Nearly 10 years have ticked by since the European Space Agency (ESA) sent its Rosetta orbiter to deep space in March 2004.

Now, after waking from 31 months of hibernation on Jan. 20, Rosetta is on its way to becoming the first mission to: rendezvous with a comet, attempt a landing on its surface and follow it as it swings around the Sun.

In August, the €1.3 billion ($1.76 billion) Rosetta orbiter is expected to meet up with Comet 67P/Churyumov-Gerasimenko, the nucleus and environment of which it will study for nearly two years after landing a small probe on the comet's surface in early November.

Matt Taylor, ESA's Rosetta project scientist, says until now, previous comet missions have been flybys, capturing only brief moments in the lives of these primitive building blocks of the Solar System.

“With Rosetta, we will track the evolution of a comet on a daily basis, and for over a year, giving us a unique insight into a comet's behavior and ultimately helping us to decipher their role in the formation of the Solar System,” Taylor says.

After emerging from its hibernation, Rosetta made contact with Earth via NASA's ground stations at Goldstone, Calif., and Canberra, Australia, 48 min. into a nail-chewing hour-long window that opened at 12:30 p.m. EST. The wake-up process had began more than 8 hr. earlier, when Rosetta's onboard “alarm clock” sounded at 5 a.m. EST, initiating warm-up of the spacecraft's star-trackers, slowing its hibernation spin and switching on other systems before finally sending telemetry from its orbit 800 million km (500 million mi.) from Earth.

Built by Airbus Defense & Space, formerly Astrium, and launched on an Ariane 5 in March 2004, Rosetta has made three flybys of Earth and one of Mars on its decade-long journey. Following the launch, the orbiter used “gravity assists” to build up sufficient speed on a trajectory toward Comet 67P, which loops around the Sun between the orbits of Jupiter and Earth. Along the way, it passed the asteroids Steins and Lutetia before being placed into a deep-space slumber in June 2011, during which it operated on solar energy alone as it cruised far from the Sun toward the orbit of Jupiter.

ESA says Rosetta's orbit has brought it back to within 673 million km of the Sun, where there is enough solar energy to power the spacecraft. Today, still about 9 million km from the comet, Rosetta is expected to be fully activated over the coming months, and in August will fly within 100 km of the comet, at which point it will slowly approach Comet 67P at about 0.5 meters per second (1.6 fps).

In October, ESA will choose a landing site for the Philae lander, which is to be deployed in early November. Equipped with 10 instruments, including a drill, Philae will send back a panoramic image of its surroundings, as well as very high-resolution pictures of the comet's surface. It will also dig more than 20 cm (8 in.) into the subsurface to collect samples for inspection by its onboard laboratory. As Philae touches down on the comet, it will use ice screws and harpoons to anchor it to the surface. The self-adjusting landing gear is designed to ensure it stays upright, even on a slope, while the lander's feet drill into the ground to secure it to the comet's surface.

The Rosetta orbiter, meanwhile, will spend more than a year following Comet 67P, measuring activity as the icy surface is warmed by the Sun. Carrying 11 instruments for remote-sensing and radio science, Rosetta will study the composition, mass distribution and dust flux of the comet's nucleus, as well as the comet's plasma environment and its interaction with the solar wind.