This image of Saturn's outer A ring features the small moon Daphnis and the waves it raises in the edges of the Keeler Gap. The image was taken by NASA's Cassini spacecraft on Sept. 13, 2017. It is among the last images Cassini sent back to Earth.

NASA’s Cassini mission will come to a spectacular close on September 15, 2017 after almost two decades in space since its launch in 1997.

This spectrogram and video show a changing pattern of radio waves from Saturn known as Saturn Kilometric Radiation, as detected by NASA's Cassini spacecraft.

Some key numbers from the Cassini-Huygens mission to Saturn.

About 200 people gathered on the mall at NASA's Jet Propulsion Laboratory, Pasadena, Calif., to wave at Saturn on July 19, 2013. At the time NASA's Cassini spacecraft had turned to take a picture of Earth from its perch in the Saturn system. The Cassini mission gave Earthlings advance notice of its picture, marking the first time people knew in advance that their picture was being taken from interplanetary distances. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington. Credit: NASA/JPL-Caltech

This graphic shows Cassini's final plunge toward Saturn from a side view. 

Clara, Sugar Plum Fairy, move aside. Saturn's moons give Tchaikovsky's classic ballet, "The Nutcracker," a graceful new spin in this video compiled from some 61 images taken by the Cassini spacecraft.

This short animation created by Cassini's mission planning team shows how a Titan flyby will be used to move the spacecraft's course from orbiting Cassini's outer ring (F ring) to an orbit that takes the spacecraft in the narrow gap between the innermost ring (D ring) and the giant planet's cloud tops. 

Keeping a close watch on the outer portion of Saturn's B ring, NASA's Cassini spacecraft records the complex inward and outward movement of the edge of the ring.

This computer-generated view shows the view from the perspective of the Cassini spacecraft as it dives between the rings and Saturn's cloud tops.

NASA's Cassini spacecraft discovered hydrogen in the plume of gas and icy particles spraying from Saturn's moon Enceladus. The discovery means the small, icy moon — which has a global ocean under its surface — has a source of chemical energy that could be useful for microbes, if any exist there.

Release of Probe

Jean-Pierre Lebreton

A set of eight stickers created from images taken by the Cassini spacecraft.  

As the solar wind flows from the sun, it creates a bubble in space known as the "heliosphere" around our solar system.

This illustrated timeline features milestones in the journey of NASA's Cassini spacecraft.

This graphic illustrates Cassini's trajectory, or flight path, during the final two phases of its mission. The view is toward Saturn as seen from Earth. The 20 Ring-Grazing Orbits are shown in gray; the 22 Grand Finale Orbits are shown in blue. The final partial orbit is colored orange.

This view of Saturn's A ring features a lone "propeller" -- one of many such features created by small moonlets embedded in the rings as they attempt, unsuccessfully, to open gaps in the ring material. 

Members of Cassini’s navigation team monitor the spacecraft’s radio signal on a display in the Spaceflight Operations Facility at NASA’s Jet Propulsion Laboratory. 

Artist's concept of Cassini orbiter diving between Saturn's inntermost rings and cloud tops.

The small moon Mimas passes in front of the larger moon Rhea, which is partly obscured by Saturn's rings, in this movie from NASA's Cassini spacecraft.

As NASA's Cassini spacecraft turned its imaging cameras to Earth, scientists, engineers and visitors at NASA's Jet Propulsion Laboratory, Pasadena, Calif., gathered to wave at our robotic photographer in the Saturn system on July 19, 2013. About 200 people gathered on JPL's mall area. The Cassini mission gave Earthlings advance notice of its picture, marking the first time people knew in advance that their picture was being taken from interplanetary distances. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate in Washington. Credit: NASA/JPL-Caltech

An artist's concept of what it might look like from the surface of Saturn's giant moon Titan. 

This false-color view from NASA's Cassini spacecraft gazes toward the rings beyond Saturn's sunlit horizon, where a thin haze can be seen along the limb.

This artist's concept shows the European Space Agency's Huygens probe descent sequence.