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Rev 96: December 5 Ė December 13, 2008
Cassini continues its extended tour of the Saturn system with Rev96, the spacecraftís 97th orbit around the Ringed Planet.
Cassini begins Rev96 on December 5 at its farthest distance from Saturn, called apoapse. At this point, Cassini is 1.19 million km (741,000 mi) from the planet, just beyond the orbit of Saturnís largest moon Titan. The spacecraft is in a high-inclination orbit here, as it is for most of 2008, providing opportunities to view the ring system from high above the ring plane. Cassini starts Rev96 shortly after the T48 encounter with Titan in Rev95. Cassiniís last few observations of Titan spill into Rev96. Later on December 6, Cassini will turn its cameras to the ring system. The Composite Infrared Spectrometer (CIRS) will acquire a temperature map of the unlit side of the rings, while ISS will search for spokes. On December 7, Cassini will take a look at several of Saturnís small, inner satellites, including Prometheus, Telesto, Janus, Pandora, and Pan, as part of an observation campaign designed to study the orbital motions of these objects.
On December 8, Cassini will perform three additional observations of Saturnís rings. First, ISS will acquire a partial azimuthal scan of the outer edge of the B ring and the inner portion of the Cassini Division. Next, the Ultraviolet Imaging Spectrometer (UVIS) will observe the star Beta Centauri as it passes behind the ring system and Saturn. UVIS will use this stellar occultation to measure the ultraviolet opacity of the rings and the hazes in Saturnís upper atmosphere. Afterward, ISS will take an azimuthal scan of the narrow F ring.
On December 9, Cassini reaches periapse, its closest point to Saturn on Rev96. At that point, Cassini will be 347,000 km (215,000 mi) from Saturnís center. Near periapse, Cassini will quickly pass high over the north polar region of Saturn before descending below the ring plane 17 minutes before periapse. Two observations are planned for December 9, both acquired before periapse. The first is a Visual and Infrared Spectrometer (VIMS) observation of spokes in Saturnís B ring. The second is a CIRS observation of the northern sub-Saturn hemisphere of Tethys just as it passes into Saturnís shadow. Following periapse, on December 10, ISS will take a full, 250-image, azimuthal scan of the 1.47-Rs ringlet in the outer C ring. Cassini ISS will also make a movie of the F ring, looking for changes in the streamers and channels caused by the gravitational influence of Prometheus and Pandora.
On December 11 and 12, Cassini will acquire two more observations of Saturnís rings as well as three satellite sequences. In both observations of the rings, ISS will search for spokes within the B ring. Cassini ISS will also observe several of Saturnís small, inner satellites, including Prometheus, Atlas, Pallene, Anthe, and Pan, as part of the ISS teamís orbit determination campaign. Finally, Cassini will look for clouds over Titanís sub-Saturn hemisphere.
On December 13, as Cassini approaches apoapse, ISS will acquire two more orbit determination observations of Saturnís small satellites, including Epimetheus, Janus, Polydeuces, Pandora, Anthe, Calypso, Helene, Atlas, Pan, and Prometheus. Cassini ISS will also image Saturnís F ring, monitoring changes in the channels and streamers within the ring. Finally, UVIS will observe Enceladusí plumes at low phase angles.
Cassini will reach apoapse on December 13, beginning Rev97. Rev97 includes the final Titan encounter of 2008, T49.
Image products created in Celestia. Tethys basemap by Steve Albers. All dates in Coordinated Universal Time (UTC).