To be fair, there are real world safety considerations when putting radioactive material into orbit. It&#x27;s not just a knee jerk reaction, in all likelihood. The risk for Cassini was calculated at 1:1400 (For context, humans have launched something like 8000 man made objects into orbit). That&#x27;s certainly acceptable when there&#x27;s no other reasonable way to provide the power that the mission profile requires, but it makes sense that they would go with a more conventional source where possible.