In the wee hours of the morning today, Cassini made its 127th and final close flyby of Saturn’s giant moon Titan, the second largest satellite in the solar system. There were many targeted observations planned on this final encounter, including radar studies of the “magic island”, a landform that has appeared and disappeared in Ligeia Mare, one of Titan shallow methane seas. It’s presumed this disappearing trick is the work of changing levels in the sea, but more data is needed.
But there’s more to this flyby than just some great science. Cassini has relied heavily on Titan’s mass to adjust its trajectory for very little fuel expenditure, and today was no exception. Today, Cassini used Titan’s gravity to lower its orbit significantly, bringing the periapsis (the low point) within the rings, and shortening the entire orbit to just about a week. Cassini will make twenty two dives into the area within Saturn’s rings, low enough to begin to directly sample some of Saturn’s tenuous upper atmosphere, gradually sinking on each closest approach until finally, next September, its predicted to impact the giant planet’s cloud decks and burn up.
It’s bittersweet, to be sure. Cassini has functioned like a champ, long past its original design life. But all things must come to and end, and Cassini will go out with a bang.
So as we prepare to say farewell in a few months, here’s a parting shot from Cassini: the last photograph it will be able to take of the Earth and Moon. This was taken on April 12, taking advantage of a viewing geometry that will not occur again on the mission, where Earth peeked through the gap between the A ring and the F ring: