Cassini braces for final plunge into Saturn

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NASA's Cassini probe is counting down the hours until the final plunge into Saturn on September 15. This will cap a fruitful 13-year mission that greatly expanded knowledge about the gaseous giant.

While orbiting Saturn nearly 300 times, Cassini made major discoveries, such as the liquid methane seas of the planet's giant moon Titan and the sprawling subsurface ocean of a small moon named Enceladus.

"Cassini-Huygens is an extraordinary mission of discovery that has revolutionized our understanding of the outer solar system," said Alexander Hayes, assistant professor of astronomy at Cornell University.

Data collected by Cassini's spectrometer while passing through a vapor plume at Enceladus's south pole showed hydrogen shooting up through cracks in its ice layer.

The gas was a sign of hydrothermal activity favorable to life, scientists said in April when they presented the finding.

Launched in 1997 and equipped with a dozen scientific instruments, the 2.5-ton probe entered Saturn's orbit in 2004, landing on Titan in December of that year.

On Apr 22, it began the maneuvers for its final journey.

NASA's Cassini spacecraft prepares to make one of its dives between Saturn and its innermost rings on April 6, 2017. /AFP Photo

Moving closer to Titan, the spacecraft took advantage of the massive moon's gravitational push to make the first of 22 weekly dives between Saturn and its rings - venturing for the first time into the uncharted 1,700-mile (2,700 kilometers) space.

Cassini's last five orbits will take it through Saturn's uppermost atmosphere, before a final plunge directly into the planet on September 15.

Last goodbyes

Cassini flew by Titan one last time on Tuesday before transmitting images and scientific data from the flight.

Mission engineers will use the information gathered from the encounter - dubbed "the goodbye kiss" - to make sure the vessel is following the right path when plunging into the gaseous giant's atmosphere.

"The Cassini mission has been packed full of scientific firsts, and our unique planetary revelations will continue to the very end of the mission as Cassini becomes Saturn's first planetary probe, sampling Saturn's atmosphere up until the last second," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory.

"We'll be sending data in near real time as we rush headlong into the atmosphere - it's truly a first-of-its-kind event at Saturn."

NASA's Cassini spacecraft captures a near-infrared, color mosaic on October 31, 2014, showing the sun glinting off of Titan's north polar seas. /AFP Photo

Cassini is expected to lose communications with Earth one or two minutes into its final dive, but 10 of its 12 scientific instruments will be working right up until the last moment to analyze the atmosphere's composition.

That data could help understand how the planet formed and evolved.

On the eve of its final descent, other instruments will make detailed observations of Saturn's aurora borealis, temperatures and polar storms.

Grand finale

Cassini's final maneuvers begin at 8:37 GMT Friday. At 11:53 GMT, the spacecraft is due to enter Saturn's atmosphere with its antennas pointed toward Earth and its motors running at full power in order to hold its trajectory.

Just a minute later, at some 940 miles (1,510 kilometers) above Saturn's clouds, the probe's communications will stop before Cassini begins to disintegrate moments later, NASA predicts.

The spinning vortex of Saturn's north polar storm is seen from NASA's Cassini spacecraft on November 27, 2012. /AFP Photo

"The Grand Finale represents the culmination of a seven-year plan to use the spacecraft's remaining resources in the most scientifically productive way possible," said Earl Maize, Cassini project manager at NASA's Jet Propulsion Laboratory in Pasadena, California.

"By safely disposing of the spacecraft in Saturn's atmosphere, we avoid any possibility Cassini could impact one of Saturn's moons somewhere down the road, keeping them pristine for future exploration."

The mission is a cooperative project of NASA, the European Space Agency (ESA) and Italy's space agency. NASA's European and Italian partners built the Huygens probe Cassini carried until dropping it on Titan.

The Cassini-Huygens mission's total cost is about 3.26 billion US dollars, including 1.4 billion US dollars for pre-launch development, 704 million US dollars for mission operations, 54 million US dollars for tracking and 422 million US dollars for the launch vehicle.

The United States contributed 2.6 billion US dollars to the project, the European Space Agency 500 million US dollars and the Italian Space Agency 160 million US dollars.

Italian astronomer Giovanni Cassini discovered Saturn's four moons in the 17th century. During the same era, Dutch mathematician Christiaan Huygens found that Saturn had rings. He also was the first person to observe Titan.

Source(s): AFP