nasa's cassini spacecraft

Saturnian Hexagon Collage. This collage of images from NASA Cassini spacecraft shows Saturn northern hemisphere and rings as viewed with four different spectral filters; each is sensitive to different wavelengths of light and reveals clouds and hazes at different altitudes.

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This view from NASA’s Cassini spacecraft showcases some of the amazingly detailed structure of Saturn’s rings.

The rings are made up of many smaller ringlets that blur together when seen from a distance. But when imaged up close, the rings’ structures display quite a bit of variation. Ring scientists are debating the nature of these features — whether they have always appeared this way or if their appearance has evolved over time.

This view looks toward the sunlit side of the rings from about 4 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 24, 2016.

The view was acquired at a distance of approximately 283,000 miles (456,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 32 degrees. Image scale is 17 miles (27 kilometers) per pixel.

Image Credit: NASA/JPL-Caltech/Space Science Institute/ Cassini

Time And Space

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NASA Saturn Mission Prepares for ‘Ring-Grazing Orbits’

First Phase in Dramatic Endgame for Long-Lived Cassini Spacecraft

A thrilling ride is about to begin for NASA’s Cassini spacecraft.

Engineers have been pumping up the spacecraft’s orbit around Saturn this year to increase its tilt with respect to the planet’s equator and rings.

And on Nov. 30, following a gravitational nudge from Saturn’s moon Titan, Cassini will enter the first phase of the mission’s dramatic endgame.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004 for an up-close study of the planet, its rings and moons. During its journey, Cassini has made numerous dramatic discoveries, including a global ocean within Enceladus and liquid methane seas on Titan.

Between Nov. 30 and April 22, Cassini will circle high over and under the poles of Saturn, diving every seven days – a total of 20 times – through the unexplored region at the outer edge of the main rings.

“We’re calling this phase of the mission Cassini’s Ring-Grazing Orbits, because we’ll be skimming past the outer edge of the rings,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. “In addition, we have two instruments that can sample particles and gases as we cross the ringplane, so in a sense Cassini is also 'grazing’ on the rings.”

On many of these passes, Cassini’s instruments will attempt to directly sample ring particles and molecules of faint gases that are found close to the rings. During the first two orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking the two small moons Janus and Epimetheus. Ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring.

“Even though we’re flying closer to the F ring than we ever have, we’ll still be more than 4,850 miles (7,800 kilometers) distant. There’s very little concern over dust hazard at that range,” said Earl Maize, Cassini project manager at JPL.

The F ring marks the outer boundary of the main ring system; Saturn has several other, much fainter rings that lie farther from the planet. The F ring is complex and constantly changing: Cassini images have shown structures like bright streamers, wispy filaments and dark channels that appear and develop over mere hours. The ring is also quite narrow – only about 500 miles (800 kilometers) wide. At its core is a denser region about 30 miles (50 kilometers) wide.

So Many Sights to See
Cassini’s ring-grazing orbits offer unprecedented opportunities to observe the menagerie of small moons that orbit in or near the edges of the rings, including best-ever looks at the moons Pandora, Atlas, Pan and Daphnis.

Grazing the edges of the rings also will provide some of the closest-ever studies of the outer portions of Saturn’s main rings (the A, B and F rings). Some of Cassini’s views will have a level of detail not seen since the spacecraft glided just above them during its arrival in 2004. The mission will begin imaging the rings in December along their entire width, resolving details smaller than 0.6 mile (1 kilometer) per pixel and building up Cassini’s highest-quality complete scan of the rings’ intricate structure.

The mission will continue investigating small-scale features in the A ring called “propellers,” which reveal the presence of unseen moonlets. Because of their airplane propeller-like shapes, scientists have given some of the more persistent features informal names inspired by famous aviators, including “Earhart.” Observing propellers at high resolution will likely reveal new details about their origin and structure.

And in March, while coasting through Saturn’s shadow, Cassini will observe the rings backlit by the sun, in the hope of catching clouds of dust ejected by meteor impacts.

Preparing for the Finale
During these orbits, Cassini will pass as close as about 56,000 miles (90,000 kilometers) above Saturn’s cloud tops. But even with all their exciting science, these orbits are merely a prelude to the planet-grazing passes that lie ahead. In April 2017, the spacecraft will begin its Grand Finale phase.

After nearly 20 years in space, the mission is drawing near its end because the spacecraft is running low on fuel. The Cassini team carefully designed the finale to conduct an extraordinary science investigation before sending the spacecraft into Saturn to protect its potentially habitable moons.

During its grand finale, Cassini will pass as close as 1,012 miles (1,628 kilometers) above the clouds as it dives repeatedly through the narrow gap between Saturn and its rings, before making its mission-ending plunge into the planet’s atmosphere on Sept. 15. But before the spacecraft can leap over the rings to begin its finale, some preparatory work remains.

To begin with, Cassini is scheduled to perform a brief burn of its main engine during the first super-close approach to the rings on Dec. 4. This maneuver is important for fine-tuning the orbit and setting the correct course to enable the remainder of the mission.

“This will be the 183rd and last currently planned firing of our main engine. Although we could still decide to use the engine again, the plan is to complete the remaining maneuvers using thrusters,” said Maize.

To further prepare, Cassini will observe Saturn’s atmosphere during the ring-grazing phase of the mission to more precisely determine how far it extends above the planet. Scientists have observed Saturn’s outermost atmosphere to expand and contract slightly with the seasons since Cassini’s arrival. Given this variability, the forthcoming data will be important for helping mission engineers determine how close they can safely fly the spacecraft.

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Saturn’s Moon Mimas on January 30, 2017

At the top is a rough composite of the two lower images taken by NASA’s Cassini spacecraft on 2017-01-30 and received on Earth 2017-02-01.

The bottom photo of Mimas and Pandora was taken earlier in the mission.

Having studied the Saturn system since 2004 the Cassini mission is now in its grand finale phase the highly productive mission will end this September (2017) with a dive into Saturn itself sparing the rings and moons from any accidental Earth-borne contamination after the craft exhausts the last of its fuel supply.

Image credits: NASA/composite by JN with Photoshop

Map of Jupiter’s South

This map of Jupiter is the most detailed global color map of the planet ever produced. The round map is a polar stereographic projection that shows the south pole in the center of the map and the equator at the edge. It was constructed from images taken by Cassini on Dec. 11 and 12, 2000, as the spacecraft neared Jupiter during a flyby on its way to Saturn.

The map shows a variety of colorful cloud features, including parallel reddish-brown and white bands, the Great Red Spot, multi-lobed chaotic regions, white ovals and many small vortices. Many clouds appear in streaks and waves due to continual stretching and folding by Jupiter’s winds and turbulence. The bluish-gray features along the north edge of the central bright band are equatorial “hot spots,” meteorological systems such as the one entered by NASA’s Galileo probe. Small bright spots within the orange band north of the equator are lightning-bearing thunderstorms. The polar region shown here is less clearly visible because Cassini viewed it at an angle and through thicker atmospheric haze.

Image Credit: NASA/JPL/Space Science Institute

Infrared Saturn Clouds : This false-color view from NASAs Cassini spacecraft shows clouds in Saturns northern hemisphere. The view was made using images taken by Cassinis wide-angle camera on July 20, 2016, using a combination of spectral filters sensitive to infrared light at 750, 727 and 619 nanometers.

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Titan Touchdown

On Jan. 14, 2005, ESA’s Huygens probe made its descent to the surface of Saturn’s hazy moon, Titan. Carried to Saturn by NASA’s Cassini spacecraft, Huygens made the most distant landing ever on another world, and the only landing on a body in the outer solar system. This video uses actual images taken by the probe during its two-and-a-half hour fall under its parachutes.

It may look as though Saturn’s moon Mimas is crashing through the rings in this image taken by NASA’s Cassini spacecraft, but Mimas is actually 28,000 miles (45,000 kilometers) away from the rings. There is a strong connection between the icy moon and Saturn’s rings, though. Gravity links them together and shapes the way they both move.

  Credit: NASA/JPL-Caltech/Space Science Institute

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An Ice World…With an Ocean?

How a puzzling sensor reading transformed NASA’s Cassini Saturn mission and created a new target in the search for habitable worlds beyond Earth.

On Feb. 17, 2005, NASA’s Cassini spacecraft was making the first-ever close pass over Saturn’s moon Enceladus as it worked through its detailed survey of the planet’s icy satellites. Exciting, to be sure, just for the thrill of exploration. But then Cassini’s magnetometer instrument noticed something odd.

Since NASA’s two Voyager spacecraft made their distant flybys of Enceladus about 20 years prior, scientists had anticipated the little moon would be an interesting place to visit with Cassini. Enceladus is bright white – the most reflective object in the solar system, in fact – and it orbits in the middle of a faint ring of dust-sized ice particles known as Saturn’s E ring. Scientists speculated ice dust was being kicked off its surface somehow. But they presumed it would be, essentially, a dead, airless ball of ice.

What Cassini saw didn’t look like a frozen, airless body. Instead, it looked something like a comet that was actively emitting gas. The magnetometer detected that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world. Could it be that the moon was actively replenishing gases it was breathing into space?

Thus began a hunt for clues that has turned out to be Cassini’s most riveting detective story. “Enceladus was so exciting that, instead of just three close flybys planned for our four-year primary mission, we added 20 more, including seven that went right through the geysers at the south pole,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

By following the trail of scientific breadcrumbs, Cassini eventually found that Enceladus harbors a global ocean of salty water under its icy crust, possibly with hydrothermal vents on its seafloor. The trail of clues that began with a puzzling magnetometer reading led to an understanding that the moon – and perhaps many small, icy moons like it throughout the cosmos – could potentially have the ingredients needed for life.

“Half the excitement of doing science is that you sometimes find yourself going in a totally different direction than you expected, which can lead to amazing discoveries,” said Spilker. “That little anomaly in Cassini’s magnetometer signal was unusual enough that it eventually led us to an ocean world.”

Launched in 1997, the Cassini mission is currently in its final year of operations, performing weekly ring-grazing dives just past the outer edge of Saturn’s rings. In April, the spacecraft will begin its Grand Finale, plunging through the gap between the rings and the planet itself, leading up to a final plunge into Saturn on September 15.

Cassini has been touring the Saturn system since arriving in 2004 for an up-close study of the planet, its rings and moons, and its vast magnetosphere. Cassini has made numerous dramatic discoveries, besides the activity at Enceladus, including liquid methane seas on another moon, Titan.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the mission for NASA’s Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

TOP IMAGE….Dramatic plumes, both large and small, spray water ice out from many locations along the famed “tiger stripes” near the south pole of Saturn’s moon Enceladus. The tiger stripes are fissures that spray icy particles, water vapor and organic compounds. More than 30 individual jets of different sizes can be seen in this image and more than 20 of them had not been identified before. At least one jet spouting prominently in previous images now appears less powerful.
This mosaic was created from two high-resolution images that were captured by the narrow-angle camera when NASA’s Cassini spacecraft flew past Enceladus and through the jets on Nov. 21, 2009. Imaging the jets over time will allow Cassini scientists to study the consistency of their activity. The south pole of the moon lies near the limb in the top left quadrant of the mosaic, near the large jet that is second from left. Lit terrain seen here is on the leading hemisphere of Enceladus (504 kilometers, 313 miles across).
Cassini scientists continue to study the question of whether reservoirs of liquid water exist beneath the surface of the moon. The view was obtained at a distance of approximately 14,000 kilometers (9,000 miles) from Enceladus and at a sun-Enceladus-spacecraft, or phase, angle of 145 degrees. Image scale is 81 meters (267 feet) per pixel.


LOWER IMAGE….This artist concept shows the detection of a dynamic atmosphere on Saturn’s icy moon Enceladus. The Cassini magnetometer instrument is designed to measure the magnitude and direction of the magnetic fields of Saturn and its moons. During Cassini’s three close flybys of Enceladus – Feb. 17, March 9 and July 14, 2005–the instrument detected a bending of the magnetic field around Enceladus due to electric currents generated by the interaction of atmospheric particles and the magnetosphere of Saturn.

The graphic shows the magnetic field observed by Cassini, as well as the predicted neutral cloud being vented from the south pole. Cassini’s magnetometer observed bending of the magnetic field consistent with its draping around a conducting object. That indicates that the Saturnian plasma is being diverted away from an extended atmosphere.

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 magnetometer team is based at Imperial College in London, working with team members from the United States and several European countries.