On Monday (20.01.2013), an alarm went off in space to wake up Europe's Rosetta spacecraft from its deep sleep. If all goes according to plan, the satellite will land a probe on a comet in November.
For more than three years, the European Space Agency (ESA) spacecraft, known as Rosetta, has been in deep-space hibernation. All systems were shut down more than 31 months ago, when the craft traveled so far from the sun that its solar cells could no longer charge its batteries.
But after 957 days of beauty sleep, Rosetta will return to a range where it can tank up on sunlight - and close enough to Earth to send its greetings to the world.
After the alarm, the craft needs time to wake up and get to full functionality - like any of us would.
Good morning, sunshine!
Rosetta will then fire up its computers to see if its eyes and feelers still work, and its organs are functioning smoothly. Then it'll stretch out its arms - in this case solar panels - and warm up in the cold of space by catching some of the sun's rays. And it will have to save up a lot of energy for the tasks ahead.
Rosetta will restock its energy supplies with massive solar panels, shown here at their testing phase
If all goes to plane, it will send a short radio signal to Earth reporting on its status. But because the craft is more than 500 million miles (807 million kilometers) from Earth, the message won't arrive until about 5:30 p.m. By then controllers at the ESA headquarters in Darmstadt, Germany, will likely be celebrating, if all is well with the craft.
The scientists who have participated for decades in the development, construction, and space deployment of Rosetta are anxiously awaiting Rosett's awakening. It has been among the most protracted and complicated projects in the entire history of space exploration.
It's been 20 years since the ESA decided to build Rosetta, and on March 2 of this year, it will be ten years since an Ariane 5G+ rocket sent Rosetta toward the sun. Rosetta will reach its goal this November: after traveling 4.4 billion miles (7.1 billion km). Then, scientists hope Rosetta will send its Philae probe to the core of the comet 67P/Churyumov-Gerasimenko.
Don't slip on the ice
Gravitational pull from the comet will not be enough to allow the 220-pound (100-kilo) Philae probe, developed under the aegis of the German Aerospace Center (DLR), to land on its own. Two harpoons will help the probe pull itself to the comet, where screws on each of its three legs will then burrow into the ice of the surface. This will be particularly tricky, given that it's the first such attempted landing.
The comet itself measures two to three miles across - not large enough to have its own effective gravitational force. It's likely composed of gritty ice or snow, and probably has a very hard surface, though researchers aren't completely sure of this.
Search for life
If Philae lands successfully, it could reveal secrets about the origins of our solar system. Comet 67P/Churyumov-Gerasimenko comes from the so-called Kuiper belt, a distant region of our solar system beyond Neptune.
There, chunks of ice float around at random, and occasionally some of them enter into the sun's gravitational pull, like this comet. The current orbit of the comet has brought it close to Jupiter, allowing it to be observed by Kim Churyumov and Svetlana Gerasimenko in 1969.
Never before have scientists been able to find out what such a comet is made of. Philae will analyze samples for various chemicals - researchers are particularly interested in finding organic compounds like amino acids, and arrays of atoms.
These could give them clues to the origins of life - because comets are the universe's deep-freezers, and are thought to hold information about the origin of our solar system some 4.6 billion years ago.
The robotic probe also has other instruments, like an x-ray spectrometer, and devices to measure sound, light, and electromagnetic waves, with which researchers hope to gaze directly into the comet's core.
Even if the landing maneuver fails, the mission will not have been in vain, as Rosetta has sent back pictures and data on the many encounters it's had during its five trips around the sun. In 2007 Rosetta was near Mars, a year later it closed in on the Steins asteroid, and then in 2010 its orbit brought it close to the Lutetia asteroid.