SCIENCE WEEK IRELAND: Two satellites launched 25 years ago will soon cross into the "interstellar void", the first time a man-made object will take measurements beyond the influence of the sun. Both satellites are still fully operable and should continue sending data back to earth for another 20 years.
The intrepid journey of Voyager I and Voyager II across the solar system was recounted last night by Mr Kevin Nolan, a lecturer in physics at the Institute of Technology Tallaght. His talk was organised by the Irish Research Scientists Association as part of Science Week Ireland.
The two space probes were launched in July and September 1977. "Over the next 12 years they surveyed all of the outer planets of the solar system," he said. "What is amazing is that 25 years later they are both still working."
Both satellite missions were hugely successful. They took pictures and measurements of Jupiter, Saturn, Uranus and Neptune as they sailed along on a journey that has so far taken them 12 billion kilometres into space.
He spoke about this "grand tour" and "the sense of excitement it created at the time". The launch was carefully planned to allow the probes to get so far. "The planets aligned in 1979 in a way that only happens once every 270 odd years," Mr Nolan said. "They were able to sling-shot the probes from one planet to the next over the next 12 years."
The information returned was so comprehensive it "provided the pattern for all future space missions", he said. For example, information returned about the Saturnian moon Titan indicated it was a place that merited a return visit, hence the dispatch of the Cassini/Huygens probe that will reach the moon in 2004.
Now the two satellites are about to cross into true space, the interstellar medium that exists beyond the influence of the sun. This should be reached in a year or two at most, he said, and for the first time measuring devices will be able to sample what exists between stars, well past the particles that stream outwards from the sun on its "solar wind".
