April 4 (UPI) -- Cassini is nearing its final days -- and final orbits. On Wednesday, April 26, the probe will begin its "Grand Finale," as it makes a succession of dives through the 1,500-mile-wide gap between Saturn's atmosphere and its rings.

"No spacecraft has ever gone through the unique region that we'll attempt to boldly cross 22 times," Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate in Washington, D.C., said in an update. "What we learn from Cassini's daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve. This is truly discovery in action to the very end."


The probe has spent the last few weeks flying by Saturn's outer rings during what scientists dubbed the "ring-grazing orbits." The orbits yielded intimate high-res images of Saturn's rings, as well as its moons.

During the craft's deep dives, Cassini will dip as close as 1,012 miles above the Saturn's clouds. Its final orbits will squeeze almost entirely inside the ring gap before the probe makes one final dive into Saturn's atmosphere -- all the while beaming back valuable data to scientists on Earth.

Researchers are preparing to update the probe's final scientific instructions. During its final orbits, the probe will study the composition of the gas giant's main and inner rings, as well as its clouds.

"Based on our best models, we expect the gap to be clear of particles large enough to damage the spacecraft," said Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory in California. "But we're also being cautious by using our large antenna as a shield on the first pass, as we determine whether it's safe to expose the science instruments to that environment on future passes."

Of course, there are risks involved the final phase of Cassini's life, but researchers are anxious for the probe to sample Saturn's atmospheric layers.

"Cassini's grand finale is so much more than a final plunge," said Linda Spilker, Cassini project scientist at JPL. "It's a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission."