Luckily the Cassini space did flyby the Earth on August 18, 1999 carrying 72.3 lbs (32,8 kg) of deadly plutonium on board. Luckily it didn't inadvertently enter the Earth's atmosphere at 42,000 mph, burn up and expose five billion people to 99% or more of the radiation from the plutonium (which could have happened according to the NASA Environmental Impact Statement).
However, more plutonium carrying spacecraft launches are planned by NASA in preperation for the development and deployment of high energy lasers and battle platforms in space.
Much more information is contained in the links listed below.
The Cassini Fly-by - News Items
