NASA's Cassini begins "ring-grazing" mission at Saturn

NASA's Cassini spacecraft on Wednesday began what the U.S. space agency called a "ring-grazing" mission to study Saturn's rings and moons.

Cassini is using a gravitational nudge from Saturn's moon Titan to get into an orbit that is closer to perpendicular with respect to the rings of Saturn and its equator.

The "thrilling" ride, according to NASA, marked the first phase of a "dramatic endgame" for the 19-year-old spacecraft, and over the next five months, Cassini will circle high over and under the poles of Saturn every seven days for a total of 20 times.

"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," Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory (JPL), said in a statement.

"In addition, we have two instruments that can sample particles and gases as we cross the ringplane, so in a sense Cassini is also 'grazing' on the rings."

During the first two orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking Saturn's two small moons Janus and Epimetheus.

Then, ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring, which marks the outer boundary of the planet's main ring system.

Saturn has several other, much fainter rings that lie farther from the planet.

"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 kilometers) distant. There's very little concern over dust hazard at that range," said Earl Maize, Cassini project manager at JPL.

Cassini's ring-grazing orbits also offer "unprecedented opportunities to observe the menagerie of small moons" that orbit in or near the edges of the rings, including best-ever looks at the moons Pandora, Atlas, Pan and Daphnis, said NASA.

However, these orbits are merely a prelude to the spacecraft's "Grand Finale phase" that will begin in April 2017, when Cassini is scheduled to fly through the 1,500-mile (2,350-kilometer) gap between Saturn and its rings.

Finally, the long-lived spacecraft will make a mission-ending plunge into the planet's atmosphere on Sept. 15.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004. During its journey, Cassini has made numerous dramatic discoveries, including a global ocean within Enceladus and liquid methane seas on Titan. But the mission is drawing near its end because the spacecraft is running low on fuel. Endit