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Rev 89: October 13 Ė October 20, 2008
Cassini continues its series of week-long orbits with Rev89, the spacecraftís 90th orbit around the Ringed Planet.
Cassini begins Rev89 on October 13 at its farthest distance from Saturn, called apoapsis. At this point, Cassini is 1.21 million km (756,000 mi) from Saturn. 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. Such an orbit provides an opportunity to study Saturnís rings as well as the polar regions of Saturn and its satellites. Cassini ISSís first two observations of Rev89 cover several of Saturnís small, inner satellites as part of the imaging teamís orbit determination campaign.
On October 14, Cassini turns its cameras to Titan, hoping to monitor clouds on that satelliteís northern leading hemisphere. Cassini, over the last few orbits, has been conducting a series of observations to search for cloud features on Titan northern hemisphere. Most of the clouds observed in the last couple of months have been located in the leading hemisphere. The cause of this longitudinal confinement is currently unknown. Also on October 14, Cassini will observe Saturnís F ring over a 12-hour period in order to look for short-term changes.
On October 16, Cassini will acquire a partial azimuthal scan of the Columbo ringlet in the outer C ring while Cassini is high above the unlit side of the rings.
On October 17, Cassini reaches periapse, its closest point to Saturn on Rev89. At that point, Cassini will be 240,000 km (150,000 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 periapse. Cassini ISSís first observation after periapse occurs early on October 18. In this case, Cassini will observe Prometheus while that small satellite is in Saturnís shadow. ISS and the Visual and Infrared Mapping Spectrometer (VIMS) will then observe the B ring in order to look at spokes.
On October 19, Cassini ISS will observe Mimasís leading hemisphere from a distance of 1.1 million km (690,000 mi). The next day, ISS will take a look at Tethysís leading hemisphere from a distance of 1.1 million km (690,000 mi). Both observations are designed to study the photometry of these regions of Mimas and Tethys.
On October 20, Cassini will acquire two observations intended to determine the orbit of some of Saturnís small inner satellites. Cassini will also image Titanís trailing hemisphere, a bright arc in the G ring, and an occultation of the small satellite Prometheus by Mimas.
Cassini begins Rev90 on October 20.
Image products created in Celestia. Mimas basemap by Steve Albers. All dates in Coordinated Universal Time (UTC).