It took the long way

This beautiful animated page shows how Rosetta made its way through our solar system to meet with comet 67P/CG.

Rosetta starts using Earth's gravity as a slingshot to get out beyong the orbit of Mars, twice, before coming back in for another gravity slingshot. Then it heads out even faster while the comet it's destined to meet is coming toward the inner solar system on its last pass before this one. That whole process took 4 years.

One more slingshot pass by Earth gives it the speed to start catching up with the comet, which is now on its way out toward the Oort cloud. The next time we would see Rosetta would be 4.5 years later, dancing with the comet.