FLUG REVUE January 2006: Venus Express launched

January 2006

VENUS EXPRESS IS ON THE WAY

By Matthias Gründer

As Mars Express continues to send inspiring images back to Earth from the Red Planet, European scientists are planning to take a look below the veil of Venus. They expect to gain an insight into a world that is hostile to life.

Venus Express (Artist Impression)

Our knowledge of our planetary neighbour which lies between us and the Sun is very limited. Up to the 1950s scientists and sci-fi writers were still agreed that Venus was a genuine sister planet to our old Earth, capable of supporting life and possibly even inhabited. The only problem was that it was impossible to find anything out about the planet's surface structure as even the most powerful telescopes on Earth were not capable of penetrating the dense cloud cover that envelops Venus. But this only inspired the imagination of writers, painters and film makers all the more, while more down-to-earth planetologists had to wait for some hard facts to emerge.

Both sides experienced a rude awakening when on 12 June 1967, after several failed attempts, a Soviet space probe named Venera 4 finally penetrated the thick fog of cloud, dropped gently onto the surface and sent the first solid data about the planet back to Earth: the 465ºC surface temperature and an atmospheric pressure 90 times higher than ours put paid to even the most daring dreams of contact with alien life forms amidst the storms of Venus.

In succeeding years another 20 explorer probes, 14 Soviet and six American, were launched from Earth and either flew directly to Venus or else flew past it. Most of them only confirmed and restated the initial measurements to a greater degree of precision, while a few of them also sent somewhat limited images suggestive of an incandescent, rocky landscape back to Earth. But the high atmospheric pressure and temperature ensured that these measuring devices soon gave up the ghost. It was not until 4 May 1989 that the NASA-launched Magellan space probe finally succeeded in radar mapping 95% of our planetary neighbour, and the 75m resolution images it took revealed a surface pitted with vast craters and consisting predominantly of basalt. As befitted the enormous environmental temperature, the specialists on Earth elected to have the imagery presented in shades of red and yellow, so that we gained a glimpse of a terrible, stormy, incandescent landscape covered with lava flows. Certainly not a place to support life.

But scientific interest in Venus continues unabated. After all, along with Mercury and Mars it is one of a group of planets similar to Earth in having a solid surface, as compared with the gaseous giants and finally the transuranic elements with their endless icy deserts far out in the universe. Only if we explore them thoroughly will we find out where our origins lie, and how first the universe, then our solar system and finally life itself came about. To further this cause, on 11 July 2002 ESA's Scientific Programme Committee resolved to conduct mission Venus Express with a space probe whose architecture would be similar to that of Mars Express, thus keeping development and operating costs down to an acceptable level, €82.4 million.

According to the scientific programme, after only 162 days' flying time, the space probe will begin exploring the atmosphere of Venus and continue searching for clues as to its structure, composition and dynamics, for two Venus years (equivalent to 500 days on Earth). From a pronouncedly elliptical polar orbit at an altitude of between 250 and 66,000km the following devices will be used to furnish data enabling scientists on Earth to draw conclusions regarding long-term climatic evolution on Earth:

PFS (High Resolution Infrared Fourier Spectrometer, Italy) – this will accurately measure the temperature at altitudes of between 55 and 100 kilometres and also on the surface. This should make it possible to search for volcanic activity.
SPICAV/SOIR (UV and IR Spectrometer for solar/stellar occultation and Nadir Observations, France) – this will search for traces of water, which is suspected despite the heat in the atmosphere, and for sulphur compounds and molecular oxygen. At the same time, density and temperature are to be ascertained at altitudes of between 80 and 180 kilometres.
VIRTIS (UV-visible-near IR imaging spectrometer, France) – this will investigate the composition of the lower atmosphere in layers of cloud at an altitude of between 35 and 40 kilometres by sampling the ultraviolet and infrared wavelengths.
ASPERA (Analyser of Space Plasma and Energetic Atoms, Sweden) – this is to investigate the interaction of solar wind and planetary atmosphere.
VeRa (Venus Radio Science, Germany) – this will use the radio connection between the space probe and the ground station on Earth to explore the ionosphere, take measurements of mass, density, temperature and pressure at altitudes of between 35 and 100 kilometres and measure the electrical properties of the surface and specific characteristics of the solar wind in the inner solar system.
VMC (Venus Monitoring Camera, Germany) – this is a wide-angle multi-channel camera for taking photographs of the surface and cloud formations in the infrared, ultraviolet and visible wavebands.
MAG (Magnetometer, Austria) – this will measure the magnetic interaction between planetary atmosphere and solar wind.

The 1270 kg space probe has been built by a consortium led by prime contractor Astrium France and makes extensive use of reserve components of predecessor space vehicles Mars Express and Rosetta, while the solar generators, bulk storage, high-voltage supply and onboard engines have all been supplied by Germany. The mission will be controlled from the European satellite control centre in Darmstadt, where a Venus Express Mission Operations Centre (VMOC) has been set up expressly for this purpose.

On 9 November 2005, 04:33 CET, the mission finally got under way when the Soyuz launcher vehicle lifted off faultlessly in Baikonur. Shortly after 6am Venus Express separated from the Fregat upper stage to begin the five-month journey to its destination planet. Initial contact with the ground station was achieved successfully and indicated that all the onboard systems were fully operational. Now it is a matter of waiting until it reaches Venus in April 2006.

From FLUG REVUE 1/2006

Last updated 9 December 2005

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