Cassini to conduct last, closest flyby of Titan
As NASA’s Cassini spacecraft moves toward its Grand Finale, it will conduct its final and closest flyby of Saturn’s moon Titan on April 22, 2017. This last visit is a targeted flyby, meaning that Cassini will use either its rocket engine or thrusters to alter its course.
At 2:08 a.m. EDT (06:08 GMT) April 22, 2017, the probe will make its 127th flyby of the large moon. It will pass over Titan’s surface at just 608 miles (979 kilometers), where the spacecraft’s instruments will conduct closeup observations of the hydrocarbon lakes near the moon’s north pole and use radar to look through its atmospheric haze and image surface detail.
While the spacecraft speeds by at 13,000 mph (21,000 km/h), its RADAR instrument will embark on its longest-duration observation of Titan’s surface, searching for changes in its methane lakes and seas.
For the first time, RADAR will attempt to measure the depths of Titan’s smaller lakes. The instrument will also take a last look at the strange features in Titan’s seas, dubbed “magic islands”, features in the seas that seem to appear, disappear, and often reappear.
Mission scientists hope that the close flyby will provide answers as to whether these “islands” are bubbles, floating debris, waves, or something else yet to be identified.
At the same time, Cassini’s Ion and Neutral Mass Spectrometer (INMS) will take samples of both ions and neutral particles near Titan, which scientists hope will help them to gain a better understanding of changes in the densities of diffuse gas particles in the moon’s upper atmosphere.
While Titan does not have its own magnetic field, it does have a magnetotail produced by the interaction between its ionosphere and gases in Saturn’s magnetosphere. Cassini’s Magnetometer (MAG) instrument will take advantage of the close flyby to study the northern part of Titan’s magnetotail.
With its Imaging Science Subsystem (ISS) visible light camera, Cassini will capture both regional and global mosaics of the hemisphere facing the spacecraft, focusing especially on mid-southern latitudes, including a basin named Hotei Regio, which appears to have had active ice volcanoes in its recent past.
The Titan flyby will give Cassini a gravity assist, altering the spacecraft’s trajectory and moving its orbit from just outside Saturn’s rings to the narrow area between the rings and the giant planet’s upper atmosphere.
This makes the flyby the transition between the ring-grazing orbits the spacecraft has been conducting since Nov. 30, 2016, and the Grand Finale in which it will conduct 22 dives between the rings and the planet. The dives will be conducted approximately every seven days.
“We hope to accomplish a lot of incredible science, things that we have never been able to do before with the Cassini mission,” said Morgan Cable, Cassini project scientist. “We’re going to go screaming over the top of Saturn. We’ll be able to study the hexagon at Saturn’s north pole in greater detail than ever before. We’re going to go shooting between Saturn and its rings, threading the needle, which means we’ll be able to taste the ring particles, be able to understand more about what those are made of.
Cable said the spacecraft’s instruments will be able to “taste” the atmosphere of Saturn.
“We’re also going to get a better idea of the interior structure because we’ll be getting closer to Saturn than we’ve ever been,” Cable said.
Now almost out of fuel, Cassini will be set on a collision course with Saturn by the maneuver that will send it flying over Titan. On Sept 15, 2017, it will plunge into Saturn’s atmosphere, collecting and returning data as long as possible.
Because Saturn’s moons Titan and Enceladus might be habitable, the probe will be flown into Saturn’s atmosphere to avoid any possible contamination of these moons with bacteria from Earth that might have somehow survived on the spacecraft.
Video courtesy of NASA’s Jet Propulsion Laboratory
Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.