NASA���s Cassini Spacecraft Prepares for Ring-Grazing Phase | Space Exploration |

NASA���s Cassini Spacecraft Prepares for Ring-Grazing Phase | Space Exploration |

NASA’s Cassini Spacecraft Prepares for Ring-Grazing Phase

In the final year of its epic voyage, on Nov. 30, NASA’s Cassini orbiter will begin a daring set of ‘ring-grazing orbits,’ skimming past the outside edge of Saturn’s main rings.

Artist’s concept of NASA’s Cassini spacecraft at Saturn. Image credit: NASA.

Artist’s concept of NASA’s Cassini spacecraft at Saturn. Image credit: NASA.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004 for an up-close study of the gas giant, its rings and moons.

During its journey, the probe has made numerous discoveries, including a global ocean within Enceladus and liquid methane seas on Titan.

On Nov. 30, following a gravitational nudge from Titan, Cassini will enter the first phase of the mission’s dramatic endgame.

Cassini will fly closer to Saturn’s rings than it has since its 2004 arrival. It will begin the closest study of the rings and offer unprecedented views of moons that orbit near them.

These orbits, a series of 20, are called ring-grazing orbits, or F-ring orbits.

During these weekly orbits, Cassini will approach to within 4,850 miles (7,800 km) of the center of the narrow F ring, with its peculiar kinked and braided structure.

Cassini’s instruments will attempt to directly sample ring particles and molecules of faint gases.

“Even though we’re flying closer to the F ring than we ever have, we’ll still be more than 4,850 miles distant. There’s very little concern over dust hazard at that range,” said Cassini project manager Dr. Earl Maize, from NASA’s Jet Propulsion Laboratory (JPL).

The F ring marks the outer boundary of the main ring system. This 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 km) wide. At its core is a denser region about 30 miles (50 km) wide.

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

“During the F-ring orbits we expect to see the rings, along with the small moons and other structures embedded in them, as never before,” said Cassini project scientist Dr. Linda Spilker, also from JPL.

“The last time we got this close to the rings was during arrival at Saturn in 2004, and we saw only their backlit side.”

“Now we have dozens of opportunities to examine their structure at extremely high resolution on both sides.”

During ring-grazing orbits, the spacecraft will pass as close as about 56,000 miles (90,000 km) above Saturn’s cloud tops. But even with all their exciting science, these orbits are merely a prelude to the planet-grazing passes that lie ahead.

In April 2017, Cassini will begin its Grand Finale phase. After nearly 20 years in space, the mission is drawing near its end because the spacecraft is running low on fuel.

The Cassini team carefully designed the finale to conduct an extraordinary science investigation before sending the spacecraft into Saturn to protect its potentially habitable moons.

During this phase, the probe will pass as close as 1,012 miles (1,628 km) above the clouds as it dives repeatedly through the narrow gap between Saturn and its rings, before making its mission-ending plunge into the planet’s atmosphere on Sept. 15, 2017.

November 28, 2016 at 01:50PM
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