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."

The summaries posted on this page for each ring-grazing orbit include only a few highlights of the many unparalleled science investigations that Cassini performs during these ambitious orbits.

Ring-Grazing Orbits Countdown

Final Ring-Grazing Orbit

Current Orbit: 270

This is Cassini's final ring-grazing orbit. The next - and final - phase of the mission is called the Grand Finale.

  • During this orbit, Cassini’s visible light camera, the Imaging Science Subsystem (ISS), collects a series of images of Saturn’s C ring.
  • Just as with five previous orbits, the spacecraft’s Ion and Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA) sample gases and particles near the plane of Saturn’s rings.
  • The ISS instrument also observes some ring propellers.
  • Cassini will pass within 5,100 miles (8,200 kilometers) of Saturn’s F ring during this orbit.
  • T-126 Titan Flyby: This orbit also includes the final close flyby of Saturn’s largest moon Titan, whose gravity Cassini has used for nearly all of the spacecraft’s major trajectory changes. Cassini will pass within about 600 miles (about 1,000 kilometers) of the Mercury-sized moon on Saturday, April 22. Closest approach to Titan occurs at 3:26 a.m. Eastern time. The spacecraft will use Titan’s gravity as a pivot point to change the shape of Cassini’s orbit in a fateful way -- from this point forward, the spacecraft's orbit will eventually impact Saturn, even if controllers on Earth take no further action. The flyby alters Cassini's orbit so that, instead of flying just outside of the rings, the spacecraft will shoot through the narrow space between Saturn’s upper atmosphere and its innermost rings. The spacecraft will repeat that dive once per week until the end of the mission in September. The Titan flyby marks the end of Cassini’s Ring-Grazing Orbits, and sets the stage for the mission’s Grand Finale to begin.

For the complete list of F Ring orbits, visit our Ring-Grazing Orbits Quick Reference.


Ring-Grazing Orbit Summaries

Orbit 251

On Cassini’s first Ring-Grazing dive past Saturn's F ring, the spacecraft’s Radio Science instrument transmits a radio signal to Earth through Saturn’s rings in a uniquely long sweep. Cassini will also study Saturn's northern hemisphere and atmosphere. Cassini’s Visual and Infrared Mapping Spectrometer will make a nine-hour movie of Saturn's north pole, and several instruments will measure the boundaries of Saturn's upper atmosphere, a critical observation because future orbits will take Cassini down into the atmosphere for direct sampling. This orbit also features observations of Enceladus' active south pole and search the moon Tethys for more observations of its mysterious red-striped regions.

Orbit 252

On this ring-grazing orbit, Cassini will cross Saturn’s ring plane within 6,867 miles (11,051 kilometers) of Saturn’s F ring.

To calibrate Cassini’s magnetometer for later, the spacecraft will roll for part of its second ring-grazing orbit. The sun will be between Earth and Saturn in what’s called a conjunction, during which the sun’s solar wind/plasma interferes with normal radio communications and radio science experiments. Cassini will take advantage of the alignment by using its radio science instrument to study that interference for the benefit of future missions.

Cassini will also practice for its Grand Finale Orbits, in which the spacecraft passes in the unexplored narrow space between the planet and its rings. Inward and outward from Saturn’s dense, visible rings, a less-dense population of hard-to-see particles reside in the ring plane and can pose a hazard to the spacecraft. To minimize the hazard from ring particles, the spacecraft will orient its high-gain antenna toward the direction the spacecraft is traveling (called RAM position) like a snow plow. Only a few of Cassini’s instruments extend beyond the diameter of the spacecraft’s high-gain antenna. So during the first Grand Finale Orbit, the dish will serve as a shield when Cassini punctures Saturn’s ring plane at thousands of miles per hour. As a result, most instruments should be relatively safe from ring particles.

Cassini will practice that positioning during its ring-plane crossing on Rev 252. As part of the exercise, the spacecraft’s Radio and Plasma Wave Science instrument will “listen” to particle collisions, and the Cosmic Dust Analyzer will scoop up and analyze particles. Scientists will use data from the two instruments during this pass to calibrate them for the first ring-plane crossing of Cassini’s Grand Finale Orbits, which will happen during Rev 271.

Orbit 253

In this orbit, Cassini’s imaging camera will get its best views yet of Saturn’s moon Pandora, including the first views of the moon’s northern hemisphere. The camera will also take some of the highest-resolution images yet of Saturn’s A ring, and will try to capture ring features known as propellers, straw, spiral waves, and ringlets. Elsewhere in the same orbit, multiple imaging instruments will observe Saturn’s largest moon Titan. Together they will track cloud motion and evolution, compare the moon’s surface to how it looked three years earlier, and fill missing parts of Cassini’s surface and temperature maps of Titan.

Also during this orbit, Cassini will pass within 6,157 miles (9,909 kilometers) of Saturn’s F ring when the spacecraft crosses the ring plane.

Orbit 254

When Cassini makes the nearer of this orbit’s two ring-plane crossings, the spacecraft will be within 6,093 miles (9,806 kilometers) of Saturn’s F ring. And for the first time, Cassini’s Cosmic Dust Analyzer will scoop and analyze particles in the outer layers of Saturn’s F ring during this ring-grazing orbit.

The spacecraft’s Ultraviolet Imaging Spectrometer (UVIS) will image the upper layers of Saturn’s atmosphere to help the mission team plan for Cassini’s Grand Finale Orbits, in which the spacecraft zips through the unexplored region between Saturn’s rings and atmosphere. Because gases expand when their temperatures increase and shrink when they cool, Saturn’s atmosphere swells and shrinks as its temperature changes. If the atmosphere cools and shrinks too much for Cassini’s Grand Finale Orbits, the spacecraft won’t be low enough to sample atmospheric gases as thoroughly as scientists would prefer. If the atmosphere heats and swells too much, Cassini will travel through thicker atmosphere than planned, altering its trajectory and potentially affecting the mission. That’s why the UVIS instrument is keeping an eye on Saturn’s atmosphere.

Also during this orbit, Cassini’s Composite Infrared Spectrometer has another look at the south polar region of Enceladus where water jets blast into space. Scientists will compare the observations with previous ones to understand how temperatures there change over time.

Orbit 255

During this ring-grazing orbit the spacecraft’s visible light camera called the (Imaging Science Subsystem [ISS]) will capture high-resolution images of Saturn’s B and C rings during the earlier part of the orbit, and of Saturn’s F and A rings during the latter part of the orbit. If all goes well, the images will be of exceptionally high resolution.

When the spacecraft approaches Saturn’s ring plane, Cassini will use its radar instrument in a way it never has before. The instrument will “ping” the rings Jan. 1 (Happy new year!) with radar signals for the first time and listen for the echo. The experiment will produce maps of the A ring at higher resolution than ever before, potentially providing new insights about the structure of ring particles.

When Cassini crosses Saturn’s ring plane on this orbit, it will do so with its high-gain antenna dish facing the direction the spacecraft is traveling (known as “RAM” position) as it did in Rev 252, and Cassini’s Cosmic Dust Analyzer and Radio and Plasma Wave Science instruments will again study the region immediately around the spacecraft. Cassini’s trajectory will put it within 5,956 miles (9,585 kilometers) from the center of Saturn’s F ring during one of the two ring-plane crossing at closest approach to Saturn on this orbit.

Orbit 256

In this, Cassini’s fifth ring-grazing orbit, the spacecraft’s Ultraviolet Imaging Spectrograph (UVIS), as well as its visible light camera called the Imaging Science Subsystem (ISS) will stare at Saturn’s south pole to capture images of the planet's southern aurora (which scientists have found is purple in color) from a closer vantage point than ever before.

Cassini’s ISS cameras will also capture high-resolution color images of Saturn’s B ring and C ring to better understand ring regions that are known to vary in color.

The spacecraft’s trajectory will put it within 5,878 miles (9,460 kilometers) of Saturn’s F ring during this orbit’s ring-plane crossing close to Saturn, during which Cassini’s Ion and Neutral Mass Spectrometer (INMS) will sample the faint atmosphere of gas that gently hugs the rings.

Orbit 257

Cassini’s Visible and Infrared Mapping Spectrometer (VIMS) will make images and maps of Saturn’s north pole on this ring-grazing orbit. The Composite Infrared Spectrometer (CIRS) will then spend six hours looking edge-on through Saturn’s atmosphere to study the layers and temperatures of the upper atmosphere for the first time.

Cassini will also spend 2.5 hours enjoying its best-ever view of Saturn’s moon Daphnis. Discovered by the Cassini team in 2005, Daphnis is a bit smaller than 5 miles (8 kilometers) in diameter and completes an orbit of Saturn once every 14 hours or so. The tiny moon travels within the Keeler Gap in Saturn’s A ring. Despite its small size, Daphnis’s gravitational influence produces waves in the edges of the gap -- not only withing the ring plane but also above and below, producing spectacular shapes. Cassini’s instruments will study the reflectivity and composition of the little wave-making moon, and scientists hope the observations will help them better understand not only the origin of Daphnis, but of other small moons and of Saturn’s rings as well.

Cassini’s trajectory will put it within 5,912 miles (9,515 kilometers) of Saturn’s F ring during this orbit’s close ring-plane crossing. 

Orbit 258

During this ring-grazing orbit, multiple instruments on the spacecraft will study Saturn’s poles to observe Saturn’s auroras. Cassini’s Cosmic Dust Analyzer (CDA) and Ion and Neutral Mass Spectrometer (INMS) will again sample ring particles and gases in the outer reaches of Saturn’s F ring. The spacecraft’s Magnetospheric Imaging Instrument (MIMI), the first instrument designed to create an image of a planet’s magnetosphere, will also make several observations of the F ring. Like a few previous Revs, Cassini will perform several hours of rolls to continue calibrating its magnetometer (MAG), and the spacecraft will pass within 6,000 miles (about 10,000 kilometers) of the F ring.

Orbit 259

In Cassini’s ninth ring-grazing orbit, the spacecraft will take a good look at a few of Saturn’s many moons, including a new look at one of the most puzzling.

After capturing some images of Enceladus and Tethys with its visible light camera (the Imaging Science Subsystem [ISS]), the spacecraft will spend several hours of this orbit studying Saturn’s northern aurora using its Ultraviolet Imaging Spectrograph (UVIS). Then the focus will turn primarily back toward Saturn’s moons.

Cassini’s will make a close study of Tethys using the ISS instrument. Scientists were perplexed when Cassini observed red streaks across the surface of Tethys in 2015. One might expect the strange streaks to be located with surface features, like fractures or valleys, but they aren't. The streaks run over mountains and down into valleys and craters. So the red streaks on Tethys remain a mystery, and scientists hope this observation will help solve it.

The spacecraft will also spend part of this orbit taking its last, and perhaps best, look at the potato-shaped moon Epimetheus using its ISS cameras. When nearest, Cassini will be only about 3,600 miles (5,800 kilometers) from the little moon, which measures less than 85 miles (135 kilometers) wide.

The ISS instrument will also observe Saturn’s moon Mimas, and Cassini’s Composite Infrared Spectrometer (CIRS) will make the fourth in a series of temperature observations of the southernmost region of the moon Enceladus, which sprays water ice into space and produces Saturn’s E ring.

Cassini should pass within about 6,000 miles (about 10,000 kilometers) of Saturn’s F ring during this orbit.

Orbit 260

During Cassini’s tenth ring-grazing orbit,  which marks the halfway point in this phase of the mission, the spacecraft’s radar instrument will perform two observations of Saturn’s rings. For nearly two hours, when Cassini is in the segment of its orbit in which it is nearest Saturn, the radar will bounce signals off Saturn’s rings like a flash camera, but using radio wavelengths instead of visible light wavelengths. Radar scientists will use data from the observation to produce the first high-resolution radar image of the rings.

Three hours later, the radar will again observe the rings, this time for about three hours and in a passive mode, meaning the instrument will only look, rather than transmitting radio signals, like taking pictures with the flash off. The observation might reveal information about the non-icy material in Saturn’s rings.

Around the end of Cassini’s science observations for this orbit, the spacecraft’s Imaging Science Subsystem (ISS) will attempt to capture images of ring features known as propellers. Scientists hope the images will help them better understand the quickly-changing orbits of the objects that produce the propellers, i.e., moonlets too small for Cassini's cameras to resolve.

Cassini should pass within 6,800 miles (about 11,000 kilometers) of Saturn’s F ring during this orbit. 

Orbit 261

In this ring-grazing orbit, the Imaging Science Subsystem (ISS), along with Cassini’s Ultraviolet Imaging Spectrograph (UVIS) and Visible and Infrared Mapping Spectrometer (VIMS), will study the structure and composition of Saturn’s upper atmosphere, including how hydrocarbons are distributed vertically. The VIMS instrument will also produce a mosaic map of Saturn’s north pole by staring at the northern hemisphere for 10 hours.

The spacecraft’s Cosmic Dust Analyzer will sample and analyze particles in the outer regions of Saturn’s F-ring as it did during Rev 254, and the Composite Infrared Spectrometer (CIRS) will map temperatures in the hurricane-like vortex in Saturn’s south polar region.

Cassini should pass within 6,800 miles (about 11,000 kilometers) of Saturn’s F ring during this orbit.

Orbit 262

  • During this orbit, Cassini’s Ultraviolet Imaging Spectrograph (UVIS) performs a stellar occultation of Saturn’s rings using light from B-type star beta Crucis.
  • The Visible and Infrared Mapping Spectrometer (VIMS) performs a stellar occultation of the star VY Canis Majoris, using the spacecraft’s motion to scan across Saturn’s rings to study their composition.
  • Cassini’s visible light camera, the Imaging Science Subsystem (ISS), observes Saturn’s moon Epimetheus for about an hour.
  • The ISS also captures high-resolution images of a propeller structure called "Santos-Dumont" in Saturn’s rings in both sunlit and unlit conditions. (The larger propellers are informally named for famous aviators.) The image resolution should be better than 1 kilometer per pixel, revealing new details of propeller structure.
  • Cassini will pass within 5,400 miles (8,700 kilometers) of Saturn’s F ring during this orbit.

Orbit 263

Orbit 264

  • During this orbit, Cassini’s Ultraviolet Imaging Spectrograph (UVIS) collaborates with the spacecraft’s Visible and Infrared Mapping Spectrometer (VIMS) instrument to observe Saturn’s aurora around the north pole.
  • VIMS and the Composite Infrared Spectrometer (CIRS) work together to try to pin down Saturn’s ratio of hydrogen to helium. It’s the first of many such observations during the ring-grazing orbits.
  • CIRS then observes Saturn’s limb in high resolution to study the temperatures and distributions of hydrocarbons in the layered atmosphere.
  • Cassini’s visible light camera, the Imaging Science Subsystem (ISS), observes the ring propeller called "Earhart" at better resolution than 1 kilometer per pixel, revealing new details of propeller structure. (The larger propellers are informally named for famous aviators.)
  • While in Saturn's shadow, Cassini will look at the Saturn’s rings with the sun almost directly behind, in the hopes of catching clouds of impact ejecta dust due to meteors striking the rings.
  • ISS will also capture its best-ever images of Saturn’s moon Pan, which orbits within and maintains the rings’ Encke gap. Taken from a distance of around 15,500 miles (25,000 kilometers), the image should be about eight times better than the best previous image of Pan.
  • Cassini will pass within 5,000 miles (8,000 kilometers) of Saturn’s F ring during this orbit.

Orbit 265

Orbit 266

  • During this orbit, Cassini’s visible light camera, the Imaging Science Subsystem (ISS), observes the ring propeller Earhart at better resolution than 1 kilometer per pixel, with hopes to reveal new details of the propeller’s structure. (The larger propellers are informally named for famous aviators.)
  • The spacecraft’s Visible and Infrared Mapping Spectrometer (VIMS) stares at Saturn’s aurora at the south pole to make a 4-by-3-image mosaic.
  • The Cosmic Dust Analyzer (CDA) samples dust as the spacecraft passes through Saturn’s ring plane.
  • The ISS instrument takes distant images of Hyrrokkin, one of Saturn’s irregular moons.
  • Cassini will pass within 4,900 miles (7,900 kilometers) of Saturn’s F ring during this orbit.

Orbit 267

Orbit 268

  • During this orbit, Cassini’s Ion and Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA) sample gases and particles near the plane of Saturn’s rings. The spacecraft continues that work in Rev 270.
  • Cassini’s visible light camera, the Imaging Science Subsystem (ISS), will scan Saturn’s A and B rings to produce a mosaic of the unlit side of the rings with a resolution at about 0.6 mile (1 kilometer) per pixel or better.
  • The ISS instrument will also target and track some ring propellers to image them and better understand them.
  • The spacecraft’s Radio and Plasma Wave Science (RPWS) instrument will observe plasma waves near Saturn’s magnetic equator, and will record variations in ring-dust impacts upon the spacecraft.
  • Cassini will pass within 4,900 miles (7,900 kilometers) of Saturn’s F ring during this orbit. 

Orbit 269

  • During this orbit, Cassini’s visible light camera, the Imaging Science Subsystem (ISS), will collect images of Saturn’s C and B rings to better understand how the rings evolve.
  • The spacecraft’s Ultraviolet Imaging Spectrograph (UVIS) scans Saturn’s northern polar region to image Saturn’s aurora.
  • The ISS instrument leads a multi-instrument campaign to observe Saturn’s moon Atlas while the spacecraft is about 8,100 miles (13,000 kilometers) from the moon. Atlas is one of Saturn’s two flying-saucer-shaped moons (the other being Pan), and this is the closest view Cassini will get of the little moon in the entire mission.
  • The ISS instrument also observes the ring propeller named Bleriot at a resolution better than 0.6 miles (1 kilometer) per pixel, with the goal of revealing new details of propeller structure.
  • The spacecraft’s Radio and Plasma Wave Science (RPWS) instrument studies dust and plasma waves around the time Cassini is nearest to Saturn.
  • With the Sun safely behind Saturn, ISS the ISS instrument’s wide-angle camera will image the rings to produce a mosaic of the fainter components of the ring system.
  • Cassini will pass within 5,100 miles (8,200 kilometers) of Saturn’s F ring during this orbit.

Orbit 270

  • During this orbit, Cassini’s visible light camera, the Imaging Science Subsystem (ISS), collects a series of images of Saturn’s C ring.
  • Just as with five previous orbits, the spacecraft’s Ion and Neutral Mass Spectrometer (INMS) and Cosmic Dust Analyzer (CDA) sample gases and particles near the plane of Saturn’s rings.
  • The ISS instrument also observes some ring propellers.
  • Cassini will pass within 5,100 miles (8,200 kilometers) of Saturn’s F ring during this orbit.
  • T-126 Titan Flyby: This orbit also includes the final close flyby of Saturn’s largest moon Titan, whose gravity Cassini has used for nearly all of the spacecraft’s major trajectory changes. Cassini will pass within about 600 miles (about 1,000 kilometers) of the Mercury-sized moon on Saturday, April 22. Closest approach to Titan occurs at 3:26 a.m. Eastern time. The spacecraft will use Titan’s gravity as a pivot point to change the shape of Cassini’s orbit in a fateful way -- from this point forward, the spacecraft's orbit will eventually impact Saturn, even if controllers on Earth take no further action. The flyby alters Cassini's orbit so that, instead of flying just outside of the rings, the spacecraft will shoot through the narrow space between Saturn’s upper atmosphere and its innermost rings. The spacecraft will repeat that dive once per week until the end of the mission in September. The Titan flyby marks the end of Cassini’s Ring-Grazing Orbits, and sets the stage for the mission’s Grand Finale to begin.

For the complete list of F Ring orbits, visit our Ring-Grazing Orbits Quick Reference.