Cassini skims Saturn's atmosphere

[nitpicker]

http://www.bbc.com/news/science-environment-40902774

Cassini skims Saturn's atmosphere

By Jonathan Amos
BBC Science Correspondent

2 hours ago

From the section Science & Environment


The Cassini probe is beginning the final phase of its mission to Saturn. The satellite is executing the first of five ultra-close passes of the giant world, dipping down far enough to brush through the top of the atmosphere. It promises unprecedented data on the chemical composition of Saturn. It also sets the stage for the probe's dramatic end-manoeuvre next month when it will plunge to destruction in the planet's atmosphere.

Cassini is currently flying a series of loops around Saturn that thread the gap between its atmosphere and its rings. Monday's swing-by sees the spacecraft go closer than ever before to the cloud tops - skimming just 1,600km (1,000 miles) above them, at 04:22 GMT (05:22 BST) on Monday. This allows the probe to directly sample the gases of the extended upper-atmosphere.

Saturn's bulk composition is thought to be about 75% hydrogen with the rest being helium (bar some trace components), explains Nicolas Altobelli, the European Space Agency's Cassini project scientist. "It's expected that the heavier helium is sinking down," he told BBC News. "Saturn radiates more energy than it's absorbing from the Sun, meaning there's gravitational energy which is being lost. And so getting a precise measure of the hydrogen and helium in the upper layers sets a constraint on the overall distribution of the material in the interior."

Dipping down into the atmosphere will create a drag on the spacecraft, and Cassini may need to use its thrusters to maintain a stable flight configuration and stop itself from tumbling. But the mission's scientists think the buffeting effects can be adequately managed and are hopeful of going even lower on the remaining four passes before 15 September's goodbye plunge.
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[frogmarch]

1. My daughter was on the Cassini launch team, and

it was her first job as a full-fledged scientist. She's still in the space biz and still loves it. Proud of her.

[Judi Lynn]

2. Cassini Probes Last Saturn Mysteries 1 Month from Demise

By Ian O'Neill, Space.com Contributor | August 15, 2017 04:07pm ET

- video -


The end is nigh for NASA's trailblazing Cassini mission to Saturn as the veteran spacecraft enters its final month in orbit. The probe will burn up like an artificial meteor in the gas giant's upper atmosphere on Sept. 15, ending a 13-year odyssey at the ringed planet.

As the concluding phase of its "Grand Finale," the spacecraft has begun a series of daring, ultraclose passes of the planet to end its mission in style. Cassini's current orbit takes the spacecraft high over the planet's poles and through the gap between the planet's innermost ring and upper atmosphere — close passes that will ultimately end with Cassini careening deep into Saturn's upper atmosphere.

"It's very bittersweet," said Jo Pitesky, Cassini project science system engineer at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "But [Cassini's] doing what she was built for. She's going on to explore and to see the mission acquire great science and not go out with a whimper. … It's tremendously fulfilling." [Cassini's 'Grand Finale' at Saturn: NASA's Plan in Pictures]

On Monday (Aug. 14), Cassini made its closest flyby of Saturn yet, swooping just 1,000 miles (1,600 kilometers) above the planet's cloud tops. At this distance, the spacecraft's cameras can see atmospheric features just 16 miles (25 km) across, 100 times smaller than it could see at any time before the Grand Finale phase of the mission, NASA officials wrote in a statement. But as Cassini gets closer, it will also be able to take direct measurements of the atmosphere, ultimately becoming an atmospheric probe itself.

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https://www.space.com/37808-cassini-saturn-probe-one-month-mission-end.html?utm_source=notification