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Feature story

Europe's Rosetta comet-chasing spacecraft is readied for an early 2004 liftoff

December 8, 2003

Checkout of the Rosetta satellite is shown in the Spaceport's S1B building.

The European Space Agency's Rosetta deep space probe has undergone checkout and modification at the Spaceport in preparation for its new launch date on an ambitious mission to catch a comet.

Rosetta was assigned a new comet target - 67P/Churyumov-Gerasimenko - after its original January 2002 launch on Ariane 5 was postponed. Liftoff now is targeted for February 2004, with the spacecraft scheduled to encounter Churyumov-Gerasimenko in November 2014.

Once in the vicinity of Churyumov-Gerasimenko, the main Rosetta spacecraft will follow the comet for many months as they head towards the Sun. This provides time for detailed mapping of the nucleus, and for the pinpointing of a touchdown spot for a small lander that is to be deployed from Rosetta.

The change in Rosetta's launch resulted in a modification of the lander to ensure the deployable 100-kg. spacecraft will be able to make history's first soft touchdown on the surface of a comet. Since Churyumov-Gerasimenko is much larger than the originally targeted comet, 46P/Wirtanen, the Rosetta lander's touchdown speed will be higher. To avoid a cometary rebound, a small bracket - called a tilt limiter - was attached to the lander's bottom, restricting the amount its landing gear can flex at touchdown.

Rosetta's large solar panels contain new non-reflective silicon cells.

After making contact with the comet's surface, two harpoons will anchor the lander to the surface, allowing it to operate for a minimum of 65 hours, although surface operations may continue for many months.

In addition to the bracket installation, the deployment of Rosetta's solar panels has been validated in the S3B clean room at the Spaceport. Rosetta will be the first space mission to go beyond the main asteroid belt while relying solely on solar sells for power generation. The two large solar panels contain new non-reflective silicon cells that will provide up to 8,700 Watts of power in the inner Solar System and 400 Watts for the comet encounter - where sunlight levels are only 4 percent of those on Earth.

The use of solar panels is unique for such a mission, taking the place of the radioisotope thermal generators (RTGs) traditionally employed on deep-space flights.

The Rosetta/lander combination will have a mass of about 3,000 kg. at liftoff on Ariane 5.