Rosetta: A space sophisticate
EUROPEAN SPACE AGENCY NEWS RELEASE
Posted: February 16, 2004
The European Space Agency's Rosetta mission will be getting under way in February 2004. The Rosetta spacecraft will be pairing up with Comet 67P/Churyumov-Gerasimenko and accompanying it on its journey, investigating the comet's composition and the dynamic processes at work as it flies sunwards. The spacecraft will even deposit a lander on the comet.
The trip is certainly not short: Rosetta will need ten years just to reach the comet. This places extreme demands on its hardware; when the probe meets up with the comet, all instruments must be fully operational, especially since it will have been in "hibernation" for two-and-a-half years of its journey. During this 'big sleep', all systems, scientific instruments included, are turned off. Only the on-board computer remains active.
Twelve cubic metres of technical wizardry
For trajectory and attitude control and for the major braking maneuvers, Rosetta is equipped with 24 thrusters each delivering 10 N. That corresponds to the force needed here on Earth to hold a bag containing 10 apples. Rosetta sets off with 1650 kg of propellant on board, accounting for more than half its mass at lift-off.
Just 20 percent of total mass is available for scientific purposes. So when developing the research instruments the same rule applied as for supermodels: make every gram count. The calculation seems to have worked out right: the main probe will be carrying 11 scientific instruments and the Rosetta lander a further ten. They will analyse the composition and structure of the comet's nucleus and study its interaction with the solar wind and the interplanetary plasma.
Rosetta - unplugged
These dimensions are also essential because when Rosetta meets Churyumov-Gerasimenko it will be 675 million kilometres away from the Sun. At that distance solar radiation is very weak and the solar collectors will supply only 440 W of power - compared with 8000 W towards the end of the mission when the two companions come closest to the Sun (at some 150 million kilometres from our star distance).
"The probe is also equipped with a set of four 10-amp-hour batteries to maintain power supply while Rosetta flies in the shadow of the comet."
Rosetta lander - standing on its own three legs
At the same moment, the lander fires a harpoon to anchor it to the ground - an opportunity also to investigate the mechanical properties of the surface.
"If everything goes according to plan, the mission results could well fundamentally expand our knowledge of comets, just as the Rosetta Stone, after which the probe is named, helped unravel the mystery of Egyptian hieroglyphics," said Manfred Warhaut.