After 20 years in space and 13 years around Saturn, NASA’s Cassini spacecraft begins the final chapter of its remarkable story of exploration and discoveries: ‘Grand Finale.’ Between April and September 2017, the orbiter will dive 22 times through the unexplored space between Saturn and its innermost ring. On September 15, Cassini mission will come to an end with a plunge into the ringed planet. The finale is designed to keep the spacecraft from impacting and possibly contaminating Saturn’s scientifically intriguing moons Enceladus and Titan.
This illustration shows Cassini above Saturn’s northern hemisphere prior to making one of its Grand Finale dives. Image credit: NASA / JPL-Caltech.
During its time at Saturn, Cassini has made numerous dramatic discoveries, including a global ocean that showed indications of hydrothermal activity within Enceladus, and liquid methane seas on Titan.
Now two decades since launching from Earth, and after 13 years orbiting the ringed planet, Cassini is running low on the rocket fuel used for adjusting its course.
In 2010, NASA decided to end the mission with a purposeful plunge into Saturn this year in order to protect and preserve the planet’s moons for future exploration.
But the beginning of the end for Cassini is, in many ways, like a whole new mission.
Using expertise gained over the mission’s many years, Cassini engineers designed a flight plan that will maximize the scientific value of sending the spacecraft toward its fateful plunge into the planet in September.
As it ticks off its terminal orbits during the next five months, the mission will rack up an impressive list of scientific achievements.
“This planned conclusion for Cassini’s journey was far and away the preferred choice for the mission’s scientists. Cassini will make some of its most extraordinary observations at the end of its long life,” said Cassini project scientist Dr. Linda Spilker, from NASA’s Jet Propulsion Laboratory.
The Cassini team hopes to collect some incredibly rich and valuable information that was too risky to obtain earlier in the mission:
(i) Cassini will make detailed maps of Saturn’s gravity and magnetic fields, revealing how the second largest planet in the Solar System is arranged internally, and possibly helping to solve the irksome mystery of just how fast Saturn is rotating;
(ii) the final dives will vastly improve our knowledge of how much material is in the rings, bringing us closer to understanding their origins;
(iii) the orbiter’s particle detectors will sample icy ring particles being funneled into the atmosphere by Saturn’s magnetic field;
(iv) Cassini’s cameras will take amazing, ultra-close images of Saturn’s rings and clouds.
According to the team, Cassini will transition to its grand finale orbits, with a last close flyby of Titan, on April 22.
On April 26, the spacecraft will make the first in a series of dives through the 1,500-mile (2,400 km) wide gap between Saturn and its rings.
In mid-September, following a distant encounter with Titan, the spacecraft’s path will be bent so that it dives into the gas giant.
When Cassini makes its final plunge into Saturn’s atmosphere on September 15, it will send data from several instruments until its signal is lost.
“Cassini’s grand finale is so much more than a final plunge,” Dr. Spilker said.
“It’s a thrilling final chapter for our intrepid spacecraft, and so scientifically rich that it was the clear and obvious choice for how to end the mission.”
