The Rosetta spacecraft awoke after 30 months of hibernation - Le Figaro

The craft of European exploration en route to a comet emitted the signal confirming the recovery of its activity.

suspense lasted 45 minutes at the control center of the European Space Agency (ESA) in Darmstadt, Germany, but the long-awaited signal finally arrived Monday evening at 7:17 p.m., proving that Rosetta was awake. After thirty months of hibernation, the ESA probe is out of its torpor Monday morning at 11 am to begin its first maneuvers for its encounter with Comet Churyumov-Gerasimenko in July. The mission of EUR 1 billion, the most ambitious ever undertaken by Europe, to better understand these balls of ice and rock, remnants of the first moments of the solar system, which are occasionally disintegrate aims approaching too close to the Sun. Sent in March 2004, she was in space for nearly ten years.

When his alarm clock rang, the first reflex Rosetta was warm his “numb” instruments cold. “The probe is on a highly elliptical orbit that sent in July 2011 to more than 4.5 astronomical units (673 million miles) from the Sun,” says Philippe Gaudon, project leader at CNES in Toulouse in charge of French participation in this extraordinary mission. At these distances, the power generated by the solar panels 32 meter wingspan – the equivalent of three bus butt – represents less than 5% of the available Earth orbit. It is not sufficient to maintain all equipment operating temperature (between 5 and 40 ° C depending on the device) in the extreme cold space (- 160 ° C)

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“Only a few vital components such as the onboard computer programming waking or propellant tanks were heated,” says Vincent Guillaud, director of engineering at Airbus scientific satellites Defense and Space (ex-Astrium) . “Rosetta is the first modern probe to go as far in the solar system without nuclear battery,” says the manufacturer.

During hibernation, the spacecraft was traveling at a cruising speed of more than 30,000 km / h while spinning on itself to stabilize its trajectory. Rosetta has now put an end to this long tendril before measuring its position relative to the stars through its stellar sensors. After this identification, it pointed its antenna toward Earth to send a signal indicating that the entire automated procedure Wake had taken place correctly. It is so far from us – 800 million kilometers – that message has 45 minutes to reach us. He was received at 18:30 by the telescope 70 meters Goldstone, operated by NASA, the only one capable of detecting a tenuous signal and then transmitted to the control center of the ESA (ESOC) in Darmstadt, Germany.

Rosetta is literally chasing the comet. As it goes a little faster (1 km / s more), it is catching up gradually. “From the end of May, the probe will be slowed to sync with its target,” says Gerhard Schwehm, former chief scientist and director of the mission to ESA. In late August, Rosetta should thus be at a stable 100 km behind the ice ball pursued. This “encounter” with a comet is a first. Previous European comet mission, Giotto, had merely quick overviews several hundred kilometers of two comets, including Halley’s comet. Rosetta will accompany this time its object of study for several months, until December 2015.

But that’s not all: the probe also has a lander, Philae, it will drop in the gravitational field of the comet in November. For this, it will have to approach only a few kilometers of the surface gravity is about 100,000 times smaller than on Earth. Philae will then “fall” on the comet. The operation is difficult on such a small planet: contact a little too abrupt can cause catastrophic rebound LG

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The precise place of operations remains very uncertain. “We do not know the density, the exact terrain or soil hardness of the comet, says Philippe Gaudon. We just know that the comet is an ellipsoid 3 km 5 km and it takes a ride on itself about 12 hours. “Philae was therefore designed to adapt to different types of situations. It has notably harpoons to grab the comet and not be ejected. The powerful camera onboard Rosetta Osiris – the first telescope built in silicon carbide, ceramic very sensitive to temperature changes – should determine these parameters between July and October. This will leave only four months to space engineers Science Operation and Navigation Center (SONC) at CNES to define a specific landing site and develop the corresponding automated program.

After dropping its lander, Rosetta will move away to a few tens of kilometers to continue to monitor the comet until December 2015. The lander will he, a few days to a few months of life according to the conditions that prevail on the surface of the star. As as it is closer to the Sun, the comet ice will vaporize, causing the formation of a very bright atmosphere of several thousand kilometers thick, her hair, and a long trail of dust several million kilometers, its tail. If all goes as planned, Rosetta will be ringside to watch this amazing show.