NASA Voyager-1 and Humankind set to cross the final frontier to Interstellar Space

It will be one of the most important milestones in human history as, for the first time, an ambassador for humankind moves beyond the confines and protection of our solar system.

NASA scientists are preparing for the moment, any day now, when the first of two spacecraft launched in the late 1970s crosses the invisible boundary that marks the start of "interstellar space".

Already they have passed some of the furthest planets of the solar system, transmitting spectacular images of the worlds that circle the sun.

This artist's concept by NASA/JPL-Caltech shows Voyager 1 and Voyager 2 at the edge of the solar system. 

The Voyager 1 probe, which is now about 17.7 billion kilometres from Earth, has entered a "transition zone" at the edge of the solar system, scientists say.  

Photo: AFP/NASA/JPL-Caltech

Voyager 1 is about 11 billion miles from Earth and hurtling away at a rate of 13 kilometres a second. Its sister craft, Voyager 2, is not far behind.

Each carries an array of instruments to gather information about outer space - and also a gold-plated copper disc with sounds and images intended to convey a sample of what life is like on Earth should they ever encounter other intelligent life.

Should an alien ever find one of the craft, the first human to whom they will be introduced - assuming they can decode the technology - will be Ann Druyan, now 63, an author and television producer who fell in love with the US astronomer Dr Carl Sagan while they were working on the Voyager mission.

A file photo released by NASA in 1970 shows the golden record on Voyager 1, launched on September 5, 1977, with a cartridge and a needle to play it.  

Photo: AFP/NASA