Final answer:
A significant technical challenge for the Rosetta mission was plotting a precise course to intercept a moving comet, which required a gravitational assist and careful management of solar power without access to plutonium-based power sources.
Step-by-step explanation:
One of the major technical hurdles for the Rosetta spacecraft landing on the comet 67P/Churyumov-Gerasimenko was the navigation and propulsion required to reach a small, distant, and rapidly moving target. The mission's spacecraft, after launching from Earth and traveling 6.4 billion kilometers, executed a complex path involving a gravitational assist from Mars to correct its trajectory towards the comet.
The mission also faced the challenge of adapting to solar power due to a lack of access to plutonium-fueled power sources. Building adequate solar panels and an automatic timer for power management were critical solutions that enabled the spacecraft to conserve energy during the most distant part of its journey and then reactivate as it neared the Sun.