Tag: Cassini

Cool image time! The image on the right, cropped and reduced to show here, captures the same propeller feature in Saturn’s A ring, with the top image showing the sunlight side and the bottom image the side away from the Sun.

Cassini scientists have been tracking the orbit of this object for the past decade, tracing the effect that the ring has upon it. Now, as Cassini has moved in close to the ring as part of its ring-grazing orbits, it was able to obtain this extreme close-up view of the propeller, enabling researchers to examine its effects on the ring. These views, and others like them, will inform models and studies in new ways going forward.

…The propeller’s central moonlet would only be a couple of pixels across in these images, and may not actually be resolved here. The lit-side image shows that a bright, narrow band of material connects the moonlet directly to the larger ring, in agreement with dynamical models. That same thin band of material may also be obscuring the moonlet from view.

Lengthwise along the propeller is a gap in the ring that the moonlet has pried open. The gap appears dark on both the lit and unlit sides. Flanking the gap near the moonlet are regions of enhanced density, which appear bright on the lit side and more mottled on the unlit side.

The scale of the two images is slightly different, 0.33 and 0.44 miles, as they were taken as Cassini was zipping past during one of its ring-grazing orbits on February 21.

To my eye, the effect here faintly resembles a wake produced by a boat in water, except that the wake moves in opposite directions on opposite sides of the tiny moonlet as it plows through the A ring.

Cool image time! The photo at the right, reduced to show here, was taken by Cassini on October 28, 2016 as it was shifting its orbit to prepare for the spacecraft’s last year at Saturn, where it will make repeated dives down past and even inside the gas giant’s rings. As they note at the link,

No Earth-based telescope could ever capture a view quite like this. Earth-based views can only show Saturn’s daylit side, from within about 25 degrees of Saturn’s equatorial plane. A spacecraft in orbit, like Cassini, can capture stunning scenes that would be impossible from our home planet.

It is interesting to compare this image with this July image. Comparing the two provides a sense of Cassini’s travels.

Cool image time! And this is only the start. The Cassini science team has released the first images taken by Cassini during its first of 42 close flybys of the rings of Saturn. The image on the right, cropped from the full image, shows Saturn’s north polar vortex. The storm at the polar really does look like a whirlpool that is descending down into the gas giant’s depth.

I must emphasize that photography was not the focus of this first flyby. These images were taken the two days before the flyby on December 4. Later flybys are going to produce far better images, as they will be taking pictures throughout.

Cassini has begun its last year at Saturn, making its first close fly-by of the gas giant’s rings yesterday.

Cassini’s imaging cameras obtained views of Saturn about two days before crossing through the ring plane, but not near the time of closest approach. The focus of this first close pass was the engine maneuver and observations by Cassini’s other science instruments. Future dives past the rings will feature some of the mission’s best views of the outer regions of the rings and small, nearby moons.

Each of Cassini’s orbits for the remainder of the mission will last one week. The next pass by the rings’ outer edges is planned for Dec. 11. The ring-grazing orbits — 20 in all — will continue until April 22, when the last close flyby of Saturn’s moon Titan will reshape Cassini’s flight path. With that encounter, Cassini will leap over the rings, making the first of 22 plunges through the 1,500-mile-wide (2,400-kilometer) gap between Saturn and its innermost ring on April 26.

On Sept. 15, the mission will conclude with a final plunge into Saturn’s atmosphere. During the plunge, Cassini will transmit data on the atmosphere’s composition until its signal is lost.

Now for a bit of reality: When Cassini’s mission ends on September 15, 2017, it will likely be a minimum of 20 years before another spacecraft returns.

Link here. The article does a nice job of outlining, with videos, what will happen as the spacecraft makes multiple dives inside rings.

Cassini’s final acts, which will play out over the next year. That pass placed Cassini in a high-inclination orbit tilted 60° relative to the ring plane. Cassini will perform 20 passes just 620 miles (1000 kilometers) outside the F ring of Saturn in a phase known as the Ring-Grazing Orbits, which runs from late November 2016 through April 2017.

Cassini already reached apoapse, or its farthest point from Saturn, on Wednesday, November 30th. The first ring crossing is coming right up this weekend on Sunday, December 4th, at 7:09 a.m. EST / 13:09 UT. During the first periapse pass on Sunday, Cassini will also burn its main engine for the 183rd and final time for the mission. All later fine course corrections will be made using thrusters only.

Things get even more interesting after April, when the series of Grand Finale Orbits will begin, taking the spacecraft through the 1240-mile-wide (2000-kilometer-wide) gap between the planet’s cloud tops and rings for 22 final orbits. The Grand Finale Orbits start with the spacecraft’s 126th and final pass near Titan, which will set the spacecraft up for much tighter final orbits.

Cool image time! The image on the right, reduced in resolution to show here, shows Saturn from above as Cassini began re-positioning itself into a higher inclination orbit for its last year of orbit dives near and inside the planet’s rings.

The view looks toward the sunlit side of the rings from about 41 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on July 16, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 1 million miles (2 million kilometers) from Saturn. Image scale is 68 miles (110 kilometers) per pixel.

A comparison of images taken by Cassini in 2012 and then in 2016 of Saturn’s north polar region shows a significant change in color.

Scientists are investigating potential causes for the change in color of the region inside the north-polar hexagon on Saturn. The color change is thought to be an effect of Saturn’s seasons. In particular, the change from a bluish color to a more golden hue may be due to the increased production of photochemical hazes in the atmosphere as the north pole approaches summer solstice in May 2017.

Cool image time! The image on the right, reduced to fit here, is a recent Cassini image, taken July 2, 2016, that shows the rings as well as the moon Pan nestled within the ring’s narrow gap

Pan (17 miles or 28 kilometers across, left of center) holds open the Encke gap and shapes the ever-changing ringlets within the gap (some of which can be seen here). In addition to raising waves in the A and B rings, other moons help shape the F ring, the outer edge of the A ring and open the Keeler gap. This view looks toward the sunlit side of the rings from about 8 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 2, 2016.

The image also highlights the incredible and quite magical beauty of Saturn’s rings, which remain to me one of the solar system’s most amazing wonders.

Cool image time. The Cassini science team have released a beautiful full-color image of Saturn, shown cropped on the right, as well as a movie, both produced from images taken in April.

This view shows Saturn’s northern hemisphere in 2016, as that part of the planet nears its northern hemisphere summer solstice in May 2017. Saturn’s year is nearly 30 Earth years long, and during its long time there, Cassini has observed winter and spring in the north, and summer and fall in the south. The spacecraft will complete its mission just after northern summer solstice, having observed long-term changes in the planet’s winds, temperatures, clouds and chemistry.

Cassini scanned across the planet and its rings on April 25, 2016, capturing three sets of red, green and blue images to cover this entire scene showing the planet and the main rings. The images were obtained using Cassini’s wide-angle camera at a distance of approximately 1.9 million miles (3 million kilometers) from Saturn and at an elevation of about 30 degrees above the ring plane. The view looks toward the sunlit side of the rings from a sun-Saturn-spacecraft angle, or phase angle, of 55 degrees. Image scale on Saturn is about 111 miles (178 kilometers) per pixel.

The exposures used to make this mosaic were obtained just prior to the beginning of a 44-hour movie sequence.

The only real tragedy here is that the Cassini mission is ending soon. When it does, it will be decades, at a minimum, before we have another spacecraft in orbit around Saturn and capable of giving us this view.

Update: NASA today issued a press release detailing what will happen during Cassini’s final year at Saturn, including 22 plunges between Saturn and its rings!

Cool image time! The image to the right (reduced in resolution to show here) was posted today on the Cassini gallery page. The release focused on the bright spot in the widest ring just above the center of the image.

An ethereal, glowing spot appears on Saturn’s B ring in this view from NASA’s Cassini spacecraft. There is nothing particular about that place in the rings that produces the glowing effect — instead, it is an example of an “opposition surge” making that area on the rings appear extra bright. An opposition surge occurs when the Sun is directly behind the observer looking toward the rings. The particular geometry of this observation makes the point in the rings appear much, much brighter than would otherwise be expected.

I however am more interested in the black outline at Saturn’s limb that visually separates the planet from the rings. Is that natural or introduced intentionally in data processing to make the image more pleasing? If it is natural than I wonder how Saturn’s top cloud layer could produce such an opaque and sharply defined region able to so successfully block the light coming from the rings. If introduced intentionally I question the wisdom, as I can’t see any reason to do it and therefore am worried that they might have done some other unnecessary manipulation that makes it difficult to draw any honest conclusions from the image.

Either way, from an aesthetic perspective the image still remains breath-taking. It also underlines once again the amazing engineering that made it possible. All things remain possible, if we maintain our ability to build this kind of engineering.

Cool image time! The picture on right, cropped by me to show here, was taken by Cassini on April 2, 2016. You can see the moons Dione (on left) and Epimetheus (on right) above the rings. The full image can be seen here.

I am sure there is a lot of important science contained within this image. I post it here however not because of any scientific reason but entirely because it is simply damn spectacular. More than a decade after Cassini arrived at Saturn, every new picture of the planet’s giant ring system still seems incredibly unbelievable.

The universe is an amazing place, isn’t it?

Cool image time! The image on the right, reduced in resolution to post here, shows how, because of the seasonal tilt of Saturn, the shadow of its rings is now cover much of the gas giant’s southern hemisphere.

When NASA’s Cassini spacecraft arrived at Saturn 12 years ago, the shadows of the rings lay far to the north on the planet. As the mission progressed and seasons turned on the slow-orbiting giant, equinox arrived and the shadows of the rings became a thin line at the equator. This view looks toward the sunlit side of the rings from about 16 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on March 19, 2016.

We will continue to get from Cassini increasingly beautiful images of Saturn and its rings as the spacecraft positions itself better for its final flight down into the planet’s atmosphere.

Cool image time! The picture below, taken by Cassini in April, looks down at Saturn’s vast rings and shows a disruption in Saturn’s outermost F ring, likely caused by an interaction of objects within the ring.

Cool image time! Be sure to click on this link to see the full resolution Cassini version of the image on the right. Its resolution is 10 miles per pixel, and even so the giant planet cannot be fit in the frame.

One moon, Tethys, is visible, though to make it so required its brightness to be increased by 2. Also, if you look close at the bands at the north pole you can see their strange still-not-understood pentagon shape.