ESA's Venus Express to Aerobrake

After eight years in orbit, the European Space Agency's Venus Express is ready for a new challenge, a possible mission ending aero braking phase that could provide engineers with mass and fuel saving options in the design of future planetary probes.

 

 

Artist's concept of Venus Express during the aerobraking phase.  ESA

 

That phase is scheduled to begin June 18 and extend through July 11. If the 1,500 pound spacecraft survives dip after dip into the torrid, turbulent conditions, Venus Express may return to operational altitudes to continue probing the secrets of the Earth's cloud shrouded twin -- if only for a few more months.

"It is only by carrying out daring operations like these that we can gain new insights, not only about usually inaccessible regions of the planet's atmosphere, but also how the spacecraft and its components respond to such a hostile environment," said Patrick Martin, Venus Express mission manager, in a May 16 statement announcing  an end to routine science operations.

The close out was driven by declining propellant levels.

Venus Express launched from the Baikonur Cosmodrome in Kazakhstan atop a Soyuz/Fregat on Nov. 9, 2005, to start a $300 million exploration campaign -- as valued in current year terms.  Since maneuvering into orbit around Venus five months later, the spacecraft's seven instruments have streamed back findings that point to remarkable similarities with and differences from Earth.

As is the Earth, Venus is losing parts of its upper atmosphere to space. The loss, as measured by Venus Express, is twice as much hydrogen as oxygen, suggesting that native water is breaking up in the Venusian atmosphere. The quantity of water of Earth is calculated at 100,000 times that of Venus. Because the two planets are roughly equivalent in size and of similar age, they volume of water on the two planets was likely similar after they formed, scientists believe.

NASA's 1989 Magellan mission to Venus, which concluded 20 years ago, revealed a rugged surface altered by large numbers of volcanoes in the past. 

Venus Express, however, has raised prospects of current day volcanic activity, with findings of activity as recent as 2.5 million years ago.

Large variations in the levels of sulphur dioxide in the planet's atmosphere suggest, though, that Venus may host active volcanoes to this day.

 

 

Artists concept of lighting on Venus. ESA

 

On the planet's surface, temperatures at Venus top 450 degrees C, which is likely why it seldom surfaces as a candidate for colonization. At the South Pole, a vortex in the planet's already turbulent atmosphere swirls like a hurricane on the Earth. Lightning is a feature of the chemically charged Venusian atmosphere.

"Venus Express has taught us just how variable the planet is on all timescales and, furthermore, has given us clues as to how it might have changed since its formation 4.6 billion years ago," according to Håkan Svedhem, the ESA project scientist. "This information is helping us decipher how Earth and Venus came to lead such dramatically different lives, but we've also noticed that there are some fundamental similarities."

ESA's aero braking strategy will take the probe out of a highly elliptical 24 hour orbit that takes it 66,000 kilometers above the South Pole for global views before dropping to 250 kilometers over the North Pole, where it flies close to the top of the atmosphere.

Durign the braking phase, the spacecraft will plunge within 165 kilometers of the surface, perhaps as close as 130 kilometers.