Dione

Moon of Saturn

Discovery	1684 by Cassini
Orbital characteristics:
Distance from Saturn	377,396 km
Eccentricity	0.002
Orbital periode about Saturn	2.737 days
Orbital speed	10.03 km/s
Inclination to Saturn equator	0.019 deg
Rings	No
Physical characteristics:
Radius	561.7 km
Surface area	3,965,000 km²
Volume	7.4 x 10⁸ km³
Mass	1.095 x 10²¹ kg
Density	1.48 g/cm³
Equatorial gravity	0.231 m/s²
Escape velocity	0.510 km/s
Rotation period	2.737 days
Axial tilt	0 deg
Surface temperature	87 K
Atmospheric composition	-

Cassini's plasma spectrometer instrument detected ions of molecular oxygen during a flyby of Dione in April 2010.
Dione's atmosphere is extremely thin, about 5 trillion times less dense than the atmosphere at Earth's surface. Cassini's measurements indicate there is just one oxygen ion for every 0.67 cubic inches, or 2,250 ions per cubic foot.

Cassini captured this image of Dione, backdropped by Saturn and its rings, in October 2005. Credit: NASA/JPL-Caltech/Space Science Institute

Name	Launch Date	Launch rocket	Weight (kg)	Mission
Cassini (USA,ESA)	15-Oct-97	Titan-Centaur	5.634 kg	The Cassini spacecraft made a 7461 km flyby of Titan at 1550 UTC on Apr 5, 2010 and is on course to pass Dione at an altitude of 500 km at 0516 UTC on Apr 7. The Cassini probe made a 99 km flyby of Dione on Dec 12, 2011

Ref.: #7(JR651), #12, #98 - update: 12.03.12