Cassini spacecraft vanishes, ending historic mission to Saturn

Source:Xinhua Published: 2017/9/16 10:39:19

After a 13-year tour of Saturn, the US National Aeronautics and Space Administration (NASA)'s Cassini spacecraft made a fateful plunge into the atmosphere of the ringed planet early Friday morning, ending the mission just one month shy of its 20th launch anniversary.

"Earth received @CassiniSaturn's final signal at 7:55 a.m. ET (1155 GMT). Cassini is now part of the planet it studied," Cassini's team said on Twitter Friday morning.

The last signal was received by NASA's Deep Space Network antenna complex in Canberra, Australia.

Head of spacecraft operations Julie Webster called "loss of signal," followed by Project Manager Earl Maize announcing "end of mission" as the spacecraft began to break up in Saturn's atmosphere.

"Congratulations to you all," Maize told the team. "It's been an incredible mission, incredible spacecraft, and you are an incredible team."

The probe was running low on fuel, so the 13-year tour of the Saturn system mission had to end.

The spacecraft made a deliberate plunge into Saturn's atmosphere to avoid the small possibility of it crashing into a potentially habitable moon, in particular Enceladus.

"It's a bittersweet, but fond, farewell to a mission that leaves behind an incredible wealth of discoveries that have changed our view of Saturn and our solar system, and will continue to shape future missions and research," Michael Watkins, director of NASA's Jet Propulsion Laboratory (JPL), said in a statement.

Traveling at approximately 113,000 km per hour, Cassini entered Saturn's atmosphere at an altitude of about 1,915 km above the planet's estimated cloud tops about 3:31 a.m. PDT (1031 GMT), according to JPL's choreographed plan.

Then, the spacecraft stopped communicating with Earth one minute later.

Within three more minutes, Cassini's 12 scientific instruments were torn apart. Then they melted, and vaporized.

Due to the travel time for radio signals from Saturn, which changes as both Earth and the ringed planet travel around the Sun, events took place there 83 minutes before they were observed on Earth.

This means that, the signal from that event would not be received on Earth until 83 minutes later.

Cassini has made groundbreaking scientific observations of Saturn.

Before contact was lost, eight of Cassini's 12 scientific instruments were operating during the final plunge.

In particular, the spacecraft's Ion and Neutral Mass Spectrometer was directly sampling the atmosphere's composition, which cannot be done from orbit.

As planned, data from eight of Cassini's science instruments were beamed back to Earth, according to NASA.

Mission scientists will examine the spacecraft's final observations in the coming weeks for new insights about Saturn, including hints about the planet's formation and evolution, and processes occurring in its atmosphere.

Cassini's plunge brings to a close a series of 22 weekly "Grand Finale" dives between Saturn and its rings, a feat never before attempted by any spacecraft.

The probe's imaging camera has taken a last look at the Saturn system on the day before the plunge and was off during this final descent.

Launched in 1997, the 3.26-billion-US-dollar Cassini-Huygens mission has been touring the Saturn system since arriving there in 2004.

The Huygens lander separated from Cassini and plopped down on the surface of Saturn's moon Titan shortly after the arrival.

The Cassini probe had been scheduled to study the Saturn system until 2008, but the mission was given two extensions that stretched its lifetime into 2017.

During its journey, Cassini has made numerous dramatic discoveries.

"Cassini's discovery of ocean worlds at Titan and Enceladus changed everything, shaking our views to the core about surprising places to search for potential life beyond Earth," Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at NASA headquarters in Washington, said in a statement.

"This is the final chapter of an amazing mission, but it's also a new beginning," Zurbuchen said.

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