Cassini's Last Hurrah

[bystander]

NASA Saturn Mission Prepares for 'Ring-Grazing Orbits'
NASA | JPL-Caltech | Cassini | 2016 Nov 22

Click to play embedded YouTube video.

This graphic illustrates the Cassini spacecraft's trajectory, or flight path, during the final two phases of its mission. The view is toward Saturn as seen from Earth. The 20 ring-grazing orbits are shown in gray; the 22 grand finale orbits are shown in blue. The final partial orbit is orange. (Credit: NASA/JPL-Caltech/SSI)

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A thrilling ride is about to begin for NASA's Cassini spacecraft. Engineers have been pumping up the spacecraft's orbit around Saturn this year to increase its tilt with respect to the planet's equator and rings. And on Nov. 30, following a gravitational nudge from Saturn's moon Titan, Cassini will enter the first phase of the mission's dramatic endgame. ...

Between Nov. 30 and April 22, Cassini will circle high over and under the poles of Saturn, diving every seven days -- a total of 20 times -- through the unexplored region at the outer edge of the main rings.

"We're calling this phase of the mission Cassini's Ring-Grazing Orbits, because we'll be skimming past the outer edge of the rings," said Linda Spilker ...

Cassini's ring-grazing orbits offer unprecedented opportunities to observe the menagerie of small moons that orbit in or near the edges of the rings, including best-ever looks at the moons Pandora, Atlas, Pan and Daphnis.

Grazing the edges of the rings also will provide some of the closest-ever studies of the outer portions of Saturn's main rings (the A, B and F rings). Some of Cassini's views will have a level of detail not seen since the spacecraft glided just above them during its arrival in 2004. The mission will begin imaging the rings in December along their entire width, resolving details smaller than 0.6 mile (1 kilometer) per pixel and building up Cassini's highest-quality complete scan of the rings' intricate structure. ...

During these orbits, Cassini will pass as close as about 56,000 miles (90,000 kilometers) above Saturn's cloud tops. But even with all their exciting science, these orbits are merely a prelude to the planet-grazing passes that lie ahead. In April 2017, the spacecraft will begin its Grand Finale phase. ...

[bystander]

Cassini Makes First Ring-Grazing Plunge
NASA | JPL-Caltech | Cassini | 2016 Dec 05

This graphic shows the closest approaches of Cassini's final two orbital phases. Ring-grazing orbits are shown in gray (at left); Grand Finale orbits are shown in blue. The orange line shows the spacecraft's Sept. 2017 final plunge into Saturn. (Credit: NASA/JPL-Caltech)

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NASA's Saturn-orbiting Cassini spacecraft has made its first close dive past the outer edges of Saturn's rings since beginning its penultimate mission phase on Nov. 30.

Cassini crossed through the plane of Saturn's rings on Dec. 4 at 5:09 a.m. PST (8:09 a.m. EST) at a distance of approximately 57,000 miles (91,000 kilometers) above Saturn's cloud tops. This is the approximate location of a faint, dusty ring produced by the planet's small moons Janus and Epimetheus, and just 6,800 miles (11,000 kilometers) from the center of Saturn's F ring.

About an hour prior to the ring-plane crossing, the spacecraft performed a short burn of its main engine that lasted about six seconds. About 30 minutes later, as it approached the ring plane, Cassini closed its canopy-like engine cover as a protective measure. ...

A few hours after the ring-plane crossing, Cassini began a complete scan across the rings with its radio science experiment to study their structure in great detail. ...

Cassini's imaging cameras obtained views of Saturn about two days before crossing through the ring plane, but not near the time of closest approach. The focus of this first close pass was the engine maneuver and observations by Cassini's other science instruments. Future dives past the rings will feature some of the mission's best views of the outer regions of the rings and small, nearby moons. ...

Cassini Ring-Grazing Orbit Details

[bystander]

Cassini Beams Back First Images from New Orbit
NASA | JPL-Caltech | Cassini | 2016 Dec 06

This collage of images from Cassini shows Saturn's northern hemisphere and rings as viewed with four different spectral filters. Each filter is sensitive to different wavelengths of light and reveals clouds and hazes at different altitudes. Clockwise from top left, the filters used are sensitive to violet (420 nm), red (648 nm), near-infrared (728 nm), and infrared (939 nm) light. (Credit: NASA/JPL-Caltech/SSI)

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NASA's Cassini spacecraft has sent to Earth its first views of Saturn's atmosphere since beginning the latest phase of its mission. The new images show scenes from high above Saturn's northern hemisphere, including the planet's intriguing hexagon-shaped jet stream.

Cassini began its new mission phase, called its Ring-Grazing Orbits, on Nov. 30. Each of these weeklong orbits -- 20 in all -- carries the spacecraft high above Saturn's northern hemisphere before sending it skimming past the outer edges of the planet's main rings.

Cassini's imaging cameras acquired these latest views on Dec. 2 and 3, about two days before the first ring-grazing approach to the planet. Future passes will include images from near closest approach, including some of the closest-ever views of the outer rings and small moons that orbit there. ...

The next pass by the rings' outer edges is planned for Dec. 11. The ring-grazing orbits will continue until April 22, when the last close flyby of Saturn's moon Titan will once again reshape Cassini's flight path. With that encounter, Cassini will begin its Grand Finale, leaping over the rings and making the first of 22 plunges through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its innermost ring on April 26.

On Sept. 15, the mission's planned conclusion will be a final dive into Saturn's atmosphere. During its plunge, Cassini will transmit data about the atmosphere's composition until its signal is lost. ...

[bystander]

NASA to Preview ‘Grand Finale’ of Cassini Saturn Mission
NASA | JPL-Caltech | Cassini | 2017 Mar 29

NASA will hold a news conference at 3 p.m. EDT Tuesday, April 4, at the agency’s Jet Propulsion Laboratory (JPL) in Pasadena, California, to preview the beginning of Cassini's final mission segment, known as the Grand Finale, which begins in late April. The briefing will air live on NASA Television and the agency’s website. ...

[bystander]

Cassini Mission Prepares for 'Grand Finale' at Saturn
NASA | JPL-Caltech | Cassini | 2017 Apr 04

Click to play embedded YouTube video.

NASA's Cassini spacecraft, in orbit around Saturn since 2004, is about to begin the final chapter of its remarkable story. On Wednesday, April 26, the spacecraft will make the first in a series of dives through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its rings as part of the mission's grand finale.

"No spacecraft has ever gone through the unique region that we'll attempt to boldly cross 22 times," said Thomas Zurbuchen, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "What we learn from Cassini's daring final orbits will further our understanding of how giant planets, and planetary systems everywhere, form and evolve. This is truly discovery in action to the very end."

During its time at Saturn, Cassini has made numerous dramatic discoveries, including a global ocean that showed indications of hydrothermal activity within the icy moon Enceladus, and liquid methane seas on its moon Titan.

Now 20 years since launching from Earth, and after 13 years orbiting the ringed planet, Cassini is running low on fuel. In 2010, NASA decided to end the mission with a purposeful plunge into Saturn this year in order to protect and preserve the planet's moons for future exploration -- especially the potentially habitable Enceladus.

But the beginning of the end for Cassini is, in many ways, like a whole new mission. Using expertise gained over the mission's many years, Cassini engineers designed a flight plan that will maximize the scientific value of sending the spacecraft toward its fateful plunge into the planet on Sept. 15. As it ticks off its terminal orbits during the next five months, the mission will rack up an impressive list of scientific achievements. ...

[bystander]

Cassini Heads Toward Final Close Encounter with Titan
NASA | JPL-Caltech | Cassini | 2017 Apr 19

Click to play embedded YouTube video.

Crazy Engineering: Astrodynamics -- Credit: NASA/JPL-Caltech

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NASA's Cassini spacecraft will make its final close flyby of Saturn's haze-enshrouded moon Titan this weekend. The flyby marks the mission's final opportunity for up-close observations of the lakes and seas of liquid hydrocarbons that spread across the moon's northern polar region, and the last chance to use its powerful radar to pierce the haze and make detailed images of the surface.

Closest approach to Titan is planned for 11:08 p.m. PDT on April 21 (2:08 a.m. EDT April 22). During the encounter, Cassini will pass as close as 608 miles (979 kilometers) above Titan's surface at a speed of about 13,000 mph (21,000 kph).

The flyby is also the gateway to Cassini's Grand Finale -- a final set of 22 orbits that pass between the planet and its rings, ending with a plunge into Saturn on Sept. 15 that will end the mission. During the close pass on April 21, Titan's gravity will bend Cassini's orbit around Saturn, shrinking it slightly, so that instead of passing just outside the rings, the spacecraft will begin its finale dives which pass just inside the rings. ...

[bystander]

Cassini Completes Final -- and Fateful -- Titan Flyby
NASA | JPL-Caltech | Cassini | 2017 Apr 24

This unprocessed image of Saturn's moon Titan was captured by NASA's Cassini spacecraft during its final close flyby of the hazy, planet-sized moon on April 21, 2017. (Credit: NASA/JPL-Caltech/Space Science Institute)

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NASA's Cassini spacecraft has had its last close brush with Saturn's hazy moon Titan and is now beginning its final set of 22 orbits around the ringed planet.

The spacecraft made its 127th and final close approach to Titan on April 21 at 11:08 p.m. PDT (2:08 a.m. EDT on April 22), passing at an altitude of about 608 miles (979 kilometers) above the moon's surface.

Cassini transmitted its images and other data to Earth following the encounter. Scientists with Cassini's radar investigation will be looking this week at their final set of new radar images of the hydrocarbon seas and lakes that spread across Titan's north polar region. The planned imaging coverage includes a region previously seen by Cassini's imaging cameras, but not by radar. The radar team also plans to use the new data to probe the depths and compositions of some of Titan's small lakes for the first (and last) time, and look for further evidence of the evolving feature researchers have dubbed the "magic island." ...

[bystander]

NASA Spacecraft Dives Between Saturn and Its Rings
NASA | JPL-Caltech | Cassini | 2017 Apr 27

These unprocessed images show features in Saturn's atmosphere from closer than ever before. The view was captured by NASA's Cassini spacecraft during its first Grand Finale dive past the planet on April 26, 2017. (Credit: NASA/JPL-Caltech/Space Science Institute)

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NASA's Cassini spacecraft is back in contact with Earth after its successful first-ever dive through the narrow gap between the planet Saturn and its rings on April 26, 2017. The spacecraft is in the process of beaming back science and engineering data collected during its passage, via NASA's Deep Space Network Goldstone Complex in California's Mojave Desert. The DSN acquired Cassini's signal at 11:56 p.m. PDT on April 26, 2017 (2:56 a.m. EDT on April 27) and data began flowing at 12:01 a.m. PDT (3:01 a.m. EDT) on April 27. ...

As it dove through the gap, Cassini came within about 1,900 miles (3,000 kilometers) of Saturn's cloud tops (where the air pressure is 1 bar -- comparable to the atmospheric pressure of Earth at sea level) and within about 200 miles (300 kilometers) of the innermost visible edge of the rings.

While mission managers were confident Cassini would pass through the gap successfully, they took extra precautions with this first dive, as the region had never been explored. ...

The gap between the rings and the top of Saturn's atmosphere is about 1,500 miles (2,000 kilometers) wide. The best models for the region suggested that if there were ring particles in the area where Cassini crossed the ring plane, they would be tiny, on the scale of smoke particles. The spacecraft zipped through this region at speeds of about 77,000 mph (124,000 kph) relative to the planet, so small particles hitting a sensitive area could potentially have disabled the spacecraft.

As a protective measure, the spacecraft used its large, dish-shaped high-gain antenna (13 feet or 4 meters across) as a shield, orienting it in the direction of oncoming ring particles. This meant that the spacecraft was out of contact with Earth during the ring-plane crossing, which took place at 2 a.m. PDT (5 a.m. EDT) on April 26. Cassini was programmed to collect science data while close to the planet and turn toward Earth to make contact about 20 hours after the crossing.

Cassini's next dive through the gap is scheduled for May 2. ...

[Jim Leff]

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The spacecraft zipped through this region at speeds of about 77,000 mph (124,000 kph) relative to the planet
========

That's double the current speed of Voyager. Is this the fastest a human object has ever traveled?

Edit: Just learned that New Horizons was "the fastest spacecraft ever launched because it left Earth at 58,000 kilometers per hour (36,000 mph)." That's not even in the same league as Cassini!

[sillyworm]

Just curious to hear the thoughts from "EXPERT" Astronomers & Fans on the newest recent photos of Saturn's NORTH POLE/Storms/Cloud features,etc. Pretty amazing photos! Looking forward to the processed shots.

[sillyworm]

https://www.nasa.gov/mission_pages/cass ... index.html What do you believe these white wisp clouds(?) represent?

[sillyworm]

https://saturn.jpl.nasa.gov/galleries/raw-images/ RAW images from the recent fly by.

[neufer]

Just curious to hear the thoughts from "EXPERT" Astronomers & Fans on the newest recent photos of Saturn's NORTH POLE/Storms/Cloud features,etc. Pretty amazing photos! Looking forward to the processed shots.

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<<"A Descent into the Maelström" is an 1841 short story by Edgar Allan Poe. In the tale, a man recounts how he survived a shipwreck and a whirlpool. It has been grouped with Poe's tales of ratiocination and also labeled an early form of science fiction.

Inspired by the Moskstraumen, it is couched as a story within a story, a tale told at the summit of a mountain climb in Lofoten, Norway. The story is told by an old man who reveals that he only appears old—"You suppose me a very old man," he says, "but I am not. It took less than a single day to change these hairs from a jetty black to white, to weaken my limbs, and to unstring my nerves." The narrator, convinced by the power of the whirlpools he sees in the ocean beyond, is then told of the "old" man's fishing trip with his two brothers a few years ago.

Driven by "the most terrible hurricane that ever came out of the heavens", their ship was caught in the vortex. One brother was pulled into the waves; the other was driven mad by the horror of the spectacle, and drowned as the ship was pulled under. At first the narrator only saw hideous terror in the spectacle. In a moment of revelation, he saw that the Maelström is a beautiful and awesome creation. Observing how objects around him were attracted and pulled into it, he deduced that "the larger the bodies, the more rapid their descent" and that spherical-shaped objects were pulled in the fastest. Unlike his brother, he abandoned ship and held on to a cylindrical barrel until he was saved several hours later. The "old" man tells the story to the narrator without any hope that the narrator will believe it.

The story's opening bears a similarity to Samuel Taylor Coleridge's The Rime of the Ancient Mariner (1798): in both, an excited old man tells his story of shipwreck and survival. The tale is one of sensation, emphasizing the narrator's thoughts and feelings, especially his terror of being killed in the whirlpool. The narrator uses his reasoning skills to survive and the story is considered one of Poe's early examples of science fiction. The maelstrom's attractive power forecasts certain aspects of the Black Hole theory.>>

[bystander]

Cassini Finds 'The Big Empty' Close to Saturn
NASA | JPL-Caltech | Cassini | 2017 May 01

The sounds and spectrograms in these two videos represent data collected by the Radio and Plasma Wave Science, or RPWS, instrument on NASA's Cassini spacecraft, as it crossed the plane of Saturn's rings on two separate orbits. (Credit: NASA/JPL-Caltech/University of Iowa)

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Cassini Crossing a Faint Saturn Ring (Dec. 18, 2016)
Cassini Crossing Saturn's Planet-Ring Gap (April 26, 2017)

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As NASA’s Cassini spacecraft prepares to shoot the narrow gap between Saturn and its rings for the second time in its Grand Finale, Cassini engineers are delighted, while ring scientists are puzzled, that the region appears to be relatively dust-free. This assessment is based on data Cassini collected during its first dive through the region on April 26.

With this information in hand, the Cassini team will now move forward with its preferred plan of science observations. ...

A dustier environment in the gap might have meant the spacecraft's saucer-shaped main antenna would be needed as a shield during most future dives through the ring plane. This would have forced changes to how and when Cassini's instruments would be able to make observations. Fortunately, it appears that the "plan B" option is no longer needed. (There are 21 dives remaining. Four of them pass through the innermost fringes of Saturn's rings, necessitating that the antenna be used as a shield on those orbits.)

Based on images from Cassini, models of the ring particle environment in the approximately 1,200-mile-wide (2,000-kilometer-wide) region between Saturn and its rings suggested the area would not have large particles that would pose a danger to the spacecraft.

But because no spacecraft had ever passed through the region before, Cassini engineers oriented the spacecraft so that its 13-foot-wide (4-meter-wide) antenna pointed in the direction of oncoming ring particles, shielding its delicate instruments as a protective measure during its April 26 dive.

Cassini's Radio and Plasma Wave Science (RPWS) instrument was one of two science instruments with sensors that poke out from the protective shield of the antenna (the other being Cassini's magnetometer). RPWS detected the hits of hundreds of ring particles per second when it crossed the ring plane just outside of Saturn's main rings, but only detected a few pings on April 26. ...

Cassini will next cross through the ring plane Tuesday, May 2, at 12:38 p.m. PDT (3:38 p.m. EDT) in a region very close to where it passed on the previous dive. During this orbit, in advance of the crossing, Cassini's cameras have been looking closely at the rings; in addition, the spacecraft has rotated (or "rolled") faster than engineers have ever allowed it to before, in order to calibrate the magnetometer. As with the first finale dive, Cassini will be out of contact during closest approach to Saturn, and is scheduled to transmit data from this dive on May 3. ...

[neufer]

NASA Spacecraft Dives Between Saturn and Its Rings
NASA | JPL-Caltech | Cassini | 2017 Apr 27

NASA's Cassini spacecraft is back in contact with Earth after its successful first-ever dive through the narrow gap between the planet Saturn and its rings on April 26, 2017. As it dove through the gap, Cassini came within about 3,000 kilometers of Saturn's cloud tops (where the air pressure is 1 bar -- comparable to the atmospheric pressure of Earth at sea level) and within about 300 kilometers of the innermost visible edge of the rings. The gap between the rings and the top of Saturn's atmosphere is about 2,000 kilometers wide.

[b][color=#0000FF]The C ring, which occupies the bottom half of this image, clearly outshines its neighbor. The D ring appears fainter than the C ring because it is comprised of less material. This view looks toward the unilluminated side of the rings from about 12 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera at a Sun-Saturn-spacecraft, or phase, angle of 133 degrees.[/color][/b]

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<<The D ring is the innermost ring, and is very faint. In 1980, Voyager 1 detected within this ring three ringlets designated D73, D72 and D68, with D68 being the discrete ringlet nearest to Saturn. Some 25 years later, Cassini images showed that D72 had become significantly broader and more diffuse, and had moved planetward by 200 kilometres.

Present in the D ring is a finescale structure with waves 30 kilometres apart. First seen in the gap between the C ring and D73, the structure was found during Saturn's 2009 equinox to extend a radial distance of 19000 km from the D ring to the inner edge of the B ring. The waves are interpreted as a spiral pattern of vertical corrugations of 2 to 20 m amplitude; the fact that the period of the waves is decreasing over time (from 60 km in 1995 to 30 km by 2006) allows a deduction that the pattern may have originated in late 1983 with the impact of a cloud of debris (with a mass of ~10¹² kg) from a disrupted comet that tilted the rings out of the equatorial plane. A similar spiral pattern in Jupiter's main ring has been attributed to a perturbation caused by impact of material from Comet Shoemaker-Levy 9 in 1994.>>

[bystander]

New Movie Shows Cassini's First Dive over Saturn
NASA | JPL-Caltech | Cassini | 2017 May 03

Click to play embedded YouTube video.

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Cassini's First Fantastic Dive Past Saturn
Credit: NASA/JPL-Caltech/Space Science Institute/Hampton University

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A new movie sequence of images from NASA's Cassini spacecraft shows the view as the spacecraft swooped over Saturn during the first of its Grand Finale dives between the planet and its rings on April 26.

The movie comprises one hour of observations as the spacecraft moved southward over Saturn. It begins with a view of the swirling vortex at the planet's north pole, then heads past the outer boundary of the hexagon-shaped jet stream and beyond. ...

Toward the end of the movie, the camera frame rotates as the spacecraft reorients to point its large, saucer-shaped antenna in the direction of the spacecraft’s motion. The antenna was used as a protective shield during the crossing of Saturn’s ring plane.

As the movie frames were captured, the Cassini spacecraft's altitude above the clouds dropped from 45,000 to 4,200 miles (72,400 to 6,700 kilometers). As this occurred, the smallest resolvable features in the atmosphere changed from 5.4 miles (8.7 kilometers) per pixel to 0.5 mile (810 meters) per pixel. ...

[bystander]

Cassini Looks on as Solstice Arrives at Saturn
NASA | JPL-Caltech | Cassini | 2017 May 24

These natural color views from Cassini show how the color of Saturn’s
north-polar region changed between June 2013 (left) and April 2017
(right), as the northern hemisphere headed toward summer solstice.
Credits: NASA/JPL-Caltech/SSI/Hampton Univ

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NASA's Cassini spacecraft still has a few months to go before it completes its mission in September, but the veteran Saturn explorer reaches a new milestone today. Saturn's solstice -- that is, the longest day of summer in the northern hemisphere and the shortest day of winter in the southern hemisphere -- arrives today for the planet and its moons. The Saturnian solstice occurs about every 15 Earth years as the planet and its entourage slowly orbit the sun, with the north and south hemispheres alternating their roles as the summer and winter poles.

Reaching the solstice, and observing seasonal changes in the Saturn system along the way, was a primary goal of Cassini's Solstice Mission -- the name of Cassini's second extended mission. ...

[bystander]

Saturn Surprises as Cassini Continues Its Grand Finale
NASA | JPL-Caltech | Cassini | 2017 Jul 24

Haze on the Horizon - This false-color view from NASA's Cassini spacecraft gazes toward the rings beyond Saturn's sunlit horizon, where a thin haze can be seen along the limb. (Credit: NASA/JPL-Caltech/Space Science Institute)

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As NASA's Cassini spacecraft makes its unprecedented series of weekly dives between Saturn and its rings, scientists are finding -- so far -- that the planet's magnetic field has no discernible tilt. This surprising observation, which means the true length of Saturn's day is still unknown, is just one of several early insights from the final phase of Cassini's mission, known as the Grand Finale.

Other recent science highlights include promising hints about the structure and composition of the icy rings, along with high-resolution images of the rings and Saturn's atmosphere.

Cassini is now in the 15th of 22 weekly orbits that pass through the narrow gap between Saturn and its rings. The spacecraft began its finale on April 26 and will continue its dives until Sept. 15, when it will make a mission-ending plunge into Saturn's atmosphere. ...

[Ann]

Cassini Looks on as Solstice Arrives at Saturn
NASA | JPL-Caltech | Cassini | 2017 May 24

NASA's Cassini spacecraft still has a few months to go before it completes its mission in September, but the veteran Saturn explorer reaches a new milestone today. Saturn's solstice -- that is, the longest day of summer in the northern hemisphere and the shortest day of winter in the southern hemisphere -- arrives today for the planet and its moons. The Saturnian solstice occurs about every 15 Earth years as the planet and its entourage slowly orbit the sun, with the north and south hemispheres alternating their roles as the summer and winter poles.

Reaching the solstice, and observing seasonal changes in the Saturn system along the way, was a primary goal of Cassini's Solstice Mission -- the name of Cassini's second extended mission. ...

That's amazing!

Saturn's north polar hexagon changed color from green, even blue-green, to a kind of pale ochre?

Ann

[MargaritaMc]

There is a very nice OVERVIEW OF THE CASSINI MISSION from the American Geophysical Union in their journal Eos. It includes a video of the Huygens landing on Titan and a helpful spelling out of the most significant findings that Cassini-Huygens has made in the years it's been at Saturn.
https://eos.org/features/saturn-unveile ... ni-huygens

[bystander]

Saturn Plunge Nears for Cassini Spacecraft
NASA | JPL-Caltech | Cassini | 2017 Aug 29

NASA's Cassini spacecraft is shown heading for the gap between Saturn and its rings during one of 22 such dives of the mission's finale in this illustration. The spacecraft will make a final plunge into the planet's atmosphere on Sept. 15. (Credit: NASA/JPL-Caltech)

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NASA's Cassini spacecraft is 18 days from its mission-ending dive into the atmosphere of Saturn. Its fateful plunge on Sept. 15 is a foregone conclusion -- an April 22 gravitational kick from Saturn's moon Titan placed the two-and-a-half ton vehicle on its path for impending destruction. Yet several mission milestones have to occur over the coming two-plus weeks to prepare the vehicle for one last burst of trailblazing science. ...

The spacecraft is expected to lose radio contact with Earth within about one to two minutes after beginning its descent into Saturn's upper atmosphere. But on the way down, before contact is lost, eight of Cassini's 12 science instruments will be operating. In particular, the spacecraft's ion and neutral mass spectrometer (INMS), which will be directly sampling the atmosphere's composition, potentially returning insights into the giant planet's formation and evolution. On the day before the plunge, other Cassini instruments will make detailed, high-resolution observations of Saturn's auroras, temperature, and the vortices at the planet's poles. Cassini's imaging camera will be off during this final descent, having taken a last look at the Saturn system the previous day (Sept. 14).

In its final week, Cassini will pass several milestones en route to its science-rich Saturn plunge. (Times below are predicted and may change slightly; see https://go.nasa.gov/2wbaCBT for updated times.)

• Sept. 9 Cassini will make the last of 22 passes between Saturn itself and its rings -- closest approach is 1,044 miles (1,680 kilometers) above the clouds tops.
• Sept. 11 -- Cassini will make a distant flyby of Saturn's largest moon, Titan. Even though the spacecraft will be at 73,974 miles (119,049 kilometers) away, the gravitational influence of the moon will slow down the spacecraft slightly as it speeds past. A few days later, instead of passing through the outermost fringes of Saturn's atmosphere, Cassini will dive in too deep to survive the friction and heating.
• Sept. 14 -- Cassini's imaging cameras take their last look around the Saturn system, sending back pictures of moons Titan and Enceladus, the hexagon-shaped jet stream around the planet's north pole, and features in the rings.
• Sept. 14 (5:45 p.m. EDT / 2:45 p.m. PDT) -- Cassini turns its antenna to point at Earth, begins a communications link that will continue until end of mission, and sends back its final images and other data collected along the way.
• Sept. 15 (4:37 a.m. EDT / 1:37 a.m. PDT) -- The "final plunge" begins. The spacecraft starts a 5-minute roll to position INMS for optimal sampling of the atmosphere, transmitting data in near real time from now to end of mission.
• Sept. 15 (7:53 a.m. EDT / 4:53 a.m. PDT) -- Cassini enters Saturn's atmosphere. Its thrusters fire at 10 percent of their capacity to maintain directional stability, enabling the spacecraft's high-gain antenna to remain pointed at Earth and allowing continued transmission of data.
• Sept. 15 (7:54 a.m. EDT / 4:54 a.m. PDT) -- Cassini's thrusters are at 100 percent of capacity. Atmospheric forces overwhelm the thrusters' capacity to maintain control of the spacecraft's orientation, and the high-gain antenna loses its lock on Earth. At this moment, expected to occur about 940 miles (1,510 kilometers) above Saturn's cloud tops, communication from the spacecraft will cease, and Cassini's mission of exploration will have concluded. The spacecraft will break up like a meteor moments later.

...

[bystander]

After Cassini: Pondering the Saturn Mission's Legacy
NASA | JPL-Caltech | Cassini | 2017 Sep 07

Cassini's discoveries are feeding forward into future exploration of the solar system. (Credit: NASA/JPL-Caltech/Space Science Institute)

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As the Cassini spacecraft nears the end of a long journey rich with scientific and technical accomplishments, it is already having a powerful influence on future exploration. In revealing that Saturn's moon Enceladus has many of the ingredients needed for life, the mission has inspired a pivot to the exploration of "ocean worlds" that has been sweeping planetary science over the past decade.

"Cassini has transformed our thinking in so many ways, but especially with regard to surprising places in the solar system where life could potentially gain a foothold," said Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate at Headquarters in Washington. "Congratulations to the entire Cassini team!" ...

• Onward to Europa
  Returning to Saturn
  Giant Planet Atmospheres

[MargaritaMc]

ESA: CELEBRATING EUROPE’S SCIENCE HIGHLIGHTS WITH CASSINI

The international Cassini­-Huygens mission has explored Saturn and its rings and moons for 13 years, and will conclude by plunging into the planet’s atmosphere next week. This article highlights some of the mission’s exciting discoveries led by European teams.

Cassini is an international programme: a collaboration between NASA, ESA and Italy’s ASI space agency plus several separate European academic and industrial contributors. Nineteen nations contributed to building the spacecraft, and international science teams across the world have gained a better understanding of Saturn and its environment through the mission’s suite of 12 scientific instruments. Two of the instruments – the Cosmic Dust Analyser and the Magnetometer – are led by European principal investigator teams, but all teams are truly international. In total, 27 nations have participated in the mission.

[saturno2]

Saturn the enigmatic,
wonderful and rare planet
has an appointmant
with the spacecraft Cassini
in September, 15, 2017.
Cassini will traverse
for the first time
the mysterious rings
and, in stoic mission
will enter the atmosphere
until the surface of the planet
then, ... the transmissions will cease !!
Spacecraft Cassini
is a modern hero
a cosmic Spartacus
of the XXI Century.

[rstevenson]

And you, saturno2, are a poet.

Rob