(10/10/1997) -- At Launch Complex 40 on Cape Canaveral Air Station, workers are installing three Radioisotope Thermoelectric Generators (RTGs) on the Cassini spacecraft. RTGs are lightweight, compact spacecraft electrical power systems that have flown successfully on 23 previous U.S. missions over the past 37 years. These generators produce power by converting heat into electrical energy; the heat is provided by the natural radioactive decay of plutonium-238 dioxide, a non-weapons-grade material. RTGs enable spacecraft to operate at significant distances from the Sun where solar power systems would not be feasible. Cassini will travel two billion miles to reach Saturn and another 1.1 billion miles while in orbit around Saturn. Cassini is undergoing final preparations for liftoff on a Titan IVB/Centaur launch vehicle, with the launch window opening at 4:55 a.m. EDT, Oct. 13