NASA has released a movie sequence created from raw images captured by the Cassini spacecraft as the probe plunged from high above Saturn's north pole, down towards the "big empty" separating the planet's upper atmosphere and iconic ring system. The images featured in the video represent only one hour of Cassini's dramatic journey, which saw the probe fly within 1,900 miles (3,000 km) of Saturn's cloud tops – the closest any spacecraft has ever come to the gas giant's atmosphere.
The video begins with Cassini poised some 45,000 miles (72,400 km) above the gas giant's north polar vortex. This colossal storm churns at the center of a hexagonal Jet stream spanning roughly 20,000 miles (30,000 km) across – easily large enough to swallow two Earths side by side.
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"I was surprised to see so many sharp edges along the hexagon's outer boundary and the eye-wall of the polar vortex," said Kunio Sayanagi, an associate of the Cassini imaging team based at Hampton University in Virginia, who helped produce the new movie. "Something must be keeping different latitudes from mixing to maintain those edges."
Saturn's north polar vortex as seen by Cassini during its April 16 Grand Finale dive (Credit: NASA/JPL-Caltech/Space Science Institute)
As Cassini draws closer to Saturn's equator, the orientation of the images can be seen to change as the probe's handlers maneuvered the spacecraft's dish to face its direction of travel. By placing the 4-meter-wide (13 ft) antenna at the "front" of the spacecraft, NASA effectively created an improvised shield to protect the delicate equipment housed inside the probe from any potential particle impacts upon passing through Saturn's ring plane.
Data from the probe's Radio and Plasma Wave Science (RPSW) instrument has since revealed that the planet-ring gap is surprisingly devoid of particles large enough to damage Cassini, allowing NASA to do away with the shield approach for future dives. This will allow a greater level of freedom as to when and how the probe gathers data during its remaining Grand Finale dives.
Shot of Saturn and its rings as taken by Cassini on May 3, 2017 (Credit: NASA/JPL-Caltech/Space Science Institute)
Over the course of the video, Cassini's altitude drops from 45,000 miles to 4,200 miles (72,400 to 6,700 km) above Saturn's atmosphere, giving shots at the end of the movie a resolution of 0.5 miles (810 m) per pixel.
The raw images from Cassini's first and second dives are already available on the NASA website, showcasing breathtaking views of Saturn's surface and its majestic ring system. Only 20 dives remain before Cassini is directed to end its marathon mission by cannonballing into the planet it has dedicated its life to studying.
So, just a little under four months and 11 days until Cassini bids us farewell. September 15, 2017 will be a bittersweet day for all who have worked on the Cassini mission over the years, not to mention those countless individuals who have been inspired by its haunting imagery and incredible scientific achievements.
Mark it in your calendar, it's going to be a tearjerker.
Scroll down to view the NASA video of Cassini's first Grand Finale dive.