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NASA's Cassini mission

PostPosted: Thu Apr 23, 2009 9:52 am
by Darragh
NASA's Cassini spacecraft is now a nearly a year into its extended mission, called Cassini Equinox (after its initial 4-year mission ended in June, 2008). The spacecraft continues to operate in good health, returning amazing images of Saturn, its ring system and moons, and providing new information and science on a regular basis. The mission's name, "Equinox" comes from the upcoming Saturnian equinox in August, 2009, when its equator (and rings) will point directly toward the Sun. The Equinox mission runs through September of 2010, with the possibility of further extensions beyond that. Collected here are 24 more intriguing images from our ringed neighbour.
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This natural color mosaic was acquired by the Cassini spacecraft as it soared 39 degrees above the unilluminated side of Saturn's rings. Little light makes its way through the rings to be scattered in Cassini's direction in this viewing geometry, making the rings appear somewhat dark compared to the reflective surface of Saturn (120,536 km/74,898 mi across). The view combines 45 images taken over the course of about two hours, as Cassini scanned across the entire main ring system. The images in this view were obtained on May 9, 2007 at a distance of approximately 1.1 million kilometers (700,000 miles) from Saturn. (NASA/JPL/SSI)
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Pan, a small ring-embedded moon (28 km/17 mi wide) coasts into view from behind Saturn. The view of the rings is distorted near Saturn by the planet's upper atmosphere. The view was acquired at a distance of approximately 1.8 million km (1.1 million mi) from Pan. Image scale is 11 km (7 mi) per pixel on Pan. (NASA/JPL/SSI) #
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Rhea (1,528 km/949 mi wide) drifts in front of Saturn. The view was acquired at a distance of approximately 576,000 km (358,000 mi) from Rhea. Image scale is 3 km (2 mi) per pixel. (NASA/JPL/SSI) #
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Cassini peers through Saturn's delicate, translucent inner C ring to see the diffuse yellow-blue limb of Saturn's atmosphere. The image was taken on April 25, 2008 at a distance of approximately 1.5 million km (913,000 mi) from Saturn. Image scale is 8 km (5 mi) per pixel. (NASA/JPL/SSI) #
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Rhea passes in front of Saturn's larger, hazy moon Titan (which is lit from behind by the sun) in June of 2006. (NASA/JPL/SSI) #
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This mosaic of two Cassini images shows Pan and Prometheus creating features in nearby rings. Pan (28 km/17 mi wide), in the Encke Gap at left, is trailed by a series of edge waves in the outer boundary of the gap. Prometheus (86 km/53 mi wide) just touches the inner edge of Saturn's F ring at right, and is followed by a series of dark channels in the ring. The view was obtained at a distance of approximately 1.2 million km (746,000 mi) from Pan and Prometheus. Image scale is 7 km (5 mi) per pixel on both moons. (NASA/JPL/SSI) #
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This image was taken during Cassini's close approach to the moon Iapetus in Sept. 2007. The image was taken on Sept. 10, 2007 with the Cassini spacecraft wide-angle camera at a distance of approximately 3,870 km (2,400 mi) from Iapetus. Image scale is 230 meters (755 feet) per pixel. (NASA/JPL/SSI) #
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Cassini tracks the shepherd moon Prometheus as it orbits Saturn. Prometheus is just about to pass behind the planet, and a faint streamer of ring material lies below and to the right of Prometheus (86 km/53 mi wide), in the faint, inner strand of the F ring. The view was acquired at a distance of approximately 1.3 million km (804,000 mi) from Prometheus. Image scale is 8 km (5 mi) per pixel. (NASA/JPL/SSI) #
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Saturn's high north is a seething cauldron of activity filled with roiling cloud bands and swirling vortices. A corner of the north polar hexagon is seen at upper left. The image was taken on Aug. 25, 2008 at a distance of approximately 541,000 km (336,000 mi) from Saturn. Image scale is 29 km (18 mi) per pixel. (NASA/JPL/SSI) #
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Numerous stars provide a serene background in this view of Enceladus captured by the Cassini spacecraft while the moon was in eclipse, within Saturn's shadow. The view looks up at Enceladus' south pole. The image was taken on Oct. 9, 2008 at a distance of approximately 83,000 km (52,000 mi) from Enceladus. Image scale is 5 km (3 mi) per pixel. (NASA/JPL/SSI) #
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In this image of the F ring, taken shortly after its ring particles encountered the shepherd moon Prometheus, the disruption to the ring caused by the moon is evident. The bright core of the ring and its neighboring faint strands show kinks where the moon's gravity has altered the orbits of the ring particles. The image was taken on Oct. 23, 2008 at a distance of approximately 444,000 km (276,000 mi) from Saturn. Image scale is 2 km (1 mile) per pixel. (NASA/JPL/SSI) #
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Dark irregular patterns dot the bright outer B ring just left of the large Huygens Gap in the center of this image from Cassini. Cassini scientists speculate that these features are likely the result of transient gravitational clumping. The outer edge of the B ring is anchored and sculpted by a powerful gravitational resonance with the moon, Mimas (396 km/246 mi wide). The mutual gravity between particles may pull them into clumps as they are periodically forced closely together by the action of Mimas. The image was taken on Dec. 8, 2008 at a distance of approximately 710,000 km (441,000 mi) from Saturn. Image scale is 4 km (2 mi) per pixel. (NASA/JPL/SSI) #
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The terminator engulfs Penelope (foreground), one of the largest craters on Saturn's moon, Tethys. The image was taken on Nov. 24, 2008 at a distance of approximately 62,000 km (38,000 mi) from Tethys. Image scale is 366 meters (1,202 feet) per pixel. (NASA/JPL/SSI) #
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Against a background of muted atmospheric bands in Saturn's northern hemisphere, Mimas forges onward in its orbit around the Ringed Planet. Aside from the large crater Herschel, all features on Mimas are named after people and places in Arthurian legend or the legends of the Titans. In fact, the largest crater near the terminator in this view is named Arthur (64 km, 40 mi across). The image was taken on Nov. 26, 2008 at a distance of approximately 915,000 km (569,000 mi) from Mimas. Image scale is 5 km (3 mi) per pixel. (NASA/JPL/SSI) #
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Small, battered Epimetheus before Saturn's A and F rings, and and smog-enshrouded Titan (5,150 km/3,200 mi wide) beyond. The color information in the colorized view is artificial: it is derived from red, green and blue images taken at nearly the same time and phase angle as the clear filter image. This color information was overlaid onto a previously released clear filter view in order to approximate the scene as it might appear to human eyes. The view was acquired on April 28, 2006, at a distance of approximately 667,000 km (415,000 mi) from Epimetheus and 1.8 million km (1.1 million mi) from Titan. The image scale is 4 km (2 mi) per pixel on Epimetheus and 11 km (7 mi) per pixel on Titan. (NASA/JPL/SSI) #
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Half an hour after Prometheus tore into Saturn's F ring, Cassini snapped this image just as the moon was creating a new streamer in the ring. The dark pattern shaped like an upside down check mark in the lower left of the image is Prometheus and its shadow. The potato shaped moon can just be seen coming back out of the ring. The moon's handiwork also is apparent in two previous streamer-channel formations on the right of the image. The darkest streamer-channel stretching from the top right to the center of the image shows Prometheus' previous apoapse passage about 15 hours earlier. Prometheus (86 km/53 mi across) dips into the inner edge of the F ring when it reaches apoapse, its farthest point from Saturn. At apoapse, the moon's gravity pulls out particles of the ring into a streamer. As Prometheus moves back toward periapse - its orbit's closest point to the planet - the streamer gets longer. Then, as Prometheus moves back toward apoapse, the streamer breaks apart which results in a dark channel. This streamer-channel cycle repeats once every orbit. The image was taken on Jan. 14, 2009 at a distance of approximately 555,000 km (345,000 mi) from Saturn. Image scale is 3 km (2 mi) per pixel. (NASA/JPL/SSI) #
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This bizarre scene shows the cloud-streaked limb of Saturn in front of the planet's B ring. The ring's image is warped near the limb by the diffuse gas in Saturn's upper atmosphere. The image was taken on June 24, 2008 using a spectral filter sensitive to wavelengths of infrared light, at a distance of approximately 657,000 km (408,000 mi) from Saturn. Image scale is 4 km (2 mi) per pixel. (NASA/JPL/SSI) #
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Cassini looks toward Rhea's cratered, icy landscape with the dark line of Saturn's ringplane and the planet's murky atmosphere as a background. Rhea is Saturn's second-largest moon, at 1,528 km (949 mi) across. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired on July 17, 2007 at a distance of approximately 1.2 million km (770,000 mi) from Rhea. Image scale is 7 km (5 mi) per pixel. (NASA/JPL/SSI) #
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This image of Saturn's rings and the shadow of nearby Mimas was taken on April 08, 2009. The rings are now oriented nearly edge-on toward the Sun, and very long moon shadows frequently drape across them. Interesting to note in this image are the various jagged shadows along the outer edge of the B ring. Scientists are closely studying this phenomenon now, and a preliminary hypothesis suggests that the shadows are of clumpy, disturbed ring material, stretching up to 3 km above the ring plane - contrasted with an estimated normal ring thickness of only 10 meters or so. (The ring-shaped mark at right is a camera artifact) (NASA/JPL/SSI) #
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Cassini peers through the fine, smoke-sized ice particles of Saturn's F ring toward the cratered face of Mimas (396 km/246 mi wide). The F ring's core is dense enough to completely block the light from Mimas. The image was taken on Nov. 18, 2007 at a distance of approximately 772,000 km (480,000 mi) from Mimas. Image scale is 5 km (3 mi) per pixel on the moon. (NASA/JPL/SSI) #
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Gray Mimas appears to hover above the colorful rings. The large crater seen on the right side of the moon is named for William Herschel, who discovered Mimas in 1789. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired on Sept. 9, 2007 at a distance of approximately 3.151 million km (1.958 million mi) from Mimas. Image scale is 19 km (12 mi) per pixel. (NASA/JPL/SSI) #
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Saturn is seen through the thick smoggy haze of Titan's upper atmosphere in this December, 2005 image. The image was taken at a distance of approximately 25,404 kilometers (15,785 mi) from Titan. (NASA/JPL/SSI) #
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The shadow of Tethys drifts across the face of Saturn. Nearby, shadows of the planet's rings form a darkened band above the equator. The image was taken on Oct. 1, 2008 at a distance of approximately 615,000 km (382,000 mi) from Saturn. Image scale is 37 km (23 mi) per pixel. (NASA/JPL/SSI) #
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Saturn's northern hemisphere is seen here against its nested rings. The rings have been brightened relative to the planet to enhance visibility. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were acquired with the Cassini spacecraft wide-angle camera on Feb. 24, 2009 at a distance of approximately 866,000 km (538,000 mi) from Saturn. Image scale is 38 km (24 mi) per pixel. (NASA/JPL/SSI) #

Enceladus up close - October 24th, 2008
Saturn's tiny, icy moon Enceladus has recently been visited by NASA's Cassini orbiter on several very close approaches - once coming within a mere 25 kilometers (15 miles) of the surface. Scientists are learning a great deal about this curious little moon. Only about 500 kilometers wide (310 miles), it is very active, emitting internal heat, churning its surface, and - through cryovolcanism - ejecting masses of microscopic ice particles into Saturnian orbit. Cassini has been orbiting Saturn for over 4 years now, and has provided some amazing views of tiny Enceladus, some collected here. Another close flyby is scheduled for Halloween, October 31st.
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Ring shadows line the face of distant Saturn, providing a backdrop for the brilliant, white sphere of Enceladus. This image looks toward the leading side of Enceladus. North is up. The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on June 28, 2007. The view was acquired at a distance of approximately 291,000 kilometers (181,000 miles) from Enceladus. Image scale is 2 kilometers (1 mile) per pixel. (NASA/JPL-Caltech)
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Re: NASA's Cassini mission (56k thread not in this thread)

PostPosted: Thu Apr 23, 2009 11:54 am
by Blossom
Mods, is there any chance you could remove the picture size limit for this thread?
There doesn't seem t be a button for that. Maybe it's something admin can do
P.S that spam is getting quite irritating.
We're working on that.

Re: NASA's Cassini mission (56k thread not in this thread)

PostPosted: Thu Apr 23, 2009 12:25 pm
by Darragh
Thanks for the reply. The wallpaper thread doesn't have the limit so I was hoping it's simply an option for every thread. I guess a red coat might be able too...but which red coat will log in first.

I'm betting Peter!

I will summon him with baby red pandas.
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Re: NASA's Cassini mission (56k thread not in this thread)

PostPosted: Thu Apr 23, 2009 12:52 pm
by Peter
Thanks for the reply. The wallpaper thread doesn't have the limit so I was hoping it's simply an option for every thread. I guess a red coat might be able too...but which red coat will log in first.

I'm betting Peter!

I will summon him with baby red pandas.
3_461.jpg
Hmm. Nice as a snack on toast, but not as yummy as roasted baby giant panda.

The 800px width limit is global and, so far as I can tell, not changeable on a thread-by-thread basis. I've had a look on the wallpaper thread and I can see nothing there that's wider than 800px.

I share your pain - there's nothing like a nice big hires pic especially if it's astronomical. All I can suggest is that you link to the photos rather than use IMG tags. I think the 800px limit should stand for now as there are still people with screens only 800px or 1024px wide.

Re: NASA's Cassini mission

PostPosted: Thu Apr 23, 2009 1:26 pm
by Darragh
Thanks Peter, I edited the first post so would someone mind deleting the replies made so far?

Re: NASA's Cassini mission

PostPosted: Thu Apr 23, 2009 1:41 pm
by Peter
Thanks Peter, I edited the first post so would someone mind deleting the replies made so far?
I think I'll leave them there actually as they're quite informative. Stunning pictures, BTW. I wish I'd given Hally rings now but it orbits too close to the Blessèd sun for them to survive.