 | | Storms on Saturn - This false color infraded-red image from September 28, 2004 is produced by displaying 938 nm infrared light as orange, 727 nm near infrared light as bluegreen, and 619 nm orange light as violet. This particular combination of color assignments brings out many details in the atmospheric circulation. 938 nm is a methane transmission band, meaning that what appears orange here has come from lower in the atmosphere, under the methane haze that covers Saturn. |
 | | Rings and Shadow - This true color image from Ocober 6, 2004 shows the rings projected in front of the planet. The bluish tint at the top is caused by two factors: we are looking through more bluish upper haze when looking near the limb, and the dark side of the rings scatter a lot of blue light. We are looking at the sunlit side here, so the far side of the planet from our vantage is illuminated by light that filters through the rings. |
 | | Atmospheric Turbulance - This false color infraded image from October 9, 2004 is produced by displaying 938 nm infrared light as orange, 889 nm infrared light as bluegreen, and 727 nm near infrared light as violet. This particular combination of color assignments brings out many details in the atmospheric circulation. 938 nm and 727 nm are methane transmission bands, meaning that orange and violet in this image come from lower in the atmosphere, under the methane haze that covers Saturn. Note the diagonal streaks in the "reddish" region. The rings appear very different in these colors. They are made of very different stuff than the atmosphere of Saturn, and the fact that both planet and rings appear yellow or brown to us is an accident of the particular colors to which we are sensitive. |
 | | Iapetus - This unprocessed image of the moon Iapetus was captured on October 15, 2004, just before Cassini passed it on the way in to its second Saturn encounter. It shows part of the dark patch that covers half of the weird moon, and a curious alignment of features: several white spots where the dark patch reaches the terminator (near center) and a linear fissure extending in line with them around the far side. |
 | | The South Pole and Tethys in Expanded Colors - This false color picture from October 18, 2004 expands three similar red and infrared colors (750 nm, 727 nm, and 619 nm) so that they span the color range from red to blue. It shows the South Pole and the moon Tethys. Tethys is not actually above the pole but behind it or in front of it. Light of these colors can pass through to various levels in Saturn's atmosphere and back out again, so each illuminates different features. To our unaded eyes the whole southern polar region would appear dusty yellow, and the multitude of tiny round storms would be barely visible, but in these colors, they are clearly seen. |
 | | Saturn in Color - This true color picture is made from images taken on October 18, 2004, just after the passage of Iapetus and ten days before the periapsis (closest approach to Saturn) of October 28, 2004. |
 | | Storms on Saturn - This false color image from October 20, 2004 was the first I produced. I have the colors out of order. The longest wavelength (889 nm infrared) is assigned to red, the shortest (727 nm IR) to green, and the middle wavelength (750 nm IR) to blue. The 889 nm and 750 nm are also exposed through the IR polarization filter. Therefore, in no way is this a "well composed" image, but it is so pretty I kept it anyway, and it shows spectacularly well that the rings are made of different stuff than the planet. |
 | | Is Iapetus Polarized? - This fascinating image was produced from images taken on October 21, 2004, after Cassini had passed Iapetus while inbound to Saturn. The bright crescent is the sunlit side mostly out of view. The rest is illuminated by light reflected from Saturn. This is "Saturnshine", the analog of seeing "the new moon in the old moon's arms" on Earth. The colors are made by combining light from three polarization filters, assigning one to red, green, and blue. The colored streeks behind the moon are stars that slid by int he background as the camera was locked on Iapetus and collected light through each filter. The filters themselves do not add color, but if Iapetus reflected light with one polarization better than the others, then that color would be enhanced and tint the moon. There is no such color. Iapetus appears grey. Therefore it does not polarize light. This can be used to determine facts about the grains of dust or ice on the surface. |
 | | Xanadu - This false color image from October 23, 2004, is produced by using two infrared pictures (Continuum band 3 at 938 nanometers and Methane Band 3 at 889 nanometers as red and green) and UV3 at 343 nm as blue, then adjusting to bring out the surface features, which appear in the 938 nm (red) image. The blue halo is real, and extends hundreds of kilometers above Titan. We'll know momentarily what it consists of when Cassini flies through on October 26. The bright pinkish feature on Titan is Xanadu, the first "Titanic" feature identified from Earth. The bright clutter near the left limb is cloud near the south pole. Huygens will land at a point that is just over the limb at the top. |
 | | Outer Part of the Rings - (LARGE - c. 550Kb.) This true color image is produced from twelve images taken October 24, 2004. Resolution is around 12 Km/pixel. It shows the Cassini Division, the A Ring (to the outside or right) and part of the B Ring (inside or left). |
 | | The Armosphere of Titan - This false color image shows the hazes and outer atmosphere of Titan, taken as Cassini was only hours away from its October 26, 2004 closest approach of the moon. It is composed of an image in the broad-band IR filter centered at 928 nm (colored red) the narrow-band red filter at 619 nm (colored green) and the broad-band UV filter centered at 343 nm (colored blue). It shows layers of high atmospheric haze hundreds of miles above the moon's surface. |
 | | The Globe within the Shroud - This is a simulation made from an mosaic of nine Titan surface images produced by JPL and images that show different layers in the atmosphere. It shows the solid globe and its features in its proper place within the thick atmosphere. The nine were taken on October 26, 2004 hours before closest approach to produce the mosaic, which can be downloaded here at the NASA Photojournal site. The filter used was the 938 nm CB3 filter in the infrared, which I colored red in this composite. This color of light can reach and reflect off the surface, while most other colors cannot. To illustrate the atmosphere I used two images from October 23, when the cameras were able to image the entire moon at once. A 889 nm infrared image was colored green, and shows methane, and a 343 nm UV image was colored blue, which shows upper atmospheric hazes. The dark features are still unexplained, but may be wind-driven liquids or particles streaked across plains and/or or backed up on topographic features. |
 | | Minutes Past Totality - This spectacular true color image was made from images taken with the Wide Angle Camera hours after Cassini had passed Titan on October 26, 2004, and munutes after emerging from the shadow of Titan. Looking back at the moon, we see sunlight scattered back through the atmosphere. We are essentially looking at sunset from thousands of miles away. This is also similar to what one would see looking at Earth from the Moon during a lunar eclipse, when the Moon is in Earth's shadow. A similar image prroduced at JPL shows a composition made fromt he same three images, plus another taken from the sunlet side showing the same layers of haze in the upper atmosphere. That picture can be seen here at the Planetary Photojournal site. |
 | | The Dark Side of the Rings - This view of the rings was imaged on October 27, 2004, after Cassini's had passed Titan and crossed the ring plane, so that now it looks south onto rings illuminated from below. (It is summer in the southern hemisphere of Saturn, so the light comes from the south, or "below" the planet in this point of view.) The large dark band in the middle of the rings is the outer B Ring, which is so thick that it simply blocks the sunlight and appears dark. The inner B Ring and outer C Ring closer to the planet are transparent enough for light to pass through. The bright band outside the B Ring is the Cassini Division, which is filled with tiny particles that scatter light in all directions very well, so they are bright while the rest of the rings are dark. The larger of the moons visible should be Mimas, but I'm not sure. |
 | | Tethys in Color - This image was produced from images taken on October 28, 2004, near Cassini's closest approach to Tethys. The colors are produced by using red, green, and blue images, but the balance is done to match those done with Voyager images in 1980 and 1981. There isn't much color in any case. Any apparent variations across the disk except the slight yellowing of the mid-section of the moon is an artifact of processing. |
 | | Tethys in Compressed Color - This image was produced from images taken on October 28, 2004, near Cassini's closest approach to Tethys. "Compressed color" means that I assigned the 343 nm mear UV filter to blue, green to green, and the 727 nm near IR filter to red, thus a wide range of color is compressed into a narrow range. Now color variation shows up which is real. The reddish patch near lower left of the disk may be an artifact of the CCD that took the images. |
 | | Is Tethys Polarized in IR? - This image was produced from images taken on October 28, 2004, near Cassini's closest approach to Tethys. The colors are made by combining light from three polarization filters, assigning one to red, green, and blue. All of the light was also passed through the 727 nm near infrared filter. The filters themselves do not add color, but if Tethys reflected light with one polarization better than the others, then that color would be enhanced and tint the moon. There is no such color. Tethys appears grey. Therefore it does not polarize 727 nm light. This can be used to de like Iapetustermine facts about the grains of ice on the surface. |
 | | Prometheus Bound - This picture is a mosaic of four images taken on October 29, 2004. It shows the satellite Prometheus connected to the F Ring by a tendril of ring particles. Prometheus is inducing some kinkiness in the F Ring. Interior to Prometheus is the Encke Gap within which are two rings. The main ring is kinked and knotted, possibly by some interaction with Prometheus, though their appearance together may be a coincidence. The "Kinky Encke" ring was one of the original great mysteries of the Voyager I encounter, made more mysterious when Voyager II seemingly failed to see kinks in this ring. Solving this and other mysteries involved understanding interactions of the rings, the larger moons of Saturn, and "shepherd moons" like Prometheus. (In Nobember 1980 a humorous JPL scientist drew a picture of Darth Vader in a spaceship with claws, using the claws to twist the F Ring. The spaceship was stuck to the ring just like Prometheus. One of these days I'll find that picture and it will go here.) The image also thows a common feature of many objects in orbit. Prometheus is lined up so its long axis points toward Saturn. This is the minimum energy configuration (one heavy end points down to where gravity is stronger, the other to where the "centrifugal force" is stronger.) |
 | | C Ring(s) in Color - This true-color picture from October 29, 2004 shows part of the C Ring, a more or less tenuous collection of ringlets near the inside of the ring system. Distinct colors actually show up here, a result of the fact that material is less mixed in this region. Mixing between ringlets is prevented by the presence of gaps, which in turn are caused by the gravitational influence of satellites. (The green streaks near the bottom right are strips where data was incomplete due to a software-imposed bandwidth-saving limit on how much data will be returned for any one strip in an image.) |
 | | A Ring(s) in Color - This and the next two images are all from the same series taken on October 29, 2004, of the A Ring, the outermost of the Saturn Rings visible from Earth. The A Ring is composed of many ringlets arranged in three sections. The Cassini Division (out of frame below the "bottom" of these pictures) is the inner boundary of the three. Two gaps divide the A Ring into its parts. The Encke Division is one, and is the large one here in the middle of the frame. The outer division is called the Keeler Gap, which is the tiny dark division. Outside the Keeler Gap the Ring is brighter. |
 | | A Ring(s) in Stretched Color - This image is the same as the previous, but with the colors stretched by the Photoshop saturation function. It shows slight variations in color more obviously. The colored boundaries of the bright areas are an artifact of the composition process. The greenish color of the ringlets inside the Encke Division may be as well. The "rainbow" like effect at the edge of the Encke Division and in the rings below that is not real, but it is caused by a real process at Saturn. There is a wavelike ripple in the inner boundary of the Encke Division that has moved between the time the red, green, and blue color frames were taken. (Or the spacecraft moved relative to it) The colors do not line up there, so they appear in this image. A similar density wave must exist in the narrow band below the Division, which makes the other "rainbow" strip. |
 | | A Ring(s) in Compressed Color - Similarly to the second Tethys image above, this image is produced from an IR band at 827 nm, green (569 nm), and near UV (343 nm). No enhancement has been done. As with Tethys, the choice of these colors shows enhanced contrast. |
 | | Crescent Saturn - This picture is a mosaic of three images taken on October 30, 2004. The images were taken across quite a large span of time, probably several hours, so some distortion was involved in merging them. The individual images were not of high quality, but one side effect of that is the discrete contours that are visible on the dark side of the planet. The boundaries seen there are not real, but artifacts of there not being enough really dark shades in the original image. They can be considered "isophotes" or lines of equal brightness. In this case, what is illuminating the planet is the sun reflecting off the rings. The peculiar thing about it is that the brightest illumination is on a region of the planet where part of the rings that could be illuminating it are in shadow. In other words, something is going on other than just how much sunlit ring is in the sky. (The black square is a section for which there were no images taken.) |
 | | Mimas in Transit over Saturn - This true color image from November 7, 2004 shows the rings in front of Saturn, the ring shadows, and the moon Mimas. This was produced from three images taken in isolation in red, green, and blue, which makes me believe they were planned to catch this transit of Mimas. Composing the image took some work, since Mimas had moved considerably between the frames. It had to be composited separately and the individual colored Mimas images edited out of the Saturn picture. Then I put Mimas back along its line of transit, within the extremes of the three images, but at a place where it would look most aesthetically pleasing. In addition to being spectacular, the image allows the reconstruction of the true color of Mimas. Colors are balanced so Saturn is right, and this shows that Mimas is pale yellow, like the more yellow of Saturn's clouds. |
 | | Panorama of the Rings - This true color image from November 18, 2004 shows a portion of the rings. This particular mosaic was chosen purely for its artistic quality. We are looking at the south face of the rings illuminated from below and to the right in the frame. The moon below is probably Janus. |
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