A runaway Soviet nuclear-powered satellite will fall back to Earth between Oct. 4 and 8 but poses no radiation danger, the official Tass news agency said. Although Soviet scientists are tracking its flight, they cannot yet tell exactly where it will land, Tass added. The satellite, Cosmos 1900, was launched in December, 1987, but radio contact was lost earlier this year. Tass said Cosmos 1900 is equipped with two safety systems. One is designed to propel the craft’s atomic power plant into a higher orbit before the satellite re-enters the Earth’s atmosphere, while a fall-back system is designed to eject the nuclear core to ensure that it burns up well above the Earth’s surface.