Less than three weeks after its last visit to the saturn moon enceladus, NASA’s
Cassini spacecraft returns for an encore. At closest approach on April 14, the spacecraft will be just as low over the moon’s south polar region as it was on March 27 46 miles, or 74 kilometers. Saturn moon Enceladus is the sixth-largest of the moons of Saturn. It was discovered in 1789 by William Herschel. Until the two Voyager spacecraft passed near it in the early 1980s very little was known about this small moon besides the identification of water ice on its surface. Like the last, this latest flyby is mainly designed for Cassini’s ion and neutral mass spectrometer, which will taste the particles in the curious jets spraying from the moon’s south polar region. Combined with the March 27 flyby and a similar flyby on October 1, 2011, this close encounter will provide a sense of the jets’ three-dimensional structure and help determine how much they change over time. On Cassini’s outbound leg, the spacecraft will pass by another saturn moon enceladus , Tethys, at a distance of about 6,000 miles (9,000 kilometers).Tethys or Saturn III is a mid-sized moon of Saturn about 1,060 km (660 mi) across. It was discovered by G. D. Cassini in 1684 and is named after titan Tethys of Greek mythology. The composite infrared spectrometer will look for patterns in Tethys’ thermal signature. Other instruments will study the moon’s composition and geology. The imaging cameras are expected to obtain new views of Enceladus and Tethys.