ESA - Venus Express

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Thanks to data from Venus Express we have the best idea yet of how Venus' atmosphere works, but there is still a long way to go, delegates at this year's International Venus Co...........

Venus Express latest release.

Andrew Brown.


SDC : Lightning on Venus Strikingly Similar to Earth's
By Staff

posted: 22 September 2010
06:49 pm ET

Lightning on Venus and Earth may spark in much the same way despite vast differences in the atmospheres of the two planets, scientists say.

"Venus and Earth are often called twin planets because of their similar size, mass and interior structure," said Christopher Russell, lead author of the new lightning study and a professor at the University of California, Los Angeles." The generation of lightning is one more way in which Venus and Earth are fraternal twins."

Russell and his colleagues used new data from Venus Express to show that lightning is similar in strength on Earth and Venus at the same altitudes on both worlds.

"We have analyzed 3.5 Earth-years of Venus lightning data using the low-altitude Venus Express data (10 minutes per day)," Russell said. "By comparing the electromagnetic waves produced at the two planets, we found stronger magnetic signals on Venus, but when converted to energy flux we found very similar lightning strength."

The data also show that lightning is more prevalent on the planet's dayside than at night, and occurs more often at low latitudes, where the solar input to the atmosphere is strongest.

These results will help scientists better understand the chemistry, dynamics and evolution of the atmospheres of the two neighboring planets. Russell will present the findings tomorrow (Sept. 23) at the European Planetary Science Congress in Rome. : European Planetary Science Congress 2010
The European Planetary Science Congress (EPSC) 2010 will take place at the Angelicum Centre – Pontifical University of Saint Thomas Aquinas, Rome, Italy, from Sunday 19 September to Friday 24 September 2010.

The EPSC is the major European meeting on planetary science and attracts scientists from Europe and around the World. Around 550 scientists are expected to attend EPSC 2010. The programme comprises 48 sessions and workshops covering a wide range of planetary topics.


Guest : Venus Express finds planetary atmospheres such a drag
7 October 2010

The polar atmosphere of Venus is thinner than expected. How do we know? Because ESA’s Venus Express has actually been there. Instead of looking from orbit, Venus Express has flown through the upper reaches of the planet’s poisonous atmosphere.

Venus Express atmospheric drag measurements :
SpaceFellowship | October 07, 2010
This animation demonstrates the orbital perturbations to Venus Express caused by the atmospheric drag experienced as the spacecraft skims the atmosphere of Venus. To experience the drag, the spacecraft must pass the planet at altitudes below 200 km.

The orbital perturbation results in a shrinking of the elliptical orbit of Venus Express. The farthest point from the planet lowers and the orbit becomes slightly more circular. This effect has been exaggerated in the animation.

Venus Express went diving into the alien atmosphere during a series of low passes in July–August 2008, October 2009, and February and April 2010. The aim was to measure the density of the upper polar atmosphere, an experiment that had never been attempted before at Venus.

The campaign has returned 10 measurements so far and shown that the atmosphere high above the poles is a surprising 60% thinner than predicted. This could indicate that unanticipated natural processes are at work in the atmosphere. A team led by Ingo Mueller-Wodarg of Imperial College, London, are currently investigating.

The density is critical information for mission controllers, who are investigating the possibility of driving the spacecraft even lower into the atmosphere in order to change its orbit and extend the lifetime of the mission.

“It would be dangerous to send the spacecraft deep into the atmosphere before we understand the density,” says team member Pascal Rosenblatt, Royal Observatory of Belgium.

Venus Express does the twist
SpaceFellowship | October 07, 2010

This animation shows the alignment of the solar panels that makes Venus Express twist in the upper atmosphere of Venus. It is known as the torque technique and allows scientists to measure the density of the atmosphere at the North Pole of Venus, which Venus Express can be made to skim.

The technique requires the solar panels on board Venus Express to be positioned at an angle to each other. The effect is maximum when the angle corresponds to 90 degrees, with one of the panels perpendicular to the incoming flow and the other seeing it edge on.

Due to this difference, the atmosphere causes the spacecraft to turn. Instruments called reaction wheels inside Venus Express compensate for the twist, keeping the spacecraft in the right attitude. The readings from the reaction wheels are recorded so that scientists on Earth can translate them into a density estimate.

The fact that Venus Express can make these measurements at all is remarkable. The spacecraft was not designed for it and so does not have instruments capable of directly sampling the atmosphere. Instead, radio tracking stations on Earth watch for the drag on the spacecraft as it dips into the atmosphere and is decelerated by the Venusian equivalent of air resistance.

In addition, operators at ESA’s European Space Operations Centre in Darmstadt, Germany, turned one solar wing edge-on and the other face-on so that air resistance would twist the spacecraft.

Venus’ atmosphere extends from the surface up to an altitude of around 250 km. During April, Venus Express briefly skimmed down to 175 km above the planetary surface.

As well as the surprisingly low density overall, the twisting of the spacecraft has also registered a sharp density change from the day to the night side of the planet. Next week, Venus Express will go diving again, this time lowering itself to 165 km.

Venus's polar vortex

These measurements may be used eventually to help make changes to the orbit of Venus Express, halving the time it takes to circle the planet and providing new opportunities for additional scientific measurements.

The current elliptical orbit takes 24 hours to complete and loops from 250 km to 66 000 km. When Venus Express is far away from the planet, it is pulled off course slightly by the Sun’s gravity. So, every 40-50 days, its engines must be fired to compensate. The fuel to do this will run out in 2015 unless the orbit can be lowered using the drag of Venus’ atmosphere to slow the spacecraft. It is a delicate, potentially dangerous operation and cannot be rushed.

“The timetable is still open because a number of studies have yet to be completed,” says Håkan Svedhem, ESA Project Scientist Venus Express. “If our experiments show we can carry out these manoeuvres safely, then we may be able to lower the orbit in early 2012.”

In the meantime, Venus Express may be feeling it’s all a bit of a drag, but the science teams involved are happier than ever with their new data. “We couldn’t see this region with our instruments because the atmosphere was too thin to register, but now we are sampling it directly,” says Dr Mueller-Wodarg.
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