In its 13-year sojourn at Saturn, NASA’s Cassini spacecraft has methodically studied practically every cloud and bit of orbiting rock the planet has to offer. Now Cassini will finally take a leap into some of the only territory it has yet to explore: the gap between Saturn and its rings.

On Tuesday, NASA officials will outline the details of Cassini’s “Grand Finale,” the five-month exploration of the narrow gulf between Saturn’s cloud tops and its glittering rings. Never before has a spacecraft entered that realm. Cassini’s wanderings there will be its final act. On Sept. 15, the spacecraft will plunge into Saturn’s atmosphere and disintegrate.

But before that violent end, Cassini will see Saturn as it has never been seen before, swooping so close to the planet that it will brush the outer fringes of its atmosphere. To get there, Cassini will slingshot off Saturn’s moon Titan on April 22. That will push it onto precisely the right path to thread the needle between the giant planet and its closest ring, the wispy D ring, whose innermost edge lies only 1,240 miles from Saturn’s atmosphere.

Cassini will circle Saturn through its rings 22 times, starting its first orbit on April 26. In its final research campaign, the spacecraft will gather information that should reveal Saturn’s inner structure. It will also provide new details on the rings that could help pin down how they formed, whether from a moon that ventured too close to its parent planet or from material that never got a chance to gather into a moon.

Cassini, which launched in 1997, is now running out of the fuel needed to steer it. NASA has opted to send it to its death to ensure that any microbes aboard the ship do not contaminate Saturn’s moons Enceladus and Titan, which are among the most likely places in the solar system to host life, or to have had it once upon a time.