Washington, Dec 1 (IANS): NASA's Cassini spacecraft began a "ring-grazing" mission to study Saturn's rings and moons, media reports said.

According to NASA, the "thrilling" ride 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, Xinhua news agency reported.

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

"In addition, we have two instruments that can sample particles and gases as we cross the ring-plane, 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.

Cassini's ring-grazing orbits also offer "unprecedented opportunities to observe the menagerie of small moons", 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 2,350 km gap between Saturn and its rings.

Finally, the long-lived spacecraft will make a mission-ending plunge into the planet's atmosphere on September 15, 2017.

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.