Dr Ian Griffin: Final hours for Saturn's space probe

Camille Francis
September 15, 2017

And above all, the Cassini mission helped us better understand the atmosphere and global mechanisms of Saturn itself.

Cassini is the most distant planetary orbiter ever launched and has made many astonishing discoveries in its near 14 year adventure.

"The spacecraft's final signal will be like an echo, " said Earl Maize, Cassini project manager at JPL.

"That will enable sampling instruments, particularly the ion and neutral mass spectrometer, to get data as deep into the atmosphere as Cassini will permit it", he said. "Almost like we've taken a magnifying glass to the planet and the rings". Navigators will also be analyzing this information in the hopes of confirming that Cassini is precisely on track and ready to plunge into Saturn at the designated time, location, and altitude. "But Cassini will not go quietly".

- The Jet Propulsion Laboratory-managed Cassini spacecraft was on its final approach Wednesday toward Saturn - and its ultimate doom.

According to NASA, this final flyby of Titan was also Cassini's closest one as the spacecraft lowered to just 73,974 miles above the moon's surface.

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Mission scientists and operators are giving Cassini this fiery send-off on goal. Scientists still haven't been able to differentiate between Saturn's magnetic field axis and its rotation axis, which surprises even them: "We figured it'd kind of jump out at us", Neiber says. It astonished scientists by finding conditions potentially suitable for life beneath the surface of one of Saturn's icy moons, Enceladus.

Both Titan and Enceladus are now considered two of the best places to search for alien life in the Solar System, and the reason why NASA chose to ensure that the spacecraft will, in its final act, be programmed to take a trajectory that will ensure it burns up in Saturn's upper atmosphere.

The Cassini mission has provided some incredibly close-up and striking images of Saturn and its moons, with a camera that was five times the resolution of the one on Voyager (plus a radar to see through Titan's atmosphere).

To protect those Enceladus and Titan from contamination with Earth life, Cassini is going to dive down into Saturn's atmosphere before the probe runs out of fuel, which could have left it drifting on a collision course with the planet's moons. This is another reason the mission scientists decided on Cassini's particular end-game. And surely that will continue with its final dive, she said.

Because Saturn is so far from Earth, Cassini will have been gone for about 83 minutes by the time its final signal reaches NASA's Deep Space Network station in Australia on September 15.

It is known as the Cassini-Huygens mission because it delivered ESA's Huygens probe to Titan - the "first descent and landing on a world in the outer solar system", according to NASA. The mission launched in 1997, and has essentially revolutionized our understanding of how Saturn and its complex system of 53 official moons works. Cassini was officially assigned a four years prime mission, but it was extended twice and resulted in an astonishing 13 years long mission highlighting the enormous capacity of the space craft. Saturn has been Cassini's home for the last 13 years. The Grand Finale is necessitated to prevent the possibility of Earthly bacteria that has been living on Cassini for the last 20 years contaminating an object orbiting Saturn - an unlikely but possible occurrence.

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