Story highlights Cassini probe is nearing the end of its 20-year mission to explore Saturn

Unmanned spacecraft will carry out a series of weekly dives through the planet's icy rings

In September, Cassini will enter Saturn's atmosphere and burn up, like a meteor

(CNN) NASA's Cassini spacecraft has begun an unprecedented series of space dives that will see it plunge through the icy rings of Saturn, in the final phase of its 20-year mission.

For the first of 22 weekly plummets, the unmanned probe has altered its trajectory, allowing it to maneuver through the 1,500-mile-wide gap between the planet and its rings, at a top speed of more than 76,800 mph (120,000 kph).

Because the region has never been explored before, Cassini's controllers are using the craft's dish-shaped antenna as a shield, to protect it against particles of debris, while it voyages past the rings.

This means it will be out of contact with Earth through the dive, but the Cassini team says it expects to regain a signal from the probe by about 3:00 a.m. ET Thursday.

This is it! Through the gap between #Saturn and its rings. Instruments are on, but we're out of contact with Earth. Here we goooooo! pic.twitter.com/3J7aRZS0IH — CassiniSaturn (@CassiniSaturn) April 26, 2017

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