Ground control bids farewell to Philae comet lander
When I asked the team live on Google Hangout chat why they didn't use RTG, for a mission where solar power is a risky bet, their answer was that there were too many political obstructions to getting any reasonable amount of fissile material on-board. I'm certain RTG would greatly increase the chances of mission success, given the reactors proven reliability and capacity, just like they serve our Voyagers.