Others say the impact may be visible to the naked eye. If not for this, the mission would be of no interest.
Events in space don't have to be visible to the naked eye to be interesting. The Mars rovers aren't visible to observers on earth, but they have sent back very interesting photos. When Comet Shoemaker-Levy 9 collided with Jupiter in 1994, it wasn't visible to the naked eye on earth, but we later saw photos of the impact.