A satellite the size of a double-decker bus, carrying 72lb of radioactive plutonium, will be launched into orbit from Cape Canaveral in Florida this morning. The Cassini satellite, which lifts off at about 9 a.m. (Irish time) on a seven-year, two-billion-mile voyage to Saturn, has attracted an unprecedented level of protest because of its plutonium cargo, the largest of its kind ever to be sent into space.
Protesters were last night camped along the launch centre's perimeter fence. They argue that an explosion during lift-off would spread dangerous plutonium over a wide area.
The US National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA), which own Cassini, counter that a launch failure is unlikely and that the plutonium is safely encased in special unbreakable containers.
The bitter argument over the launch ends 30 years of almost unquestioning public support for the US space programme.
That programme has always had its detractors on scientific and safety grounds, and Congress frequently badgered NASA about budgets.
But until now there had been no widespread protests against what were seen as exciting missions to neighbouring planets.
The powerful anti-nuclear lobby has led the charge against the launch on safety grounds.
Plutonium is extremely persistent and would remain in the environment for many thousands of years if released in an accident.
Cassini's opponents maintain that plutonium dust would be distributed over a wide area if the Titan IVB launch vehicle blew up. The dust could be inhaled and lead to a massive increase in lung cancers.
They point out that the Titan launcher has a failure rate of one in 20, and that other nuclear-powered spacecraft have crashed to Earth, including a US navy satellite carrying 2lb of plutonium in 1964.
NASA and ESA dismissed these claims, saying that there had been only one Titan failure in 19 launches.
Supporters claimed that the plutonium could not be dispersed because it was in ceramic form and was sealed in containers.
