Updates Cassini Mission News and Updates

i find it slightly humorous that Mr. Plait had to draw a diagram to figure out why the stripes are rings in silhouette. i guess most of us here are probably pretty good at visualizing stuff 3 dimensionally, and maybe not everybody can do that. :cheers:
 
NASA / NASA JPL:
Cassini Instrument Learns New Tricks

December 20, 2012

For seven years, a mini-fridge-sized instrument aboard NASA's Cassini spacecraft reliably investigated weather patterns swirling around Saturn; the hydrocarbon composition of the surface of Saturn's moon Titan; the aerosol layers of Titan's haze; and dirt mixing with ice in Saturn's rings. But this year the instrument -- the visual and infrared mapping spectrometer - has been testing out some new telescopic muscles.

This Friday, Dec. 21, the spectrometer will be tracking the path of Venus across the face of the sun from its perch in the Saturn system. Earthlings saw such a transit earlier this year, from June 5 to 6. But the observation in December will be the first time a spacecraft has tracked a transit of a planet in our solar system from beyond Earth orbit.

Cassini will collect data on the molecules in Venus's atmosphere as sunlight shines through it. But learning about Venus actually isn't the point of the observation. Scientists actually want to use the occasion to test the VIMS instrument's capacity for observing planets outside our solar system.

"Interest in infrared investigations of extrasolar planets has exploded in the years since Cassini launched, so we had no idea at the time that we'd ask VIMS to learn this new kind of trick," said Phil Nicholson, the VIMS team member based at Cornell University, Ithaca, N.Y., who is overseeing the transit observations. "But VIMS has worked so well at Saturn so far that we can start thinking about other things it can do."

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This false-color composite image, constructed from data obtained by NASA's Cassini spacecraft, shows Saturn's rings and southern hemisphere. The composite image was made from 65 individual observations by Cassini's visual and infrared mapping spectrometer in the near-infrared portion of the light spectrum on Nov. 1, 2008. The observations were each six minutes long.
Credit: NASA/JPL/University of Arizona​
|This graphic shows the path of Venus across the face of the sun on Dec. 21, 2012, as will be seen by NASA's Cassini spacecraft in the Saturn system.
Image credit: NASA/JPL-Caltech​
|This image shows the visual and infrared mapping spectrometer instrument just before it was attached to NASA's Cassini spacecraft.
Image credit: NASA/JPL-Caltech/University of Arizona​
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VIMS will be able to complement exoplanet studies by space telescopes such as NASA's Hubble and Spitzer space telescopes. VIMS scientists are particularly interested in investigating atmospheric data - such as signatures of methane -- from far-off star systems in near-infrared wavelengths.

The pointing has to be very accurate to get one of those extrasolar planets in VIMS's viewfinder, but the instrument has had lots of practice pointing at other stars. Earlier this year, VIMS obtained its first successful observation of a transit by the exoplanet HD 189733b. Scientists want to improve these observations by reducing the amount of noise in the signal.

In April, VIMS demonstrated another kind of flexibility by turning its eyes to the warm fissures slashing cross the surface of Saturn's moon Enceladus. VIMS is particularly good at taking thermal data in temperatures around minus 100 degrees Fahrenheit (200 kelvins). So while it is good at tracking hotspots and turbulent clouds on Saturn, VIMS is generally unable to detect thermal emission from Titan, the icy satellites or the rings, since their temperatures are much colder than that.

But the fissures on Enceladus, which scientists have called tiger stripes, are just hot enough for VIMS to detect heat coming from them.

"For the first time, we were able to see that the jets coming from the surface of Enceladus originated in very small, very hot spots," said Bonnie Buratti, a VIMS scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "This new observation is good evidence for liquid water underneath the surface."

VIMS is one of 12 instruments on Cassini, which launched in 1997 and began orbiting Saturn in 2004. "We built Cassini to be hardy, and we're pleased that the spacecraft has been weathering the extreme conditions of the Saturn system remarkably well," said Robert Mitchell, Cassini program manager at JPL. "It isn't too tired to try something new."

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CICLOPS: Rev178: Dec 29 '12 - Jan 12 '13:
Cassini continues its exploration of the Saturn system with the 13-day Rev178, which begins on December 29 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.65 million kilometers (1.03 million miles) from Saturn's cloud tops. Rev 178 occurs seven months into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. The inclined phase will allow for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Fifteen ISS observations are planned for Rev 178 with the majority focused on Saturn's atmosphere.

On December 30, ISS begins its observations for Rev 178 an hour and a half after apoapse with a quick observation of Saturn using the wide-angle camera (WAC). These observations are part of a series of "Storm Watch" observation sequences 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. Another Storm Watch observation is planned 12 hours later. Immediately after the second observation, ISS will acquire an 11-hour movie of the Encke Gap. This 325-kilometer (202-mile) gap in the outer A ring is carved by the gravitational effects of the small moon Pan, which orbits in the middle of the gap. The movie will focus on observing the crenulations that are visible along the edge of the gap as well as the narrow dust ring that accompanies Pan.

On January 2, ISS will acquire a series of images of Saturn rings using the WAC. These images will be tracking spokes -- a ring phenomenon Cassini has monitored throughout the mission -- over the B ring. With Cassini over the unlit side of the rings and with Saturn at a high phase angle, the spokes, if visible, will be brighter than the dark B ring. On January 3, ISS will ride along with a pair of Ultraviolet Imaging Spectrometer (UVIS) observations of Saturn's south polar aurora. In addition to making a movie of the planet's aurorae, the images will be used to independently measure the rotation period of Saturn's magnetic field. ISS will also look at Saturn's aurora during a Visual and Infrared Mapping Spectrometer (VIMS) observation of Saturn's south pole on January 4.

On January 5 at 15:10 UTC, Cassini will reach periapse for Rev 178 at an altitude of 388,080 kilometers (241,140 miles) from Saturn. Late in the day on January 4, ISS will image the limb of Saturn while the Sun is behind the planet. These images will provide an excellent opportunity for observing the various haze layers in the planet's upper atmosphere. Early on January 5, ISS will observe a half-phase Titan from a distance of 1.16 million kilometers (0.72 million miles). This observation is designed to look for clouds in the moon's atmosphere as part of the "Titan Monitoring Campaign" (TMC). The observation on January 5 is designed to monitor clouds over the moon's sub-Saturn hemisphere. ISS will also be taking shorter-wavelength images to study changes in Titan's upper haze layers. Afterward, ISS will acquire a pair of WAC images during two VIMS stellar occultation observations. These stellar occultations involve the stars Epsilon Eridiani and L2 Puppis passing behind the night side limb of Saturn. Finally, late in the day on the 5th, ISS will ride along with VIMS to acquire a mosaic of Saturn's north polar region using the Wide-Angle Camera (WAC). Spring has progressed far enough that the entirety of the hexagonal jet stream that lies near 77 degrees North latitude will be in sunlight. ISS will be imaging the hexagon with a two-by-two mosaic rather than centering the field-of-view on the north pole like it did in November.

On January 6, ISS will acquire a set of color images using the Narrow-Angle Camera (NAC) while pointed at Saturn's limb, near the equator. Combined with the early observation taken when Cassini was in Saturn's shadow, images from this observation will be used to better understand the structure of Saturn's upper atmosphere. Immediately afterward, ISS will ride along with VIMS to acquire several, WAC mosaics of Saturn's atmosphere. Finally, on January 12, just a few hours before the end of the orbit, ISS will search for clouds across Titan's Fensal-Aztlan region from a distance of 2.54 million kilometers (1.58 million miles).

On January 12, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev179.

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NASA JPL:
Cassini Suggests Icing on a Lake

January 08, 2013

It's not exactly icing on a cake, but it could be icing on a lake. A new paper by scientists on NASA's Cassini mission finds that blocks of hydrocarbon ice might decorate the surface of existing lakes and seas of liquid hydrocarbon on Saturn's moon Titan. The presence of ice floes might explain some of the mixed readings Cassini has seen in the reflectivity of the surfaces of lakes on Titan.

"One of the most intriguing questions about these lakes and seas is whether they might host an exotic form of life," said Jonathan Lunine, a paper co-author and Cassini interdisciplinary Titan scientist at Cornell University, Ithaca, N.Y. "And the formation of floating hydrocarbon ice will provide an opportunity for interesting chemistry along the boundary between liquid and solid, a boundary that may have been important in the origin of terrestrial life."

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Lakes on Saturn's moon Titan reflect radio waves in varying ways in this image from NASA's Cassini spacecraft. Scientists think the variations in reflectivity, or brightness, have to do with the smoothness or texture of the surface. If a lake is fully liquid, it looks dark, but if it is only partially liquid, it looks brighter.
Image credit: NASA/JPL-Caltech/ASI/Cornell​
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Titan is the only other body besides Earth in our solar system with stable bodies of liquid on its surface. But while our planet's cycle of precipitation and evaporation involves water, Titan's cycle involves hydrocarbons like ethane and methane. Ethane and methane are organic molecules, which scientists think can be building blocks for the more complex chemistry from which life arose. Cassini has seen a vast network of these hydrocarbon seas cover Titan's northern hemisphere, while a more sporadic set of lakes bejewels the southern hemisphere.

Up to this point, Cassini scientists assumed that Titan lakes would not have floating ice, because solid methane is denser than liquid methane and would sink. But the new model considers the interaction between the lakes and the atmosphere, resulting in different mixtures of compositions, pockets of nitrogen gas, and changes in temperature. The result, scientists found, is that winter ice will float in Titan's methane-and-ethane-rich lakes and seas if the temperature is below the freezing point of methane -- minus 297 degrees Fahrenheit (90.4 kelvins). The scientists realized all the varieties of ice they considered would float if they were composed of at least 5 percent "air," which is an average composition for young sea ice on Earth. ("Air" on Titan has significantly more nitrogen than Earth air and almost no oxygen.)

If the temperature drops by just a few degrees, the ice will sink because of the relative proportions of nitrogen gas in the liquid versus the solid. Temperatures close to the freezing point of methane could lead to both floating and sinking ice - that is, a hydrocarbon ice crust above the liquid and blocks of hydrocarbon ice on the bottom of the lake bed. Scientists haven't entirely figured out what color the ice would be, though they suspect it would be colorless, as it is on Earth, perhaps tinted reddish-brown from Titan's atmosphere.

"We now know it's possible to get methane-and-ethane-rich ice freezing over on Titan in thin blocks that congeal together as it gets colder -- similar to what we see with Arctic sea ice at the onset of winter," said Jason Hofgartner, first author on the paper and a Natural Sciences and Engineering Research Council of Canada scholar at Cornell. "We'll want to take these conditions into consideration if we ever decide to explore the Titan surface some day."

Cassini's radar instrument will be able to test this model by watching what happens to the reflectivity of the surface of these lakes and seas. A hydrocarbon lake warming in the early spring thaw, as the northern lakes of Titan have begun to do, may become more reflective as ice rises to the surface. This would provide a rougher surface quality that reflects more radio energy back to Cassini, making it look brighter. As the weather turns warmer and the ice melts, the lake surface will be pure liquid, and will appear to the Cassini radar to darken.

"Cassini's extended stay in the Saturn system gives us an unprecedented opportunity to watch the effects of seasonal change at Titan," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We'll have an opportunity to see if the theories are right." The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and ASI, the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.

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Universe Today: Chunks of Frozen Hydrocarbons May be Floating on Titan’s Lakes
 
Now we need an amphibious rover to drive around titan. I can't wait to see the surface pictures!
 
CICLOPS: Rev179: Jan 12 - Jan 25 '13:
Cassini continues its exploration of the Saturn system with the 13-day Rev179, which begins on January 12 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.66 million kilometers (1.03 million miles) from Saturn's cloud tops. Rev 179 occurs eight months into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. The inclined phase will allow for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Twenty-two ISS observations are planned for Rev 179 with the majority focused on Saturn's atmosphere and rings.

On January 13, ISS begins its observations for Rev 179 a day and a half after apoapse with a quick observation of Saturn using the wide-angle camera (WAC). These observations are part of a series of "Storm Watch" observation sequences 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. Seven more observations are planned between January 14 and 17, while another three will be taken after periapse on January 24 and 25. Immediately after the first observation, ISS will acquire a movie of the F ring, observing its various channels and streamers created by the interaction between the ring material and the nearby moon, Prometheus. On January 15, ISS will acquire an astrometric observation of Saturn's small, inner moons. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy moons. Another astrometric observation will be taken on January 25. On January 16, ISS will acquire a series of images of Saturn rings using the WAC. These images will be tracking spokes -- a ring phenomenon Cassini has monitored throughout the mission -- over the B ring. With Cassini over the unlit side of the rings and with Saturn at a high phase angle, the spokes, if visible, will be brighter than the dark B ring.

On January 18 at 22:16 UTC, Cassini will reach periapse for Rev 179 at an altitude of 388,620 kilometers (241,480 miles) from Saturn. Late in the day on January 17, ISS will acquire a high-resolution movie of the inner D ring at high phase angles. This movie will be used to assess the density of dust in the inner portion of the ring system, a region Cassini will pass through in its final orbits in 2017. Next, ISS will ride along with a Visual and Infrared Mapping Spectrometer (VIMS) observation of the F ring. Early on January 18, ISS will monitor the south polar plume of Enceladus from a distance of 775,000 kilometers (481,000 miles). These images will be at a very high phase angle, achievable because the sun will be eclipsed by Saturn during the observation. Later that day, a few minutes after periapse, ISS will image the C ring of Saturn in search of small, embedded moonlets.

To round out the periapse period on January 19 and early on the 20th, ISS will ride along with a VIMS stellar occultation by the ring system of the Mira-like, red giant star HD120285 (one of the brightest stars in the night sky, in the near-infrared). Next, ISS will image the outer A ring, looking at the propellers previously seen in this part of the ring system. Propellers are small voids in Saturn's rings created by the gravitational interaction between large ring particles and the surrounding ring. Finally, ISS will acquire a high-resolution, low-phase, color scan of Saturn's ring system.

On January 25, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev180.

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NASA / NASA JPL:
Titan Gets a Dune 'Makeover'

January 17, 2013

Titan's siblings must be jealous. While most of Saturn's moons display their ancient faces pockmarked by thousands of craters, Titan - Saturn's largest moon - may look much younger than it really is because its craters are getting erased. Dunes of exotic, hydrocarbon sand are slowly but steadily filling in its craters, according to new research using observations from NASA's Cassini spacecraft.

"Most of the Saturnian satellites - Titan's siblings - have thousands and thousands of craters on their surface. So far on Titan, of the 50 percent of the surface that we've seen in high resolution, we've only found about 60 craters," said Catherine Neish, a Cassini radar team associate based at NASA's Goddard Space Flight Center, Greenbelt, Md. "It's possible that there are many more craters on Titan, but they are not visible from space because they are so eroded. We typically estimate the age of a planet's surface by counting the number of craters on it (more craters means an older surface). But if processes like stream erosion or drifting sand dunes are filling them in, it's possible that the surface is much older that it appears.

"This research is the first quantitative estimate of how much the weather on Titan has modified its surface," adds Neish.

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This set of images from the radar instrument on NASA's Cassini spacecraft shows a relatively "fresh" crater called Sinlap (left) and an extremely degraded crater called Soi (right). Sinlap has a depth-to-diameter ratio close to what we see on Jupiter's moon Ganymede. Soi has a shallow depth compared to similar craters on Ganymede. These craters are both about 50 miles (80 kilometers) in diameter.
Image credit: NASA/JPL-Caltech/ASI/GSFC​
|The colorful globe of Saturn's largest moon, Titan, passes in front of the planet and its rings in this true color snapshot from NASA's Cassini spacecraft.
Image credit: NASA/JPL-Caltech/Space Science Institute​
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Titan is the only moon in the solar system with a thick atmosphere, and the only world besides Earth known to have lakes and seas on its surface. However, Titan has a frigid surface temperature of around minus 290 degrees Fahrenheit (94 kelvins). The rain that falls from Titan's skies is not water, but contains liquid methane and ethane, compounds that are gases at Earth's temperatures.

Neish and her team compared craters on Titan to craters on Jupiter's moon Ganymede. Ganymede is a giant moon with a water ice crust, similar to Titan, so craters on the two moons should have similar shapes. However, Ganymede has almost no atmosphere and thus no wind or rain to erode its surface.

"We found that craters on Titan were on average hundreds of yards [meters] shallower than similarly sized craters on Ganymede, suggesting that some process on Titan is filling its craters," says Neish, who is lead author of a paper about this research published online in the journal Icarus on Dec. 3, 2012.

The team used the average depth-versus-diameter trend for craters on Ganymede derived from stereo images from NASA's Galileo spacecraft. The same trend for craters on Titan was calculated using estimates of the crater depth from images made by Cassini's radar instrument.

Titan's atmosphere is mostly nitrogen with a trace of methane and other, more complex molecules made of hydrogen and carbon (hydrocarbons). The source of Titan's methane remains a mystery because methane in the atmosphere is broken down over relatively short time scales by sunlight. Fragments of methane molecules then recombine into more complex hydrocarbons in the upper atmosphere, forming a thick, orange smog that hides the surface from view. Some of the larger particles eventually rain out onto the surface, where they appear to get bound together to form the sand.

"Since the sand appears to be produced from the atmospheric methane, Titan must have had methane in its atmosphere for at least several hundred million years in order to fill craters to the levels we are seeing," says Neish. However, researchers estimate Titan's current supply of methane should be broken down by sunlight within tens of millions of years, so Titan either had a lot more methane in the past, or it is being replenished somehow.

Team members say it's possible that other processes could be filling the craters on Titan: erosion from the flow of liquid methane and ethane, for example. However, this type of weathering tends to fill a crater quickly at first, then more slowly as the crater rim gets worn down and less steep. If liquid erosion were primarily responsible for the infill, then the team would expect to see a lot of partially filled craters on Titan. "However, this is not the case," says Neish. "Instead we see craters at all stages; some just beginning to be filled in, some halfway, and some that are almost completely full. This suggests a process like windblown sand, which fills craters and other features at a steady rate."

Solid materials under stress flow very slowly over time. This is called viscous flow, and it is like what happens when someone takes a scoop out of a fresh tub of whipped cream -- the material slowly flows in to fill the hole and flatten the surface. Craters on icy satellites tend to get shallower over time as the ice flows viscously, so it's possible that some of the shallow craters on Titan are simply much older or experienced a higher heat flow than the similarly sized, fresh craters on Ganymede studied in this work.

However, Titan's crust is mostly water ice, and at the extremely low temperatures on Titan, ice shouldn't flow enough to account for such a large difference in depth compared to the Ganymede craters, according to the team. Also, just like stream erosion, deformation from viscous flow tends to happen rapidly at first, then more slowly as the material adjusts, so one would expect to see a lot of partially filled craters on Titan if its surface were deforming easily through viscous flow.

As Cassini flies past Titan on its multi-year tour of Saturn and its moons, its radar instrument gradually builds up a map of the surface. To date, the instrument has provided data in strips covering approximately 50 percent of Titan's surface. The craters measured by the team are all within about 30 degrees of the equator, a relatively dry region on Titan.

"However, the presence of liquids on the surface and in the near subsurface can also cause extensive modification to crater shape, as is observed on Earth," says Neish. "In the case of Titan, liquids consist of hydrocarbons, either as wet sediments (such as those observed at the Huygens landing site) or shallow marine environments (such as the lakes observed at the north and south poles). Craters formed in similar environments on Earth lack any significant surface topography, including the absence of a raised rim, as wet sediments slump into the crater. It is possible that the lack of topography associated with marine-target impacts may help to explain the relative scarcity of impact craters observed near the poles of Titan. If Titan's polar regions are saturated by liquid hydrocarbons, craters formed in those regions may lack any recognizable topographic expression."

The team thinks these considerations are good areas for more research. Based on the data so far, the difference in depth between craters on Titan and Ganymede is best explained by filling from windblown sand. However, erosion from liquids and viscous flow might contribute to the modification of Titan's craters.

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SpaceRef: Craters on Titan Gradually Filled With Hydrocarbon Sand

NASA JPL - Cassini Solstice Mission: Titan Gets a Dune 'Makeover'

Science Daily: Saturn's Largest Moon Titan Gets a Dune 'Makeover'
 
Unstung said:
You mean that we need a boat to float on a lake of Titan.
There's been the not selected Titan Mare Explorer and a proposed European boat.
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no i meant a rover that can drive around and then drive into the lake and become a boat :thumbup:

that way the same payload can accomplish more science goals per second.

i can't see a mission like this ever taking place, it is too awesome of an idea to work.
 
statickid said:
no i meant a rover that can drive around and then drive into the lake and become a boat :thumbup:

that way the same payload can accomplish more science goals per second.

i can't see a mission like this ever taking place, it is too awesome of an idea to work.
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Creating a spacecraft that complex would probably make the mission inefficient, risky, and cost prohibitive. Data from Huygen's Surface Science Package indicates that Titan's surface is made of loose material, making it difficult to drive on. Now that Cassini exposed a good amount of the surface on Titan, a lander would not need to be able to operate on both sea and land like Huygens. The Titan Saturn System Mission proposal includes an in situ boat and balloon. Exploring Titan using the methods outlined in TSSM are much more reasonable, employing new and practical ways to explore Titan and Enceladus for a sensible price. As with the Titan Mare Explorer, the boat might also be able to gather surface data if it is deposited on the shore.

To elaborate, the problem with the mission is not that it is too awesome (how would a balloon and lake lander be significantly less inspiring?), but that the idea appears to be very impractical.
 
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CICLOPS: Rev180: Jan 25 - Feb 7 '13:
Cassini continues its exploration of the Saturn system with the 13-day Rev180, which begins on January 25 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.66 million kilometers (1.03 million miles) from Saturn's cloud tops. Rev 180 occurs eight months into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. The inclined phase will allow for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Thirty-one ISS observations are planned for Rev 180 with the majority focused on Saturn's atmosphere and rings.

On January 26, ISS begins its observations for Rev 180 a day after apoapse with a quick observation of Saturn using the wide-angle camera (WAC). These observations are part of a series of "Storm Watch" observation sequences 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. Seven more are planned between January 28 and 30, while another eight will be taken February 3 and 7, after periapse. Later on January 26, ISS will ride along with a Visual and Infrared Mapping Spectrometer (VIMS) stellar occultation observation by the ring system of the red giant star R Lyrae (one of the brightest stars in the night sky, in the near-infrared). On January 27, ISS will acquire a movie of the F ring, observing its various channels and streamers created by the interaction between the ring material and the nearby moon, Prometheus. On January 28 and 29, ISS will acquire a series of images of Saturn rings using the WAC. These images will be tracking spokes -- a ring phenomenon Cassini has monitored throughout the mission -- over the B ring. With Cassini over the unlit side of the rings and with Saturn at a high phase angle, the spokes, if visible, will be brighter than the dark B ring. On January 30, ISS will ride along with another VIMS stellar occultation by the ring system of the Mira-like, red giant star R Cassiopeiae.

On February 1 at 05:32 UTC, Cassini will reach periapse for Rev 180 at an altitude of 388,490 kilometers (241,400 miles) from Saturn. Late on January 31, ISS will acquire a series of images of Saturn's A ring, surveying propellers in the ring. Propellers are small voids in Saturn's rings created by the gravitational interaction between large ring particles and the surrounding ring. Afterwards, on February 1, ISS will acquire high-resolution images of the F ring. On February 2, ISS will again ride along with a VIMS stellar occultation by the ring system of a Mira-like, red giant star, this time taking a look at W Hydrae. Later that day, ISS will acquire a movie of the Cassini Division and the outer edge of the B ring.

On February 3 and 4, ISS will acquire low-phase movies of Saturn's inner most ring, the faint D ring. These observations will focus on the brighter ringlets within the D ring. Also on February 3, ISS will acquire a 20-hour light curve observation of the small, outer moon, Erriapus. Light curve observations are used to determine the length of the moon's day. On February 4, ISS will acquire an astrometric observation of Saturn's small, inner moons. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy moons. Another astrometric observation will be taken on February 5. Later that day, ISS will observe Aegaeon and the arc of dust that surrounds it in the G ring for twenty-one hours.

On February 7, Cassini will reach apoapse of this orbit, bringing it to a close and starting Rev181.

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NASA / NASA JPL:
NASA's Cassini Watches Storm Choke on Its Own Tail

January 31, 2013

Call it a Saturnian version of the Ouroboros, the mythical serpent that bites its own tail. In a new paper that provides the most detail yet about the life and death of a monstrous thunder-and-lightning storm on Saturn, scientists from NASA's Cassini mission describe how the massive storm churned around the planet until it encountered its own tail and sputtered out. It is the first time scientists have observed a storm consume itself in this way anywhere in the solar system.

"This Saturn storm behaved like a terrestrial hurricane - but with a twist unique to Saturn," said Andrew Ingersoll, a Cassini imaging team member based at the California Institute of Technology, Pasadena, who is a co-author on the new paper in the journal Icarus. "Even the giant storms at Jupiter don't consume themselves like this, which goes to show that nature can play many awe-inspiring variations on a theme and surprise us again and again."

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Storm Head, Meet Tail​
This set of images from NASA's Cassini mission shows the evolution of a massive thunder-and-lightning storm that circled all the way around Saturn and fizzled when it ran into its own tail. The storm was first detected on Dec. 5, 2010. That month, it developed a head of bright clouds quickly moving west and spawned a much slower-drifting clockwise-spinning vortex.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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Northern Storm in Full Force​
This mosaic of images from NASA's Cassini spacecraft shows the trail of a great northern storm on Saturn raging in full force. The contrast in the images has been enhanced to make the turbulent parts of the storm (in white) stand out without losing the details of the surrounding regions.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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First Chapter of the Northern Storm​
This mosaic of false-color images from NASA's Cassini spacecraft shows what a giant storm in Saturn's northern hemisphere looked like about a month after it began. The bright head of the storm is on the left. The storm also spawned a clockwise-spinning vortex, seen as the light blue circular feature framed with a curl of bright clouds a little to the right of the storm head.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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Earth's hurricanes feed off the energy of warm water and leave a cold-water wake. This storm in Saturn's northern hemisphere also feasted off warm "air" in the gas giant's atmosphere. The storm, first detected on Dec. 5, 2010, and tracked by Cassini's radio and plasma wave subsystem and imaging cameras, erupted around 33 degrees north latitude. Shortly after the bright, turbulent head of the storm emerged and started moving west, it spawned a clockwise-spinning vortex that drifted much more slowly. Within months, the storm wrapped around the planet at that latitude, stretching about 190,000 miles (300,000 kilometers) in circumference, thundering and throwing lightning along the way.

Terrestrial storms have never run into their own wakes - they encounter topographic features like mountains first and expend themselves. But Saturn has no land to stop its hurricanes. The bright, turbulent storm head was able to chomp all the way around the planet. It was only when the head of the storm ran into the vortex in June 2011 that the massive, convective storm faded away. Why the encounter would shut down the storm is still a mystery.

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Which Way the Wind Blows​
This image from NASA's Cassini spacecraft reveals the wind patterns within a large vortex that was spawned by a giant northern storm on Saturn. The arrows indicate the local direction of the winds. The vortex, a clockwise-spinning swirl, was spun off from the head of this storm in early December 2010, shortly after the storm erupted. The bright head of the storm moved swiftly in a westward direction around the planet, while this vortex drifted more slowly.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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Swirling Vortex​
This three-frame animation from NASA's Cassini spacecraft shows the swirling clouds in a vortex spawned by a great northern storm on Saturn. The clouds are moving in a clockwise direction.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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By Aug. 28, after 267 days, the Saturn storm stopped thundering for good. While Cassini's infrared detectors continue to track some lingering effects in higher layers of Saturn's atmosphere, the troposphere -- which is the weather-producing layer, lower in the atmosphere - has been quiet at that latitude.

"This thunder-and-lightning storm on Saturn was a beast," said Kunio Sayanagi, the paper's lead author and a Cassini imaging team associate at Hampton University in Virginia. "The storm maintained its intensity for an unusually long time. The storm head itself thrashed for 201 days, and its updraft erupted with an intensity that would have sucked out the entire volume of Earth's atmosphere in 150 days. And it also created the largest vortex ever observed in the troposphere of Saturn, expanding up to 7,500 miles [12,000 kilometers] across."

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Click on images for details​

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Great Disturbances​
This set of images from NASA's Cassini spacecraft shows cloud patterns in a band around Saturn before a monstrous thunder-and-lightning storm erupted and again after the head of the storm had disappeared. The images cover a band from 20 to 40 degrees north latitude. A comparison of the two images shows that the storm left the region in a highly disturbed, turbulent state. This kind of turbulence had never before been seen on Saturn and scientists are continuing to monitor the aftermath.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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Staring into the Vortex​
A vortex that was part of a giant storm on Saturn slowly dissipates over time in this set of false color images from NASA's Cassini spacecraft . This clockwise vortex spun off the bright head of the storm shortly after the thunder-and-lightning storm erupted in early December 2010.
Image credit: NASA/JPL-Caltech/SSI/Hampton University​
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The vortex grew to be as large as the giant storm known as Oval BA on Jupiter. But Oval BA and Jupiter's more famous storm - the Great Red Spot - are not thunder-and-lightning storms. Jupiter's storms also have a quiet center, unlike the violence at the center of Saturn's storms.

"Cassini's stay in the Saturn system has enabled us to marvel at the power of this storm," said Scott Edgington, Cassini's deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We had front-row seats to a wonderful adventure movie and got to watch the whole plot from start to finish. These kinds of data help scientists compare weather patterns around our solar system and learn what sustains and extinguishes them."

This storm was the longest running of the massive storms that appear to break out in Saturn's northern hemisphere once every Saturn year (30 Earth years). The longest storm of any size ever detected on Saturn actually unfolded over 334 days in 2009 in an area known as "Storm Alley" in the southern hemisphere, but it was about 100 times smaller in area than the latest northern storm.

{...}



CICLOPS:
NASA JPL - Cassini Solstice Mission:
Phys.org: Cassini watches storm choke on its own tail

Slate - Bad Astronomy: Monster Saturn Storm Chokes on Its Own Tail

Saturn Daily: NASA's Cassini Watches Storm Choke on Its Own Tail

The Planetary Society Blog: Saturn's Hexagon Viewed from the Ground:

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saturn_vims_north-pole_hexagon_animation_PIA09187.gif


This movie of Saturn's north pole was taken by Cassini's VIMS spectrometer at a mid-infrared wavelength of 5 microns. It was winter at Saturn's north pole; all illumination is thermal radiation (heat) welling up from Saturn's depths.​
NASA / JPL / UA​
[/table]​
 
CICLOPS: Rev181: Feb 7 - Feb 20 '13:
Cassini continues its exploration of the Saturn system with the 13-day Rev181, which begins on February 7 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.66 million kilometers (1.03 million miles) from Saturn's cloud tops. Rev 181 occurs nine months into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. The inclined phase will allow for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Twenty-two ISS observations are planned for Rev 181 with the majority focused on Saturn's atmosphere and rings, as well as the T89 flyby of Titan.

On February 9, ISS begins its observations for Rev 181 two days after apoapse with a quick observation of Saturn using the wide-angle camera (WAC). These observations are part of a series of "Storm Watch" observation sequences 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. Six more observations are planned between February 9 and 11. On February 9, ISS will acquire an astrometric observation of Saturn's small, inner moons. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy moons. Finally, ISS will acquire a movie of the F ring, observing its various channels and streamers created by the interaction between the ring material and the nearby moon, Prometheus.

On February 11, ISS will acquire a series of images of Saturn rings using the WAC. These images will be tracking spokes -- a ring phenomenon Cassini has monitored throughout the mission -- over the B ring. With Cassini over the unlit side of the rings and with Saturn at a high phase angle, the spokes, if visible, will be brighter than the dark B ring. On February 12, ISS will acquire a NAC movie of the Encke Gap, which includes the small moon Pan.

On February 14 at 12:50 UTC, Cassini will reach periapse for Rev 181 at an altitude of 387,760 kilometers (240,940 miles) from Saturn. On February 13, ISS will acquire a high-resolution movie of the inner D ring at high phase angles. This movie will be used to assess the density of dust in the inner portion of the ring system, a region Cassini will pass through in its final orbits in 2017. Next, ISS will ride along with a Visual and Infrared Mapping Spectrometer (VIMS) observation of the F ring, measuring its brightness at high phase angles. Afterward, ISS will ride along with VIMS again to look for small, cometary impacts in the C ring as Cassini is eclipsed by Saturn, followed by another photometry observation of the F ring with VIMS. Early on February 14, ISS will monitor the south polar plume of Enceladus from a distance of 290,000 kilometers (180,000 miles). Afterward, ISS will perform a long observation of the A ring. The A ring is host to thousands of propellers, which are gravitationally-formed voids created by large ring particles. This observation will be used to search for these propellers in the region between the Encke Gap (itself carved by the small moon Pan) and the Keeler Gap (a narrower gap carved by Daphnis). Of particular importance for this observation is to re-image previously observed propellers to better measure their sizes and orbits. Finally, ISS will ride along with a VIMS stellar occultation observation by the ring system of the red giant star W Hydrae (one of the brightest stars in the night sky, in the near-infrared).

Three days after periapse, Cassini encounters Titan on February 17 at 10:22 UTC for the 90th time. This is the first of nine Titan flybys planned for 2013, with the next encounter scheduled for April 5 during Rev185. T89 is a relatively high altitude flyby with a close-approach altitude of 1,978 kilometers (1,229 miles). This flyby will allow for imaging of the Adiri region and the southern anti-Saturn hemisphere of Titan outbound from the encounter. For the 12 hours before and after closest approach, the Radio Sub-System (RSS) will be used to measure Titan's gravity field. The High-gain antenna will be pointed at Earth during the encounter, and the effect of Titan's gravity on the spacecraft will be measured by looking at the Doppler Effect on Cassini's signal. This information will be used (along with previous and later RSS gravity passes) to refine our understanding of Titan's internal structure. ISS will ride along with observations by the Composite Infrared Spectrometer (CIRS), taken before and after the RSS pass.

As the spacecraft departs from Titan and nears apoapse, ISS will ride along with a pair of CIRS observations of Titan, each observation will last around 24 hours and are designed to monitor and track cloud patterns across Titan's southern hemisphere while the spacecraft is near apoapse.

On February 20, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev182. The next orbit includes a close, non-targeted encounter with Titan.

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Click to expand...

(In my next post in this thread later today, there will be some news I bookmarked a couple of days ago about Titan I meant to post in free time, but I forgot...)
 
Unstung said:
Creating a spacecraft that complex would probably make the mission inefficient, risky, and cost prohibitive. Data from Huygen's Surface Science Package indicates that Titan's surface is made of loose material, making it difficult to drive on. Now that Cassini exposed a good amount of the surface on Titan, a lander would not need to be able to operate on both sea and land like Huygens. The Titan Saturn System Mission proposal includes an in situ boat and balloon. Exploring Titan using the methods outlined in TSSM are much more reasonable, employing new and practical ways to explore Titan and Enceladus for a sensible price. As with the Titan Mare Explorer, the boat might also be able to gather surface data if it is deposited on the shore.

To elaborate, the problem with the mission is not that it is too awesome (how would a balloon and lake lander be significantly less inspiring?), but that the idea appears to be very impractical.
Click to expand...


True, which I see now regret and apologise for incorrectly formatting my original comment

<idiotic humor>Now we need an amphibious rover to drive around titan. I can't wait to see the surface pictures!</idiotic humor>
 
NASA / NASA JPL:
Cassini Sees Titan Cooking up Smog

February 04, 2013

A paper published this week using data from NASA's Cassini mission describes in more detail than ever before how aerosols in the highest part of the atmosphere are kick-started at Saturn's moon Titan. Scientists want to understand aerosol formation at Titan because it could help predict the behavior of smoggy aerosol layers on Earth.

[table="head;width=225"]
Click on image for details​



This image shows the first flash of sunlight reflected off a lake on Saturn's moon Titan. The glint off a mirror-like surface is known as a specular reflection. This kind of glint was detected by the visual and infrared mapping spectrometer (VIMS) on NASA's Cassini spacecraft on July 8, 2009. It confirmed the presence of liquid in the moon's northern hemisphere, where lakes are more numerous and larger than those in the southern hemisphere. Scientists using VIMS had confirmed the presence of liquid in Ontario Lacus, the largest lake in the southern hemisphere, in 2008.
Image Credit: NASA/JPL/University of Arizona/DLR​
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According to the new paper, published this week in the Proceedings of the National Academy of Sciences, Titan's trademark reddish-brown smog appears to begin with solar radiation on molecules of nitrogen and methane in the ionosphere, which creates a soup of negative and positive ions. Collisions among the organic molecules and the ions help the molecules grow into bigger and more complex aerosols. Lower down in the atmosphere, these aerosols bump into each other and coagulate, and at the same time interact with other, neutral particles. Eventually, they form the heart of the physical processes that rain hydrocarbons on Titan's surface and form lakes, channels and dunes.

The paper was led by Panayotis Lavvas, a Cassini participating scientist based at the University of Reims, Champagne-Ardenne, France. The team analyzed data from three Cassini instruments -- the plasma spectrometer, the ion and neutral mass spectrometer, and the radio and plasma wave science experiment. They compared their results to those obtained by ESA's Huygens probe on its descent through the Titan atmosphere in 2005 and found they were compatible.

{...}



NASA JPL - Cassini Solstice Mission: Cassini Sees Titan Cooking up Smog

SpaceRef: Cassini Sees Titan Cooking up Smog

Phys.org: Cassini sees Titan cooking up smog
 
CICLOPS: Rev182: Feb 20 - Mar 4 '13:
Cassini continues its exploration of the Saturn system with the 12-day Rev182, which begins on February 20 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.47 million kilometers (0.91 million miles) from Saturn's cloud tops. Rev 182 occurs nine months into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. The inclined phase will allow for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Eight ISS observations are planned for Rev 182.

On February 22, ISS begins its observations for Rev 182 two days after apoapse with a distant observation of Titan. ISS will be riding along with the Composite Infrared Spectrometer (CIRS) during this 11-hour observation. The camera system will be monitoring clouds that may exist across the moon's southern trailing and sub-Saturn hemispheres. On February 23, ISS will ride along with an Ultraviolet Imaging Spectrometer (UVIS) observation of Saturn's south polar aurora. In addition to making a movie of the planet's aurorae, the images will be used to independently measure the rotation period of Saturn's magnetic field.

On February 26 at 04:27 UTC, Cassini will reach periapse for Rev 182 at an altitude of 424,780 kilometers (263,950 miles) from Saturn. On February 25, ISS will monitor the south polar plume of Enceladus from a distance of 660,000 kilometers (410,000 miles). Late on February 26 and early on the 27th, ISS will ride along with VIMS to acquire a mosaic of Saturn's north polar region using the Wide-Angle Camera (WAC). Spring has progressed far enough that the entirety of the hexagonal jet stream that lies near 77 degrees North latitude will be in sunlight. ISS will be imaging the hexagon with a two-by-two mosaic rather than centering the field-of-view on the north pole like it did in November. On February 27, ISS will track cloud features as they rotate on Saturn. Images will be taken at a variety of latitudes at low, medium, and high emission angles to see how these features different in appearance at different viewing angles. This is useful to understand the structure of Saturn's high-altitude haze layers.

On the outbound leg of Rev182, ISS will focus on Saturn's distant, outer satellites. On February 28 and March 1, ISS will acquire three observations of these small moons, two focused on Hati and another that will take a look at Erriapus. These three observations will be used to measure the rotation period of the two moons. Given their small size and great distance from Saturn, they do not rotate synchronously like Saturn's closer and larger icy moons. Hati is six kilometers (3.7 miles) across and will be 16.5 million kilometers (10.2 million miles) away. Erriapus is 10 kilometers (6.2 miles) across and will be 26.6 million kilometers (16.5 million miles) away.

On March 4, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev183. The next orbit includes a targeted encounter with Rhea.

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