NASA’s Cassini spacecraft returned new images of Saturn’s moon Dione during its flyby of 17 August 2015. The probe zoomed in as close as 295 miles (474 km) above the icy moon’s surface at 2:33 p.m. EDT (11:33 a.m. PDT). This was the fifth and final targeted encounter with Dione during Cassini’s long tour at Saturn.
This view from Cassini looks toward 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. The view was acquired at distances ranging from approximately 106,000 miles (170,000 km) to 39,000 miles (63,000 km) from the icy moon and at a Sun-Dione-spacecraft, or phase, angle of 35 degrees. At lower right is the large, multi-ringed impact basin Evander, which is about 220 miles (350 km) wide. The canyons of Padua Chasma, features that form part of Dione’s bright, wispy terrain, reach into the darkness at left. Scientists combined nine visible light images to create this mosaic view: eight from Cassini’s 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. Image credit: NASA / JPL-Caltech / Space Science Institute.
“I am moved, as I know everyone else is, looking at these exquisite images of Dione’s surface, and knowing that they are the last we will see of this far-off world for a very long time to come,” said Dr Carolyn Porco of the Space Science Institute in Boulder, Colorado.
“Right down to the last, Cassini has faithfully delivered another extraordinary set of riches. How lucky we have been.”
The main scientific focus of this flyby was gravity science, not imaging. This made capturing the images tricky, as Cassini’s camera was not controlling where the spacecraft pointed.
“We had just enough time to snap a few images, giving us nice, high resolution looks at the surface. We were able to make use of reflected sunlight from Saturn as an additional light source, which revealed details in the shadows of some of the images,” said Dr Tilmann Denk of Freie University in Berlin, Germany, a scientist for the Cassini mission.
Cassini gazes out upon a rolling, cratered landscape in this oblique view of Dione. A record of impacts large and small is preserved in the moon’s ancient, icy surface. The image was obtained in visible light with Cassini’s wide-angle camera during a close flyby of the moon on August 17. The view was acquired at an altitude of approximately 470 miles (750 km) above Dione. North on Dione is down. Image credit: NASA / JPL-Caltech / Space Science Institute.
Members of the Cassini team will study data from the gravity science experiment and magnetosphere and plasma science instruments over the next few months as they look for clues about Dione’s interior structure and processes affecting its surface.
Only a handful of close flybys of Saturn’s satellites remain for Cassini.
The probe is scheduled to make three approaches to Enceladus in October and December 2015.
Dione hangs in front of Saturn and its icy rings in this view. The image was obtained in visible light with the wide-angle camera on Cassini on August 17. The view was acquired at a distance of approximately 45,000 miles (73,000 km) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 35 degrees. North on Dione is up. Image credit: NASA / JPL-Caltech / Space Science Institute.
After December, and through the mission’s conclusion in late 2017, there are a handful of distant flybys planned for Saturn’s large moons at ranges of less than 30,000 miles (50,000 km).
Cassini will, however, make nearly two dozen passes by a menagerie of Saturn’s small moons – including Daphnis, Telesto, Epimetheus and Aegaeon – at similar distances during this time.
For its grand finale, the spacecraft will repeatedly dive through the space between Saturn and its rings.
