Dione and Cassini

Saturn’s icy moon Dione, with Saturn and its rings in the background, seen from NASA’s Cassini spacecraft August 17, 2015. Image Credit: NASA/JPL-Caltech/Space Science Institute

“This view from NASA’s Cassini spacecraft looks toward Saturn’s icy moon Dione, with giant Saturn and its rings in the background, just prior to the mission’s final close approach to the moon on August 17, 2015.

At lower right is the large, multi-ringed impact basin named Evander, which is about 220 miles (350 kilometers) wide. The canyons of Padua Chasma, features that form part of Dione’s bright, wispy terrain, reach into the darkness at left.

Imaging scientists combined nine visible light (clear spectral filter) images to create this mosaic view: eight from the narrow-angle camera and one from the wide-angle camera, which fills in an area at lower left. The scene is an orthographic projection centered on terrain at 0.2 degrees north latitude, 179 degrees west longitude on Dione. An orthographic view is most like the view seen by a distant observer looking through a telescope. North on Dione is up.

The view was acquired at distances ranging from approximately 106,000 miles (170,000 kilometers) to 39,000 miles (63,000 kilometers) from Dione and at a sun-Dione-spacecraft, or phase, angle of 35 degrees. Image scale is about 1,500 feet (450 meters) per pixel.” – excerpt from caption released with image.

Cassini’s Closest Views of Dione. Image Credit: NASA/JPL-Caltech/Space Science Institute

Terrain on Saturn’s moon Dione lit entirely by reflected light from Saturn – Saturnshine. Image Credit: NASA/JPL-Caltech/Space Science Institute

Oblique view of Dione’s rolling, cratered landscape, Image credit: NASA/JPL-Caltech/Space Science Institute

Dione hangs in front of Saturn’s rings. Image Credit: NASA/JPL-Caltech/Space Science Institute

Cassini’s parting view of Saturn’s moon Dione following the spacecraft’s final close flyby of the moon on Aug. 17, 2015. Image Credit: NASA/JPL-Caltech/Space Science Institute

I wondered what the orbit of the Cassini spacecraft would look like during the Dione encounter, so I fired up NASA’s Eyes on the Solar System (a free downloadable app) and set the app date to that of the encounter:

Cassini spacecraft orbit during Dione encounter, August 17, 2015. Image credit: NASA Eyes on the Solar System.

Cassini, Dione, and Saturn during the Dione encounter. Image credit: NASA Eyes on the Solar System

The Cassini mission is nearing its end; during April of 2017, Cassini will have an encounter with Titan, which will alter its trajectory into what is called a proximal orbit – bringing the spacecraft between Saturn’s innermost D-ring, and cloud tops (hopefully not impacting any unseen ring material at this altitude – mission specialists did look for it there).

Cassini proximal orbit. Credit: NASA Eyes on the Solar System app.

At this position, Cassini will be able to observe ring vistas that were formerly only the realm of Science Fiction artists.

There are a proposed 22 of these proximal orbits planned, after which the Cassini spacecraft will dip into Saturn’s atmosphere and incinerate, leaving behind the legacy of a fantastically successful outer planet mission