Author Topic: NASA - Cassini updates  (Read 169883 times)

Offline marsavian

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Re: NASA - Cassini updates
« Reply #40 on: 04/15/2008 05:29 PM »
Excellent news.

Offline iamlucky13

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Re: NASA - Cassini updates
« Reply #41 on: 04/15/2008 06:52 PM »
Awesome. I've been waiting to hear this for a while.

I noticed that the original mission completed 62 revolutions in 4 years. The extension will do 60 revs in 2 years. I guess they've over time through gravity assists off the moons and perhaps thruster burns reduced the apoapsis?

Does anyone know how much fuel is left? Is there just enough for RCS needs, or will they be able tailor the flyby's as they've been doing? Has NASA determined if they will need to (or even can) ultimately terminate Cassini's mission a la Galileo for planetary protection purposes?

Offline Lampyridae

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Re: NASA - Cassini updates
« Reply #42 on: 04/16/2008 04:32 AM »
I guess this must be how people felt when the first radar maps of Venus started coming in. This is really fascinating, really wonderful science being done by the Cassini crowd. I'm already itching for a second probe to Titan!
SKYLON... The League of Extraordinary Gentlemen's preferred surface-to-orbit conveyance.

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Re: NASA - Cassini updates
« Reply #43 on: 04/17/2008 07:20 PM »
NEWS RELEASE: 2008-065                                                                        April 17, 2008

Saturn Images Showcased in New York City

A selection of the best images from Saturn, its rings and moons will appear in an exhibition opening on April 26 at the American Museum of Natural History in New York City.

The show, called "Saturn: Images from the Cassini-Huygens Mission," will run through March 29, 2009. It features dramatic, up-close-and-personal images in small individual views and super-large mosaics. Roughly 50 images taken by the Cassini-Huygens mission in visible light, infrared and radar have been hand-picked by a team of Cassini scientists.

"The images show the Saturn system as we had never seen it before. They perfectly blend exploration, science and beauty," said Joe Burns, the exhibit's guest co-curator and a Cassini imaging scientist at Cornell University, Ithaca, N.Y. "We are excited to have the opportunity to show these breathtaking photographs to the broader public in one of the world's greatest science museums." Burns, along with colleagues at Cornell University and on the Cassini project, has been collaborating with museum curators for the past year on the image selection, scientific captions and exhibit design.

The Cassini spacecraft has been in orbit around Saturn for nearly four years. It is the first orbiter to study Saturn in detail. The piggybacked Huygens probe, provided by the European Space Agency, plunged through the atmosphere of Saturn's largest moon, Titan, in 2005. Huygens was the first probe to land on the surface of a moon other than our own. The orbiter and probe have shown birdseye and ground-level views of Titan, an Earth-like world featuring river valley networks and lakes filled with hydrocarbons. Cassini has discovered water-ice geysers spewing from Enceladus, a smaller moon of Saturn, and has detected five new moons and observed a very dynamic ring system.

For exhibition information see: http://www.amnh.org/exhibitions/photo/saturn/ .   More information about the Cassini-Huygens mission is available at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL.

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Re: NASA - Cassini updates
« Reply #44 on: 04/29/2008 08:50 PM »
Image Advisory: 2008-069                            April 29, 2008

NASA Spacecraft Tracks Raging Saturn Storm

PASADENA, Calif. -- As a powerful electrical storm rages on Saturn with lightning bolts 10,000 times more powerful than those found on Earth, the Cassini spacecraft continues its five-month watch over the dramatic events.

Scientists with NASA's Cassini-Huygens mission have been tracking the visibly bright, lightning-generating storm--the longest continually observed electrical storm ever monitored by Cassini.

Saturn's electrical storms resemble terrestrial thunderstorms, but on a much larger scale. Storms on Saturn have diameters of several thousand kilometers (thousands of miles), and radio signals produced by their lightning are thousands of times more powerful than those produced by terrestrial thunderstorms.

Color images of the storm are available at: http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini and http://ciclops.org .

Lightning flashes within the persistent storm produce radio waves called Saturn electrostatic discharges, which the radio and plasma wave science instrument first detected on Nov. 27, 2007. Cassini's imaging cameras monitored the position and appearance of the storm, first spotting it about a week later, on Dec. 6.

"The electrostatic radio outbursts have waxed and waned in intensity for five months now," said Georg Fischer, an associate with the radio and plasma wave science team at the University of Iowa, Iowa City. "We saw similar storms in 2004 and 2006 that each lasted for nearly a month, but this storm is longer-lived by far. And it appeared after nearly two years during which we did not detect any electrical storm activity from Saturn."



The new storm is located in Saturn's southern hemisphere--in a region nicknamed "Storm Alley" by mission scientists--where the previous lightning storms were observed by Cassini.

"In order to see the storm, the imaging cameras have to be looking at the right place at the right time, and whenever our cameras see the storm, the radio outbursts are there," said Ulyana Dyudina, an associate of the Cassini imaging team at the California Institute of Technology in Pasadena, Calif.

Cassini's radio plasma wave instrument detects the storm every time it rotates into view, which happens every 10 hours and 40 minutes, the approximate length of a Saturn day. Every few seconds the storm gives off a radio pulse lasting for about a tenth of a second, which is typical of lightning bolts and other electrical discharges. These radio waves are detected even when the storm is over the horizon as viewed from Cassini, a result of the bending of radio waves by the planet's atmosphere.

Amateur astronomers have kept track of the storm over its five-month lifetime. "Since Cassini's camera cannot track the storm every day, the amateur data are invaluable," said Fischer. "I am in continuous contact with astronomers from around the world."

The long-lived storm will likely provide information on the processes powering Saturn's intense lightning activity. Cassini scientists will continue to monitor Storm Alley as the seasons change, bringing the onset of autumn to the planet's southern hemisphere.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo. The radio and plasma wave science team is based at the University of Iowa, Iowa City.

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Re: NASA - Cassini updates
« Reply #45 on: 05/08/2008 03:14 AM »
Feature                                                         May 7, 2008

 

Saturn Does the Wave in Upper Atmosphere

 

 Two decades of scrutinizing Saturn are finally paying off, as scientists have discovered a wave pattern, or oscillation, in Saturn's atmosphere only visible from Earth every 15 years.

The discovery of the wave pattern is the result of a 22-year campaign observing Saturn from Earth (the longest study of temperature outside Earth ever recorded), and the Cassini spacecraft's observations of temperature changes in the giant planet's atmosphere over time.

The Cassini infrared results, which appear in the same issue of Nature as the data from the 22-year ground-based observing campaign, indicate that Saturn's wave pattern is similar to a pattern found in Earth's upper atmosphere. The earthly oscillation takes about two years. A similar pattern on Jupiter takes more than four Earth years. The new Saturn findings add a common link to the three planets.

Just as scientists have been studying climate changes in Earth's atmosphere for long periods of time, NASA scientists have been studying changes in Saturn's atmosphere. Glenn Orton of NASA's Jet Propulsion Laboratory in Pasadena, Calif., says patience is the key to studying changes over the course of a Saturnian year, the equivalent of about 30 Earth years.

"You could only make this discovery by observing Saturn over a long period of time," said Orton, lead author of the ground-based study. "It's like putting together 22 years worth of puzzle pieces, collected by a hugely rewarding collaboration of students and scientists from around the world on various telescopes."

The wave pattern is called an atmospheric oscillation. It ripples back and forth within Saturn's upper atmosphere. In this region, temperatures switch from one altitude to the next in a candy cane-like, striped, hot-cold pattern. These varying temperatures force the wind in the region to keep changing direction from east to west, jumping back and forth. As a result, the entire region oscillates like a wave.

A "snapshot" of the hot-cold temperature patterns in Saturn's atmosphere was captured by the Cassini Composite Infrared Spectrometer. Along with Earth-based data, the "snapshot" also uncovered other interesting phenomena. Among them: the temperature at Saturn's equator switches from hot to cold, and temperatures on either side of the equator switch from cold to hot every Saturn half-year.

Mike Flasar, co-author of the Cassini paper, and principal investigator for Cassini's Composite Infrared Spectrometer at NASA's Goddard Space Flight Center, Greenbelt, Md., said that Cassini helped define this oscillation in combination with the ground observation campaign.

"It's this great synergy of using ground-based data over time, and then getting up close and personal with the oscillation in Saturn's atmosphere through Cassini," said Flasar. "Without Cassini, we might never have seen the structure of the oscillation in detail."

Cassini scientists hope to find out why this phenomenon on Saturn changes with the seasons, and why the temperature switchover happens when the sun is directly over Saturn's equator.

More information on the Cassini-Huygens mission can be found at: http://saturn.jpl.nasa.gov, and http://www.nasa.gov/cassini.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The Composite Infrared Spectrometer team is based at NASA's Goddard Space Flight Center, Greenbelt, Md.

-- Written by Diya Chacko

Media Contact:

Diya Chacko/ Carolina Martinez    818-393-5464/354-9382


Offline eeergo

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Re: NASA - Cassini updates
« Reply #46 on: 05/08/2008 12:03 PM »
Interesting pdf about Cassini's next flyby of Titan (T48), with a detailed timeline at the end:

http://saturn.jpl.nasa.gov/multimedia/products/pdfs/20080512_titan_mission_description.pdf

Coming up this Monday!
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Re: NASA - Cassini updates
« Reply #47 on: 06/27/2008 07:16 PM »
NEWS RELEASE: 2008-122                                                                          June 27, 2008

Cassini to Earth: 'Mission Accomplished, But New Questions Await!'

PASADENA, Calif.—NASA's Cassini mission is closing one chapter of its journey at Saturn and embarking on a new one with a two-year mission that will address new questions and bring it closer to two of its most intriguing targets—Titan and Enceladus.

On June 30, Cassini completes its four-year prime mission and begins its extended mission, which was approved in April of this year.

Among other things, Cassini revealed the Earth-like world of Saturn's moon Titan and showed the potential habitability of another moon, Enceladus. These two worlds are primary targets in the two-year extended mission, dubbed the Cassini Equinox Mission. This time period also will allow for monitoring seasonal effects on Titan and Saturn, exploring new places within Saturn's magnetosphere, and observing the unique ring geometry of the Saturn equinox in August of 2009 when sunlight will pass directly through the plane of the rings.

"We've had a wonderful mission and a very eventful one in terms of the scientific discoveries we've made, and yet an uneventful one when it comes to the spacecraft behaving so well," said Bob Mitchell, Cassini program manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are incredibly proud to have completed all of the objectives we set out to accomplish when we launched.  We answered old questions and raised quite a few new ones and so our journey continues."

A new addition to the Cassini science team is Bob Pappalardo who will step into the role of Cassini Project Scientist in July, taking over for Dennis Matson, a multi-year veteran on the project who will be working on future flagship mission studies to the outer solar system. "I am honored and humbled to be able to work with such a scientifically rich mission, and with the outstanding scientists and engineers who are the backbone of Cassini," said Pappalardo.

Pappalardo is a geologist whose research focuses on processes that have shaped the icy moons of the outer solar system, including processes that power the geysers of Saturn's moon Enceladus.

He received his bachelor's degree from Cornell University, Ithaca, N.Y., and his Ph.D. in geology from Arizona State University, Tempe. He worked with the Galileo imaging team while a Postdoctoral Researcher at Brown University, Providence, RI. Prior to joining JPL in 2006, he was an assistant professor of planetary sciences at the University of Colorado at Boulder. Currently he resides in Venice, Calif.  More information on Pappalardo is at http://science.jpl.nasa.gov/people/Pappalardo .

Cassini launched Oct. 15, 1997, from Cape Canaveral, Fla., on a seven-year journey to Saturn, traversing 3.5 billion kilometers (2.2 billion miles).  The mission entered Saturn's orbit on June 30, 2004, and began returning stunning data of Saturn's rings almost immediately. The spacecraft is extremely healthy and carries 12 instruments powered by three radioisotope thermoelectric generators. Data from Cassini's nominal and extended missions could lay the groundwork for possible future missions to Saturn, Titan or Enceladus.

Information about the Cassini Equinox Mission is at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

The Cassini Equinox Mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL.


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Re: NASA - Cassini updates
« Reply #48 on: 07/31/2008 04:28 AM »
RELEASE: 08-193

NASA CONFIRMS LIQUID LAKE ON SATURN MOON

PASADENA, Calif. -- NASA scientists have concluded that at least one
of the large lakes observed on Saturn's moon Titan contains liquid
hydrocarbons, and have positively identified the presence of ethane.
This makes Titan the only body in our solar system beyond Earth known
to have liquid on its surface.

Scientists made the discovery using data from an instrument aboard the
Cassini spacecraft. The instrument identified chemically different
materials based on the way they absorb and reflect infrared light.
Before Cassini, scientists thought Titan would have global oceans of
methane, ethane and other light hydrocarbons. More than 40 close
flybys of Titan by Cassini show no such global oceans exist, but
hundreds of dark lake-like features are present. Until now, it was
not known whether these features were liquid or simply dark, solid
material.

"This is the first observation that really pins down that Titan has a
surface lake filled with liquid," said Bob Brown of the University of
Arizona, Tucson. Brown is the team leader of Cassini's visual and
mapping instrument. The results will be published in the July 31
issue of the journal Nature.

Ethane and several other simple hydrocarbons have been identified in
Titan's atmosphere, which consists of 95 percent nitrogen, with
methane making up the other 5 percent. Ethane and other hydrocarbons
are products from atmospheric chemistry caused by the breakdown of
methane by sunlight.

Some of the hydrocarbons react further and form fine aerosol
particles. All of these things in Titan's atmosphere make detecting
and identifying materials on the surface difficult, because these
particles form a ubiquitous hydrocarbon haze that hinders the view.
Liquid ethane was identified using a technique that removed the
interference from the atmospheric hydrocarbons.

The visual and mapping instrument observed a lake, Ontario Lacus, in
Titan's south polar region during a close Cassini flyby in December
2007. The lake is roughly 7,800 square miles in area, slightly larger
than North America's Lake Ontario.

"Detection of liquid ethane confirms a long-held idea that lakes and
seas filled with methane and ethane exist on Titan," said Larry
Soderblom, a Cassini interdisciplinary scientist with the U.S.
Geological Survey in Flagstaff, Ariz. "The fact we could detect the
ethane spectral signatures of the lake even when it was so dimly
illuminated, and at a slanted viewing path through Titan's
atmosphere, raises expectations for exciting future lake discoveries
by our instrument."

The ethane is in a liquid solution with methane, other hydrocarbons
and nitrogen. At Titan's surface temperatures, approximately 300
degrees Fahrenheit below zero, these substances can exist as both
liquid and gas. Titan shows overwhelming evidence of evaporation,
rain, and fluid-carved channels draining into what, in this case, is
a liquid hydrocarbon lake.

Earth has a hydrological cycle based on water and Titan has a cycle
based on methane. Scientists ruled out the presence of water ice,
ammonia, ammonia hydrate and carbon dioxide in Ontario Lacus. The
observations also suggest the lake is evaporating. It is ringed by a
dark beach, where the black lake merges with the bright shoreline.
Cassini also observed a shelf and beach being exposed as the lake
evaporates.

"During the next few years, the vast array of lakes and seas on
Titan's north pole mapped with Cassini's radar instrument will emerge
from polar darkness into sunlight, giving the infrared instrument
rich opportunities to watch for seasonal changes of Titan's lakes,"
Soderblom said.

Launched in Oct. 1997, Cassini's 12 instruments have returned a daily
stream of data from Saturn's system. The mission is a cooperative
project of NASA, the European Space Agency and the Italian Space
Agency.

Offline Orbiter

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Re: NASA - Cassini updates
« Reply #49 on: 07/31/2008 04:44 AM »
Thanks for your info!
Attended space missions: STS-114, STS-124, STS-128, STS-135, Atlas V "Curiosity", Delta IV Heavy NROL-15, Atlas V MUOS-2, Delta IV Heavy NROL-37, SpaceX CRS-9, SpaceX JCSAT-16, Atlas V GOES-R.

Online jacqmans

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Re: NASA - Cassini updates
« Reply #50 on: 08/07/2008 06:46 PM »
NEWS RELEASE: 2008-156                                                             Aug. 7, 2008

Cassini Prepares to Swoop by Saturn's Geyser-Spewing Moon

Fractures, or "tiger stripes," where icy jets erupt on Saturn's moon Enceladus will be the target of a close flyby by the Cassini spacecraft on Monday, Aug. 11.

Cassini will zoom past the tiny moon a mere 50 kilometers (30 miles) from the surface. Just after closest approach, all of the spacecraft's cameras -- covering infrared wavelengths, where temperatures are mapped, as well as visible light and ultraviolet -- will focus on the fissures running along the moon's south pole. That is where the jets of icy water vapor emanate and erupt hundreds of miles into space. Those jets have fascinated scientists since their discovery in 2005.

"Our main goal is to get the most detailed images and remote sensing data ever of the geologically active features on Enceladus," said Paul Helfenstein, a Cassini imaging team associate at Cornell University in Ithaca, NY. "From this data we may learn more about how eruptions, tectonics, and seismic activity alter the moon's surface. We will get an unprecedented high-resolution view of the active area immediately following the closest approach."

Seeing inside one of the fissures in high resolution may provide more information on the terrain and depth of the fissures, as well as the size and composition of the ice grains inside.  Refined temperature data could help scientists determine if water, in vapor or liquid form, lies close to the surface and better refine their theories on what powers the jets.

Imaging sequences will capture stereo views of the north polar terrain, and high resolution images of the south polar region will begin shortly after closest approach to Enceladus. The image resolution will be as fine as 7 meters per pixel (23 feet) and will cover known active spots on three of the prominent "tiger stripe" fractures.

In addition to mapping the moon's surface in visible light as well as infrared and ultraviolet light, Cassini will help determine the size of the ice grains and distinguish other elements mixed in with the ice, such as oxygen, hydrogen, or organics.

"Knowing the sizes of the particles, their rates and what else is mixed in these jets can tell us a lot about what's happening inside the little moon," said Amanda Hendrix, Cassini ultraviolet imaging spectrograph team member at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Other instruments will measure the temperatures along the fractures, which happen to be some of the hottest spots on the moon's surface.

"We'd like to refine our numbers and see which fracture or stripe is hotter than the rest because these results can offer evidence, one way or the other, for the existence of liquid water as the engine that powers the plumes," said Bonnie Buratti of JPL, team member on Cassini's visual and infrared mapping spectrometer.

Cassini discovered evidence for the geyser-like jets on Enceladus in 2005, finding that the continuous eruptions of ice water create a gigantic halo of ice and gas around Enceladus, which helps supply material to Saturn's E-ring. This marks Cassini's second flyby of Enceladus this year. During Cassini's last flyby of Enceladus in March, the spacecraft snatched up precious samples and tasted comet-like organics inside the little moon. Two more Enceladus flybys are coming up in October, and they may bring the spacecraft even closer to the moon. The Oct. 9 encounter is complimentary to the March one, which was optimized for sampling the plume. The Oct. 31 flyby is similar to this August one, and is again optimized for the optical remote sensing instruments.

For images, videos and a mission blog on the flyby, visit:   

http://www.nasa.gov/cassini . More information on the Cassini mission is also available at http://saturn.jpl.nasa.gov .


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Re: NASA - Cassini updates
« Reply #51 on: 08/12/2008 08:51 AM »
Mission Status Report: 2008-157                                                         Aug. 11, 2008

Cassini Begins Transmitting Data From Enceladus Flyby

Shorty after 9:03 p.m. Pacific Time, the Cassini spacecraft began sending data to Earth following a close flyby of Saturn's moon Enceladus. During closest approach, Cassini successfully passed only 50 kilometers (30 miles) from the surface of the tiny moon. 

Cassini's signal was picked up by the Deep Space Network station in Canberra, Australia, and relayed to the Cassini mission control at NASA's Jet Propulsion Laboratory in Pasadena, Calif.


"We are happy to report that Cassini's begun sending data home," said Julie Webster, Cassini team chief at JPL. "The downlink will continue through the night and into tomorrow morning.”

Closest approach occurred at approximately 3:21 p.m. PDT, while Cassini was traveling at a swift 17.7 kilometers per second (40,000 miles per hour) relative to Enceladus. 

During the flyby, Cassini focused its cameras and other remote sensing instruments on Enceladus with an emphasis on the moon’s south pole where parallel stripes or fissures dubbed "tiger stripes" line the region. That area is of particular interest because geysers of water-ice and vapor jet out of the fissures and supply material to Saturn's E-ring. Scientists hope to learn more about the fissures and whether liquid water is indeed the engine powering the geysers.


"There is a lot of anticipation and excitement about what today’s flyby might reveal" said Bob Pappalardo, Cassini project scientist, also of JPL. “Over the next few days and weeks, the Cassini teams will be analyzing the photos and other data to tease out new clues about this tiny, active world". 

Two more Enceladus flybys are planned for October. The first of those will cut Monday’s flyby distance in half and bring the spacecraft to a remarkable 25 kilometers (16 miles) from the surface. Enceladus measures about 500 kilometers (310 miles) in diameter--just one-seventh the diameter of Earth’s moon.


The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL.

For images, videos and a mission blog on the flyby, visit: http://www.nasa.gov/cassini . Raw (unprocessed) images are available at: http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list1.html .

-end-

Offline eeergo

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Re: NASA - Cassini updates
« Reply #52 on: 08/13/2008 02:29 PM »
First images are starting to appear, mesmerizing details can be seen!

Apparently, in the blog they say the surface is covered in ice blocks released from the Tiger Stripes.

Blog: http://blogs.nasa.gov/cm/blog/cassini-aug08/
Raw images: http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-list1.html

-DaviD-

Offline iamlucky13

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Re: NASA - Cassini updates
« Reply #53 on: 08/14/2008 09:57 PM »
One more image from even closer. The caption says this was taken at 545 km, which for an 0.35 degree field of view, works out to about 3 m/pix. Check out the boulders (of ice?) scattered around. I don't know if they're actually certain they're blocks ejected from the tiger stripes, or if they could be material of different consistency or composition exposed by erosion, etc.

« Last Edit: 08/14/2008 09:58 PM by iamlucky13 »

Offline robertross

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Re: NASA - Cassini updates
« Reply #54 on: 08/15/2008 12:06 AM »
quote:
{snip}
Two more Enceladus flybys are planned for October. The first of those will cut Monday’s flyby distance in half and bring the spacecraft to a remarkable 25 kilometers (16 miles) from the surface. Enceladus measures about 500 kilometers (310 miles) in diameter--just one-seventh the diameter of Earth’s moon.

Wow!! 25 km from the surface. And here I thought these images were stunning! They are doing some fantastic work with Cassini.
Remembering those who made the ultimate sacrifice for our rights & freedoms, and for those injured, visible or otherwise, in that fight.

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Re: NASA - Cassini updates
« Reply #55 on: 08/15/2008 09:57 AM »
News Release: 2008-160                                                                Aug. 14, 2008

Cassini Pinpoints Source of Jets on Saturn's Moon Enceladus

PASADENA, Calif. -- In a feat of interplanetary sharpshooting, NASA's Cassini spacecraft has pinpointed precisely where the icy jets erupt from the surface of Saturn's geologically active moon Enceladus.

New carefully targeted pictures reveal exquisite details in the prominent south polar "tiger stripe" fractures from which the jets emanate. The images show the fractures are about 300 meters (980 feet) deep, with V-shaped inner walls. The outer flanks of some of the fractures show extensive deposits of fine material. Finely fractured terrain littered with blocks of ice tens of meters in size and larger (the size of small houses) surround the fractures.

"This is the mother lode for us," said Carolyn Porco, Cassini imaging team leader at the Space Science Institute, Boulder, Colo. “A place that may ultimately reveal just exactly what kind of environment -- habitable or not -- we have within this tortured little moon.”

One highly anticipated result of this flyby was finding the location within the fractures from which the jets blast icy particles, water vapor and trace organics into space. Scientists are now studying the nature and intensity of this process on Enceladus, and its effects on surrounding terrain. This information, coupled with observations by Cassini's other instruments, may answer the question of whether reservoirs of liquid water exist beneath the surface. 

The high-resolution images were acquired during an Aug. 11, 2008, flyby of Enceladus, as Cassini sped past the icy moon at 64,000 kilometers per hour (40,000 miles per hour). A special technique, dubbed "skeet shooting" by the imaging team, was developed to cancel out the high speed of the moon relative to Cassini and obtain the ultra-sharp views.

"Knowing exactly where to point, at just the right time, was critical to this event," said Paul Helfenstein, Cassini imaging team associate at Cornell University, Ithaca, NY., who developed and used the skeet-shoot technique to design the image sequence. "The challenge is equivalent to trying to capture a sharp, unsmeared picture of a distant roadside billboard with a telephoto lens out the window of a speeding car."

Helfenstein said that from Cassini's point of view, "Enceladus was streaking across the sky so quickly that the spacecraft had no hope of tracking any feature on its surface. Our best option was to point the spacecraft far ahead of Enceladus, spin the spacecraft and camera as fast as possible in the direction of Enceladus' predicted path, and let Enceladus overtake us at a time when we could match its motion across the sky, snapping images along the way." 

For scientists, having the combination of high-resolution snapshots and broader images showing the whole region is critical for understanding what may be powering the activity on Enceladus.

"There appears to have been extensive fallout of icy particles to the ground, along some of the fractures, even in areas that lie between two jet source locations, though any immediate effects of presently active jets are subtle," Imaging scientists suggest that once warm vapor rises from underground to the cold surface through narrow channels, the icy particles may condense and seal off an active vent. New jets may then appear elsewhere along the same fracture.

"For the first time, we are beginning to understand how freshly erupted surface deposits differ from older deposits," said Helfenstein, an icy moons expert. "Over geologic time, the eruptions have clearly moved up and down the lengths of the tiger stripes."

The new images, with jet source locations labeled, are available at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org .


 

Offline iamlucky13

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Re: NASA - Cassini updates
« Reply #56 on: 08/15/2008 09:36 PM »
quote:
{snip}
Two more Enceladus flybys are planned for October. The first of those will cut Monday’s flyby distance in half and bring the spacecraft to a remarkable 25 kilometers (16 miles) from the surface. Enceladus measures about 500 kilometers (310 miles) in diameter--just one-seventh the diameter of Earth’s moon.

Wow!! 25 km from the surface. And here I thought these images were stunning! They are doing some fantastic work with Cassini.

Unfortunately, I don't think we'll be seeing much higher resolution. At 40,000 mph and with the relatively dim sun, the blur that close to the ground is hard to deal with. My understanding is for this pass they set Cassini rotating ahead of time at a rate that would allow it to pan (their so-called skeet shoot) and minimize the blur. Despite this, the closest image I've been able to find in the database was the one I posted above, taken at 545 kilometer.

But it will be really useful to the mission team to get their spectrometers up closer.

Online jacqmans

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Re: NASA - Cassini updates
« Reply #57 on: 09/05/2008 07:17 PM »
News release: 2008-172                                    Sept. 5, 2008

Cassini Images Ring Arcs Among Saturn's Moons

PASADENA, Calif. -- NASA's Cassini spacecraft has detected a faint, partial ring orbiting with one small moon of Saturn, and has confirmed the presence of another partial ring orbiting with a second moon.  This is further evidence that most of the planet's small, inner moons orbit within partial or complete rings.

Recent Cassini images show material, called ring arcs, extending ahead of and behind the small moons Anthe and Methone in their orbits. The new findings indicate that the gravitational influence of nearby moons on ring particles might be the deciding factor in whether an arc or complete ring is formed.

Both Anthe and Methone orbit Saturn in locations, called resonances, where the gravity of the nearby larger moon Mimas disturbs their orbits. Gravitational resonances are also responsible for many of the structures in Saturn's magnificent rings. Mimas provides a regular gravitational tug on each moon, which causes the moons to skip forward and backward within an arc-shaped region along their orbital paths, according to Nick Cooper, a Cassini imaging team associate from Queen Mary, University of London. "When we realized that the Anthe and Methone ring arcs were very similar in appearance to the region in which the moons swing back and forth in their orbits due to their resonance with Mimas, we knew we had a possible cause-and-effect relationship," Cooper said.

Scientists believe the faint ring arcs from Anthe and Methone likely consist of material knocked off these small moons by micrometeoroid impacts. This material does not spread all the way around Saturn to form a complete ring, because of the gravitational resonance with Mimas.  That interaction confines the material to a narrow region along the orbits of the moons.

This is the first detection of an arc of material near Anthe. The Methone arc was previously detected by Cassini's Magnetospheric Imaging Instrument, and the new images confirm its presence. Previous Cassini images show faint rings connected with other small moons either embedded within or near the outskirts of Saturn's main ring system, such as Pan, Janus, Epimetheus and Pallene. Cassini had also previously observed an arc in the G ring, one of Saturn's faint, major rings.

"This is probably the same mechanism responsible for producing the arc in the G ring," said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. Hedman and his Cassini imaging team colleagues previously determined that the G-ring arc is maintained by a gravitational resonance with Mimas, much like the new, small moon arcs. "Indeed, the Anthe arc may be similar to the debris we see in the G-ring arc, where the largest particles are clearly visible. One might even speculate that if Anthe were shattered, its debris might form a structure much like the G ring," Hedman said.

Additional analysis by scientists indicates that, while the gravitational influence of Mimas keeps the Anthe, Methone and G-ring arcs in place, the material that orbits with the moons Pallene, Janus and Epimetheus is not subject to such powerful resonant forces and is free to spread out around the planet, forming complete rings without arcs.

The intricate relationships between these ring arcs and the moons are just one of many such mechanisms that exist in the Saturn system.  Cassini Imaging Team Member and Professor Carl Murray, also from Queen Mary, University of London, said, "There are many examples in the 

Saturn system of moons creating structures in the rings and disturbing the orbits of other moons. Understanding these interactions and learning about their origins can help us to make sense of what we are seeing in the Cassini images."

Images of Anthe and Methone with their ring arcs are available at: http://www.nasa.gov/cassini, http://saturn.jpl.nasa.gov and http://ciclops.org.

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

-end-
 


Online jacqmans

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Re: NASA - Cassini updates
« Reply #58 on: 10/07/2008 01:41 PM »
NEWS RELEASE: 2008-185                                                             Oct. 6, 2008

Cassini Plans Doubleheader Flybys of Saturn's Geyser Moon

PASADENA, Calif. -- As major league baseball readies for the World Series, NASA's Cassini team will come to bat twice this month when the spacecraft flies by Saturn's geyser moon, Enceladus.

The Oct. 9 flyby is an inside pitch—the closest flyby yet of any moon of Saturn, at only 25 kilometers (16 miles) from the surface. The Oct. 31 flyby is farther out, at 196 kilometers (122 miles).

Scientists are intrigued by the possibility that liquid water, perhaps even an ocean, may exist beneath the surface of Enceladus. Trace amounts of organics have also been detected, raising tantalizing possibilities about the moon's habitability.



While Cassini's cameras and other optical instruments were the focus of an Aug. 11 flyby, during Cassini's Oct. 9 flyby, the spacecraft's fields and particles instruments will venture deeper into the plume than ever before, directly sampling the particles and gases. The emphasis here is on the composition of the plume rather than imaging the surface.

"We know that Enceladus produces a few hundred kilograms per second of gas and dust and that this material is mainly water vapor and water ice," said Tamas Gambosi, Cassini scientist at the University of Michigan, Ann Arbor. "The water vapor and the evaporation from the ice grains contribute most of the mass found in Saturn's magnetosphere.

"One of the overarching scientific puzzles we are trying to understand is what happens to the gas and dust released from Enceladus, including how some of the gas is transformed to ionized plasma and is disseminated throughout the magnetosphere," said Gambosi.

On Oct. 31, the cameras and other optical remote sensing instruments will be front and center, imaging the fractures that slash across the moon's south polar region like stripes on a tiger.

These two flybys might augment findings from the most recent Enceladus flyby, which hint at possible changes associated with the icy moon. Cassini's Aug. 11 encounter with Enceladus showed temperatures over one of the tiger-stripe fractures were lower than those measured in earlier flybys. The fracture, called Damascus Sulcus, was about 160 to 167 Kelvin (minus 171 to minus 159 degrees Fahrenheit), below the 180 Kelvin (minus 136 degrees Fahrenheit) reported from a flyby in March of this year.

"We don't know yet if this is due to a real cooling of this tiger stripe, or to the fact that we were looking much closer, at a relatively small area, and might have missed the warmest spot," said John Spencer, Cassini scientist on the composite infrared spectrometer, at the Southwest Research Institute, Boulder, Colo.

Results from Cassini's magnetometer instrument during the August flyby suggest a difference in the intensity of the plume compared to earlier encounters. Information from the next two flybys will help scientists understand these observations.

Four more Enceladus flybys are planned in the next two years, bringing the total number to seven during Cassini's extended mission, called the Cassini Equinox Mission. The next Enceladus doubleheader will be November 2 and 21, 2009.   

The Enceladus geysers were discovered by Cassini in 2005. Since then, scientists have been intrigued about what powers them, because the moon is so tiny, roughly the width of Arizona at only 500 kilometers (310 miles) in diameter.

"The October doubleheader gives Cassini two more opportunities to hit the ball out of the park," said Bob Pappalardo, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "With high scores in geology, surface heat, watery plumes and magnetospheric effects, Enceladus could win the 'world championship' title this year!"

Scientists anticipate reporting results from the two flybys in November and early December.

Cassini has been orbiting Saturn since 2004. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL.

For images, videos and a mission blog on the flyby, visit: http://www.nasa.gov/cassini .

More information on the Cassini mission is also available at http://saturn.jpl.nasa.gov .

 

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Re: NASA - Cassini updates
« Reply #59 on: 10/13/2008 05:24 PM »
IMAGE ADVISORY: 2008-192                                                                     Oct. 13, 2008

Giant Cyclones at Saturn's Poles Create a Swirl of Mystery

New images from NASA's Cassini spacecraft reveal a giant cyclone at Saturn's north pole, and show that a similarly monstrous cyclone churning at Saturn's south pole is powered by Earth-like storm patterns.

The new-found cyclone at Saturn's north pole is only visible in the near-infrared wavelengths because the north pole is in winter, thus in darkness to visible-light cameras. At these wavelengths, about seven times greater than light seen by the human eye, the clouds deep inside Saturn's atmosphere are seen in silhouette against the background glow of Saturn's internal heat.

The entire north pole of Saturn is now mapped in detail in infrared, with features as small as 120 kilometers (75 miles) visible in the images. Time-lapse movies of the clouds circling the north pole show the whirlpool-like cyclone there is rotating at 530 kilometers per hour (325 miles per hour), more than twice as fast as the highest winds measured in cyclonic features on Earth. This cyclone is surrounded by an odd, honeycombed-shaped hexagon, which itself does not seem to move while the clouds within it whip around at high speeds, also greater than 500 kilometers per hour (300 miles per hour). Oddly, neither the fast-moving clouds inside the hexagon nor this new cyclone seem to disrupt the six-sided hexagon.

New Cassini imagery of Saturn's south pole shows complementary aspects of the region through the eyes of two different instruments. Near-infrared images from the visual and infrared mapping spectrometer instrument show the whole region is pockmarked with storms, while the imaging cameras show close-up details.

The new views are available online at: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

Unlike Earth-bound hurricanes, powered by the ocean's heat and water, Saturn's cyclones have no body of water at their bases, yet the eye-walls of Saturn's and Earth's storms look strikingly similar. Saturn's hurricanes are locked to the planet's poles, whereas terrestrial hurricanes drift across the ocean.

"These are truly massive cyclones, hundreds of times stronger than the most giant hurricanes on Earth," said Kevin Baines, Cassini scientist on the visual and infrared mapping spectrometer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Dozens of puffy, convectively formed cumulus clouds swirl around both poles, betraying the presence of giant thunderstorms lurking beneath. Thunderstorms are the likely engine for these giant weather systems," said Baines.

Just as condensing water in clouds on Earth powers hurricane vortices, the heat released from the condensing water in Saturnian thunderstorms deep down in the atmosphere may be the primary power source energizing the vortex.

In the south, the new infrared images of the pole, under the daylight conditions of southern summer, show the entire region is marked by hundreds of dark cloud spots. The clouds, like those at the north pole, are likely a manifestation of convective, thunderstorm-like processes extending some 100 kilometers (62 miles) below the clouds. They are likely composed of ammonium hydrosulfide with possibly a mixture of materials dredged up from the depths. By contrast, most of the hazes and clouds seen on Saturn are thought to be composed of ammonia, which condenses at high, visible altitudes.

Complementary images of the south pole from Cassini's imaging cameras, obtained in mid-July, are 10 times more detailed than any seen before. "What looked like puffy clouds in lower resolution images are turning out to be deep convective structures seen through the atmospheric haze," said Cassini imaging team member Tony DelGenio of NASA's Goddard Institute for Space Studies in New York. "One of them has punched through to a higher altitude and created its own little vortex."

The "eye" of the vortex is surrounded by an outer ring of high clouds. The new images also hint at an inner ring of clouds about half the diameter of the main ring, and so the actual clear "eye" region is smaller than it appears in earlier low-resolution images.

"It's like seeing into the eye of a hurricane," said Andrew Ingersoll, a member of Cassini's imaging team at the California Institute of Technology, Pasadena. "It's surprising.  Convection is an important part of the planet's energy budget because the warm upwelling air carries heat from the interior. In a terrestrial hurricane, the convection occurs in the eyewall; the eye is a region of downwelling. Here convection seems to occur in the eye as well."

Further observations are planned to see how the features at both poles evolve as the seasons change from southern summer to fall in August 2009.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona. The imaging team is based at the Space Science Institute, Boulder, Colo.

 

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