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Cassiniís journey at Saturn continues with Rev 57, its 58th orbit of the ringed planet. Cassiniís slate of observations this orbit includes a distant encounter with Titan and numerous observations of Saturnís rings and small moons. Cassini begins Rev57 on January 21 at its farthest distance from Saturn, called apoapsis. At this point, Cassini is 1.81 million km (1.13 million mi) from Saturn. The first week of Rev57 is filled with observations of Titan, the F ring, and Saturnís small satellites. On January 22, Cassini performs a non-targeted encounter with Titan at a distance of 856,000 km (532,000 mi). This distant encounter will allow of observations of Titanís north polar region (though the pole itself will be in darkness, as it is still northern winter on Titan). Of particular interest will be a search for lakes and seas that may show up near the terminator in this observation. RADAR data from near this region, taken last February, suggest that the area may host numerous small lakes, as opposed to the large seas seen west of where ISS will be searching on this orbit. Two small satellite sequences are planned for January 22 and 23. The observations are designed to study the orbits of these objects and how they might evolve over short periods due to perturbations from the other satellites in the system. On January 23, an observation is planned to look at clumps and gores in the thin F ring. Finally, on January 24, ISS will search for new satellites between the orbits of Mimas and Enceladus. ISS, over the last four years, has found three new satellites in this area: Methone, Pallene, and Anthe. Cassini reaches periapse, the closest point in its orbit, on January 27 when the spacecraft is 199,000 km (124,000 mi) above Saturnís cloud tops. On January 28 and 29, Cassini will perform four imaging sequences of Saturnís ring system. The first is an azimuthal scan along the inner part of the Cassini Division. Such scans are designed to look for variations in ringlet thickness or brightness. The next observation is a nine-frame, wide-angle camera mosaic of the right side of the sunlit rings. The following observation is a seven-hour movie sequence covering the Columbo and Maxwell gaps in the inner C ring. And finally, ISS will capture a wide-angle camera mosaic of the outer diffuse rings, from the F ring to the outer E ring. During the periapse period, Cassini will perform several satellite observations. On January 28, Cassini ISS will observe both of the ring gap satellites, Pan and Daphnis, from a distance of 380,000 km (236,000 mi). While this distance is too far away to do geologic studies of these satellites, it is good for color and photometry measurements. On January 29 and 30, Cassini will take a couple of ďphoto opĒ observations of Titan disappearing and reappearing from behind Saturn, in a sequence reminiscent of New Horizonsí observations of Europa near Jupiterís limb (see PIA09361). Finally, Cassini will observe the leading hemisphere of Tethys from a distance of 1.13 million km (702,000 mi).
Cassini finishes Rev57 with several small satellite orbital determination sequences.
Cassini begins the following orbit, number 59 (ďRev58Ē), on February 2. Rev58 includes a distant flyby of Dione.