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Cassini continues its exploration of the Saturn system with the 18-day Rev162, which begins on March 1 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 2.38 million kilometers (1.48 million miles) from Saturn's cloud tops. The spacecraft is nearing the end of the first equatorial phase of the Cassini Solstice Mission, a phase which lasts until May 2012. During this phase, the spacecraft's orbits lie within the equatorial plane of the planet, providing opportunities to encounter Saturn's numerous moons, image the rings edge-on, and look at Saturn's cloud tops without the rings obscuring the view. Thirty-eight ISS observations are planned for Rev162, the vast majority dedicated to Saturn storm monitoring and to the non-targeted encounters with Rhea and Enceladus.
ISS begins its observations for Rev162 the day after apoapse on March 2 with a look at Titan from a distance of 1.96 million kilometers (1.22 million miles). The observation is an effort to look for clouds in the moon's atmosphere as part of the "Titan Monitoring Campaign" (TMC). This observation, of a crescent Titan, is designed to study changes in Titan's upper haze layers. Later that day, ISS will acquire a lengthy, 18-hour observation of Thrymr, one of Saturn's distant, irregular moons. This observation will be taken from a distance of 9.48 million kilometers (5.89 million miles), and when combined with additional observations of this irregular satellite, is designed to measure Thrymr's rotational period. Similar observations will be taken of two more outer satellites, Jarnsaxa and Mundilfari, on March 8 and 9. On March 5, 6, and 7, ISS will ride along with the Ultraviolet Imaging Spectrometer (UVIS) to monitor Saturn's aurora australis. On March 9, ISS will perform a TMC observation of Titan, this time at much lower phase angles. This will allow for monitoring of cloud features across the sub-Saturn hemisphere of the moon from a distance of 881,000 kilometers (547,000 miles).
On March 10 at 02:13 UTC, Cassini will reach periapse for Rev162 at an altitude of 135,530 kilometers (84,210 miles). ISS observations will be taken during two non-targeted encounters of Saturn's icy satellites, first of Enceladus (albeit seven hours after closest approach) and later of Rhea. Cassini will fly by Enceladus at a distance of 9,176 kilometers (5,701 miles) on March 9. A few hours later, ISS will take a look at Enceladus's leading hemisphere from a distance of 175,000 kilometers (108,000 miles). The camera system will take two sets of color and polarized filter images of the satellite, with the sets separated by an hour. ISS will then image Titan from a distance of 1.54 million kilometers (0.96 million miles).
At 15:03 UTC, Cassini will fly by Saturn's second largest moon, Rhea, at a close-approach distance of 41,858 kilometers (26,009 miles). ISS will acquire three sets of observations during this flyby. First, ISS will ride along with a series of scans of a crescent Rhea by the Composite Infrared Spectrometer (CIRS) about three hours before closest approach. During closest approach, ISS will acquire a 30-frame mosaic of Rhea's leading hemisphere, including the Mamaldi and Tirawa impact basins. Afterward, ISS will search for particles within the Rhea's possible ring system. Particles as small as 5 to 10 meters (16 to 32 feet) could be detected in these images.
On March 11, ISS will acquire four, quick observations of Saturn and its faded northern hemisphere storm. These "Storm Watch" observation sequences are designed to take advantage of short, two-minute segments when the spacecraft turns the optical remote sensing (ORS) instruments back to Saturn as a waypoint between other experiments' observations. These sequences include blue, clear, two methane band, and one full-frame, continuum band filter images. Thirteen more such observations are planned between March 12 and 18. Also on March 11, ISS will perform a TMC observation of Titan from a distance of 2.45 million kilometers (1.52 million miles). This will allow for monitoring of cloud features across the sub-Saturn hemisphere of the moon. During this image set, portions of Titan will be obscured by Saturn's rings and Janus will transit the moon's north polar region. Immediately afterward, ISS will observe Enceladus as it passes in front of Titan. ISS will take another look at Titan on March 13, from a distance of 2.88 million kilometers (1.79 million miles), this time looking at the Fensal-Aztlan region.
On March 12, ISS will acquire an astrometric observation of Saturn's small, inner moons, including Epimetheus, Helene, Pandora, Telesto, Anthe, and Methone. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy satellites. Additional astrometric observations will be taken on March 13, 15, and 17. On March 14, ISS will observe another satellite mutual event as Tethys passes in front of Dione. Tethys will be 1.69 million kilometers (1.05 million miles) away, while Dione will be 2.20 million kilometers (1.37 million miles) away.
On March 18, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev163. Rev163 includes a targeted flyby of Enceladus and non-targeted encounters with Dione and Janus.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC).