Astronomy - Cassini Begins Epic Final Year at Saturn

Cassini Begins Epic Final Year at Saturn

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004 for a close up study of the planet, its rings and moons. During its journey, Cassini has made numerous dramatic discoveries, including a global ocean within Enceladus and liquid methane seas on Titan.

 

 

Between Nov. 30 2016 and April 22 2017, Cassini will circle high over and under the poles of Saturn, diving every seven days a total of 20 times through the unexplored region at the outer edge of the main rings.

"We're calling this phase of the mission Cassini's Ring-Grazing Orbits, because we'll be skimming past the outer edge of the rings," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory. "In addition, we have two instruments that can sample particles and gases as we cross the ring plane."

On many of these passes, Cassini's instruments will attempt to directly sample ring particles and molecules of faint gases that are found close to the rings. During the first two orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking the two small moons Janus and Epimetheus.

Ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring.

Even though we're flying closer to the F ring than we ever have, we'll still be more than 4,850 miles (7,800 kilometres) distant

The F ring marks the outer boundary of the main ring system; Saturn has several other, much fainter rings that lie farther from the planet. The F ring is complex and constantly changing: Cassini images have shown structures like bright streamers, wispy filaments and dark channels that appear and develop over mere hours.

The ring is also quite narrow—only about 500 miles (800 kilometres) wide. At its core is a denser region about 30 miles (50 kilometres) wide.

Cassini is expected to determine the mass of Saturn's rings by tracking radio signals from the spacecraft as it flies close to the rings.

The rings, which are made of small, icy particles spread over a vast area, are extremely thin – generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material.

During the Grand Finale, Cassini will make the closest-ever observations of Saturn, mapping the planet's magnetic and gravity fields with exquisite precision and returning ultra-close views of the atmosphere.

Scientists also hope to gain new insights into Saturn's interior structure, the precise length of a Saturn day, and the total mass of the rings which may finally help settle the question of their age.

The spacecraft will also directly analyse dust-sized particles in the main rings and sample the outer reaches of Saturn's atmosphere both first-time measurements for the mission.

 

 

Cassini Orbits of Saturn

 

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.

The Cassini orbiter and its two on board cameras were designed, developed and assembled at JPL. The imaging operations centre is based at the Space Science Institute in Boulder, Colorado.