On August 20, 1977, the U.S. National Aeronautics and Space Administration launched the Voyager space probe from Cape Canaveral, Florida.

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It's hard to believe at times that the Voyager 1 probe is older than many of us reading this article, but it's true.

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The Great Dark Spot seen by Voyager 2, a probe which investigated the planet in 1989, disappeared within a year.

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What is certain is that the unmanned probe - which is being closely followed by Voyager II - is still functioning.

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It would be an understatement to say there's been a long build-up to the moment when Voyager 1 ventures into interstellar space: scientists thought the probe was on the edge back in 2010, and we've been waiting for the official milestone ever since.

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Ed Massey, project manager for the Voyager mission, points out that no matter how clever and autonomous a probe is, it can only get itself out of situations it has been programmed to cope with.

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