunity for researchers hoping to solve the puzzle of the Venusian atmosphere’s dynamics and composition.

This movie consists of a sequence of 6 images obtained by the VIRTIS imaging spectrometer on board ESA’s Venus Express on 5 and 6 June 2007, before and after NASA MESSENGER’s closest approach to the planet.

The panels provide a night-side view of the same region over flown and imaged by MESSENGER (first three images) and the same cloud observed by MESSENGER (last three images).

The images where obtained at 1.7 micron, revealing atmospheric details down to 50 kilometres altitude from the surface.

A composite containing the six images featured in this video can be downloaded here [ORB410_411_tot.tif]


Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

Over about 24 hours, not only did the two spacecraft observe the same clouds, but MESSENGER also flew closely over the atmospheric region. Again, these dual-spacecraft, multi-instrument observations may provide additional atmospheric details.

A ‘thermal’ map of the Venusian surface obtained by VIRTIS on 5 June 2007 (left) is compared here with a radar image of the same area obtained by NASA’s Magellan spacecraft in the 1990s (right).

VIRTIS, the imaging spectrometer on board Venus Express, obtained this image at 1 micron, a wavelength that allows detection of radiation originating from the surface. The imaged region is the same as flown over by NASA’s MESSENGER when the spacecraft made its closest approach to the planet.

Magellan’s radar imaging and altimetry maps made it is possible to measure the elevation and the radio-optical properties of the surface. Venus Express’ VIRTIS is providing the first complete set of ‘thermal maps’ of the surface of Venus. Correlations between topographic and thermal data similar to the ones shown in this image-composite will allow the scientists to understand if the measured temperature of the surface only depend only on the altitude – where ‘higher’ simply corresponds to ‘colder’, like on Earth – or if it depends on the presence of previously undetected sources of heat such as active volcanoes.

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA

A spectacular view obtained by VIRTIS (left), in the region of MESSENGER's closest approach to Venus provides, even if still unprocessed, a ‘thermal view’ of the Venusian surface. The image is compared here with an image of the same feature synthesized by data from NASA’s Magellan spacecraft in the 1990s (right).

Magellan provided radar imaging and altimetry maps, providing information on the topography (elevation) and the radar reflectivity of the surface. Venus Express’ VIRTIS is providing ‘thermal maps’ of the surface containing information on the emissivity in the infrared. Correlations between topographic and thermal data similar to the ones shown here, will allow scientists to understand if the measured temperature of the surface depends on the altitude – where ‘higher’ simply corresponds to ‘colder’ – or if it depends on the presence of previously undetected sources of heat, such as active volcanoes or other geological activities.

The Venus Express and MESSENGER scientists are now continuing the analysis of this rich and complex set of data collected at Venus. The data also involve several other instruments studying not only Venus’ cloud deck and surface, but also the plasma environment, magnetic fields, and the atmospheric oxygen airglow.

More mature results from this joint observation campaign are expected by the end of the year.


Notes

Venus Express, ESA’s first mission to Venus was launched on 9 November 2005 and reached the planet on 11 April 2006.

NASA’s MESSENGER was launched on 3 August 2004, and swung by Venus for the second time on 5 June 2007 on its way to Mercury. It is expected to be inserted into Mercury orbit in March 2011.


For more information

Håkan Svedhem, ESA Venus Express Project Scientist
Email: Hakan.Svedhem @ esa.int

Sean Solomon, Principal Investigator for the NASA MESSENGER mission, Carnegie Institution of Washington
Email: scs @ dtm.ciw.edu

Giuseppe Piccioni, VIRTIS co-Principal Investigator, IASF-INAF, Rome, Italy
Email: Giuseppe.Piccioni @ iasf-roma.inaf.it

Pierre Drossart, VIRTIS co-Principal Investigator, Observatoire de Paris, France
Email: Pierre.Drossart @ obspm.fr

Source: ESA - Venus Express

[Waspie_Dwarf]

Up, Up and Away -- To Venus

August 27, 2007

Scientists hope to learn more about climate changes here on Earth by studying Venus. A prototype balloon could eventually study the planet’s surface and examine its atmosphere and the bizarre winds and chemistry within it. A team of JPL, ILC Dover and NASA Wallops Flight Facility engineers designed, fabricated and tested the balloon.


+ Larger image
A prototype Venus balloon in a JPL cleanroom.
Image credit: NASA/JPL-Caltech

Slightly smaller than Earth, Venus is often regarded as Earth's sister planet. Both have similar densities, chemical compositions and gravities. However, its atmosphere is nearly 100 times thicker than Earth's, which causes blazing temperatures at the surface. By flying in the cool skies above Venus, the balloons would avoid that environment.

"The surface is hot enough to melt lead, which is why we can't study it for long from a lander," said Kevin Baines, JPL principal investigator for a proposed mission to Venus. "Without extreme and costly refrigeration methods, a lander would cook at those temperatures in just a few hours, but a balloon can stay in a benign environment, studying the planet for days, weeks or even months."

The spherical balloon, 18 feet in diameter, is about the size of an inflatable children's jumper. Its aluminum coating reflects sunlight to protect the balloon from becoming too hot as it flies in Venus’ upper atmosphere. Its outer transparent layer of the balloon is made of polytetrafluorethylene, also known as Teflon, the non-stick material found in cookware and on clothing. The material is highly resistant to the sulfuric acid found in clouds surrounding Venus. “The sun shines through the Teflon and reflects off the aluminum, and that keeps the balloon from overheating,” said Jeff Hall, JPL's lead balloon engineer.

The balloon's second layer has a mylar film similar to those shiny helium balloons found in a grocery store. The mylar is used to prevent gas from leaking out. The next layer is made of a Vectran fabric that provides the strength to keep the balloon from bursting due to internal pressure. The innermost layer has a polyurethane coating that enables all sections of the balloon to be glued together.

More details about the design, fabrication and testing of the balloon are reported in a paper published in the journal Advances in Space Research..

The proposed mission would have two balloons, one at a tropical latitude, the other at a polar latitude. Each helium-filled balloon would fly about 56 kilometers (about 35 miles) above Venus' oven-hot surface, in temperatures about the same as a spring afternoon in Los Angeles. It would take about four days for the helium superpressure balloons to fly completely around the planet. After the balloons are launched from Earth, they would arrive on the night side of Venus.

"The winds at that altitude are very strong, more than 320 kilometers per hour (about 200 miles an hour), and will blow the balloons around the planet," Hall said. "Engineers would not have control of where the balloons travel. Once the balloon starts flying, it is totally dependent on the winds."

Each balloon would have quite a roller coaster ride, moving up and down about a half a mile in altitude as they ride gravity waves generated by Venus’ mountainous terrain.

"This was one of the surprises of the Vega balloon mission the Soviet Union flew more than two decades ago," Baines said. "Enormous gravity waves appear to rise up more than 30 miles into the upper atmosphere, causing unexpected depositions of energy generated at the surface and producing strong vertical movements of air. We want to ride these waves, measuring their effect on Venus' bizarre high-speed winds."

Scientists believe the Venus balloons could also help us learn more about climate changes here on Earth. “Venus is a place where global warming has gone amuck,” Hall said. “It’s about the same size as our planet, but the surface is about 900 degrees Fahrenheit, and we want to find out why.”

Scientific instruments aboard the balloons would analyze the composition of Venus' atmosphere. The pressure cooker atmosphere around Venus quickly changes and is filled with specific gases, such as helium and neon, which do not interact chemically with other materials, allowing researchers to trace the formation of Venus over time. Noble gases can help scientists determine the geological history of the planet, which could lead to answers about current climate changes.

"Those gases will tell us if Venus and Earth were twin planets. Indications from previous missions suggest that Venus and Earth were quite similar at the beginning," Baines said.

Various studies indicate Venus once had oceans of water much like those on Earth, but now the planet is dry. According to Baines, Venus began as an oasis with conditions favorable for life in its first billion years. "Venus now has an extreme climate. It changed from being wet and wild, to dry and dead, and it seems to have happened in the last three billion years. We'd like to find out how this global transformation happened."

The current explanation for the dry atmosphere and extremely hot surface temperature is that Venus does not have a magnetic field to provide protection from solar winds. Those winds smash into the top of the atmosphere and drag off hydrogen that is needed for water.

A payload weighing more than 40 kilograms (about 90 pounds) would fly with each balloon to help transmit data back to Earth. Included in this payload would be a flight computer, radio transmitter and 9 kilograms (20 pounds) of electric batteries to power the equipment. Also included is a suite of science instruments:

• A gas chromatograph mass spectrometer to measure the amounts of gases on Venus and to sniff for volcanic smoke.
  
  
• An atmospheric structure instrument would measure the pressures and temperatures of the atmosphere and the vertical winds as the balloons bob up and down. This instrument also includes a nephelometer instrument to measure the size and density of cloud particles through light reflections.
  
  
• A lightning detector to measure the power and frequency of nearby lightning strikes in the atmosphere.
  
  
• A microphone to record any nearby sounds in the atmosphere, including thunder.

Ground-based radio telescopes using an interferometric technique would be used to measure how each balloon moves around the atmosphere. "We'd be able to tell its velocity within one inch per second of movement over an hour," Baines said. The telescopes would also use the Doppler effect to complete a set of 3-D measurements of each balloon's movements.

The company that built the airbags for the Mars Exploration Rover mission, ILC Dover, Frederica, Del., also helped design and build the balloons. The balloons are folded into small packages to fit inside the launch rocket that also include high pressure helium tanks and valves. Once the balloons reach the planet, the heavy tanks would drop away so the balloon could float away.

The balloon mission would likely end one of two ways: it might run out of battery power, when the balloons would be unable to communicate with ground controllers, or if a balloon develops a leak, it would eventually lose altitude and overheat the payload until it stops working. Hall and his team of engineers in JPL’s Aerobot laboratory have tested the prototype and determined it can float for up to 12 days without leaking any helium gas. A 12-day flight would be long enough to allow the balloons to circumnavigate the planet three times.

Media contact: DC Agle/JPL
818-393-9011

Source: NASA/JPL - Feature Stories