How Venus Express Will Hit The Target

European Space Agency probe Venus Express is en route to the green planet...
19 March 2006

Interview with 

Daniel Scuka, ESA




Daniel Scuka - As we speak, the European Space Agency's Venus Express is en route to its namesake destination in one of Europe's most ambitious planetary expeditions ever. Venus Express will spend 500 earth days in orbit aiming to unlock the hellish secrets of the planet's runaway greenhouse effect, atmospheric collapse and possibly still - active volcanoes. But before any orbit science can begin, Venus Express has to get there and navigating the space craft through more than 400 million kilometres of interplanetary space is one of the most difficult and mathematically challenging aspects of the voyage. It's a devilishly difficult problem as computations must take into account all sources of gravity working on the space craft. These include not only the Earth and Venus, but also the sun and other planets in our solar system. ESA scientists use good old fashioned classical physics, first clarified by Newton, Kepler and others some 400 years ago. Rudiger Cramm is a flight dynamics engineer on the Venus express team at ESA's Spacecraft Operations Centre in Darmstadt, Germany.

Rudigar - The fundamentals in classical physics is still applicable. We also have to consider effects of relativity but the main principles are all from Newton and Kepler.

Daniel - Venus Express travels to its destination following a three-part trajectory, first starting with launch, ending with escape velocity from our own planet.

Rudiger - The launcher gave us velocity high enough to escape from the Earth. The second and main part is the transfer part. The spacecraft now moves mainly under the influence of the sun for about five months until we reach Venus.

Daniel - As Venus Express approaches the planet on April 11th, it will be travelling at the incredible speed of almost five kilometres per second, with respect to Venus. This is about five times faster than a machine gun bullet. It will have to slow down by about 25% of that speed to be captured by Venus' gravity.

Rudiger - The situation there is similar to playing golf. When you play a golf ball too hard, the ball will slipover the hole. To avoid this with our spacecraft we have to perform a breaking manoeuvre and Venus can capture the spacecraft.

Daniel - The aim is to end up in a 24-hour orbit around the hothouse planet. The risk is that if any problems occur, the spacecraft could miss its window for capture, making its recovery extremely challenging. Join us again next week as we join engineers working on ESA's network of ground tracking stations to learn more on how mission control send commands to spacecraft in deep space and how data that Venus Express gathers will be returned to scientists here on Earth. For the European Space Agency, I'm Daniel Scuka...


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