A NASA spacecraft was on course on Tuesday to make a flyby within 520 kilometers of Saturn's moon Dione - its fourth flyby since the spacecraft Cassini went into orbit around Saturn in 2004, according to dpa. A fifth flyby of Dione is planned for August, before Cassini's final mission begins late this year. It will leave its path on Saturn's equatorial plane, and dive into the space between Saturn and it's rings. In Tuesday's flyby, Cassini will attempt to observe a section of Dione's terrain called "Eurotas Chasmata," which according to NASA is "an intricate network of braided canyons with bright walls." The canyon was first pictured 35 years ago by NASA's voyager spacecraft. Cassini will also try to detect the composition of any fine particles being emitted from Dione, which could indicate low-level geologic activity. Mission controllers expect images to begin arriving on Earth within a few days of Tuesday's encounter. The Cassini mission is led by NASA, the US space agency, with the European Space Agency (ESA) participating by building the Huygens probe that landed on Titan, one of Saturn's moons, in 2005. The Saturn orbiter Cassini has unlocked many of the secrets of the second-largest planet in the solar system, including metre-high water geysers and seas of methane.
