Titan flyby launches Cassini into Grande Finale
NASA’s Cassini orbiter conducted its last and closest flyby of Saturn’s large moon Titan in the early morning hours of April 22, 2017, putting it on course for the mission’s Grand Finale of 22 orbits between the innermost rings and the giant planet.
At 2:08 a.m. EDT (06:08 GMT), Cassini flew 608 miles (979 kilometers) above Titan’s surface, the closest of its 127 flybys of the large moon since arriving at Saturn in July 2004.
The flyby route took Cassini over Titan’s north polar region, observing it with radar for the first time. During previous flybys, the area was observed only by imaging cameras.
Mission scientists hope the radar observations will yield answers as to the depth and composition of Titan’s smaller lakes and answer questions about the strange “magic islands” in the lakes that at times appear, disappear, and then reappear.
Data collected during this final flyby has been already returned to Earth for study by scientists.
“Cassini’s up-close exploration of Titan is now behind us, but the rich volume of data the spacecraft has collected will fuel scientific study for decades to come,” said mission project scientist Linda Spilker of NASA’s Jet Propulsion Laboratory in California.
Video courtesy of the Jet Propulsion Laboratory
Saturday’s flyby served as a gravity assist because Titan’s gravity bent Cassini’s path, altering its orbit and sending it between Saturn’s rings and the planet.
The maneuver sealed the spacecraft’s fate, putting it on a collision course with Saturn on Sept. 15, 2017, even if no additional course correction maneuvers are made.
Having picked up speed from the gravity assist, Cassini is now traveling at a velocity of 1,925 mph (860.5 meters per second). It reached the furthest position in its current orbit, known as apoapsis, at 11:46 p.m. EDT April 22 (03:46 GMT April 23).
From this position, it will embark on its first of 22 plunges between the rings and the giant planet at approximately 5 a.m. EDT (09:00 GMT) April 26.
Mission scientists are commemorating that day as the Grand Finale’s start.
During the dive and for approximately one additional day, the spacecraft will be unable to contact Earth due to its closeness to Saturn. Its instruments will conduct science observations of the ringed planet at that time.
Radio contact with Earth is set to resume no earlier than 3:05 a.m. EDT (07:05 GMT) April 27. At that point, data and images collected during the dive will be returned to Earth.
Its 22 dives over the next several months will skim the inner edges of Saturn’s rings and explore the planet’s atmosphere, sending back information that will give scientists a better understanding of the formation and evolution of gas giants.
Flying this close to the planet posed too much of a risk to the spacecraft earlier in the mission but can be undertaken now, with Cassini soon to run out of fuel.
Between April 26 and Sept. 15, Cassini will map Saturn’s magnetic field and gravity, measure the material in the rings, sample ring particles the planet’s magnetic field is drawing into its atmosphere, and take closeup images of the rings and of Saturn’s clouds.
The spacecraft is being plunged into Saturn’s atmosphere at the end of its mission to avoid any contamination of two possibly habitable moons, Titan and Enceladus, with microbes from Earth that may have survived on the probe.
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.