NASA's Cassini spacecraft has begun its first historic dive between Saturn and its rings.

Travelling at more than 110,000 kilometres per hour, Cassini was due to travel through the gap at 7:00pm AEST on Wednesday.

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The dive is the first of 22 the probe will make between now and the end of its mission in September, in what NASA has dubbed Cassini's "grand finale".

But, with its antenna facing away from Earth, scientists will not know the spacecraft's fate for nearly 24 hours until they pick up its first signals through NASA's Deep Space Network.

"The first key things are going to be: has the space craft survived? What's the dust environment like? And how are they going to characterise that for the next trajectory in seven days?" said Glen Nagle from the Canberra Deep Space Communication Complex.

The first communications are expected to be received by a tracking station in California about 5:00pm AEST on Thursday, before the Canberra Deep Space Communication Complex picks up signals — including the first high resolution images — about 10:00pm AEST.

"This will give us the closest views of the rings and the planet," he said.

The final orbits of Cassini as it repeatedly dives between Saturn and its innermost ring. ( Supplied: NASA Jet Propulsion Laboratory )

Cassini to end mission with fatal plunge into Saturn

Cassini will make one fly-through between Saturn and its rings each week until it ends its mission by plunging into the planet on September 15.

While the dive has been planned with precision, Mr Nagle said it was still risky.

"The best models suggest [the spacecraft's path] will be relatively clear of large debris but it would only take something the size of a pea or a golf ball … to knock the spacecraft off course or even destroy [it]," Mr Nagle said.

Cassini's antenna is larger than the rest of the spacecraft. ( Supplied: NASAJPL-Caltech )

On its journey through the gap, Mr Nagle said the spacecraft's antenna would act as a protective shield, which is why there would not be any communications for almost a day.

"The antenna is larger than the spacecraft, so that can protect the delicate instrumentation, whereas that antennae can actually handle a few dings — which I'm sure it has had over the last 13 years," he said.

For now, he said the scientists would have to wait and see what happened.

"Even if you saw a picture and saw something coming it's too late to put the brakes on," he said.

"This is the risk you take in space exploration. You dare mighty things and this is a pretty mighty thing."

If it survives its first fly through it will provide valuable data about the dust levels and trajectories for each successive fly through.

"Everything else has worked out ok so far so there's no reason to think this won't go the same," said Mr Nagle.

Grand finale could reveal age of Saturn's rings

Cassini has spent 13 years in orbit around Saturn after a seven-year journey from Earth.

Among the discoveries made possible by Cassini are the presence of icy plumes containing traces of molecular hydrogen and conditions critical to life on Saturn's moon Enceladus, and the peculiar hexagon at the planet's north pole.

Astronomer Alan Duffy, an Associate Professor at Swinburne University and co-presenter of ABC podcast Cosmic Vertigo, said Cassini had revealed Saturn to be "a world more mysterious and spectacular than we could have ever hoped".

"The grand finale will provide unrivalled close-ups of the rings, perhaps finally answering the question as to their age," Dr Duffy said.

"Cassini's greatest scientific legacy will be its last, destroying itself to ensure the habitable moons of Saturn remain pristine and uncontaminated by likely Earth-microbial stowaways carried on the craft."

Plumes of water ice spray out of Enceladus. ( Supplied: NASA/JPL-Caltech/Space Science Institute )

The Canberra Deep Space Complex has followed the Cassini spacecraft since it arrived in 2004 and will be there when it meets its end.

"Our station handles the very last signals right up to the spacecraft virtually breaking apart as it enters Saturn's atmosphere in September," Mr Nagle said.