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| Ultimi arrivi - Venus |
South_Polar_Vortex-00.jpgVenusian South Polar Vortex (1)55 visiteOriginal ESA caption:"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".Lug 16, 2006
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South_Polar_Region-InfraRed-2.jpgVortexes at the South Pole of Venus (infrared) - frame 253 visiteThese 6 (4 in the previous frame plus 2 in this frame) different infrared images (in false colour) were taken by the 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 - frame 1: 12 April, from 210.000 Km; top centre - frame 1: 13 April, from 280.000 Km; top right - frame 2: 14 April, from 315.000 Km; bottom left - frame 1:16 April, from 315.000 Km; bottom centre - frame 1: 17 April, from 270.000 Km; bottom right - frame 2: 19 April, from 190.000 Km), while the spacecraft moved along a long ellipse around the Planet. Lug 04, 2006
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South_Polar_Region-InfraRed-1.jpgVortexes at the South Pole of Venus (infrared) - frame 154 visiteHigh 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?
"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.Lug 04, 2006
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Venus-South Pole-PioneerVenus_South%20PoleVortex_H.jpgThe South Pole of Venus (again)60 visiteThese 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.
Lug 04, 2006
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Venus-South Pole-Infrared-COB_combi_38b.jpgVortex over the South Pole of Venus (infrared vision)59 visiteDuring 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.
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.
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 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.
Lug 04, 2006
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Venusian_Clouds-Venus_Express-VOI_composit.jpgVenusian cloud structures: day-side and night-side53 visiteThe early infrared image making use of the windows, show complex cloud structures, all revealed by the thermal radiation coming up from different atmospheric depths. In this colour scheme, 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 Venusian 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 (O2) in the upper atmospheric layers. In fact, Venus Express has already spotted the presence of an Oxygen 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.
Lug 04, 2006
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8-Venus_from_Venus_Express-VIRTIS_COB05_vis_397_b.jpgVenus, from Venus Express (natural colors)78 visiteCaption ESA originale:"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. 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 Km altitude". Lug 03, 2006
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Venusian_Surface-Venera_09-000.jpgVenera 9: the Spacecraft65 visiteGiven the intense temperatures and pressures of Venus, it is indeed impressive that Russian engineers were able to successfully land vehicles there 10 times during the 1970s and 1980s. These were Venera 7 to 14, and Vega 1 and 2 which deployed landers and balloon-born instrument packages. Although not designed to land, one of the free-falling Pioneer atmosphere probes gets honorable mention by surviving impact and continuing to transmit for a few minutes. The atmosphere of Venus is so thick that terminal velocity was only about 30 mph.
Seen above, the six-foot-tall Venera 9 lander was the first to take pictures of the surface, on October 20, 1975. The Venera orbiter and lander was a 10,000-pound spacecraft, one of the largest unmanned vehicles ever sent into space. Besides the camera system, the Venera landers measured the sky spectrum, atmospheric gases, cloud particles, and performed chemical analysis of surface rocks.
Looking out through 1 cm quartz pressure windows, Venera 9 to 14 captured spherical panoramas of 40º by 180º. The cameras used a pivoting mirror and photomultiplier tube, giving remarkably low-noise images which were digitized to 9 bits per pixel. Venera 13 and 14 had two cameras and were able to capture images though clear, red, green and blue filters. So some portions of their panoramas contain color information. Venera 11 and 12 were unable to return pictures because of an equipment failure, but the rest of their experiments were successful.
These images have often been displayed as very poor quality pictures taken off film or even photographed off printed pages of Soviet journals. The images I show here are derived from the digital telemetry by the Russian image processing team. In the case of Venera 9 and 10, I undid a pixel replication and replaced it with a higher quality interpolation filter. For Venera 13 and 14, I combined the chroma signal from the dark somewhat noisy color images with the luminance signal of the clear-filter images.
Venera 13 and 14 survived longer than expected and returned dozens of images, repeating their program of clear and color scans. I hope to process that data into a super resolution image and to recalculate the perceptual color values.
Lug 03, 2006
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Venus-South_Pole-04.jpgVenus' South Pole (UV)60 visiteIn the 1st capture orbit, Venus Express will have 5 more 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 June, 4, 2006, when the range of distances from the Planet will be much smaller. 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 2 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.Apr 13, 2006
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Venus-South_Pole-05.jpgVenus' South Pole (UV)63 visiteFalse-colour view imaged in ultraviolet of Venus' South pole captured by VMC - onboard Venus Express - on April, 12, 2006.Apr 13, 2006
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South_Polar_Regions-2.jpgHot vortex over Venus' South Pole59 visiteESA's Venus Express has returned the first-ever images of the hothouse Planet’s South Pole from a distance of 206.452 Km, showing surprisingly clear structures and unexpected detail. The images were taken on April 12, 2006, during the spacecraft’s initial capture orbit after successful arrival on the 11th.
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.”Apr 13, 2006
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A-Venus.gifThe Phases of Venus (2) - GIF107 visiteCaption originale:"Venus goes through phases. Just like our Moon, Venus can appear as full as a disk or as a thin as a crescent. Venus, frequently the brightest object in the post-Sunset or pre-Sunrise Sky, appears so small, however, that it usually requires binoculars or a small telescope to clearly see its current phase. The above time-lapse sequence, however, was taken over the course of many months and shows not only how Venus changes phase but how it's apparent angular size also changes. In the middle negative image, Venus is in a new phase, the same phase that occurred during its rare partial eclipse of the Sun in 2004".Gen 10, 2006
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