"Кассини" !

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Jonathan McDowell‏Подлинная учетная запись @planet4589 1 ч. назад

Cassini now passing 119000 km from Titan. Although this is more than two Hill Sphere radii out, it's still enough to change Cassini's orbit


1 ч. назад

The Titan encounter lowers Cassini's Saturn periapsis by about 1800 km. Since peri was only 1200 km above the clouds before, that's fatal.

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Jonathan McDowell‏Подлинная учетная запись @planet4589 1 ч. назад

Cassini reaches its final apoapsis tomorrow morning and then begins its plunge for some extreme aerobraking on Sep 15

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Jonathan McDowell‏Подлинная учетная запись @planet4589 9 мин. назад

Cassini is now 1.26 million km from Saturn and still edging away from the planet at 2500 km/hr. 9 hours from now it will start its fall back

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 13 мин назад

After a final encounter, the gravity of Saturn's giant moon Titan has sent our spacecraft on its way one last time https://go.nasa.gov/2vQuyc5

https://saturn.jpl.nasa.gov/news/3116/cassini-makes-its-goodbye-kiss-flyby-of-titan/

September 11, 2017

Cassini Makes its 'Goodbye Kiss' Flyby of Titan

(Illustration) Cassini made its final, distant flyby of Saturn's moon Titan on Sept. 11, which set the spacecraft on its final dive toward the planet. Credit: NASA/JPL-Caltech

NASA's Cassini spacecraft is headed toward its Sept. 15 plunge into Saturn, following a final, distant flyby of the planet's giant moon Titan.

The spacecraft made its closest approach to Titan today at 12:04 p.m. PDT (3:04 p.m. EDT), at an altitude of 73,974 miles (119,049 kilometers) above the moon's surface. The spacecraft is scheduled to make contact with Earth on Sept. 12 at about 6:19 p.m. PDT (9:19 p.m. EDT). Images and other science data taken during the encounter are expected to begin streaming to Earth soon after. Navigators will analyze the spacecraft's trajectory following this downlink to confirm that Cassini is precisely on course to dive into Saturn at the planned time, location and altitude.

Спойлер

This distant encounter is referred to informally as "the goodbye kiss" by mission engineers, because it provides a gravitational nudge that sends the spacecraft toward its dramatic ending in Saturn's upper atmosphere. The geometry of the flyby causes Cassini to slow down slightly in its orbit around Saturn. This lowers the altitude of its flight over the planet so that the spacecraft goes too deep into Saturn's atmosphere to survive, because friction with the atmosphere will cause Cassini to burn up.

Cassini has made hundreds of passes over Titan during its 13-year tour of the Saturn system—including 127 precisely targeted encounters—some at close range and some, like this one, more distant.

"Cassini has been in a long-term relationship with Titan, with a new rendezvous nearly every month for more than a decade," said Cassini Project Manager Earl Maize at NASA's Jet Propulsion Laboratory in Pasadena, California. "This final encounter is something of a bittersweet goodbye, but as it has done throughout the mission, Titan's gravity is once again sending Cassini where we need it to go."

Cassini is ending its 13-year tour of the Saturn system with an intentional plunge into the planet to ensure Saturn's moons—in particular Enceladus, with its subsurface ocean and signs of hydrothermal activity—remain pristine for future exploration. The spacecraft's fateful dive is the final beat in the mission's Grand Finale, 22 weekly dives (begun in late April) through the gap between Saturn and its rings. No spacecraft has ever ventured so close to the planet before.

An online toolkit of information and resources about Cassini's Grand Finale and final plunge into Saturn is available at:

https://saturn.jpl.nasa.gov/grandfinale

The Cassini spacecraft was launched in 1997 and arrived at Saturn in 2004. During its time there, Cassini has made numerous dramatic discoveries, including a global ocean with indications of hydrothermal activity within the icy moon Enceladus, and liquid methane seas on another moon, Titan.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

More information about Cassini:

https://www.nasa.gov/cassini

https://saturn.jpl.nasa.gov

Media Contact:

Preston Dyches
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-7013
preston.dyches@jpl.nasa.gov

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https://saturn.jpl.nasa.gov/news/3114/how-two-ground-based-telescopes-support-nasas-cassini-mission/

September 11, 2017

How Two Ground-based Telescopes Support NASA's Cassini Mission

NASA's Infrared Telescope Facility sits at the summit of Maunakea in Hawaii. Credits: Copyright Ernie Mastroianni

By Elizabeth Zubritsky
 NASA's Goddard Space Flight Center, Greenbelt, Md.

When NASA's Cassini spacecraft plunges into the atmosphere of Saturn on Sept. 15, ending its 20 years of exploration, astronomers will observe the giant planet from Earth, giving context to Cassini's final measurements.

"The whole time Cassini is descending, we'll be on the ground, taking data and learning about conditions on Saturn," said Don Jennings, a senior scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and a co-investigator for a Cassini instrument called the Composite Infrared Spectrometer.

Спойлер

This farewell is fitting for a mission that has been supported by similar observations throughout its lifetime. NASA's Infrared Telescope Facility, or IRTF, and the W. M. Keck Observatory, in which NASA is a partner, have provided crucial contributions from the summit of Maunakea in Hawaii. Other U.S. and international telescopes also have investigated the Saturn system, complementing and enhancing the mission.

"IRTF and other facilities have provided direct support to the Cassini–Huygens mission and made it possible to link that data to decades' worth of earlier and ongoing ground-based studies," said IRTF director John Rayner. "Through its daytime observing capabilities IRTF is able to provide almost year-round monitoring of planets in support of NASA missions."

Ground-based observations of Titan, the giant planet's largest moon, helped with preparations for the Huygens probe mission early in Cassini's exploration of the Saturn system. The probe was released after Cassini entered Saturn orbit and descended through Titan's thick atmosphere to land on the surface.


The aftermath of a massive storm that erupted in Saturn's northern hemisphere in December 2010 continues to be tracked by researchers, including observations planned using the new high-resolution iSHELL instrument at NASA's Infrared Telescope Facility. Credits: NASA/JPL-Caltech/SSI

A coordinated ground campaign was organized to study Titan's atmosphere and surface, to measure the wind speed and direction, to look at atmospheric chemistry and to provide global imaging.

Eight facilities worldwide participated, observing before, during and after the Huygens probe mission, led by the European Space Agency. These included the Keck Observatory, which captured high-resolution images of the atmospheric weather patterns on Titan, and the IRTF, which helped determine the direction of Titan's winds.

"Ground-based observing played a crucial role, because at that time, it was the only way to determine the direction of Titan's winds, which had the potential to affect Huygens' descent to the surface," said Goddard's Theodor (Ted) Kostiuk, who led those observations at the IRTF and is now an emeritus scientist. "The Voyager flyby provided some information about Titan, but wind direction was one thing it could not tell us."

IRTF continues to be used for long-term studies of Saturn and Titan and their atmospheres, and to investigate Saturn's moons, extending and complementing Cassini findings. The facility's recently installed high-resolution infrared instrument, called iSHELL, will be deployed for ongoing studies of the aftermath of a massive storm that broke out in Saturn's northern hemisphere in 2010. With its very high spectral resolution, iSHELL has been optimized for the study of planetary atmospheres.

Cassini also has received plenty of aloha from the Keck Observatory, which has provided many sharp images and spectra of Saturn's most famous feature – its rings. These studies are made possible by the high spatial resolution of Keck's large aperture combined with a state-of-the-art adaptive optics system to correct for distortions caused by Earth's atmosphere.

"It's been exciting to be involved in ground support of the Cassini orbiter over these many years," said Observing Support Manager Randy Campbell of Keck Observatory. "This mission has given us an opportunity to work together toward a better understanding of some of the most beautiful and enigmatic objects in the night sky, Saturn and its moons."

During the summer of 2017, the Cassini team used Keck Observatory to take near-infrared spectroscopic data of the regions near Saturn's equator, just as Cassini was diving between Saturn and its rings during its final orbits. The team also took Keck data of the polar magnetic fields to better understand the planet's auroras, which are similar to Earth's northern and southern lights. The Keck Observatory data will be used to verify Cassini's data to provide a sort of "ground-truth" calibration of some of the on-board instruments of the orbiter.

After Cassini, ground-based studies will continue, building on everything the spacecraft observed, and keeping the discoveries coming.

For more information about NASA's Infrared Telescope Facility, visit:

http://irtfweb.ifa.hawaii.edu/

For more information about the Keck Observatory, visit:

http://www.keckobservatory.org/

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Jani Radebaugh‏ @radjanirad 11 мин. назад

Just a few hours ago, Cassini received the command to turn off the RADAR instrument - for the last time.    #cassini

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Jonathan McDowell‏ @planet4589  1m ago

Cassini heading outwards at only 109 km/hr, a mere 21 km inward of apoapsis. 24 minutes to turnaround

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Jonathan McDowell‏ @planet4589  1m ago

Cassini is 1,275,608 km from Saturn. It will get 10 km further out and then start falling back in.

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Jonathan McDowell‏ @planet4589  1m ago

10 minutes to Apoapsis-293

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Jonathan McDowell‏ @planet4589  1m ago

Sep 12 0539 TDB. It's all downhill from here. Cassini is now at Apoapsis-293, 1275619 km from Saturn's center. Outwards velocity zero.

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Jonathan McDowell @planet4589  1m ago

Cassini has started to fall back towards Saturn. Inward velocity only 10 km/hr now, but accelerating ever faster

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Jonathan McDowell‏ @planet4589  5m ago

At apoapsis Cassini's outward velocity was zero, but its orbital speed around Saturn was 5900 km/hr.

 Jonathan McDowell @planet4589  3m ago

By Friday, as it hits the atmosphere, it will be going 125600 km/hr. 60000 km/hr of that will be inward.

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Cassini diving into history

European Space Agency, ESA

Опубликовано: 11 сент. 2017 г.

Following over a decade of ground-breaking discoveries, Cassini is now approaching its mission end.

Спойлер

With little fuel left to correct the NASA's spacecraft trajectory, it has been decided to end the mission by plunging it into Saturn's atmosphere on 15 September 2017. In the process, Cassini will burn up, satisfying planetary protection requirements to avoid possible contamination of any moons of Saturn that could have conditions suitable for life. These include Saturn's largest moon Titan and Enceladus, which has a liquid ocean under its icy crust.

The grand finale is not only a spectacular way to complete this extraordinary mission, but will also return a bounty of unique scientific data that was not possible to collect during the previous phases of the mission. Cassini has never ventured into the area between Saturn and its rings before, so the new set of orbits is almost like a whole new mission.

These close orbits will provide the highest resolution observations ever achieved of the inner rings and the planet's clouds. The orbits will also give the chance to examine in situ the material in the rings and plasma environment of Saturn. It will also probe the planet's magnetic field at close distances.

This video explains Cassini 's final operations, what the Cassini-Huygens mission has taught us about Saturn, the potential for life on its moons and the promise of more science to come.

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(4:41)

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https://saturn.jpl.nasa.gov/mission/grand-finale/grand-finale-orbit-guide/#Orbit_23

IN PROGRESS: Orbit 293 - The Final Plunge - September 12 - 15

[TH]Event[/TH][TH]Date[/TH][TH]Spacecraft Time (UTC)[/TH][TH]Local Time (PDT)[/TH][TH]Notes[/TH]

Apoapse	Sep 12	5:27 a.m.	10:27 p.m. (Sep 11)	The start of Cassini's final plunge into Saturn. The spacecraft will downlink to the Deep Space Network at the end of the day.
Atmospheric Entry	Sep 15	10:31 a.m.	3:31 a.m.	Thrusters will maintain attitude control for about a minute. Estimated Earth Received Time (ERT) for Cassini's final signal (end of mission) is approximately 4:55 a.m. PDT on September 15. (Times are subject to change. See updated times here.)

[/li]
• 
  During this partial orbit, when Cassini is three and half hours fr om its expected end of mission, data from the spacecraft's Composite Infrared Spectrometer (CIRS), Ultraviolet Imaging Spectrograph (UVIS), and magnetospheric and plasma science instruments are transmitted to Earth in nearly real time, just seconds after each observation is made. Cassini usually holds onto those data for hours or days before turning its high-gain antenna toward Earth to transmit them.
• 
  Unlike the preceding orbits, wh ere the Cassini's lowest altitudes were chosen to avoid tumbling, the spacecraft trajectory on this orbit intentionally continues all the way into Saturn.
• 
  Cassini continues transmitting as long as possible until the force of Saturn's atmosphere overpowers the spacecraft's thrusters and Cassini can no longer point its antenna precisely enough to maintain contact with Earth.
• 
  When the spacecraft's signal is lost, the Cassini mission comes to an end.
  

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https://saturn.jpl.nasa.gov/mission/grand-finale/cassini-end-of-mission-timeline/

...

Sept 12	Event	Signal received on Earth
1:27 am EDT (10:27 pm PDT - Sept. 11)	Apoapse, or farthest point from Saturn in the orbit (800,000 miles, 1.3 million kilometers from Saturn)
7:56 pm EDT (4:56 pm PDT)	Downlink of final Titan data begins	9:19 pm EDT (6:19 pm PDT)

...

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 45 мин. назад

Why Cassini Matters: a concise look at some of the mission's scientific and engineering legacies -- https://go.nasa.gov/2vQyCcy 

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NASA Solar System‏Подлинная учетная запись @NASASolarSystem 56 мин. назад

#10Things to know about @CassiniSaturn's glorious demise on Friday. #grandfinale https://go.nasa.gov/2f0PiLc

https://solarsystem.nasa.gov/news/2017/09/11/10-things-to-know-about-cassinis-glorious-demise

10 Things to Know about Cassini's Glorious Demise

11 September 2017


In this screenshot from the short animated film Cassini's Grand Finale, the spacecraft is shown breaking apart after entering Saturn's atmosphere. The planned end of Cassini will occur on Sept. 15, 2017.

This week we say goodbye to the amazing Cassini spacecraft after almost 19 years in space. Here are 10 things to know about one of NASA's most ambitious missions to the outer solar system.

Спойлер

1. Cassini launched Oct. 15, 1997. When the mission ends Sept. 15, 2017, Cassini will be exactly one month short of 20 years in space.

More: https://saturn.jpl.nasa.gov/mission/grand-finale/why-cassini-matters/

2. You can ride along with the spacecraft in real time (and even watch its final signal travel to Earth) in the Cassini section of NASA's Eyes on the Solar System visualization.

More: https://eyes.nasa.gov/eyes-on-cassini.html

3. Why is Cassini ending? The spacecraft is low on rocket fuel, which could eventually prevent mission operators from controlling the course of the spacecraft. The solution: Cassini is being sent into Saturn's atmosphere to avoid eventually crashing into and contaminating Saturn's moons Titan or Enceladus, which could be habitable to some form of life. More: https://saturn.jpl.nasa.gov/faq/#end_of_mission

4. Spacecraft safely entering Earth's atmosphere with a heat shield are typically traveling about 17,000 mph (27,400 kph). Cassini enters Saturn's atmosphere at three times that speed with no heat shield  the spacecraft will be traveling 34 km/s, or about 76,000 mph (122,500 kph). More: https://saturn.jpl.nasa.gov/mission/saturn-tour/where-is-cassini-now/

5. Cassini will descend into Saturn so fast that the atmospheric pressure around the spacecraft will increase faster than tenfold per minute.

More: https://saturn.jpl.nasa.gov/mission/grand-finale/overview/

6. Because Cassini has used most of its propellant and also dropped the Huygens probe onto Titan, the spacecraft now weighs about one-third what it did at launch.

More: https://saturn.jpl.nasa.gov/mission/grand-finale/cassini-quick-facts/

7. Saturn has almost no oxygen, so Cassini doesn't technically burn up in the atmosphere. Instead, the spacecraft melts and the atmosphere strips off what melts until nothing is left. The process produces so much light, however, that it will look like it's burning. More: https://saturn.jpl.nasa.gov/resources/7628/?category=videos

8. Normally, Cassini stores science data for hours or days before pointing its antenna to Earth to transmit. During the plunge into Saturn, Cassini transmits four seconds after recording. The final science data Cassini sends to Earth is expected to be from about 190 miles (300 kilometers) deeper into Saturn's atmosphere than ever been before.

More: https://saturn.jpl.nasa.gov/science/saturn/

9. The Cassini mission officially ends when antennas on Earth no longer detect the spacecraft's signal. Earth will lose Cassini's signal after Saturn's atmosphere overpowers the spacecraft's thrusters, turning Cassini's transmitter away from Earth.

More: https://saturn.jpl.nasa.gov/mission/grand-finale/cassini-end-of-mission-timeline/

10. Light takes 90 minutes to get from Saturn to Earth, so the "tail" of Cassini's final signal reaches Earth more than an hour after the spacecraft has vaporized. Cassini's final signal will be received by NASA's Deep Space Network station in Canberra, Australia, because Earth spins and that's the only DSN station facing Saturn during Cassini's final hours.

More: https://saturn.jpl.nasa.gov/news/2976/cassinis-largest-science-instrument/

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Cassini's Infrared Saturn

NASA Goddard

Опубликовано: 12 сент. 2017 г.

NASA's Cassini spacecraft arrived at Saturn in 2004, beginning an epic thirteen-year tour of the ringed planet and its many moons. Cassini carried an impressive array of scientific instruments, including the Composite Infrared Spectrometer (CIRS) built at Goddard Space Flight Center. By studying the Saturn system in heat radiation, CIRS observed hot spots in a giant Saturn storm, discovered a new hydrocarbon in Titan's smoggy atmosphere, found unexpected surface heating on Mimas and Tethys, and even detected evidence of a liquid water ocean under the icy shell of Enceladus. This video explores Cassini CIRS' Greatest Hits, as told by instrument team members Michael Flasar, Conor Nixon, and Carrie Anderson.

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Jonathan McDowell‏Подлинная учетная запись @planet4589 6 мин. назад

Cassini now 1,190,000 km above the Saturnian atmosphere falling at 3800 km/hr and orbiting at 7100 km/hr (2.0 km/s)

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Разбавлю Великим и могучим
https://ria.ru/science/20170912/1504299606.html

"Кассини" вышел на траекторию столкновения с Сатурном
https://cdn1.img.ria.ru/images/149123/80/1491238022.jpg[/IMG]
© NASA/JPL
МОСКВА, 12 сен – РИА Новости. Вчера ночью зонд "Кассини" сблизился с Титаном, совершил последний гравитационный маневр и вышел на прямую траекторию столкновения с Сатурном, в атмосфере которого он сгорит в пятницу, сообщает НАСА.
"Можно сказать, что "Кассини" поддерживал очень долгие отношения с этой луной Сатурна, встречаясь с ней примерно раз в месяц на протяжении более чем 10 лет. Их последнее рандеву вызывает смешанные чувства, но, несмотря на это расставание, верный Титан в последний раз поможет зонду выйти на новую орбиту", — рассказывает Эрл Мейз (Earl Maize), руководитель миссии "Кассини" в НАСА.
Жизнь "Кассини" оборвется совсем скоро – на прошлой неделе он начал последний, 22 виток вокруг Сатурна в рамках последнего этапа миссии, получившего имя "Финал Оперы". Через пять дней, 15 сентября этого года, зонд НАСА войдет в плотные слои атмосферы Сатурна и сгорит, передавая при этом информацию об устройстве его недр на Землю.
Получив последние фотографии колец Сатурна, "Кассини" вчера ночью в последний раз сблизился с Титаном, чье притяжение поменяет траекторию полета зонда и отправит его на последнее рандеву с "властелином колец". Специалисты НАСА назвали этот гравитационный маневр "прощальным поцелуем", так как после него на судьбу "Кассини" уже ничего не изменит.
Как отмечает НАСА, зонд пролетел на расстоянии в примерно 119 километров над поверхностью Титана, получив прощальные снимки и собрав последние данные по устройству его атмосферы и поверхности. Эта информация, а также остатки других научных данных будет передана на Землю в ближайшее время и память "Кассини" будет очищена перед тем, как он начнет свой последний "нырок" в атмосферу Сатурна.
Завтра некоторые инструменты "Кассини" начнут работать таким образом, что собираемая ими информация будет передаваться на Землю в режиме реального времени, что позволит зонду вести научные наблюдения фактически до самого момента его гибели. Как ожидают ученые, это печальное событие произойдет в следующую пятницу, примерно в 3 часа дня по Москве.