For instance , the environmental impact study for the Cassini -- Huygens probe launched in 1997 estimated the probability of contamination accidents at various stages in the mission .
However , this event is not considered likely with current RTG cask designs .
The environmental impact study for the Cassini -- Huygens probe launched in 1997 estimated the probability of contamination accidents at various stages in the mission .
However , this event is not considered likely with current RTG cask designs .