[For trouble viewing the images/movies on this page, go here]
Cassiniís journey at Saturn continues with Rev 62, its 63rd orbit of the ringed planet. Cassiniís orbit around Saturn is really starting to tighten, and this orbit lasts a scant ten days. As such, Cassiniís slate of observations is more tightly focused, with sequences involving Titan, Dione, and Saturnís small satellites and rings on the schedule. Cassini begins Rev62, on March 18 at its farthest distance from Saturn, called apoapsis. At this point, Cassini is 1.63 million km (1.02 million mi) from Saturn. All the non-Titan imagery planned for this orbit takes place between March 20 and 23. On March 20 and 21, Cassini performs observations of several of Saturnís small satellites. Such opportunities are designed to study the orbits of these small objects and how they might evolve over short periods due to perturbations from the other satellites in the system. On March 22, Cassini observes Dioneís northern trailing hemisphere from a distance of 665,000 km (413,000 mi). The most prominent feature in this region is the large crater named Latinus (near the center of the moonís crescent in the view at left).
The next day, on March 23, Cassini reaches periapse, its closest point to Saturn on Rev62. At that point, Cassini will be 223,000 km (138,000 mi) from Saturnís cloud tops. About an hour after periapse, Cassini observes a portion of the A-ring edge at high resolution, looking for features created by a resonance with Janus and Epimetheus. Cassini encounters Titan for the 43rd time on March 25, with a closest approach distance of only 1,000 km (620 mi). This flyby (known as T42) will allow for imaging of the trailing hemisphere of Titan, centered northwest of the bright region named Adiri. Inbound to the encounter, when only a thin, sunlit crescent is visible from Cassini, the Visual and Infrared Mapping Spectrometer (VIMS) and Composite Infrared Spectrometer (CIRS) teams trade control of spacecraft pointing (taking turns being ďprimeĒ). VIMS will have control of spacecraft pointing for the first three hours of the encounter. CIRS will be prime for the next 8.5 hours, mostly measuring the composition of Titanís various haze layers by staring at them edge-on at the limb.
The Ion and Neutral Mass Spectrometer (INMS) and VIMS teams will be in control of spacecraft pointing during Cassiniís closest approach to Titan. INMS will use its open neutral channel to measure non-ionized gases in Titanís upper atmosphere. VIMS will use its ďnoodleĒ mode to acquire a swath of imagery stretching from just south of Hotei Arcus, west and north through the gap between Texel Facula and Mindanao Facula, and finally ending in the intermediate albedo terrain west of Dilmun. VIMS hopes to observe small-scale spectral units and dunes in Shangri-la.
Following closest approach, ISS, VIMS, and CIRS will trade control of spacecraft pointing. Two ISS mosaics are planned for this period: the first, a 15-frame mosaic covering the same terrain as the end of the VIMS swath, and taken from distances ranging from 41,000 to 83,000 km (26,000 to 52,000 mi); the second, a 13-frame, full-disk mosaic taken from distances ranging from 232,000 to 267,000 km (144,000 to 166,000 mi). VIMS will acquire distant observations of Titan designed to study cloud evolution (assuming clouds are visible at the time). CIRS will perform several scans to examine temperature and compositional differences in Titanís atmosphere.
Cassini begins the following orbit, Rev63, on March 28.