The probe Philae has been given the green light to attempt the first landing on a comet today, the European Space Agency (ESA) said.
"We've got the final go" for the operation, an ESA spokeswoman said at mission control in Darmstadt, Germany.
A science lab bearing 10 instruments, Philae will be ordered to separate from its mother ship Rosetta at 0835 GMT and head towards Comet 67P/Churyumov-Gerasimenko, the agency said, after the last of four checks.
"Final Go/NOGO complete! We're GO for separation!!!," the Rosetta mission said in a tweet.
If all goes well, Philae will touch down about seven hours later before carrying out scientific experiments on its surface -- a double first in space history.
Conceived in the 1980s, the Rosetta mission seeks to reveal secrets about the origins of the Solar System and maybe even life on Earth.
The USD 1.6-billion project was approved in 1993.
Rosetta, carrying Philae, was hoisted into space in 2004, but needed more than a decade to reach its target in August this year -- a six-billion-kilometre trek around the inner Solar System.
