New Horizons’ journey to the edge of the solar system means solar panels provide very little power, which is why NASA is using a radioactive power source (Image: JHUAPL/SwRI)
The US has officially notified the United Nations and the International Atomic Energy Agency that NASA is preparing to launch New Horizons, its Pluto-bound mission carrying 10.9 kilograms of radioactive material.
The New Horizons probe is scheduled to begin its nine-year journey on 17 January. It is carrying plutonium dioxide to power its instruments during its frozen odyssey through the solar system.
The spacecraft’s trajectory is expected to take it near southern Africa and Australia. The UN is notifying these nations of the upcoming launch, says William Armbruster, senior public diplomacy officer with the US State Department.
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NASA has estimated the probability of a launch accident involving the release of plutonium dioxide at about 4 in 1000. If there were a launch accident, the US would offer clean-up help to affected nations.
NASA’s environmental impact statement for the mission says potential launch accidents that prevented the craft leaving the Earth “could result in a release of plutonium dioxide in the launch area, southern Africa following suborbital re-entry, and other global locations following orbital re-entry. However, in each of these regions an accident resulting in a release of plutonium dioxide is unlikely.”
Less protesters
At least 25 other US spacecraft have launched into space with radioisotope power supplies. Seven of these satellites are still orbiting Earth.
Accidents have been rare. When the Apollo 13 mission was aborted in 1970, the Apollo Lunar Surface Experiments Package and its 3.8 kilograms of plutonium were lost in the Tonga Trench in the Pacific Ocean. In 1964, a radioisotope thermoelectric generator from the Transit 5BN-3 spacecraft re-entered Earth’s atmosphere and burned up, releasing 17,000 curies of radiation that was eventually scattered across Earth’s surface.
NASA says it needs plutonium for New Horizons because it is heading for Pluto, and solar arrays would not provide enough power that far away from the Sun. As New Horizons reaches the ninth planet, the solar illumination will be less than one-thousandth of that experienced on Earth.
Over the weekend, about 30 protestors gathered outside of the gates of the Cape Canaveral Air Force Station, Florida, US, where New Horizons will launch. In contrast, about 800 people protested the launch of the Saturn-bound Cassini probe in 1997. That mission actually swung past Earth once to use the planet’s gravity as a slingshot, sparking fears that it would re-enter Earth’s atmosphere and spread radioactive material around the planet.
Last week, the mission team completed inspections of the Atlas 5 rocket’s RP-1 fuel tank to look for cracks. NASA had delayed the launch by six days to conduct the checks after Lockheed Martin, which makes the Atlas 5, found a failure in a similar tank.
