In its 10-year chase of a comet, the European Space Agency’s ambitious Rosetta mission has pushed the edges of engineering ingenuity.

After three slingshot flybys of Earth to fling it at ever faster speeds to catch up with its target, Rosetta was so far from the sun that its solar arrays could not generate enough electricity, and it was, by design, put into hibernation for two and a half years.

To the relief of mission managers, Rosetta woke up from its cold, deep sleep as scheduled in January. In August, it finally pulled up alongside the comet, known as 67P/Churyumov-Gerasimenko, both flying closer to the sun at 34,400 miles per hour. In the months since, Rosetta has snapped photographs just 4.5 miles above the craggy surface.

Now it is attempting its greatest feat yet: drop a small lander onto the comet.

On Wednesday, at 3:35 a.m. Eastern time, the 220-pound lander, named Philae, detached from Rosetta and began to be pulled downward by the comet’s gravity.