European space mission controllers say they're preparing to wake a comet-hunting spacecraft from a two-year deep-space hibernation as it nears its cosmic goal.

The European Space Agency's Rosetta spacecraft is headed toward a comet knows as 67P/Churyumov-Gerasimenko to both orbit it and place a lander on it to study the role of comets in the evolution of the Solar System, an ESA release said Friday.

Rosetta, launched in March 2004, has had a long voyage including a complex series of flybys -- three times past Earth and once past Mars -- on its voyage toward its destination and an expected arrival in August 2014.

In July 2011 Rosetta was put into deep-space hibernation for the coldest, most distant leg of the journey as it traveled some 500 million miles from the Sun, close to the orbit of Jupiter.

Controllers set Rosetta's internal "alarm clock" to awaken the sleeping spacecraft in 100 days, on January 20, 2014.

Once it wakes up, Rosetta will warm up its navigation instruments and then halt its spin to point its main antenna at Earth, to let ground controllers know it is still alive.

"We are very excited to have this important milestone in sight, but we will be anxious to assess the health of the spacecraft after Rosetta has spent nearly 10 years in space," ESA Rosetta mission manager Fred Jansen said.

When it wakes up Rosetta will still be 6 million miles from the comet; its first images of 67P/Churyumov-Gerasimenko are expected in May, the ESA said.