ESA is multinational and some member countries are very opposed to nuclear technology in any form. Aside from the fact that Europe generally lacks the ability t

ESA is multinational and some member countries are very opposed to nuclear technology in any form. Aside from the fact that Europe generally lacks the ability to manufacture Pu-238 or RTGs in general. Britain is looking at developing RTG technology on its own, possibly using Am-241, which might shake things up. It's still a hard problem with so many member countries involved.