"Кассини" !

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Jeff Foust‏ @jeff_foust 55 сек. назад

X-band loss of signal was at 11:55:39 GMT, with S-band loss of signal 7 seconds later. About half a minute later than predicted.

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Jeff Foust‏ @jeff_foust 6 сек. назад

Maize: yes, sadness with end of mission, but also serenity and peace; we've done exactly what we believe is the correct thing for Cassini.

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Эх... когда следующий раз АМС будет работать у Сатурна
По хорошему, чтобы понять климат Титана, надо хотя бы один полный сатурнянский год непрерывно наблюдать - дождаться полного цикла смены сезонов

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https://nasa.tumblr.com/post/165363703919/cassini-mission-whats-next

Cassini Mission: What's Next?

It's Friday, Sept. 15 and our Cassini mission has officially come to a spectacular end. The final signal fr om the spacecraft was received here on Earth at 7:55 a.m. EDT after a fateful plunge into Saturn's atmosphere.

Спойлер

After losing contact with Earth, the spacecraft burned up like a meteor, becoming part of the planet itself.



Although bittersweet, Cassini's triumphant end is the culmination of a nearly 20-year mission that overflowed with discoveries.

But, what happens now?

Mission Team and Data

Now that the spacecraft is gone, most of the team's engineers are migrating to other planetary missions, wh ere they will continue to contribute to the work we're doing to explore our solar system and beyond.



Mission scientists will keep working for the coming years to ensure that we fully understand all of the data acquired during the mission's Grand Finale. They will carefully calibrate and study all of this data so that it can be entered into the Planetary Data System. From there, it will be accessible to future scientists for years to come.



Even beyond that, the science data will continue to be worked on for decades, possibly more, depending on the research grants that are acquired.

Other team members, some who have spent most of their career working on the Cassini mission, will use this as an opportunity to retire.

Future Missions

In revealing that Enceladus has essentially all the ingredients needed for life, the mission energized a pivot to the exploration of "ocean worlds" that has been sweeping planetary science over the past couple of decades.



Jupiter's moon Europa has been a prime target for future exploration, and many lessons during Cassini's mission are being applied in planning our Europa Clipper mission, planned for launch in the 2020s.



The mission will orbit the giant planet, Jupiter, using gravitational assists from large moons to maneuver the spacecraft into repeated close encounters, much as Cassini has used the gravity of Titan to continually shape the spacecraft's course.

In addition, many engineers and scientists from Cassini are serving on the new Europa Clipper mission and helping to shape its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer team are developing an extremely sensitive, next-generation version of their instrument for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will be invaluable to Europa Clipper, should plume activity be confirmed on Europa.



In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission's many discoveries. Mission concepts under consideration include robotic explorers to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.



Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent recommendations from a group of planetary scientists shows interest in sending such a mission to Saturn. By directly sampling Saturn's upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an potential Saturn atmospheric probe.



A variety of potential mission concepts are discussed in a recently completed study — including orbiters, flybys and probes that would dive into Uranus' atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini's mission.

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Jason Major‏ @JPMajor 4 ч. назад

#Cassini's final image of #Saturn. Subjective color-composite made from raw images captured on Sept. 14, 2017.

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NASA Mission Control Live: Cassini's Finale at Saturn (360 video)

NASA Jet Propulsion Laboratory

LIVE COVERAGE AT 4 a.m. PT (7 a.m. ET, 1100 UTC)

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http://spacenews.com/cassini-mission-ends-with-plunge-into-saturn/

Cassini mission ends with plunge into Saturn
by Jeff Foust — September 15, 2017


One of the last images taken by the Cassini spacecraft was this view of the moon Enceladus setting behind the limb of Saturn. Credit: NASA/JPL-Caltech

WASHINGTON — NASA's Cassini spacecraft ended a nearly 20-year mission Sept. 15 with a plunge into the atmosphere of the planet Saturn intended to protect the planet's potentially habitable moons from contamination.

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The last signals from the Cassini spacecraft arrived at NASA's Deep Space Network antennas near Canberra, Australia, at 7:55 a.m. Eastern, 83 minutes after the spacecraft transmitted them as it dived into Saturn's atmosphere. The loss of signal was within half a minute of predictions made in the days leading up to the encounter.

"The signal from the spacecraft is gone and, within the next 45 seconds, so will be the spacecraft," Cassini program manager Earl Maize said in mission control moments after the loss of signal. "I'm going to call this the end of mission."

The plunge into Saturn was designed by the mission managers as a way of safely disposing of the spacecraft, whose maneuvering fuel was running low. The concern was that the spacecraft, if left to drift in orbit around the planet, could one day collide with the moons Enceladus or Titan, two worlds that scientists — using data from Cassini itself — believe to be potentially habitable.

"We didn't have any choice," Maize said in an interview shortly before the end of the mission, when asked why the mission ended with a plunge into the atmosphere. "Cassini must be disposed of properly."

Cassini returned the last images of the Saturn system in the hours prior to its plunge, then reconfigured itself to transmit real-time data from eight instruments as it entered the atmosphere, providing scientific results up until its last seconds.

Of particular interest, said Linda Spilker, Cassini project scientist, were measurements of the ratio of hydrogen to helium in Saturn's atmosphere, something than can only be directly measured from within the atmosphere. "That team is hard at work right now looking at their data and trying to assess what they saw in those very final moments," she said at a post-entry press conference Sept. 15.

Maize said there was the option to send Cassini out of orbit around Saturn entirely, but the scientific return promised by a final plunge into the planet was too good to refuse. "Saturn was so compelling, so exciting, and the mission we finally came up with was so rich scientifically that we just couldn't — we had to finish up at Saturn, not some place else."

That final plunge ended a mission that started with a launch on a Titan 4 in October 1997. Cassini entered orbit around Saturn in July 2004 and studied the planet, its rings and dozens of moons for more than 13 years. The spacecraft was remarkably free of major issues throughout the entire mission, performing as expected up through its final seconds in the atmosphere.

Spacecraft designers "built a perfect spacecraft, right to the last end," said Julie Webster, spacecraft operations manager on the mission, at the press conference. "It did exactly what it said it was supposed to do," she said. "Even better."

NASA currently has no missions on the books to return to Cassini, although agency officials noted that both Saturn and its moons Enceladus and Titan are potential destinations for NASA's next New Frontiers medium-class mission, the competition for which is ongoing. NASA expects to sel ect three proposals late this year fr om a dozen submitted for further study, with a final selection planned in May 2019 for launch by the end of 2025.

Those at the post-entry news conference, though, emphasized that, sooner or later, NASA will return to Saturn and its moons. "The discoveries that Cassini has made over the past 13 years in orbit have rewritten the textbooks of Saturn, have discovered worlds that could be habitable and have guaranteed that we will return to that ringed world," said Michael Watkins, director of the Jet Propulsion Laboratory.

"I hope you're all as deeply proud of this amazing accomplishment," Maize said to the Cassini team in mission control after it lost contact. "Congratulations to you all. This has been an incredible mission, an incredible spacecraft, and you're all an incredible team."

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https://spaceflightnow.com/2017/09/15/cassini-crashes-into-saturn-ending-20-year-mission/

Cassini crashes into Saturn, ending 20-year mission
September 15, 2017 Spaceflight Now

STORY WRITTEN FOR CBS NEWS & USED WITH PERMISSION

Dutifully beaming back data to the very end, NASA's long-lived Cassini probe slammed into Saturn's atmosphere at some 77,000 mph Friday, blazing like a shooting star as it was ripped apart and incinerated in the final chapter of an enormously successful mission.

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Cassini program manager at JPL, Earl Maize, left, and spacecraft operations team manager for the Cassini mission at Saturn, Julie Webster embrace after the Cassini spacecraft plunged into Saturn. Image: NASA/Joel Kowsky.

Thirteen years after braking into orbit around Saturn, the end came at 6:32 a.m. EDT, one minute after the spacecraft plunged into the thin-but-discernible extreme upper atmosphere 1,190 miles above Saturn's cloud tops.

Cassini's flight computer attempted to maintain the probe's orientation, firing its thrusters as buffeting built up to keep the spacecraft's big dish antenna pointed at Earth so it could transmit a final trove of data.

But the thrusters were quickly overwhelmed, the spacecraft lost lock on Earth and began tumbling, according to pre-impact calculations, quickly heating up, breaking apart and melting to vapor, its constituents spreading out and merging with the atmosphere of the planet it spent its life exploring.

Cassini's final bits of data, traveling at the speed of light — 186,000 miles per second — took 83 minutes to cross the 932 million miles to Earth, reaching NASA's 230-foot-wide Deep Space Network antenna near Canberra, Australia, at 7:55:46 a.m.

At that point, Cassini's telemetry stream suddenly stopped, confirmation Cassini had met its fiery fate as expected.

"As you just heard, the signal from the spacecraft is gone and within the next 45 seconds, so will be the spacecraft," Earl Maize, the Cassini project manager at the Jet Propulsion Laboratory, told the flight control team.

"I hope you're all deeply proud of this amazing accomplishment. Congratulations to you all. This has been an incredible mission, an incredible spacecraft and you're all an incredible team. I'm going to call this the end of mission.


At 7:55:46 a.m., Cassini's signal disappeared, indicating the spacecraft had lost lock on Earth as it began tumbling before breaking apart in Saturn's extreme upper atmosphere. Image: NASA TV.

Then, for the last time, Maize said "project manager off the net," and took off his headset.

Flight controllers stood up from their computer displays, hugged and cheered along with more than 1,500 scientists, engineers, managers, friends and family members gathered at JPL to share Cassini's final moments.

"I was just overwhelmed with how professional this team is," said Thomas Zurbuchen, director of the science mission directorate at NASA Headquarters. "During the entire time, this was clearly emotional for everybody. ... But everybody was so professional to the very end. It went so fast! It's all about teamwork with this mission, and it showed in the last seconds."

Launched in October 1997, Cassini arrived at Saturn in July 2004, the first spacecraft to observe the ringed planet from orbit. The following January, Cassini dropped off a lander built by the European Space Agency that successfully completed a parachute descent to the surface of the large moon Titan, revealing an alien landscape beneath a thick, smog-like atmosphere.

Cassini's cloud-piercing radar imaging system eventually mapped the moon, revealing networks of methane rivers, lakes and seas.


Artist's impression of Cassini making one of its final dives. Image: NASA/JPL-Caltech

"To put a probe onto Titan, capture a signal on the way down, land it softly on the surface and play those images back, I still give myself goosebumps just seeing that first image," Maize said earlier. "I'll never forget it."

Cassini went on to orbit Saturn 294 times, repeatedly using Titan's gravity to alter its trajectory, setting up flybys of multiple moons and giving the spacecraft different perspectives on Saturn and its vast ring system as its seasons slowly changed.

Over the course of its 13-year mission, Cassini executed 2.5 million commands, carried out 360 engine burns, completed 162 targeted flybys of Saturn's moons, took more than 453,000 images and discovered six previously unknown moons, covering 4.9 billion miles since launch in 1997.

Most important, the spacecraft collected 635 gigabits of data resulting in nearly 4,000 peer-reviewed scientific papers.

"Not only is this an incredible engineering and scientific achievement, it is a human achievement," Maize said earlier. "The engineering and science and navigation teams have just done a phenomenal job getting absolutely everything they possibly could out of this mission. The spacecraft has been used to its fullest."

The decision to crash Cassini into Saturn was made several years ago, the result of the spacecraft's own discoveries.

Saturn's moon Enceladus is now known to harbor a saltwater ocean beneath an icy crust, with hydrothermal vents on the seafloor and jets of water ice and vapor spewing into space from cracks in the crust near the south pole.

Cassini flew through the plumes and detected organic compounds, indicating the tiny moon could, in theory, harbor a habitable environment and, possibly, life beneath its relatively thin crust — an unexpected discovery that ranks among Cassini's major achievements.

Flight controllers knew Cassini would eventually run out of gas and would no longer be controllable. To eliminate any chance of an inadvertent collision that could contaminate Enceladus with Earthly debris and possible microbes, mission managers came up with a daring end-of-mission scenario.

Rather than use up Cassini's remaining propellant to boost it into a remote orbit, bringing close-range observations to an end, the spacecraft was directed to fly by Saturn's large moon Titan in April, using the moon's gravity to put it on a trajectory that repeatedly carried it between Saturn's cloud tops and its inner most rings.

The spacecraft made 22 such orbits before a final nudge by Titan earlier this week — the "goodbye kiss" — that put Cassini on course for impact Friday.

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https://spaceflight101.com/cassinis-swan-song-flagship-nasa-mission-ends-after-20-years/

Cassini's Swan Song – Flagship NASA Mission Ends after 20 Years
September 15, 2017

Cassini – NASA's flagship planetary exploration mission for the last 20 years – found a fiery grave in Saturn's dense atmosphere on Friday, ending a remarkable mission of discovery that will keep scientists busy for years to come to decipher the secrets Saturn and its enigmatic moons hold.

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Image: NASA/JPL

The last signal fr om the falling spacecraft was received on Earth at 11:55 UTC when Cassini's thrusters could no longer cope with the forces induced by Saturn's upper atmosphere, followed not two minutes later by the incineration of the 2.5-metric ton spacecraft after 294 orbits around the solar system's second largest planet.

Seventeen countries were involved in designing NASA's milestone mission to the ringed planet with the agency's Jet Propulsion Laboratory at the forefront, in charge of assembly of the orbiter, while a European Team built the Huygens probe, destined for a landing on Saturn's moon Titan.


Cassini during final processing in 1996 – Photo: NASA/JPL

Named after the discoverer of Saturn's rings, Cassini departed Earth on October 15, 1997 atop a Titan IV rocket that successfully dispatched the 6.8-meter tall spacecraft into solar orbit. To get to its faraway destination, Cassini was facing a journey of over six and a half years – passing by Venus in 1998, Earth in 1999 and Venus again the same year to "borrow" some of the planets' momentum to slingshot out into the outer solar system.

In 2000, Cassini flew by the Gas Giant Jupiter, using its massive gravitational pull to accelerate further out to Saturn where the probe arrived on July 1st, 2004 – performing a do-or-die orbit insertion burn of 96 minutes, placing it in a highly elliptical orbit with another burn to adjust its trajectory into a 300,000 km by nine million Kilometer orbit.

Cassini was the first spacecraft to orbit Saturn, NASA's Pioneer 11 and the two Voyager probes completed flybys of the planet in 1979 through 1981. Placing a craft into orbit around Saturn promised a much greater data set than the previous flyby missions, offering an opportunity of many close encounters with the planet itself as well as its moons over a mission that was initially expected to last three years, but ended up being extended by more than nine years thanks to stellar performance by the Plutonium-powered spacecraft.



Completing nearly 300 laps around Saturn, Cassini watched seasons change, studied the planet's atmospheric make up, kept tabs on an enigmatic storm on the planet's north pole, watched icy jets emanating fr om Saturn's moon Enceladus and examined Titan in unprecedented detail – putting into perspective the possibility of life in our solar system.

Specifically, Cassini set out to address seven objectives that were to determine the three-dimensional structure and dynamic behavior of the ring system, determine the composition and history of Saturn's moons, measure the structure and dynamic behavior of Saturn's magnetosphere, and study the dynamic behavior of Saturn's atmosphere at cloud level. Concerning the moons, additional objectives included studying Titan's clouds and hazes, and determining the nature and origin of dark material in Iapetus, Saturn's third largest moon.


Image: NASA/JPL

This was made possible by a spacecraft of 2,523-Kilograms (dry mass), standing 6.8 meters tall and measuring 4 meters in diameter; featuring 14 Kilometers of wires, holding 32.7 Kilograms of radioactive Plutonium as power source and hosting a dozen science instruments. Huygens – named after the discoverer of Titan – accounted for 349 Kilograms of the spacecraft's mass and hosted six instrument packages to study the composition and dynamics in Titan's atmosphere and sensors to determine the physical characteristics of the moon's previously unknown surface.

Cassini's instrument suite included a series of optical systems designed to collect imagery in multiple wavelength bands, obtain spectrometric data in visible and infrared wavelength and conduct spectrography in the UV range. The Fields, Particles and Waves Package hosted a plasma spectrometer, an ion and neutral mass spectrometer, a cosmic dust analyzer, a magnetometer & magnetospheric imager, and a radio and plasma sensing instrument. Additionally, Cassini hosted a radar to probe Titan's hidden surface and the craft's communications system doubled as radio science instrument for atmospheric studies and gravitational measurements.


In Saturn's Shadow – Photo: NASA/JPL

Cassini relied on a 490-Newton main engine to reach Saturn and hit the brakes for orbital insertion while smaller thrusters were used for extensive orbital maneuvering with some 360 burns performed during the mission to set up over 160 flybys of Saturn's moons, also using their gravity to control its orbit in a very complex mission design circumnavigating the gaseous planet, avoiding the rings and threading the needle when flying closer than 50 Kilometers to the moons.

Over the course of its mission, Cassini burned 3.1 metric tons of propellants while electrical power was generated via three Radioisotope Thermoelectric Generators utilizing the heat released by the radioactive decay of Plutonium to generate power and heat the spacecraft as it traveled into the far reaches of the solar system with around 660 Watts of power available to the craft in the closing months of the mission.

Cassini's ground-breaking science mission started well ahead of its arrival at Saturn, collecting data during the 2000 Jupiter flyby that showed new insight into the Gas Giant's colorful cloud belts and revealed the origin of the planet's ring system as ejecta fr om meteorite impacts with moons Metis and Adrastea.


'The Day the Earth Smiled' – Cassini captured this view of Earth on July 19, 2013 fr om a distance of 1.44 billion Kilometers – Photo: NASA/JPL-Caltech/Space Science Institute

Venturing out toward Saturn, Cassini was used to put Einstein's Theory of General Relativity to the test – measuring the shift in radio waves from the spacecraft when the line of sight between Earth and Cassini was close to the sun, thus revealing that a massive object like the sun causes space-time to curve, meaning radio waves had to cover a greater distance as they traveled along the curvature.

On approach to Saturn, Cassini spotted three previously unknown moons, made its only flyby of Phoebe that revealed large amounts of water ice under its surface, and measured Saturn's rotation rate. Leading up to the July 2004 orbit insertion, Cassini braved a dangerous passage through a gap in the F and G rings – using its four-meter high-gain antenna as a shield from ring particles before re-orienting for its rocket-powered braking maneuver to enter orbit.

Just one day after its arrival, Cassini completed a flyby of Titan – the first of 127 – with its instruments peering through the moon's clouds which showed a south polar surface standing out in brightness, indicating the presence of rivers and channels on Titan's surface.


Image: ESA/NASA/JPL/University of Arizona

A much closer flyby enabled Cassini to collect radar data, showing a smooth surface and clearing the way for the Huygens landing.

The Huygens lander detached from Cassini on December 25, 2004 and continued on its own until hitting Titan's atmosphere on January 14, 2005 for a two-hour parachute-assisted descent ahead of landing on Titan's surface. On its way down, Huygens studied Titan's atmospheric structure, wind profiles relative to altitude, atmospheric composition for gases and aerosols, and some surface parameters.

Huygens captured a total of 700 images during its lengthy descent, though only 350 reached Earth due to a software error preventing Cassini from recording one of two radio channels from the lander.

Nevertheless, the Huygens mission was classed a remarkable success and to this day remains the most distant landing ever accomplished from Earth. Huygens showed Titan's surface to comprise clays and sands with a thin layer of methane haze lingering atop.

While the Huygens mission ended after less than an hour on the surface of Titan, Cassini continued to closely study the perplexing moon for many years, discovering permanent lakes of liquid hydrocarbons – methane, ethane and propane – in Titan's polar regions, making the moon the only other place in the solar system wh ere known, permanent liquid lakes exit. Cassini also detected methane rain and seasonal floods on Titan, making its final flyby on September 12, 2017 just days before the mission's planned end.


Peering through Titan's Haze – Image: NASA/JPL/University of Arizona/University of Idaho


Icy Enceladus in Enhanced Colors – Image: NASA/JPL-Caltech


Geyser Basin of Enceladus – Image: NASA/JPL/Space Science Institute

Cassini began studying another foreign world in 2005 when it first passed by Enceladus which would turn out to be the mission's most surprising target. A pair of close flybys showed Enceladus had a thin but significant atmosphere, mainly consisting of water. Cassini also observed water ice geysers erupting on the moon's south pole, giving credibility to the theory that Enceladus is responsible for Saturn's E-ring.

In 2008, Cassini made a daring flyby – passing just 50 Kilometers from the moon's surface and directly flying through the plumes of the southern geysers, detecting water ice, carbon dioxide and different hydrocarbons. Further observations between 2009 and 2012 confirmed Enceladus has a large salt-water ocean beneath its surface – one of the stand-out findings of the Cassini mission.

The presence of a liquid ocean holding nutrients and organic molecules, as confirmed from the cryovolcano ejecta, along with escaping internal heat places Enceladus "among the most likely places in the Solar System to host microbial life."

Turning its attention to the ringed planet itself, Cassini spent months studying Saturn's rings via radio occultation experiments and used its instrument suite to examine the composition of Saturn's atmosphere and magnetic environment. Saturn's Hexagon – an Earth-sized cloud pattern around the planet's north pole – was also a point of study with distinct color changes noted from a mostly blue to a golden and reddish color over the course of a five-year period, likely as the result of changing seasons on Saturn.


Saturn's Great White Spot – Image: NASA/JPL-Caltech/Space Science Institute

Cassini also watched the emergence of the Great White Spot, a northern hemisphere storm system that recurs roughly every 30 years and is the largest, hottest stratospheric vortex ever detected in the solar system, even eclipsing Jupiter's Great Red Spot. Close-up studies of the storm showed a significant spike in ethylene gas, surpassing what was thought possible for Saturn by a factor of 100.

Cassini's primary mission ended in 2008 and the craft headed into an initial mission extension of 27 months, called the Equinox Mission – comprising 60 additional orbits around the planet to study seasonal phenomena occurring around the Saturnian equinox. The Equinox Mission included 21 more Titan flybys and encounters with six other moons including Enceladus, Mimas and Tethys.

A second mission extension proposal through 2017 was approved in 2010 – named the Solstice Mission as it allowed Cassini to observe Saturn's northern hemisphere summer solstice in May 2017, giving the entire Cassini mission an observation arc of half a Saturnian year, accompanying the planet for nearly half a lap around the sun. The Solstice Mission offered Cassini the opportunity for another 155 orbits, 54 additional Titan flybys and eleven more of Enceladus.


Highest-resolution color image of Saturn's Rings, taken July 6, 2017 – Image: NASA/JPL-Caltech/Space Science Institute

Cassini entered its final mission phase – dubbed The Grand Finale – in April 2017, setting out on a series of daring orbits between Saturn and its inner rings before being nudged onto a path to destruction.

Titan played an important role in setting up for Cassini's finale, the mission's 126th flyby on April 22 used the moon's gravitational pull to alter Cassini's orbit and set up for the planned 22 ring plane crossings, passing just 3,000 Kilometers above Saturn's cloud tops and some 320 Kilometers from the inner ring edge.

Continuing collecting science through the end of the mission, Cassini mapped out Saturn's magnetic and gravitational fields in great detail to reveal its internal structure. The close approaches to the rings were also used to assess how much material was being held in the ring system, reveal its origin and directly sample icy particles being funneled into Saturn's atmosphere by its magnetic field. The distance to Saturn and the rings varied greatly for these last orbits, enabling Cassini to complete in-situ sampling of the D-ring on four occasions and the upper reaches of Saturn's atmosphere via five dips.


Cassini's Gran Finale Orbits (Titan's Orbit shown in yellow) – Image: NASA/JPL/Caltech

The end of Cassini's mission was carefully planned out to safely dispose the spacecraft and avoid a dead probe lingering in the Saturn system wh ere a collision with one of the potentially habitable moons could create biological contamination that would make future studies of extraterrestrial life impossible. Different end-of-mission scenarios like putting Cassini in a stable orbit around Titan, having it escape into the solar system or crashing it into one of Saturn's icy moons were studied.

Disposal via Saturn entry was favored over other scenarios due to a fast implementation timeline, low technical risk and science offered by placing Cassini into ring-plane crossing orbits.

Cassini's last encounter with Titan, although a distant one at 119,000 Kilometers, altered the craft's orbit by reducing its low point by 1,800 Kilometers from a periapsis of only 1,200 km – setting up a fatal dive aiming for the dayside of the planet some 10 degrees above the equator. The September 11 maneuver, affectionately called 'the kiss good bye,' marked the start of Cassini's final days – beginning with a downlink of the last data set from Titan, taking the mission's last images on Thursday, playing back all recorded data from the vehicle and reconfiguring for real time data relay, allowing Cassini to collect and transmit science data through the very end.


Cassini's Final Plunge – Image: NASA/JPL/Caltech


On of Cassini's final images, taken September 13 around 1.1 million Kilometers from Saturn – Image: NASA/JPL/Caltech

NASA's Deep Space Network was continuously listening to Cassini from 3:15 UTC on Friday, with the Canberra, Australia station in a prime role for Cassini's finale. At 7:14 UTC, Cassini was programmed to enter a five-minute roll maneuver to aim its Ion and Neutral Mass Spectrometer toward Saturn's atmosphere to collect in-situ data on atmospheric composition as it arced into layers it did not dare traverse before.

Sending data at 27 kilo-bits per second, Cassini was expected to reach the discernible Saturnian atmosphere at 10:31 UTC (spacecraft time), marking the point of Entry Interface at an altitude of 1,900 Kilometers wh ere atmospheric pressure is equivalent to sea level on Earth. Temperatures and stress acting on the falling probe increased significantly over the next minute with Cassini firing its thrusters to keep its antenna pointed toward Earth.


Image: NASA/JPL/Caltech

The stress of atmospheric entry was expected to overwhelm Cassini's thrusters at an altitude of 1,600 km above the cloud tops, around one minute after the onset of entry with the craft fully burning up in the dense layers of Saturn's atmosphere within another minute as temperatures exceeded the melting point of aluminum and iridium components on the spacecraft.

The last radio waves sent toward Earth by Cassini traversed through the vast expanse of the solar system for 83 minutes before reaching Earth at 11:55 UTC with X-Band signals vanishing first before a final blip of data coming via S-Band – confirming the spacecraft had met its end after outlasting its original mission by a decade, teaching humanity more than this generation will ever know about Saturn and showing worlds apart from our own wh ere life is a distinct possibility.

"The mission has exceeded all expectations," said Curt Niebur, Cassini program scientist during a teleconference leading up to the mission's finale. "We've been shocked by things we never expected. We've seen one of the truly weirdest features of the solar system – a hexagonal structure the size of Earth that's been at Saturn's north pole for decades.  We've learned that Enceladus has all of the ingredients needed to support life right now."

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Cassini's Last Looks at Saturn

NASA Jet Propulsion Laboratory

Опубликовано: 15 сент. 2017 г.

In its final hours, NASA's Cassini spacecraft returned these last looks at Saturn, its rings and moons, as it prepared to end its nearly 20-year voyage in space. This video includes the final image Cassini took, which shows the cloud tops where it would later plunge into the atmosphere. For more information about the Cassini mission, visit http://saturn.jpl.nasa.gov.

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http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens/Cassini_concludes_pioneering_mission_at_Saturn

Cassini grand finale

Cassini concludes pioneering mission at Saturn

15 September 2017
The international Cassini mission has concluded its remarkable exploration of the Saturnian system in spectacular style, by plunging into the gas planet's atmosphere.

Confirmation of the end of mission arrived at NASA's Jet Propulsion Laboratory at 11:55 GMT/13:55 CEST with the loss of the spacecraft's signal having occurred 83 minutes earlier at Saturn, some 1.4 billion km from Earth.

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Last Enceladus plume observation

With the rocket propellant for manoeuvering the spacecraft fully expended as planned touring Saturn and its moons for the last 13 years, the mission concluded with the intentional plunge into the gas planet. This ensures that Saturn's icy moons, in particular ocean-bearing Enceladus, do not risk being contaminated by microbes that might have remained on board the spacecraft from Earth, and are left pristine for future exploration.

Cassini spent the last five months diving between Saturn's rings and atmosphere in a series of 22 grand finale orbits culminating in a final farewell to Titan on Monday, which set it on course for Saturn.

The grand finale orbits were supported by ESA ground stations, which received signals from Cassini to gather crucial radio science and gravitational science data.


Cassini's final image – natural colour view

Atmospheric entry began about a minute before loss of signal, and the spacecraft sent scientific data in near real-time until its antenna could no longer point towards Earth. Its last images were sent yesterday, before the final plunge, and during its final moments it made the deepest ever measurements of the plasma density, magnetic field, temperatures and atmospheric composition in Saturn's atmosphere.

"Cassini has been revolutionising our views of the Saturn system since the moment it arrived, and for 13 incredible years right until the very end today," says Alvaro Giménez, ESA's Director of Science.


First colour view of Titan's surface

"This mission has changed the way we view ocean-worlds in the Solar System, offering tantalising hints of places which could offer potentially habitable environments, with Titan giving us a planet-sized laboratory to study processes that may even be relevant to the origin of life on Earth."

Launched on 15 October 1997 and arriving in Saturn's orbit on 30 June 2004 (PDT), Cassini carried ESA's Huygens probe that landed on Titan on 14 January 2005. During its two and half hour descent it revealed the surface that had been previously been hidden by the moon's thick hazy atmosphere, showing a world with eerily Earth-like landscapes.

Cassini would continue to make exciting discoveries at Titan from orbit, with its radar finding lakes and seas filled with methane and other hydrocarbons, making it the only other known place in our Solar System with a stable liquid on its surface. In the moon's atmosphere Cassini detected numerous complex organic molecules, some of which are considered building blocks of life on Earth.


Saturn's moon zoo

Saturn's moons continued to surprise, with one of the major discoveries of the entire mission the detection of icy plumes erupting from fissures in the southern hemisphere of Enceladus. Later discoveries would indicate hydrothermal activity at the bottom of a sea floor, hinting at this world as one of the most promising places to search for life beyond Earth.

The mission also showcased the unique characteristics of Saturn's many other moons, from Iapetus and its equatorial ridge to Hyperion, which looks like a giant sponge, and from ravioli-shaped Pan, to Mimas, which resembles the Death Star from Star Wars.


Saturn

Many of Cassini's discoveries can be attributed to the longevity of the mission, which included two mission extensions, allowing the spacecraft to cover half of Saturn's seasonal cycle.

First, a two-year extension was granted to observe changes as Saturn reached equinox, when the Sun shone edge-on to the rings. Subsequently, an additional seven years was given to follow up on earlier discoveries at Enceladus and Titan, and watch as summer sunlight fell on to the northern hemisphere of Saturn and its moons while winter darkness moved in on the south.

This long-term monitoring allowed scientists to watch seasonal changes, including how weather patterns in Saturn's dynamic atmosphere evolved, and revealing the long-lived north polar vortex inside a hexagon-shaped jet stream. Cassini also watched how Titan's hydrocarbon cycle evolved with the seasons, its clouds raining methane onto the surface.


Saturn's ring features

The extended mission time was also crucial to track the evolution of small-scale dynamical features in the rings, like the 'propellers', disturbances in the rings created by moonlets. Over time the 'spokes' in Saturn's rings – features that rotate along with the rings like the spokes in a wheel – appeared and disappeared with the seasons. And at equinox, the exquisite detail of the vertical structures in the rings, driven by gravitational perturbations of nearby moons, was revealed.


A last look at Titan

"Cassini and Huygens represent an astonishing scientific, technological, and human achievement," says Nicolas Altobelli, ESA's Cassini project scientist.

"The mission has inspired us with awe-inspiring images, including those humbling views looking across more than a billion kilometres of space back to the tiny blue dot of our home planet. While it is certainly sad when a mission ends, it is also a time to celebrate this pioneering journey, which leaves a rich scientific and engineering legacy to pave the way for future missions."

Mission planners already have the next generation of ocean-world explorers lined up, although this time it's Jupiter that will get the limelight. ESA is preparing to launch the Jupiter Icy Moons Orbiter, Juice, in 2022, with a key focus on the habitability potential of the large ocean-bearing satellites Europa, Ganymede and Callisto, while NASA is planning the Europa Clipper mission for dedicated flybys of that icy moon.


Final ringscape

Notes for Editors:

The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency.
 NASA's Cassini Grand Finale toolkit
 NASA's Cassini End-of-Mission press kit
 More about Europe's contributions to Cassini
Parting views: final images gallery

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NASA Recap: Saturn End of Mission

NASA Jet Propulsion Laboratory

After two decades in space, NASA's Cassini spacecraft has completed its remarkable journey of exploration. Hear from the team behind the mission and its epic Grand Finale.

Participants include:
 -- Thomas Zurbuchen, associate administrator for the Science Mission Directorate, NASA Headquarters, Washington
 -- Michael Watkins, director, JPL
 -- Earl Maize, Cassini project manager, JPL
 -- Linda Spilker, Cassini project scientist, JPL
 -- Julie Webster, spacecraft operations chief, JPL

(1:04:46)

[zandr]

https://ria.ru/science/20170915/1504851741.html

Зонд Cassini сгорел в атмосфере Сатурна
МОСКВА, 15 сен — РИА Новости. Зонд "Кассини" передал последний сигнал на Землю и закончил свое существование, сгорев в атмосфере Сатурна через две минуты после входа в ее плотные слои, сообщает НАСА.
По словам специалистов агентства, сигнал был потерян в 14 часов 56 минут по Москве, зонд сгорел примерно через 45 секунд после этого.

Спойлер

"Кассини" стал одним из самых дорогих и при этом самых долгоживущих и успешных проектов НАСА, создававшихся в прошлые, более денежные для космического агентства годы в рамках программы так называемых "флагманских" миссий. В нее, помимо "Кассини", входят зонды "Вояджер", "Викинг", автоматическая станция "Галилео", изучавшая Юпитер, а также телескоп "Чандра" и марсоход Curiosity.
"Кассини" был одним из первых проектов НАСА, в котором принимали участие не только американские ученые и инженеры, но и специалисты из Европейского космического агентства и итальянского космического ведомства ASI. Благодаря радиоизотопным источникам тепла и энергии, зонд проработал в космосе почти 20 лет и совершил десятки эпохальных открытий.

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Ученые ожидают, что последние данные, которые "Кассини" собирал во время погружения в атмосферу Сатурна, помогут им раскрыть некоторые тайны рождения Солнечной системы и то, как материя его колец превращается в экзотический дождь в верхних слоях "воздуха" планеты-гиганта.

[zandr]

https://ria.ru/science/20170915/1504880050.html

Опубликован последний снимок, сделанный Cassini
© Фото : NASA Последний снимок, сделанный Cassini
МОСКВА, 15 сен – РИА Новости. На сайте американского космического агентства NASA появился последний снимок, который был сделан зондом Cassini перед тем, как он сгорел в атмосфере Сатурна.
На черно-белом снимке изображен вид на ночную сторону планеты в отраженном от колец Сатурна свете.
На сайте также представлена цветная версия фотографии, созданная при помощи фильтров.

© Фото : NASA  Последний снимок, сделанный Cassini
Зонд Cassini — один из самых дорогих проектов НАСА, в нем участвовали также специалисты Европейского космического агентства и итальянского космического ведомства ASI.
Аппарат был запущен в космос в октябре 1997 года. Его главной задачей был сбор информации о Сатурне, его кольцах и спутниках.
Специалисты НАСА приняли решение завершить миссию, чтобы избежать столкновения аппарата с лунами Сатурна, на которых потенциально возможна жизнь.

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Cassini Post-End of Mission News Conference

NASA

Опубликовано: 15 сент. 2017 г.

On Sept. 15, NASA held a news conference from the agency's Jet Propulsion Laboratory, in Pasadena, California, following the final mission activities of the agency's Cassini mission to Saturn. Cassini, which arrived in orbit around Saturn in 2004 on a mission to study the giant planet, its rings, moons and magnetosphere, concluded its remarkable mission with an intentional plunge into Saturn's atmosphere.

(59:00)

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Goodbye Cassini

NASA

Опубликовано: 15 сент. 2017 г.

NASA's Cassini Spacecraft Ends Its Historic Exploration of Saturn A thrilling epoch in the exploration of our solar system came to a close today, as NASA's Cassini spacecraft made a fateful plunge into the atmosphere of Saturn, ending its 13-year tour of the ringed planet. 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.

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