Keep the shuttle flying: Fwd: Cassini's Final Breathtaking Close Views of Dione

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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: August 21, 2015 at 10:31:55 PM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: Cassini's Final Breathtaking Close Views of Dione

August 20, 2015
Cassini's Final Breathtaking Close Views of Dione
This view from NASA's Cassini spacecraft looks toward Saturn's icy moon Dione, with giant Saturn and its rings in the background, just prior to the mission's final close approach to the moon on August 17, 2015. Image Credit: NASA/JPL-Caltech/Space Science Institute
› Full image and caption
A pockmarked, icy landscape looms beneath NASA's Cassini spacecraft in new images of Saturn's moon Dione taken during the mission's last close approach to the small, icy world. Two of the new images show the surface of Dione at the best resolution ever.
Cassini passed 295 miles (474 kilometers) above Dione's surface at 11:33 a.m. PDT (2:33 p.m. EDT) on Aug. 17. This was the fifth close encounter with Dione during Cassini's long tour at Saturn. The mission's closest-ever flyby of Dione was in Dec. 2011, at a distance of 60 miles (100 kilometers).
"I am moved, as I know everyone else is, looking at these exquisite images of Dione's surface and crescent, and knowing that they are the last we will see of this far-off world for a very long time to come," said Carolyn Porco, Cassini imaging team lead at the Space Science Institute, Boulder, Colorado. "Right down to the last, Cassini has faithfully delivered another extraordinary set of riches. How lucky we have been."
Raw, unprocessed images from the flyby are available at:
http://saturn.jpl.nasa.gov/mission/flybys/dione20150817/
The main scientific focus of this flyby was gravity science, not imaging. This made capturing the images tricky, as Cassini's camera was not controlling where the spacecraft pointed.
"We had just enough time to snap a few images, giving us nice, high resolution looks at the surface," said Tilmann Denk, a Cassini participating scientist at Freie University in Berlin. "We were able to make use of reflected sunlight from Saturn as an additional light source, which revealed details in the shadows of some of the images."
Cassini scientists will study data from the gravity science experiment and magnetosphere and plasma science instruments over the next few months as they look for clues about Dione's interior structure and processes affecting its surface.
Only a handful of close flybys of Saturn's large, icy moons remain for Cassini. The spacecraft is scheduled to make three approaches to the geologically active moon Enceladus on Oct. 14 and 28, and Dec. 19. During the Oct. 28 flyby, the spacecraft will come dizzyingly close to Enceladus, passing a mere 30 miles (49 kilometers) from the surface. Cassini will make its deepest-ever dive through the moon's plume of icy spray at this time, collecting valuable data about what's going on beneath the surface. The December Enceladus encounter will be Cassini's final close pass by that moon, at an altitude of 3,106 miles (4,999 kilometers).
After December, and through the mission's conclusion in late 2017, there are a handful of distant flybys planned for Saturn's large, icy moons at ranges of less than about 30,000 miles (50,000 kilometers). Cassini will, however, make nearly two dozen passes by a menagerie of Saturn's small, irregularly shaped moons -- including Daphnis, Telesto, Epimetheus and Aegaeon -- at similar distances during this time. These passes will provide some of Cassini's best-ever views of the little moons.
During the mission's final year -- called its Grand Finale -- Cassini will repeatedly dive through the space between Saturn and its rings.
The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA's Jet Propulsion Laboratory in Pasadena, California, manages the mission for the agency's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. The Cassini imaging operations center is based at the Space Science Institute in Boulder, Colo.
For more information about Cassini, visit:
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov

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

2015-276

NASA probe makes last visit to Saturn's moon Dione
August 20, 2015 by Stephen Clark
The Cassini spacecraft snapped this view of Dione backdropped by Saturn on Monday. Credit: NASA/JPL-Caltech/Space Science Institute
Scientists are getting a final look at Saturn's icy moon Dione for decades to come with fresh imagery streaming down this week from NASA's Cassini spacecraft, which made its last close flyby of the Texas-sized satellite Monday.
The raw images from Cassini's camera show Dione projected against a dramatic backdrop of Saturn's hazy atmosphere and famous rings and close-up views of Dione's frozen, cratered surface.
Cassini targeted a trajectory passing about 295 miles — 474 kilometers — from Dione. The prime science objectives of the flyby included image-taking, gathering gravity science data to study Dione's internal structure, mapping regions on the moon thought to be thermal traps, and searching for dust particles emitted from Dione.
High-resolution photos of Dione's north pole were also expected.
Dione eclipses one of Saturn's rings. Credit: NASA/JPL-Caltech/Space Science Institute
Dione measures about 698 miles — 1,123 kilometers — in diameter and completes one lap around Saturn every 2.7 day. It circles the gas giant at about the same distance as the moon orbits Earth.
Researchers hope data from the flyby, which is still being transmitted from Cassini, will help determine whether Dione is geologically active like some of Saturn's other moons.
Cassini's four previous nearby encounters with Dione revealed brilliant wispy streaks across its surface. Sharp imagery showed the features to be part of a canyon system with towering walls covered in bright ice.
"Dione has been an enigma, giving hints of active geologic processes, including a transient atmosphere and evidence of ice volcanoes. But we've never found the smoking gun. The fifth flyby of Dione (was) our last chance," said Bonnie Buratti, a Cassini science team member at NASA's Jet Propulsion Laboratory in Pasadena, California.
This raw image of Dione was captured during Cassini's encounter Monday. Credit: NASA/JPL-Caltech/Space Science Institute
In its 12th year orbiting Saturn, Cassini is busily ticking off a series of "lasts" on its to-do list as the spacecraft heads for a destructive dive into Saturn in September 2017. The probe is running low on propellant, so scientists devised a plan to guide Cassini into an uncharted region inside of Saturn's rings before the end of the mission.
But the flight plan means Cassini will no longer pass through Saturn's extensive moon system.
Cassini's last flyby of Hyperion, a moon with a striking sponge-like appearance, occurred in May. After Monday's final encounter with Dione, Cassini heads for a series of three flybys of Enceladus, which has geysers erupting near its south pole spitting out material from an underground ocean.
One of the flybys scheduled for Oct. 28 will place Cassini just 30 miles over Enceladus and is timed for when the moon's plumes are at maximum output. The mission's last close visit to Enceladus is set for Dec. 19.
Regular flybys of Titan, Saturn's largest moon with a thick nitrogen-methane atmosphere, will continue through late 2016.
"This will be our last chance to see Dione up close for many years to come," said Scott Edgington, Cassini mission deputy project scientist at JPL, before Monday's flyby. "Cassini has provided insights into this icy moon's mysteries, along with a rich data set and a host of new questions for scientists to ponder."
© 2015 Spaceflight Now Inc.

Saturn's Moon Dione: Photos from Cassini's Final Close Flyby
2015, August, 21 11:35
NASA's Cassini spacecraft flew close to Saturn's moon one final time on Aug. 17, 2015. See the final flyby images here.
http://www.space.com/30330-saturn-moon-dione-cassini-flyby-photos.html

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