"Кассини" !

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 4 ч. назад

Staggering structure—this image offers a close look at complex waves in Saturn's rings. Details: https://go.nasa.gov/2gM4vjT

https://saturn.jpl.nasa.gov/resources/7767/

Staggering Structure

Спойлер

Photojournal: PIA21627

[свернуть]

September 6, 2017

This view fr om NASA's Cassini spacecraft shows a wave structure in Saturn's rings known as the Janus 2:1 spiral density wave. Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn's rings are much more tightly wound. In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times.

Спойлер

This is the only major density wave visible in Saturn's B ring. Most of the B ring is characterized by structures that dominate the areas wh ere density waves might otherwise occur, but this innermost portion of the B ring is different.

The radius from Saturn at which the wave originates (toward lower-right in this image) is 59,796 miles (96,233 kilometers) from the planet. At this location, ring particles orbit Saturn twice for every time the moon Janus orbits once, creating an orbital resonance. The wave propagates outward from the resonance (and away from Saturn), toward upper-left in this view. For reasons researchers do not entirely understand, damping of waves by larger ring structures is very weak at this location, so this wave is seen ringing for hundreds of bright wave crests, unlike density waves in Saturn's A ring.

The image gives the illusion that the ring plane is tilted away from the camera toward upper-left, but this is not the case. Because of the mechanics of how this kind of wave propagates, the wavelength decreases with distance from the resonance. Thus, the upper-left of the image is just as close to the camera as the lower-right, while the wavelength of the density wave is simply shorter.

This wave is remarkable because Janus, the moon that generates it, is in a strange orbital configuration. Janus and Epimetheus (see "Cruising Past Janus") share practically the same orbit and trade places every four years. Every time one of those orbit swaps takes place, the ring at this location responds, spawning a new crest in the wave. The distance between any pair of crests corresponds to four years' worth of the wave propagating downstream from the resonance, which means the wave seen here encodes many decades' worth of the orbital history of Janus and Epimetheus. According to this interpretation, the part of the wave at the very upper-left of this image corresponds to the positions of Janus and Epimetheus around the time of the Voyager flybys in 1980 and 1981, which is the time at which Janus and Epimetheus were first proven to be two distinct objects (they were first observed in 1966).

Epimetheus also generates waves at this location, but they are swamped by the waves from Janus, since Janus is the larger of the two moons.

This image was taken on June 4, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of 47,000 miles (76,000 kilometers) away from the area pictured. The image scale is 1,730 feet (530 meters) per pixel. The phase angle, or sun-ring-spacecraft angle, is 90 degrees.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at https://ciclops.org.

Credit

NASA/JPL-Caltech/Space Science Institute

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 36 мин. назад

The main engine cover (at left in this illustration) has been closed for the last time. More about the spacecraft: https://go.nasa.gov/1tjpevV 

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Jonathan McDowell‏Подлинная учетная запись @planet4589 3 ч. назад

Cassini now 1.04 million km from Saturn headed inward to periapsis 292 on Sep 9

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 53 мин. назад

An at-a-glance look at the long and winding road to our #GrandFinale: https://go.nasa.gov/2gr6pWR 

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https://saturn.jpl.nasa.gov/resources/7769/

Colorful Structure at Fine Scales



Photojournal: PIA21628

September 7, 2017

These are the highest-resolution color images of any part of Saturn's rings, to date, showing a portion of the inner-central part of the planet's B Ring. The view is a mosaic of two images that show a region that lies between 61,300 and 65,600 miles (98,600 and 105,500 kilometers) fr om Saturn's center.

Спойлер

The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.

The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini's mission.

The different ringlets seen here are part of what is called the "irregular structure" of the B ring. Cassini radio occultations of the rings have shown that these features have extremely sharp boundaries on even smaller scales (radially, or along the direction outward from Saturn) than the camera can resolve here. Closer to Saturn, the irregular structures become fuzzier and more rounded, less opaque, and their color contrast diminishes.

The narrow ringlets in the middle of this scene are each about 25 miles (40 kilometers) wide, and the broader bands at right are about 200 to 300 miles (300 to 500 kilometers) across. It remains unclear exactly what causes the variable brightness of these ringlets and bands—the basic brightness of the ring particles themselves, shadowing on their surfaces, their absolute abundance, and how densely the particles are packed, may all play a role.

Figure B

The second image (Figure B) is a color-enhanced version. Blue colors represent areas wh ere the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), while red colors represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths). Observations from the Voyager mission and Cassini's visual and infrared mapping spectrometer previously showed these color variations at lower resolution, but it was not known that such well-defined color contrasts would be this sharply defined down to the scale (radial scale) of a couple of miles or kilometers, as seen here.

Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the color-enhanced version are also richer in water ice.


Figure C

The third image (Figure C) is a composite of the "true" and "enhanced" color images for easy comparison.

This image was taken on July 6, 2017, with the Cassini spacecraft narrow-angle camera. The image was acquired on the sunlit side of the rings from a distance of 47,000 miles (76,000 kilometers) away from the area pictured. The image scale is about 2 miles (3 kilometers) per pixel. The phase angle, or sun-ring-spacecraft angle, is 90 degrees.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at https://ciclops.org.

Credit

NASA/JPL-Caltech/Space Science Institute

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https://saturn.jpl.nasa.gov/mission/grand-finale/grand-finale-orbit-guide/#Orbit_22

IN PROGRESS: Orbit 292 - September 5 - 12

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

Apoapse	Sep 5	6:47 p.m.	11:47 a.m.
Periapse	Sep 9	12:18 a.m.	5:18 p.m. (Sep 8 )	Last of the "Final Five" dips into Saturn's atmosphere.
Downlink	Sep 9	1:07 p.m.	6:07 a.m.	Estimated Earth Received Time (ERT) is 7:29 a.m. PDT on September 9.

[/li]
• 
  This is Cassini's final full orbit of Saturn before the mission ends.
• 
  During this orbit, Cassini's Composite Infrared Spectrometer (CIRS) and Visible and Infrared Mapping Spectrometer (VIMS) instruments work together to determine the abundance of helium in Saturn's atmosphere.
• 
  This is the fifth of five orbits in which Cassini's elliptical orbit carries it so low that the spacecraft passes briefly through Saturn's atmosphere. Cassini's reaction control thrusters are at the ready to correct the spacecraft's orientation in case Saturn's atmosphere pushes on the spacecraft hard enough to cause any rotation.
• 
  During the period in which the spacecraft is nearest Saturn, Cassini's Ion and Neutral Mass Spectrometer (INMS) performs its fourth session directly sampling Saturn's upper atmosphere. The instrument measures densities of different species of molecular hydrogen, helium and a variety of ions in the immediate vicinity of the spacecraft.
• 
  The spacecraft's RADAR and Imaging Science Subsystem (ISS) instruments also operate during the INMS observation, with RADAR continuing its study of ammonia in Saturn's atmosphere and the ISS instrument capturing an iconic image of the rings seen looking outward from Saturn.
• 
  At the end of this orbit, Cassini makes a distant flyby of the Mercury-size moon Titan, whose gravity alters the spacecraft's trajectory one final time. This gravitational nudge, which the team calls "the goodbye kiss," ensures that the spacecraft is disposed of in a controlled manner. Instead of passing safely into and out of Saturn's outermost atmosphere on the next orbit, Cassini will instead dip so deeply into the atmosphere that the spacecraft will burn up like a meteor.
  

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Jonathan McDowell‏Подлинная учетная запись @planet4589 5 мин. назад

Cassini plunging towards the rings again, 85000 km above the north polar cloudtops right now

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Jonathan McDowell‏Подлинная учетная запись @planet4589 31 мин. назад

Cassini now 45000 km from the cloud tops (within the B ring radius but at higher latitude)


8 мин. назад

Cassini now dropping through 20000 km above the clouds and heading south, about 45N right now

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Jonathan McDowell‏Подлинная учетная запись @planet4589 10 мин. назад

30 minutes to Periapsis -292. Then back out to Apoapsis-293 on Sep 12 and Periapsis-293 on Sep 15. There will be no Apoapsis-294.


2 мин. назад

Cassini now within 10000 km of Saturn's clouds, 20 minutes to periapsis

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Jonathan McDowell‏Подлинная учетная запись @planet4589 11 мин. назад

Cassini now within 5000 km of the clouds. 13 min to periapsis

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Jonathan McDowell‏Подлинная учетная запись @planet4589 3 сек. назад

Cassini now passing through Periapsis-292 at 0019 TDB (0017 UTC)., 1700 km above Saturn's clouds

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Jonathan McDowell‏Подлинная учетная запись @planet4589 1 мин. назад

Cassini heading south over Saturn's southern hemisphere, ascending through 2000 km as it begins its final loop around the planet

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NASA's Cassini Spacecraft: A Journey's End

NASA Jet Propulsion Laboratory

Опубликовано: 8 сент. 2017 г.

The Cassini mission's epic 13-year exploration of Saturn is coming to a close. On Sept. 15, the spacecraft will make a planned plunge into the atmosphere of Saturn in order to protect pristine icy moons that warrant future exploration. As the mission nears its end, team members reflect on this historic, international collaboration. The video uses a combination of animation and actual imagery returned over the course of the mission. For more information about the Cassini mission, visit https://saturn.jpl.nasa.gov. For specific information about the mission's Grand Finale, visit https://saturn.jpl.nasa.gov/mission/gov.

(2:21)

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 1 ч. назад

Our final crossing between Saturn and the rings was successful. Track the spacecraft's position at: https://go.nasa.gov/2aNCy6t  #GrandFinale

[ОАЯ]

http://www.houstonchronicle.com/news/article/How-to-steer-a-spacecraft-into-Saturn-12185406.php

Это просто математика.

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 3 ч. назад

14 hours watching the plume at Saturn's moon Enceladus, our last dedicated observation of this singular scene https://go.nasa.gov/2gPwLhW

https://saturn.jpl.nasa.gov/resources/7770/

Last Enceladus Plume Observation

Спойлер

Photojournal: PIA21887

[свернуть]

September 8, 2017

This movie sequence of images is from the last dedicated observation of the Enceladus plume by NASA's Cassini spacecraft.

Спойлер

The images were obtained over approximately 14 hours as Cassini's cameras stared at the active, icy moon. The view during the entire sequence is of the moon's night side, but Cassini's perspective Enceladus shifts during the sequence. The movie begins with a view of the part of the surface lit by reflected light from Saturn and transitions to completely unilluminated terrain. The exposure time of the images changes about halfway through the sequence, in order to make fainter details visible. (The change also makes background stars become visible.)

The images in this movie sequence were taken on Aug. 28, 2017, using Cassini's narrow-angle camera. The images were acquired at a distance from Enceladus that changed from 684,000 to 539,000 (1.1 million to 868,000 kilometers). Image scale changes during the sequence, from 4 to 3 miles (7 to 5 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini. The Cassini imaging team homepage is at https://ciclops.org.

Credit

NASA/JPL-Caltech/Space Science Institute

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ESA Science‏Подлинная учетная запись @esascience 2 ч. назад

The week ahead for @CassiniSaturn, from tonight's Titan flyby to Friday's #GrandFinale plunge: http://ow.ly/CP2N30f3HBY 



ESA Operations‏Подлинная учетная запись @esaoperations 4 мин. назад

ESA's deep-space ground station at #NewNorcia #Australia will catch signals from @CassiniSaturn during the final #GrandFinale plunge on Fri

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 2 ч. назад

We've spent nearly half a Saturnian year at the Ringed Planet, allowing us to observe the course of its seasons https://go.nasa.gov/2ePEUlC

https://saturn.jpl.nasa.gov/resources/7771/

So Far from Home



Photojournal: PIA21345

September 11, 2017

With this view, Cassini captured one of its last looks at Saturn and its main rings from a distance. The Saturn system has been Cassini's home for 13 years, but that journey is nearing its end.

Спойлер

Cassini has been orbiting Saturn for nearly a half of a Saturnian year but that journey is nearing its end. This extended stay has permitted observations of the long-term variability of the planet, moons, rings, and magnetosphere, observations not possible from short, fly-by style missions.

When the spacecraft arrived at Saturn in 2004, the planet's northern hemisphere, seen here at top, was in darkness, just beginning to emerge from winter (see Cassini's Holiday Greetings​). Now at journey's end, the entire north pole is bathed in the continuous sunlight of summer.

Images taken on Oct. 28, 2016 with the wide angle camera using red, green and blue spectral filters were combined to create this color view. This view looks toward the sunlit side of the rings from about 25 degrees above the ringplane.

The view was acquired at a distance of approximately 870,000 miles (1.4 million kilometers) from Saturn. Image scale is 50 miles (80 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

For more information about the Cassini-Huygens mission visit https://saturn.jpl.nasa.gov and https://www.nasa.gov/cassini . The Cassini imaging team homepage is at http://ciclops.org .

Credit

NASA/JPL-Caltech/Space Science Institute

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CassiniSaturn‏Подлинная учетная запись @CassiniSaturn 1 ч. назад

Happening now: Titan's "goodbye kiss." Saturn's moon will nudge the spacecraft toward its final plunge. More: https://go.nasa.gov/2wbaCBT 

Спойлер

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

...

Sept 11
3:04 pm EDT (12:04 pm PDT)	Final, distant Titan flyby (aka, the "goodbye kiss" ) closest approach (altitude 73,974 miles, 119,049 kilometers above Titan's surface)

...