The signal came at 18:16 GMT. Rosetta, the comet-chasing space probe launched by the European Space Agency a decade ago, had woken up.
The craft’s first words, tweeted from 501 million miles away as it hurtled through the darkest reaches of the solar system, were simple: “Hello, world!”
But the relief they sparked at the mission’s ground control centre in Darmstadt, Germany was tangible. Because of Rosetta’s distance, it took 45 minutes for the signal to reach the ground stations - with every second of delay feeding fears that a technical glitch may have ruined the mission.
After 31 months of sleep, the probe is now ready resume its mission to drop a lander on the surface of a comet, furthering our knowledge of how the solar system first came into existence.
Rosetta is chasing 67P/Churyumov-Gerasimenko, an icy comet formed from cosmic debris some 4.6bn years ago, before material had formed to create the Earth and at a time when the sun was little but a new born star.
See the spaceship in plan, being constructed.. and on its way
In pictures: European Space Agency's Rosetta mission
In pictures: European Space Agency's Rosetta mission
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Image of Comet 67P/CG taken by the Philae lander from a distance of approximately 3km from the surface
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Rosetta's lander Philae took this parting shot of its mothership shortly after separation
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Parting shot of the Philae lander after separation, captured by one of Rosetta's cameras
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A technician celebrates after the successful landing of the Philae lander, in the control room at the ESA headquarters in Darmstadt
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Scientists celebrate at a mission observation centre in Toulouse, southern France as they receive information that Philae has landed on the Churyumov-Gerasimenko comet
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Astronomer Klim Ivanovych Churyumov, who discovered the comet 67P/ Churyumov-Gerasimenko in 1969, reacts after the successful landing of the Philae lander on the comet
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A model demonstrates how the landing device Philae, of the space probe Rosetta, stands on the comet 67P/Churyumov-Gerasimenko at the press center of the satellite control center of the European Space Agency in Darmstadt, Germany
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An artist impression of Rosetta's lander Philae on the surface of comet
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Picture taken on October 28 by the navigation camera on Rosetta shows the boulder-strewn neck region of comet 67/P Churyumov-Gerasimenko. It was captured from a distance of 9.7 km from the center of the comet
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Picture taken on October 24 shows a raised plateau on the larger lobe of the comet
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The probe is supposed to fly to a comet and put down a small laboratory on the top of it
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A scientist from the European Space Agency with an airworthy copy of space probe 'Rosetta' in the control center in Darmstadt, Germany
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Maneuvers designed for the actual space probe are simulated with the replica. 'Rosetta' will be woken up from an energy saving hibernation after 957 days
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A European Space Agency employee sits in the control room for the Rosetta mission in Darmstadt, Germany
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Scientists at the European Space Agency are expecting their comet-chasing probe Rosetta to wake from almost three years of hibernation
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Europe's Rosetta probe on a NASA mission
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NASA is participating in the European Space Agency's Rosetta mission, whose goal is to observe one such space-bound icy dirt ball from up close for months on end
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An impression of the Philae lander
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ESA probe Rosetta with Mars in the background. The three-tonne probe blasted off aboard an an Ariane V rocket from Kourou, French Guiana in 2004
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Rosetta orbiter deploying the Philae lander to comet 67P/Churyumov–Gerasimenko, the spacecraft measures 32 m across including the solar arrays, while the comet nucleus is thought to be about 4 km wide
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The spacecraft, festooned with 25 instruments between its lander and orbiter (including three from NASA), is programmed to 'wake up' from hibernation
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An Ariane V carrying the three-tonne probe Rosetta blasting off from Kourou, beginning a decade-long quest to hunt a comet in the depths of the Solar System and shadow it around the Sun in a bid to tease out secrets of how life began on Earth
Scientists hope the craft, which launched in 2004 from Kourou, French Guiana, will have closed the gap on its target ready for a landing by the end of the year.
Speaking after the signal came through, Andrea Accomazzo, the craft’s spacecraft operations manager, said: “I think it was the longest hour of my life, but also one of the most rewarding.”
Over the next few months Rosetta will chase down 67P before harpooning the frozen ball of dirty ice and attempting to make a soft landing on its surface. ESA scientist Matt Taylor compared the mission to the film ‘Armageddon’ - in which Bruce Willis’s character lands on an asteroid to prevent it from destroying Earth. “We look at comets as being a time capsule, they are relics from the beginning of the solar system,” he said.
The craft was effectively “put to sleep” to conserve power as it headed to regions as distant as the planet Jupiter, where the Sun's weak rays provide only limited amounts of energy. Unlike other long-distance space probes the craft has no nuclear batteries and instead relies on electricity generated by ultra-sensitive 15-metre long solar panels.
Ian Wright, Professor of Planetary Sciences at The Open University, said: “Now that Rosetta has woken up, we go back to waiting and hoping for the ongoing success of the mission. We hope the spacecraft will be operational, that our instrument survived hibernation, that the landing will be successful, that the drilling system will deliver samples of surface materials to Ptolemy, that the instrument operates as intended, and that the data can be communicated from the lander to the orbiter, and then back to Earth. Only then can we answer some of our questions. Even though Rosetta has woken up, many things still need to go right. Here’s to hoping that they do.”