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EADS SPACE contribution to the success of Huygens

* EADS SPACE Transportation’s thermal protection for Huygens probe works according to plan
* Technology of EADS SPACE stands the test in deep space

Paris, 14 January 2005

Perfect operation of the Huygens re-entry system: EADS SPACE Transportation’s contribution, both the aerodynamic calculations made at the Les Mureaux site and the manufacturing of the probe’s thermal protection system (heat shield) in Aquitaine, has proven completely successful.

EADS SPACE sites in France, Germany and Spain made major contributions to the Hugens mission. The German location in Ottobrunn was even responsible for the final integration of this demanding planet visitor.

During the transit flight, the instruments on Huygens remained dormant, except for occasional conditional checks. The instruments are housed and protected in the structure of the descent module, also containing all subsystems for probe operation. The structure was built by EADS Astrium Spain, as well as the harness subsystem for power and data distribution.

At a speed of 22,000 kilometres per hour, the spacecraft races towards Titan. When descending through the atmosphere, all onboard instruments are briefly exposed to sixteen times the gravitational acceleration and the ceramic heat shield will heat to up to 1,800 degrees Celsius. EADS SPACE Transportation near Bordeaux, Aquitaine, was responsible for developing and producing the heat shield. The front shield with a diameter of 2.7 metres was designed to slow down the probe's descent to Titan and to protect the scientific instruments against strong thermal radiation during this phase. Heat protection is enhanced by a protective cap mounted on the probe's rear part and enclosing the experimental platform.

Strong winds in the atmosphere push the probe up to speeds of 250 kilometres per hour. With the help of a Doppler wind experiment it is possible to determine the direction and intensity of the zonal winds. To do this, the frequency, or Doppler, shift of the radio signal will be relayed by Huygens to the Cassini orbiter for extremely precise measurement. These measurements enable an altitude profile of the wind speed over a range of 160 kilometres to be determined with an accuracy of less than one metre per second. This can only be achieved during an extremely stable carrier signal from the radio transmitter. The transmitter's frequency stability of 0.4 Hz is ensured by an ultra-stable rubidium oscillator which was developed and built by EADS Astrium (Ottobrunn). A particular challenge was to build the oscillator so that its stability is not affected, either by the various accelerations or the increase in atmospheric pressure during landing.

A small transmitter on board Huygens will relay the data collected by the instruments to the Cassini orbiter at eight kilobits per second. Received via the primary antenna, the data will be stored on board and subsequently transmitted to Earth. Huygens has been designed so that it can survive the impact and even if it lands in an ocean it can ‘swim’ for some time. Provided that the landing is successful – as is hoped by the scientists – Huygens will send unique data and images from the Titan surface to Cassini until the instruments stop working. At temperatures reaching minus 180 degrees Celsius, the battery can provide power for up to two and a half hours. The landing site can be determined by the researchers with the help of the ultra-stable oscillator.

With a launch mass of 5.6 tons, Cassini/Huygens is the heaviest interplanetary probe ever built. Cassini is 6.70 metres high and has a diameter of approximately four metres; Huygens weighs 340 kg and its heat shield has a diameter of 2.70 metres.

EADS SPACE is a wholly-owned subsidiary of EADS, which is dedicated to providing for civil and military space systems. Its activities are mainly distributed to three companies: EADS SPACE Transportation for launcher systems and orbital infrastructure, EADS Astrium for satellites and ground stations and EADS SPACE Services providing satellite-based services. In 2003, EADS SPACE had a turnover of more than 2.4 billion euros and about 12,000 employees in France, Germany, the United Kingdom and Spain.

EADS is a global leader in aerospace, defence and related services. In 2003, EADS generated revenues of 30.1 billion euros and employed a workforce of more than 100,000.

The European Probe Huygens

Total mass 343 kg
Instruments mass 48 kg
Number of instruments 6
Diameter (heat shield) 2.70 m
Power supply 750 W (max. 153 minutes)

Saturn moon Titan and Earth's moon

Titan Earth's moon
Diameter 5,150 km 3,476 km
Orbit days around planet 15.95 27.32
Surface temperature -180 °C +110/–150°C
Atmosphere 95 % nitrogen (N2)
5 % methane (CH4)


Tel.: +33 (0) 1 42 24 27 34

Dr. Christian W Erles
Tel.: +33 (0) 1 39 06 32 53

Francisco LECHÓN
Tel.: +34 (0) 91 586 37 41

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