The Complicated Trajectory to Understand a Comet

In the summer of 2014 the Rosetta spacecraft approached and entered orbit around the comet 67P/Churyumov-Gerasimenko. No mission had ever done that before; humans had sent missions flying past comets, and even one to smash into a comet, but no long-term stay had ever been attempted. Comets have very little gravity, so the term "orbit" is a bit loose here. Rosetta shifted around the comet, constantly changing its trajectory to accomplish the science needed to better understand the bizarre little ...