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Cassini continues its series of seven-day-long orbits with Rev86, the spacecraftís 87th orbit around the ringed planet. Cassini begins Rev86 on September 21 at its farthest distance from Saturn, called apoapsis. At this point, the spacecraft is 1.22 million km (761,000 mi) from Saturn. Like most of the orbits during 2008, Cassini travels around Saturn at a high-inclination, providing many opportunities to view the ring system from high above the ring plane. During this orbit Cassini will view the rings in several of such observations. The first of these occurs on September 15, when Cassini will acquire multiple images of the F-ring as part of a campaign to monitor several clumps in the ring for changes over time. On September 21, Cassini will continue its cloud monitoring program at Titan by acquiring several images from a distance of 2.04 million km (1.27 million mi). This observation will cover the hemisphere that includes Senkyo, Aaru, and Kraken Mare. Another observation on September 21 involves several of Saturnís small satellites as part of Cassiniís orbit determination campaign. On September 25, Cassini reaches periapse, its closest point to Saturn on Rev86. At that point, the spacecraft will be 237,537 km (147,599 mi) from Saturnís cloud tops. Near periapse, Cassini will quickly pass high over the north polar region of Saturn before descending below the ring plane 38 minutes before closest approach. In the hours leading up to periapse, Cassini ISS and the Composite Infrared Spectrometer (CIRS) will observe the northern sub-Saturn hemisphere of Tethys from a distance of 110,274-160,000 km (68,521-100,000 mi). During the latter half of the observation, Tethys will pass through the shadow of Saturn.
Following periapse, Cassini will acquire a radial scan of Saturnís ring system. This scan will consist of a mosaic of high resolution images running from the D ring out to the F ring. Also on September 25, Cassini will image the sub-Saturn hemisphere of Titan from a distance of 1.66 million km (1.04 million mi).
On September 26, two satellite observations are planned. During the first, Cassini will observe several of Saturnís small, inner satellites as part of the ongoing orbit determination campaign. Immediately afterward, Cassini will turn its cameras toward Rhea, as the spacecraft observes that icy moonís southern leading hemisphere from a distance of 463,000 km (288,000 mi). Later in the day, Cassini will image the lit side of the B ring, looking for forming spokes. On September 27, Cassini will again observe Saturnís small, inner moons to continue to refine our orbital estimates for these moons. The spacecraft will also again observe the F ring as part of the Imaging Teamís monitoring campaign. Finally, Cassini will observe the faint E ring at high phase angle. This observation will help imaging scientists better understand the size of particles within the ring.
Rev86 finishes up with another small satellite observation on September 28. Cassini will also observe the leading hemisphere of Mimas from a distance of 1.17 million km (725,000 mi).
Cassini begins Rev87 on September 28.
Image products created in Celestia. Tethys and Rhea basemaps by Steve Albers. Saturn basemap by BjŲrn Jůnsson. All dates in Coordinated Universal Time (UTC).