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Cassini continues its extended tour of Saturn on Feb. 8 with Rev103, the spacecraft's 104th orbit around the Ringed Planet. Cassini begins Rev103 shortly after the spacecraft's 51st flyby of Titan at its farthest distance from Saturn, called apoapse. At this point, Cassini is 1.17 million kilometers (743,000 miles) from Saturn. The Titan flyby at the end of the previous orbit acted to increase the periapse distance, making the closest point in the spacecraft's orbit farther from Saturn, as well as lengthening Cassini's orbital period from 9.5 days to 12 days. The spacecraft remains in a high-inclination orbit, providing an opportunity to study the rings and the polar regions of Saturn and its satellites.
For the first five days of this revolution, ISS and the other optical remote sensing (ORS) instruments will focus on Saturn's ring system and satellites. Following a downlink session near apoapse, Cassini will spend much of Feb. 8 staring at Saturn's south polar region. The next day, Feb. 9, Cassini will observe several of Saturn's small satellites and make astrometric observations of Janus, Prometheus, Anthe, and Pandora and Atlas (both should be visible in the same field of view). Astrometric observations are designed to improve our knowledge of the orbits of Saturn's small satellites. Next, ISS will take an 11-hour long observation of Prometheus, watching it as goes through about three-quarters of its orbit around Saturn. Scientists will be watching Prometheus's interactions with the neighboring F ring. On Feb. 10, ISS will acquire a similar observation, but this time ISS will stare at the F ring, allowing F ring material, streamers, and channels to rotate into the field of view. The RADAR instrument will then acquire a distant radiometry observation of Titan early on Feb. 11. After an optical navigation observation of Mimas and Enceladus, Cassini will then transmit the data it recorded to Earth.
On Feb. 11, ISS will acquire a distant observation of the small satellite Methone. Following this astrometric sequence, the Composite Infrared Spectrometer (CIRS) will make several radial scans of the unlit side of Saturn's ring system, taking the temperature of the rings. Next, ISS will look at several of Saturn's small moons, including Pandora, Pan, Janus, and Anthe. On Feb. 12, RADAR will acquire a radiometry observation of Saturn's night-side atmosphere while CIRS will acquire another series of short azimuthal scans and several radial scans at different longitudes of the ring system.
Cassini reaches periapse, its closest point to Saturn during Rev103, early on Feb. 14. At this point, Cassini will be 758,590 kilometers (471,366 miles) from Saturn's center, between the orbits of Rhea and Titan. Prior to periapse, on Feb. 13, CIRS will perform a temperature scan of Titan during a non-targeted flyby. During this encounter, Cassini will pass within 707,000 kilometers (439,000 miles) of Saturn's largest moon, Titan. Shortly after this observation, ISS will acquire a narrow-angle camera movie of the inner Cassini Division, focusing on some of the ringlets in this part of the ring system. Following periapse, CIRS will take additional temperatures scans of the ring system before Cassini downlinks its data to Earth.
On Feb. 15, ISS will acquire several satellites observations. These include a nine-hour long observation of Titan where ISS will search for clouds and hopefully watch them move across the southern part of the sub-Saturn hemisphere. This distant observation will also provide an opportunity to look at Mezzoramia, a dark albedo region in Titan's mid-Southern latitudes. Distance to Titan varies during this long observation between 1.2 and 1.37 million kilometers (749,000 and 851,000 miles). Next, ISS will take an astrometric observation of several of Saturn's small moons, including Epimetheus, Pan, Atlas, and Janus. Finally, ISS will take a look at Tethys and Dione as part of an optical navigation sequence. On Feb. 15, Cassini also will observe Saturn's south polar region. On Feb. 16 and 17, CIRS will take several temperature scans of the sunlit side of the rings.
On Feb. 18, Cassini will turn its cameras to Titan again, this time from a distance of 1.85 million kilometers (1.15 million miles). ISS will search for clouds across the Fensal-Aztlan hemisphere of the large moon. ISS will acquire an optical navigation observation of Dione, Tethys, and Enceladus, while CIRS will take Saturn's temperature by staring at a point near the limb at 55 degrees south latitude. The next day, the Visual and Infrared Mapping Spectrometer and ISS will observe the left side of the unlit G ring.
Cassini reaches apoapse on Feb. 20, bringing Rev103 to an end.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC).