Closing in on Venus
BY DR EMILY BALDWIN
ASTRONOMY NOW

Posted: July 18, 2008

Unexplored regions of Venus will soon be within the reach of Venus Express, which is executing a series of manoeuvres this week to gradually bring it closer to its host planet.

Artist impression of Venus Express swooping over the planet's cloud tops. Image: ESA

Venus Express has been studying largely unknown phenomena in the Venusian atmosphere for over two years, along with the interaction between the solar wind and the planetary environment. Until now, Venus Express has occupied a highly eccentric polar orbit, swooping by the north polar regions at a distance of 250-400 kilometres, and slingshotting around the south polar regions at 66,000 kilometres. This enabled close up views of the global dynamics on the northern hemisphere, and extended observations of south pole phenomenon, such as the evolution of the South Polar Vortex.

By 4 August, the spacecraft will be settled into its new orbit at an altitude of 185-300 kilometres. This modification will enable an in depth study of the magnetic field and the plasma environment deeper in the ionosphere than previously possible.

Close up view of the double-eyed vortex at Venus's south pole. The brighter colours indicate more radiation is coming from the hot layers below. Many intricate sub-structures are visible in the vortex. Image: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA.

In a more ambitious strategy, the spacecraft will be dragged through the thick atmosphere, in order to measure its density and to learn more about drag on the spacecraft's body, which will be measured by the onboard accelerometers. As the next step, Venus Express may test aerobraking, a technique where a spacecraft uses the force exerted by the planet's atmosphere to decelerate, thus significantly changing its orbit, but in a controlled manner.

More about the Venus Express mission can be found on the dedicated pages of the ESA website.