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Here’s what Cassini heard as it made its daring dive between Saturn and its rings

By Tom Yulsman | May 2, 2017 10:57 am

A Simon and Garfunkel song comes to mind—and that has scientists scratching their heads as the spacecraft heads today for a second dive.

In this illustration, the Cassini spacecraft is shown diving between Saturn and the planet’s innermost ring. (Source: NASA/JPL-Caltech)

As the Cassini spacecraft swooped between Saturn and its innermost ring on April 26th, one of its instruments listened for the sounds of its passage through the heretofore unexplored region. What it heard was of great interest to engineers planning for the second dive, as well as to scientists who study Saturn’s rings.

The engineers were hoping to hear the sound of silence, specifically nothing indicative of lots of dust hitting the spacecraft. If the gaps between Saturn and its rings turned out to be very dusty, on future dives — including the next one, scheduled for today, May 2nd — the spacecraft would once again have to use its 13-foot-wide antenna to shield its delicate instruments.

The ring scientists, though, were expecting to hear the sound of lots of particles hitting the spacecraft — because they thought this gap would be fairly dusty.

As it turned out, the engineers came away delighted, and the scientists puzzled.

“The region between the rings and Saturn is ‘the big empty,’ apparently,” said Cassini Project Manager Earl Maize of NASA’s Jet Propulsion Laboratory, quoted in a press release. “Cassini will stay the course, while the scientists work on the mystery of why the dust level is much lower than expected.”

Let’s listen to what the spacecraft heard:

This video presents data collected by the Radio and Plasma Wave Science instrument, or RPWS, on NASA’s Cassini spacecraft. RPWS tunes in, so to speak, to radio waves, as well as plasma waves, around Saturn. In the sound accompanying the video, the whistles and squeaks you hear come from waves in the charged particle environment.

These data provide scientists with valuable information beyond what Cassini’s imaging instruments offer. As NASA puts it:

By studying radio and plasma waves around Saturn, scientists can better understand Saturn’s relationship with its moons and rings, as well as how the planet interacts with the solar wind. For example, Saturn’s auroras emit radio waves in approximately the same frequency range as AM radio stations on Earth.

But the instrument also can hear any dust that’s hitting it. Not quite like a microphone on a recorder, though. Instead, data on particle strikes are converted to an audio format, producing pops and cracks.

In the audio track above, there is virtually no detectable peak in pops and cracks from dust particles striking the spacecraft as it shoots through the gap, labeled as “Ring Plane Crossing.”

“It was a bit disorienting — we weren’t hearing what we expected to hear,” said William Kurth, RPWS team lead at the University of Iowa, quoted in the NASA press release. “I’ve listened to our data from the first dive several times and I can probably count on my hands the number of dust particle impacts I hear.”

In stark contrast, here’s what it sounded like when Cassini passed through a faint, dusty ring on Dec. 18, 2016:

That peak in pops and cracks toward the middle is the sound of a very dusty environment. And it is obviously very different from what Cassini heard as it shot through the gap on April 26th.

That dive, and the second one scheduled for today, are part of Cassini’s ‘Grand Finale.’ This final chapter in Cassini’s epic journey will include 22 dives between the rings and the planet. It will all culminate on September 15, 2017, when Cassini is scheduled to dive into Saturn’s atmosphere, putting an end to the mission.

CATEGORIZED UNDER: Astronomy, Planetary Science, select, Solar System, Space Exploration, Top Posts

MORE ABOUT: Cassini, dust, Grand Finale, rings, RPWS, Saturn

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Come again? NASA’s Cassini spacecraft traveled 750 million miles to Saturn only to find a ‘noodle’?

By Tom Yulsman | July 26, 2017 4:33 pm

Okay, to be more accurate, Cassini produced a noodle. Well, actually, it’s a noddle-shaped movie. Sort of…

This video pans across a continuous long and narrow mosaic of 137 images of Saturn captured by NASA’s Cassini spacecraft when it dove between the giant gaseous planet and its rings on April 26th, 2017. Please click on the image to watch the video. As for why NASA scientists are calling this a “noodle,” read on… (Source: NASA/JPL-Caltech/Space Science Institute/Hampton University)

Yes, my tongue is poking into my cheek — but only part way.

NASA’s just come out with a Cassini spacecraft movie that takes us on a swooping journey low over Saturn’s cloud tops. And, in fact, the video pans across something the agency’s imaging wizards really are calling a “noodle.”

I happen to think it looks more like a nematode than a noodle, or maybe a hookworm. But you can decide for yourself: 

Source: NASA/JPL-Caltech/Space Science Institute/Hampton University

You’re looking at a mosaic of 137 images captured in the near-infrared by Cassini as it dove for the first time through the gap between Saturn and its rings on April 26th, 2017. This was the kick-off to the spacecraft’s “Grand Finale,” a series of 22 daring dives culminating on Sept. 15, 2017 when the spacecraft will plunge into Saturn’s atmosphere and burn up.

The video at the top of this post pans along the length of the mosaic, which the imaging scientists are calling a “noodle” because of its long, narrow shape.

NASA released an earlier video consisting of the same imagery. But in that video, each image made up a single movie frame. For this much improved version, scientists significantly increased the contrast and sharpness of each image, and then they combined them into the single, continuous mosaic over which the video pans.

The noodle covers an extremely long but narrow swath of Saturn’s atmosphere, from the north polar vortex to the boundary of the hexagon-shaped jet stream, to swirling and banded details at middle latitudes and beyond.

The first frame of the mosaic centers on Saturn’s north pole, according to NASA’s release.  The final frame shows a region at 18 degrees north latitude. During the dive, Cassini swooped from 45,000 miles above the clouds to as close as 3,200 miles.

Source: NASA/JPL-Caltech/Space Science Institute/Hampton University

NASA scientists have also produced a second noodle mosaic, using images acquired by Cassini as it was making another plunge between the Saturnian cloud tops and rings on June 29, 2017. Click on the thumbnail at right to view it, and then click again to enlarge it to see detail in the cloud tops.

According to NASA:

For the first frame of the mosaic, Cassini’s camera was pointed toward a location at approximately 80 degrees north latitude, as the spacecraft was flying 16,000 miles (26,000 kilometers) above the top of the clouds at 45 degrees north latitude. When the last frame was captured, the orbiter was 8,000 miles (13,000 kilometers) above 30 degrees north latitude and looking straight down at the planet.

Those scientists are so busy making noodles that I’m wondering whether the next release from NASA will be a veritable plate of spaghetti.

In any case, I think they’re pretty tasty.

So is this completely different image — exquisitely beautiful in its simplicity:

View of Saturn from NASA’s Cassini spacecraft. (Source: NASA/JPL-Caltech/Space Science Institute)

This false-color view from Cassini, acquired on July 16, 2017, at a distance of about 777,000 miles, shows Saturn’s sunlit horizon. A thin, bluish haze can be seen along the limb — the planet’s visual edge. (“Limb” comes from the Latin word limbus which means border.) Beyond are Saturn’s rings.

From NASA:

Cassini will pass through Saturn’s upper atmosphere during the final five orbits of the mission, before making a fateful plunge into Saturn on Sept. 15, 2017. The region through which the spacecraft will fly on those last orbits is well above the haze seen here, which is in Saturn’s stratosphere. In fact, even when Cassini plunges toward Saturn to meet its fate, contact with the spacecraft is expected to be lost before it reaches the depth of this haze.

Between now and then I’m sure we’re going to be treated to more spectacular imagery. So stay tuned.

CATEGORIZED UNDER: Astronomy, Planetary Science, select, Space Exploration, Top Posts

MORE ABOUT: Cassini, Grand Finale, noodle, planetary science, Saturn, Space Exploration