Cassini made it! On April 26, 2017, NASA’s Saturn-exploring spacecraft made its closest pass by the planet since its arrival in 2004, beginning the final phase of its mission with its first “Grand Finale” orbital pass that took it between the top of the planet’s atmosphere and the innermost edge of the ring system. It’s literally a journey that no other spacecraft has ever made—and now the pictures are coming in!
It’s also the closest Cassini has come to Saturn itself; at closest point Cassini was only about 1,900 miles (3,000 km) above the tops of Saturn’s swirling clouds. It’s amazing to think that the images we’re seeing were captured with Cassini’s wide angle camera—typically views like this have had to use its “zoom” narrow-angle camera!
Check out an animation below of some of Cassini’s views captured during the pass over Saturn’s north pole.
The white puffy areas in the images are high-altitude clouds, most likely made of water or ammonia ices. Deeper cloud bands can be seen behind them, drawn into long lines by Saturn’s strong winds.
The large dark circular shape is the center of the 1,800-mile-wide vortex that has long been observed over Saturn’s north pole. In monochrome images it looks black; in color composites its increasingly bright blue color is revealed.
(Unfortunately no color filter images have come in from this pass yet so I can’t make any color pics.)
The risky stunt of flying through the space between Saturn and the rings was saved for the very end of the mission; it took a lot of observations to determine if the spacecraft would survive the pass. Even with some assurance, Cassini angled its dish-like antenna forward to help protect it from any stray ring particles it might encounter.
“No spacecraft has ever been this close to Saturn before. We could only rely on predictions, based on our experience with Saturn’s other rings, of what we thought this gap between the rings and Saturn would be like,” said Cassini Project Manager Earl Maize of NASA’s Jet Propulsion Laboratory in Pasadena, California. “I am delighted to report that Cassini shot through the gap just as we planned and has come out the other side in excellent shape.”
Cassini’s next dive through the gap will occur on May 2. In the meantime I’ll be looking forward to more images from the actual ring crossing itself…stay tuned to this blog and my Twitter feed for the latest updates!
UPDATE: color data have come in, so here’s a recent view of Saturn’s polar vortex from the 4/26 pass!