This very detailed image taken during the Cassini spacecraft's closest approach to Saturn's moon Dione on Dec. 14, 2004 is centered on the wispy terrain of the moon.

This very detailed image taken during the Cassini spacecraft's closest approach to Saturn's moon Dione on Dec. 14, 2004 is centered on the wispy terrain of the moon. 

Dione 'D-2' Flyby: Search for Activity

Cassini swooped down to within about 500 kilometers (311 miles) of Dione to 'sniff' the moon. Particle and fields instruments will try to determine if Dione is actively spewing particles.

The Composite Infrared Spectrometer (CIRS) began observations on the approach to this Dione flyby by making a map of the satellite while Dione is in Saturn’s shadow, so the heat from the sun is not measured, but any heat from Dione is gauged. The Ultraviolet Imaging Spectrograph (UVIS) and Visible and Infrared Mapping Spectrometer (VIMS) also imaged Dione. The Cassini Plasma Spectrometer then took control for closest-approach to observe the interaction between Dione and Saturn's magnetosphere, with most of the other instruments also taking data. UVIS then mapped Dione’s surface albedo in ultraviolet to measure composition, while other Optical Remote Sensing instruments obsered the terrain. The Imaging Science Subsystem (ISS) followed UVIS to do a 20-panel mosaic with the other remote sensing instruments also taking data, to get compositional, thermal and geological information about Dione’s sub-Saturnian hemisphere.