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Old 03-16-2012, 09:35 AM   #91
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CICLOPS: Rev163: Mar 18 - Apr 5 '12:
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Cassini continues its exploration of the Saturn system with the 18-day Rev163, which begins on March 18 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 2.37 million kilometers (1.47 million miles) from Saturn's cloud tops. The spacecraft is nearing the end of the first equatorial phase of the Cassini Solstice Mission, a phase which lasts until May 2012. During this phase, the spacecraft's orbits lie within the equatorial plane of the planet, providing opportunities to encounter Saturn's numerous moons, image the rings edge-on, and look at Saturn's cloud tops without the rings obscuring the view. Thirty-eight ISS observations are planned for Rev163, the vast majority dedicated to Saturn storm monitoring and to encounters with Enceladus, Janus, and Dione.

ISS begins its observations for Rev163 the day after apoapse on March 19 with three, quick observations of Saturn and its faded northern hemisphere storm. These "Storm Watch" observation sequences are designed to take advantage of short, two-minute segments when the spacecraft turns the optical remote sensing (ORS) instruments back to Saturn as a waypoint between other experiments' observations. These sequences include blue, clear, two methane band, and one full-frame, continuum band filter images. Ten more such observations are planned between March 20 and 25, with another five planned between April 1 and 3. Also on March 19, ISS will acquire an astrometric observation of Saturn's small, inner moons, including Calypso, Helene, Methone, Anthe, Epimetheus, and Pandora. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy satellites. Additional astrometric observations will be taken on March 23, 24, and April 3.

On March 20, ISS will take a look at Titan from a distance of 1.32 million kilometers (0.82 million miles). The observation is an effort to look for clouds in the moon's atmosphere as part of the "Titan Monitoring Campaign" (TMC). This observation, of a half-phase Titan, is designed to monitor clouds over the moon's Shangri-La dune field. On March 21, ISS will search for possible satellites at Titan's L4 point, a Lagrangian point that lies 60 degrees ahead of the large moon on its orbit. Similar moons have been found at Dione's and Tethys' L4 points (Helene and Telesto, respectively). An observation covering Titan's L5 point, which lies 60 degrees behind Titan, will be taken on March 26. On March 25, ISS will preform a unique observation of Saturn's shadow on the Phoebe ring. The ring lies along the orbit of the outer moon Phoebe and is likely composed of particles ejected from micrometeorite impacts on the small moon, not unlike the faint dust rings associated with Saturn's inner small moons, such as Anthe or Atlas. The camera system will be pointed at the edge of Saturn's shadow on the ring. On March 26, ISS will perform a TMC observation of Titan that will allow for monitoring of cloud features across the Senkyo dune field from a distance of 1.44 million kilometers (0.89 million miles).

On March 27 at 21:32 UTC, Cassini will reach periapse for Rev163 at an altitude of 135,950 kilometers (84,460 miles) from Saturn. ISS observations during the periapse period will be taken during a targeted encounter of Enceladus and later during non-targeted encounters of Janus and Dione.

Cassini will fly by Enceladus (E17) at an altitude of 74 kilometers (46 miles) at 18:30 UTC on March 27. ISS will image the icy satellite's south polar plume from distances of 335,000 kilometers (208,000 miles) down to 113,500 kilometers (70,500 miles) while the satellite is just a thin crescent. Next, the Composite Infrared Spectrometer (CIRS) will acquire a series of mid-infrared scans across the night side of Enceladus, as well as a pair of scans across the south polar terrain (found in earlier flybys of Enceladus to be a thermal hotspot) as well as a far-infrared raster scan using CIRS's FP1 channel. During the two hours surrounding closest approach, the Ion and Neutral Mass Spectrometer (INMS) will be prime, analyzing the composition of Enceladus' south polar plume as the spacecraft flies through it. The spacecraft's path will take it along the length of Baghdad Sulcus, allowing INMS to resolve individual jets from this "tiger stripe" fracture. Finally, ISS will acquire a nine-frame, clear and UV3 filter mosaic of Enceladus' leading hemisphere terrain as the spacecraft recedes from the moon.

At 21:34 UTC, Cassini will fly by one of Saturn's smaller satellites, Janus, at a close-approach distance of 43,851 kilometers (27,247 miles). ISS will acquire a series of images using many of the narrow-angle camera's filters. All of these images save the final one will be taken with Saturn as a backdrop, though only the second set of images will be against Saturn's day side. A total of 29 images are planned for this observation. At 05:07 UTC on March 28, Cassini will perform a non-targeted encounter of Dione at a distance of 43,997 kilometers (27,338 miles). ISS will acquire a nine-frame mosaic of Dione a couple of hours later, covering the moon's anti-Saturn hemisphere. At the end of the mosaic, the narrow-angle camera will be used to watch as Mimas and Tethys pass behind the limb of Dione.

Later on March 28, ISS will perform a TMC observation of Titan from a distance of 1.88 million kilometers (1.17 million miles). This will allow for monitoring of cloud features across the Fensal-Aztlan region of the moon. Afterward, ISS will search for moons at Rhea's L5 Lagrangian point. Next, ISS will ride along with a CIRS observation of Rhea. ISS will image several mutual events of various moons, including an occultation of Mimas. Finally, ISS will acquire a long series of images of Rhea. These images are designed to improve the photometric calibration of ISS images as well as the camera's shutter offset.

On April 3, ISS will take another look at Titan, this time from a distance of 1.65 million kilometers (1.02 million miles) looking at western Xanadu and eastern Shangri-La. Later that day, ISS will acquire a lengthy, nine-hour observation of Thrymr, one of Saturn's distant, irregular moons. This observation will be taken from a distance of 10.3 million kilometers (6.41 million miles), and when combined with additional observations of this irregular satellite, is designed to measure Thrymr's rotational period. On April 5, ISS will ride along with the Visual and Infrared Mapping Spectrometer to image the G ring.

On April 5, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev164. Rev164 includes a targeted flyby of Enceladus and close, non-targeted flyby of Tethys.

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Old 03-19-2012, 07:05 PM   #92
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NASA / NASA JPL:
Cassini Plasma Spectrometer Resumes Operations

March 19, 2012

CASSINI MISSION STATUS REPORT

PASADENA, Calif. -- The Cassini plasma spectrometer instrument (CAPS) aboard NASA's Cassini spacecraft at Saturn has resumed operations. Mission managers received confirmation on Friday, March 16, that it was turned on. They plan to monitor the instrument for any unusual behavior.

Last June, short circuits in the instrument led to unexpected voltage shifts on the spacecraft. As a precaution, mission managers turned off the CAPS instrument while engineers investigated the issue. The investigation led to the conclusion that tin plating on electronics components had grown "whiskers." The whiskers were very small, less than the diameter of a human hair, but they were big enough to contact another conducting surface and carry electrical current. Researchers are still trying to understand why whiskers grow on tin and other metals, but they know now that whiskers can grow in space and on Earth. It is believed that these or additional tin whiskers that may grow on Cassini cannot carry enough current to cause problems, but will burn out on their own like a lightweight fuse.

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SPACE.com: NASA Resurrects Saturn Science Tool on Cassini Spacecraft
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Old 03-19-2012, 08:47 PM   #93
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NASA / NASA JPL:
Cassini Sees Saturn Stressing out Enceladus

March 19, 2012

Images from NASA's Cassini spacecraft have, for the first time, enabled scientists to correlate the spraying of jets of water vapor from fissures on Saturn's moon Enceladus with the way Saturn's gravity stretches and stresses the fissures. The result is among the Cassini findings presented today at the Lunar and Planetary Science Conference at The Woodlands, Texas.

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These images, based on ones obtained by NASA's Cassini spacecraft, show how the pull of Saturn's gravity can deform the surface of Saturn's moon Enceladus in the south polar region crisscrossed by fissures known as "tiger stripes."
Image credit: NASA/JPL-Caltech/SSI/LPI/GSFC


"This new work gives scientists insight into the mechanics of these picturesque jets at Enceladus and shows that Saturn really stresses Enceladus," said Terry Hurford, a Cassini associate based at NASA Goddard Space Flight Center in Greenbelt, Md.

Enceladus is unique in the Saturn system in having jets of water vapor and organic particles spray from long fissures in its south polar region. The long fissures have been nicknamed the "tiger stripes."

Hurford and colleagues suggested a few years ago that tidal pulls from Saturn's gravity could explain the existence of the jets, but they had not been able to correlate specific jets with calculated stresses until now. They studied the jets emerging from the warmest regions within the tiger stripes Baghdad Sulcus and Damascus Sulcus.

The scientists found that the greatest stresses pulling apart the tiger stripes, occurred right after Enceladus made its closest approach to Saturn in its orbit. The scientists found that Saturn's gravitational pull could also deform the fissure by making one side move relative to the other side. That kind of deformation seemed to occur quite often during Enceladus' orbit around the planet, even when Enceladus was very far away.

The finding suggests that a large reservoir of liquid water - a global or local ocean - would be necessary to allow Enceladus to flex enough to generate stresses great enough to deform the surface, Hurford said. That process would control the timing of the jet eruptions. The finding also suggests that Saturn's tides create an enormous amount of heat in the area.

The conference will also include a talk presenting highlights of the Cassini mission by Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. She will present images showing the evolution of an enormous storm that roiled the northern hemisphere of Saturn, the effect of seasonal rain storms on Saturn's moon Titan, and what Cassini will hope to observe in the next few years of its extended mission.

"Cassini's seven-plus years roaming the Saturn system have shown us how beautifully dynamic and unexpected the Saturn system is over time," Spilker said. "We're looking forward to new discoveries as the seasons turn."

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SPACE.com: Saturn's Gravity Warps Icy Moon's Erupting Jets
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Old 03-20-2012, 09:01 PM   #94
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Universe Today: Photo Treat: Enceladus, Titan and Saturnís Rings


Color-composite image from Cassini raw data acquired on March 12, 2012. (NASA/JPL/SSI/J. Major)
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Old 03-21-2012, 09:18 PM   #95
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Universe Today: Two Moons In Passing


Animation of Tethys passing in front of Dione from Cassini's point of view.



Tethys and Dione (NASA/JPL/SSI)
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Old 03-22-2012, 10:33 PM   #96
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NASA / NASA JPL:
Cassini Mission Receives Air and Space Museum Award

March 22, 2012

PASADENA, Calif. -- The Smithsonian's National Air and Space Museum has bestowed its highest group honor, the Trophy for Current Achievement, on NASA's Cassini mission to Saturn. The annual award recognizes outstanding achievements in the fields of aerospace science and technology.

The trophy was presented Wednesday, March 21, during an evening ceremony at the museum in Washington. Established in 1985, the award has been presented to seven NASA planetary mission teams.

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NASA's Cassini-Huygens mission to Saturn was awarded the 2012 National Air and Space Museum Trophy for Current Achievement on March 21 at a black-tie dinner in Washington, D.C. Pictured (from left to right) - Wayne Clough, secretary of the Smithsonian; Robert Mitchell, Cassini program manager based at NASA's Jet Propulsion Laboratory, Pasadena, Calif.; and Gen. Jack Dailey, director of the museum.
Image credit: Smithsonian National Air and Space Museum


"This joint mission has produced an unprecedented science return," said William Knopf, Cassini program executive at NASA Headquarters in Washington. "Missions like Cassini pave the way for future robotic and human exploration throughout our solar system and beyond."

Launched in 1997, the Cassini spacecraft entered Saturn's orbit in June 2004 with the European Space Agency's (ESA) Huygens probe bolted to its side. In December 2004, the spacecraft successfully released Huygens, which entered the atmosphere of Saturn's largest moon, Titan. Cassini completed its prime mission in 2008 and has been extended twice. It is now in its so-called solstice mission, which will enable scientists to observe seasonal changes in Saturn and its moons during the planet's northern summer solstice. The mission will last through September 2017.

"We look forward to sailing around the Saturn system for several more years to see how our views of the planet and its magnificent moons change as we get into northern summer solstice," said Robert Mitchell, the Cassini program manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who accepted the award on behalf of the team.

The Cassini spacecraft carries 12 science instruments and investigations, with an additional six aboard Huygens. Cassini mission highlights to date include the discovery of four new moons and two new rings around Saturn. Cassini observed spraying water vapor and icy particle jets from the moon Enceladus. In Saturn's northern hemisphere, the spacecraft watched the evolution of a monster storm, a sign of seasonal change from northern winter into northern spring.

Cassini and Huygens has also revealed new characteristics about Titan, the only body in the solar system other than Earth with stable liquid on its surface.

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NASA Press Release: RELEASE : 12-092 - NASA'S Cassini Mission Receives Smithsonian National Air and Space Museum's Highest Honor
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Old 03-26-2012, 10:03 PM   #97
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NASA / NASA JPL:
Cassini to Make Closest Pass Yet over Enceladus South Pole

March 26, 2012

NASA's Cassini spacecraft is preparing to make its lowest pass yet over the south polar region of Saturn's moon Enceladus, where icy particles and water vapor spray out in glittering jets. The closest approach, at an altitude of about 46 miles (74 kilometers), will occur around 11:30 a.m. PDT (2:30 p.m. EDT) on March 27.

This flyby is primarily designed for Cassini's ion and neutral mass spectrometer, which will attempt to "taste" particles from the jets. Scientists using this spectrometer will utilize the data to learn more about the composition, density and variability of the plume. The Cassini plasma spectrometer, which team members worked to return to service so it could gather high-priority measurements during this flyby, will also be analyzing Saturn's magnetic and plasma environment near Enceladus and sampling the plume material near closest approach.

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Artist's concept of the Mar. 27, 2012, flyby of Saturn's moon Enceladus by NASA's Cassini spacecraft.
Image credit: NASA/JPL-Caltech
At least four distinct plumes of water ice spew out from the south polar region of Saturn's moon Enceladus in this dramatically illuminated image.
Image credit: NASA/JPL/Space Science Institute


In addition, the composite infrared spectrometer will also be looking for hot spots on Enceladus, and the imaging cameras will be snapping pictures.

A flyby in October 2015 will bring Cassini about 16 miles (25 kilometers) closer to the Enceladus surface near the south pole. Cassini's closest approach to any part of Enceladus occurred on Oct. 9, 2008, when it flew within about 16 miles (25 kilometers) of the surface at the equator.

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The Planetary Society Blog: Notes from the Lunar and Planetary Science Conference: Making Cassini's radar images prettier
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Old 03-28-2012, 02:39 PM   #98
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[email protected]: Is it Snowing Microbes on Enceladus?

Universe Today: “Snowing Microbes” On Saturn’s Moon?:
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Enceladus, Saturn’s 318-mile-wide moon that’s become famous for its ice-spraying southern jets, is on astronomers’ short list of places in our own solar system where extraterrestrial life could be hiding — and NASA’s Cassini spacecraft is in just the right place to try and sniff it out.

On March 27, Cassini came within 46 miles (74 km) of Enceladus’ south pole, the region where the moon’s many active water-ice jets originate from. This was Cassini’s closest pass yet over the southern pole, allowing the spacecraft to use its ion and neutral mass spectrometer — as well as its plasma spectrometer, recently returned to service — to taste the icy spray emanating from deep fissures called “tiger stripes” that scar Enceladus’ surface.

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Old 03-28-2012, 10:53 PM   #99
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CICLOPS:
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Old 03-28-2012, 11:36 PM   #100
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NASA / NASA JPL:
Icy Moons through Cassini's Eyes

March 28, 2012

These raw, unprocessed images of Saturn's moons Enceladus, Janus and Dione were taken on March 27 and 28, 2012, by NASA's Cassini spacecraft.

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Enceladus Plume

This raw image from NASA's Cassini spacecraft was taken on March 27, 2012. The camera was pointing toward Saturn's moon Enceladus at approximately 144,281 miles (232,197 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Enceladus Crescent

This raw image from NASA's Cassini spacecraft was taken on March 27, 2012. The camera was pointing toward Saturn's moon Enceladus at approximately 69,475 miles (111,809 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Enceladus Terrain

This raw image from NASA's Cassini spacecraft was taken on March 27, 2012. The camera was pointing toward Saturn's moon Enceladus at approximately 19,810 miles (31,881 kilometers) away.
Portrait of Janus

This raw image from NASA's Cassini spacecraft was taken on March 27, 2012. The camera was pointing toward Saturn's moon Janus.
Image Credit: NASA/JPL/Space Science Institute
Icy Dione

This raw image from NASA's Cassini spacecraft was taken on March 28, 2012. The camera was pointing toward Saturn's moon Dione at approximately 49,087 miles (78,998 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Dione Close-Up

This raw image from NASA's Cassini spacecraft was taken on March 28, 2012. The camera was pointing toward Saturn's moon Dione at approximately 27,668 miles (44,528 kilometers) away.


Cassini passed Enceladus first on March 27, coming within about 46 miles (74 kilometers) of the moon's surface. The encounter was primarily designed for Cassini's ion and neutral mass spectrometer, which "tasted" the composition of Enceladus' south polar plume. Other instruments, including the Cassini plasma spectrometer and composite infrared spectrometer, also took measurements.

Before the closest approach of this encounter, Cassini's cameras imaged the plume, which is comprised of jets of water ice and vapor, and organic compounds emanating from the south polar region. Later, the cameras captured a nine-frame mosaic of the surface of the moon's leading hemisphere as the spacecraft left the moon.

After the Enceladus encounter, Cassini passed the small moon Janus with a closest approach distance of 27,000 miles (44,000 kilometers). The planet was in the background in some of these views.

Early on March 28, the spacecraft flew by Dione at a distance of 27,000 miles (44,000 kilometers) and collected, among other observations, a nine-frame mosaic depicting the side of the moon that faces away from Saturn in its orbit.

All of Cassini's raw images can be seen at http://saturn.jpl.nasa.gov/photos/raw/.

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Old 03-29-2012, 10:14 PM   #101
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SPACE.com: Haunting Photos of Saturn Moons Snapped by Cassini Spacecraft

Discovery News: Hanging Out With Janus, Saturn's Dinky Moon: Big Pic:


Universe Today: Postcards From Saturn

The Planetary Society Blog: Pretty picture: Janus and Saturn
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Old 04-04-2012, 09:44 PM   #102
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CICLOPS: Rev164: Apr 5 - Apr 23 '12:
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Cassini continues its exploration of the Saturn system with the 17-day Rev164, which begins on April 5 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 2.37 million kilometers (1.47 million miles) from Saturn's cloud tops. The spacecraft is nearing the end of the first equatorial phase of the Cassini Solstice Mission, a phase which lasts until May 2012. During this phase, the spacecraft's orbits lie within the equatorial plane of the planet, providing opportunities to encounter Saturn's numerous moons, image the rings edge-on, and look at Saturn's cloud tops without the rings obscuring the view. Forty-eight ISS observations are planned for Rev164, the vast majority dedicated to Saturn storm monitoring and to encounters with Enceladus and Tethys.

ISS begins its observations for Rev164 three days after apoapse on April 8 with three quick observations of Saturn and its faded northern hemisphere storm. These "Storm Watch" observation sequences are designed to take advantage of short, two-minute segments when the spacecraft turns the optical remote sensing (ORS) instruments back to Saturn as a waypoint between other experiments' observations. These sequences include blue, clear, two methane band, and one full-frame, continuum band filter images. Three more such observations are planned for April 11, with another eighteen planned between April 16 and 23. Also on April 8, ISS will take a look at Titan from a distance of 1.81 million kilometers (1.12 million miles). The observation is an effort to look for clouds in the moon's atmosphere as part of the "Titan Monitoring Campaign" (TMC). This observation of a half-phase Titan is designed to monitor clouds over the moon's Belet dune field. Later that day, ISS will acquire an astrometric observation of Saturn's small, inner moons, including Daphnis, Pallene, Helene, Janus, Methone, and Calypso. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy satellites. Additional astrometric observations will be taken on April 11, 16, 19, 20, and 23.

On April 11, ISS will perform a TMC observation of Titan that will allow for monitoring of cloud features across the Senkyo dune field from a distance of 2.31 million kilometers (1.44 million miles). Another TMC sequence will be acquired on April 13, covering Titan's Saturn-facing hemisphere from a distance of 1.79 million kilometers (1.11 million miles). Later that day, ISS will search for possible satellites at Rhea's L5 point, a Lagrangian point that lies 60 degrees behind the icy moon on its orbit. Similar moons have been found at Dione's and Tethys' L5 points (Polydeuces and Calypso, respectively). A similar sequence covering Rhea's L4 point (60 degrees ahead of it along its orbit) will be acquired on April 15.

On April 14 at 17:03 UTC, Cassini will reach periapse for Rev164 at an altitude of 135,940 kilometers (84,470 miles) from Saturn. ISS observations during the periapse period will be taken during a targeted encounter of Enceladus and later during a close, non-targeted encounter of Tethys.

Cassini will fly by Enceladus (E18) at an altitude of 74 kilometers (46 miles) at 14:02 UTC on April 14. ISS will image the icy satellite's south polar plume from distances of 340,500 kilometers (211,600 miles) down to 118,540 kilometers (73,660 miles) while the satellite is just a thin crescent. Next, the Composite Infrared Spectrometer (CIRS) will acquire a series of mid-infrared scans across the night side of Enceladus, as well as a scan across the south polar terrain (found in earlier flybys of Enceladus to be a thermal hotspot). During the two hours surrounding closest approach, the Ion and Neutral Mass Spectrometer (INMS) will be prime, analyzing the composition of Enceladus' south polar plume as the spacecraft flies through it. The spacecraft's path will take it along the length of Baghdad Sulcus, allowing INMS to resolve individual jets from this "tiger stripe" fracture. The sulcus will be in darkness, but ISS will acquire a single narrow-angle camera/wide-angle camera image pair during this observation just as the ISS field-of-view crosses onto Enceladus' day side. The frame will be centered near 74 degrees south latitude, 18 degrees west longitude and taken from an altitude of 74 kilometers (46 miles). The high velocity of the spacecraft will smear the images and leave the NAC image with an useful pixel scale of about 18 meters (59 feet) per pixel instead of what ideally would be a pixel scale of 44 centimeters per pixel (17 inches per pixel) at that range. Because of the smearing, the WAC image will have about the same useful resolution as the NAC, only it will cover a much larger area Afterward, the Composite Infrared Spectrometer (CIRS) will obtain a map of Enceladus sun-lit side using its FP3 channel, focusing particularly on the sub-solar point where the CIRS expects the highest temperatures and best signal-to-noise.

At 22:06 UTC, Cassini will fly by another of Saturn's icy satellites, Tethys, at a close-approach distance of 9,053 kilometers (5,625 miles). This is Cassini's best encounter with the moon since a targeted encounter in September 2005. After a CIRS observation of Tethys' night side, ISS will capture a frame over Tethys' night side, imaging the moon's surface features in Saturn-shine. After closest approach, it will acquire a 22-frame mosaic of Tethys' anti-Saturn hemisphere, including some frames late in the mosaic of the large impact basin Odysseus. Afterward, ISS will ride along with the Visual and Infrared Mapping Spectrometer (VIMS), imaging Tethys through a series of color filters as the moon just about fits the NAC field-of-view.

Later on April 15, ISS will perform a TMC observation of Titan from a distance of 1.51 million kilometers (0.94 million miles). This will allow for monitoring of cloud features across the Fensal-Aztlan region of the moon. Afterward, ISS will search for moons at Rhea's L4 Lagrangian point. On April 19, ISS will watch as Dione occults the southern hemisphere of Rhea. Dione will be 1.82 million kilometers (1.13 million miles) away while Rhea will be 2.44 million kilometers (1.51 million miles) away. The difference in distance will make Dione appear to be about the same size as Rhea. Later that day, ISS will acquire another TMC observation of Titan from a distance of 1.20 million kilometers (0.75 million miles), covering the boundary between Xanadu and Shangri-La. ISS will take another look at the area the next day, this time from a distance of 1.12 million kilometers (0.69 million miles). Later on the 20th, ISS will search for possible satellites at Titan's L5 point. Finally, the camera system will watch as Rhea, 1.79 million kilometers (1.12 million miles) away, occults the southern hemisphere of Tethys, 2.11 million kilometers (1.31 million miles) from Cassini.

On April 23, ISS will take another look at Titan, this time from a distance of 1.69 million kilometers (1.05 million miles) looking at the Belet dune field. Later that day, ISS will ride along with the Visual and Infrared Mapping Spectrometer to image the G ring.

On April 23, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev165. Rev165 includes a targeted flyby of Enceladus and close, non-targeted flyby of Dione.

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Old 04-13-2012, 10:09 PM   #103
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NASA / NASA JPL:
Cassini to Dip into Enceladus Spray Again

April 13, 2012

Less than three weeks after its last visit to the Saturnian moon Enceladus, NASA's Cassini spacecraft returns for an encore. At closest approach on April 14, the spacecraft will be just as low over the moon's south polar region as it was on March 27 -- 46 miles, or 74 kilometers.

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NASA's Cassini spacecraft will make a close approach to the south polar region of Saturn's moon Enceladus on April 14, 2012.
Image credit: NASA/JPL-Caltech


Like the last, this latest flyby is mainly designed for Cassini's ion and neutral mass spectrometer, which will "taste" the particles in the curious jets spraying from the moon's south polar region. Combined with the March 27 flyby and a similar flyby on Oct. 1, 2011, this close encounter will provide a sense of the jets' three-dimensional structure and help determine how much they change over time.

On Cassini's outbound leg, the spacecraft will pass by another Saturnian moon, Tethys, at a distance of about 6,000 miles (9,000 kilometers). The composite infrared spectrometer will look for patterns in Tethys' thermal signature. Other instruments will study the moon's composition and geology. The imaging cameras are expected to obtain new views of Enceladus and Tethys.

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Old 04-16-2012, 05:02 PM   #104
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CICLOPS:
Universe Today: Cassini Slips Through Enceladusí Spray


Cassini's latest view of Enceladus' icy spray, acquired on April 14, 2012.



Enceladus' southern fissures, the source of its spray.
(NASA/JPL/SSI/J. Major)



A crescent-lit Enceladus sprays its "habitable zone" out into space.



Saturn's moon Tethys, imaged by Cassini on April 14, 2012.
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Old 04-16-2012, 06:55 PM   #105
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NASA / NASA JPL:
Cassini Successfully Flies over Enceladus

April 16, 2012

These raw, unprocessed images of Saturn's moons Enceladus and Tethys were taken on April 14, 2012, by NASA's Cassini spacecraft.

Click on images for details
Arc of Enceladus

This image was taken by NASA's Cassini spacecraft on April 14, 2012. The camera was pointing toward Enceladus at approximately 75,067 miles (120,808 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Enceladus Terrain

This image was taken by NASA's Cassini spacecraft on April 14, 2012. The camera was pointing toward Enceladus at approximately 115 miles (185 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Tethys Portrait

This image was taken by NASA's Cassini spacecraft on April 15, 2012. The camera was pointing toward Tethys at approximately 115,714 miles (186,224 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute
Tethys Surface

This image was taken by NASA's Cassini spacecraft on April 14, 2012. The camera was pointing toward TETHYS at approximately 10,875 miles (17,502 kilometers) away.
Image Credit: NASA/JPL/Space Science Institute


Cassini flew by Enceladus at an altitude of about 46 miles (74 kilometers). This flyby was designed primarily for the ion and neutral mass spectrometer to analyze, or "taste," the composition of the moon's south polar plume as the spacecraft flew through it. Cassini's path took it along the length of Baghdad Sulcus, one of Enceladus' "tiger stripe" fractures from which jets of water ice, water vapor and organic compounds spray into space. At this time, Baghdad Sulcus is in darkness, but that was not an obstacle for another instrument, the composite infrared spectrometer, which can see features by their surface temperatures and which also took measurements during this flyby.

As soon as daylight passed into the spacecraft's remote sensing instruments' line of sight, Cassini's cameras acquired images of the surface. The wide-angle-camera image included in the new batch, taken from around the time of closest approach, has some smearing from the movement of the spacecraft during the exposure, but still shows the surface in vivid detail.

Cassini's cameras also imaged Enceladus' south polar plume at a high phase angle as the satellite appeared as a thin crescent and the plume was backlit.

After the Enceladus encounter, Cassini passed the moon Tethys with a closest approach distance of about 5,700 miles (9,100 kilometers). This was Cassini's best imaging encounter with Tethys since a targeted encounter in September 2005. The 2005 encounter, with a closest approach distance of about 930 miles (1,500 kilometers), provided the images of Tethys with the best resolution and captured views of the side of Tethys that faces Saturn in its orbit. This new encounter examined the opposite side of Tethys, providing some of the highest-resolution images of the side that faces away from Saturn. Cassini acquired a 22-frame mosaic of this side, which features the large impact basin named Odysseus. Scientists will use these new data in conjunction with images from previous encounters to create digital elevation maps of the moon's surface.

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