Cassini readies last plunge into Saturn

Spacecraft gets funny opera send-off

WASHINGTON, Sept 14, (Agencies): NASA’s Cassini probe is counting its final hours before one last plunge into Saturn on Friday that will cap a fruitful 13-year mission that greatly expanded knowledge about the gas 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 Enceladus, a small Saturn moon.

“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 unveiled the finding.

Launched in 1997 and equipped with a dozen scientific instruments, the 2.5-tonne probe entered Saturn’s orbit in 2004, landing on Titan in December of that year. On April 22, it began the maneuvers for its final journey.

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-km) space.

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

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 they dubbed “the goodbye kiss” to make sure the vessel is following the right path to plunge into the gas 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 in Pasadena, California.

“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.”

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.

Cassini’s final maneuvers begin at 0714 GMT Friday, although the signal will only reach NASA 86 minutes later.

At 1031 GMT, the spacecraft is due to enter Saturn’s atmosphere with its antennas pointed toward Earth and its motors running full blast in order to hold its trajectory.

Communicatons

Just a minute later, at some 940 miles (1,510 kms) above Saturn’s clouds, the probe’s communications will stop before Cassini begins to disintegrate moments later, NASA predicts. “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 the Jet Propulsion Laboratory.

“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, including $1.4 billion for pre-launch development, $704 million for mission operations, $54 million for tracking and $422 million for the launch vehicle.

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

Italian astronomer Giovanni Cassini discovered four of Saturn moons in the 17th century, although scientists have since identified more than 60. During the same era, Dutch mathematician Christiaan Huygens found that Saturn had rings. He also was the first person to observe Titan.

NASA’s Cassini spacecraft is getting a grand but hilarious opera send-off before it plunges through Saturn’s atmosphere and vaporizes Friday.

Lyrics

An actor from TV’s old “Star Trek: Voyager” series, Robert Picardo, said he dashed off the lyrics in about a minute, several weeks ago. He collaborated with the creative director of The Planetary Society, and, presto, “Le Cassini Opera” was born.

Picardo set the words to the instantly recognizable aria “La Donna e mobile” from Verdi’s “Rigoletto.”

While Cassini’s 20-year mission has been “a serious success,” Picardo said the opera is definitely a comedy. Here’s how it opens: “Goodbye, Cassini. Your mission’s fini. Bravo, Cassini! Have some linguini.” And on it goes, paying humorous tribute.

“No tragedy here. All good things — NASA missions, ‘Star Trek’ series, turkey and Swiss sandwiches with avocado — come to an end,” Picardo told The Associated Press.

Cassini’s program manager, Earl Maize, loves the performance.

“It’s very heartwarming to us,” Maize told reporters Wednesday at the Jet Propulsion Laboratory in Pasadena, California.

“Part of what we try to do is to extend everybody out to Saturn. It’s not science for the ivory tower. It’s for humanity, and so everybody to get on the ride, come with us, is just phenomenal.”

That was Picardo’s goal, too. A longtime fan of both space and opera, he merged those interests in “Star Trek: Voyager” as the holographic doctor who bursts into song. It seemed fitting that he celebrate Cassini in song, too. He actually got to see Cassini’s hitchhiking moon lander, the European Huygens, before it left Earth in 1997.

Picardo said Wednesday from Beverly Hills, California, that he sang “Le Cassini Opera” through twice. Five minutes, and that was a wrap.