Helene imaged from a distance of 340,000 km by Cassini June 18, 2011. Image credit: NASA/JPL-Caltech/Space Science Institute.
Helene is a small moon of Saturn. It was discovered on March 1, 1980, from ground-based observations at Pic du Midi Observatory and is also known as Saturn XII. It is said to be a Dione trojan because it shares the same orbit as its larger companion, preceding it by 60°. Large portions of Helene appear to have been blasted away by impacts.
The closest encounter of any spacecraft with Helene took place on March 10, 2010, when Cassini flew within 1,820 kilometers (1,131 miles) of the moon.
|discovery||1980, by P. Laques and J. Lecacheux|
|semimajor axis||377,396 km (234,553 miles)|
|diameter||36 × 32 × 30 km (22 × 20 × 19 miles)|
|orbital period||2.737 days (2 days 17 hr 41 min)|