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Cassini continues its exploration of the Saturn system with the 42-day Rev 209, which begins on October 5 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 3.13 million kilometers (1.95 million miles) from Saturn's cloud tops. Rev 209 occurs during the first inclined phase, which lasts until March 2015, of the Cassini Solstice Mission. The inclined phase allows for polar views of Saturn and Titan as well as better vistas of Saturn's rings than those Cassini had while in the earlier, equatorial phase of the Solstice Mission. Forty-five ISS observations are planned for Rev 209 with the majority focused on Saturn's atmosphere and on Titan during the T106 flyby.
On October 7, ISS will image Titan, looking for clouds across its northern sub-Saturn hemisphere, at a distance of 3.62 million kilometers (2.25 million miles). Afterward, ISS will acquire an astrometric observation of Saturn's small, inner moons. Astrometric observations are used to improve our understanding of the orbits of these small satellites, which can be influenced by Saturn's larger icy moons. Similar sequences will be acquired on October 14, 19, 30, and November 4. Finally on October 7, ISS will acquire a quick observation of Saturn using the Wide-Angle Camera (WAC). This observation is part of a series of "Storm Watch" observation sequences designed to take advantage of short, two-minute segments when the spacecraft turns the optical remote sensing (ORS) instruments back to Saturn as a waypoint between other experiments' observations. These sequences include blue, clear, two methane band, and one full-frame, continuum band filter images. Nine more storm watch observations will be taken between October 14 and 19.
On October 14, ISS will observe Titan once again, this time focusing on the northern, anti-Saturn hemisphere from a distance of 1.84 million kilometers (1.14 million miles). The camera system will observe Titan three more times before periapse, on October 16, 19, and 20, with the closest of these, on October 20, covering Titan's trailing hemisphere from a distance of 1.71 million kilometers (1.06 million miles). Also on October 14, ISS will observe the rings and ring arcs centered around Methone, Pallene, Anthe, and Aegaeon, as well as the moon Calypso. On October 17, ISS will acquire a color scan across the illuminated north face of Saturn's rings with its Narrow-Angle Camera (NAC). On October 19, the camera system will image the outer A ring, where it will be looking at propellers previously imaged by Cassini. Propellers are small voids in Saturn's rings created by the gravitational interaction between large ring particles and the surrounding ring.
On October 21 at 21:22 UTC, Cassini will reach periapse for Rev 209 at an altitude of 626,660 kilometers (389,390 miles) from Saturn's cloud tops. The ISS observations during the periapse period focus primarily on Saturn's atmosphere. On October 20, ISS will ride along with the Visual and Infrared Mapping Spectrometer (VIMS) to acquire several two-by-two mosaics of Saturn's bright limb. On October 21, ISS will ride along with a pair of VIMS observations, acquiring mosaics of Saturn's southern hemisphere and observing aurorae near its south pole. On October 22, ISS will ride along with the Composite Infrared Spectrometer (CIRS), taking a look at a crescent Saturn.
Cassini encounters Titan on October 24 at 02:41 UTC for the 107th time. This is the tenth of eleven Titan flybys planned for 2014, with the last encounter scheduled for December 10. T106 has a close-approach altitude of 1,013 kilometers (629 miles). Inbound, ISS will observe Titan's southern, sub-Saturn hemisphere. Outbound, ISS will be able to observe a crescent Titan over its northern, sub-Saturn hemisphere. Observations for this encounter will start with ISS riding along with CIRS as it acquires mid-infrared scanning observations. These can be used to measure temperatures within Titan's atmosphere. Afterward, ISS will acquire a nine-frame mosaic that will cover most of the visible, sunlit face of Titan. This mosaic will be centered near the dark-ring feature, Nath in eastern Tsegihi. Afterward, ISS will ride along with CIRS and VIMS. CIRS will acquire nadir and limb observations, measuring Titan's atmospheric temperature profile. VIMS will acquire a regional map of Titan.
At closest approach, the Radio Science Subsystem (RSS) will control pointing, acquiring a bistatic swath across eastern Kraken Mare. Bistatic data is acquired by bouncing a radio signal off Titan's surface, where it will then be picked up by antennas on Earth. This data set can be used to measure surface composition, roughness, state (whether liquid or solid), reflectivity, and dielectric constant. After closest approach, ISS will ride along with VIMS as it acquires regional maps of Titan's north polar region and CIRS as it acquires temperature map data of Titan's night side.
On October 25 and 27, as Cassini recedes from Titan, ISS will acquire a series of observations of Titan's visible crescent to monitor the north polar region for clouds. On October 27, ISS will acquire a movie of the F ring, observing its various channels and streamers created by the interaction between the ring material and the nearby moon, Prometheus. On November 2 and 3, ISS will observe the distant moon, Kiviuq, for 24 hours, in order to determine the direction its rotation axis is pointing. Kiviuq will be 14.1 million kilometers (8.78 million miles) away. On November 8 and 11, ISS will acquire a pair of cloud monitoring observations of Titan. Both observations will cover the north polar region and the northern leading hemisphere. The November 11 observation will be taken from a distance of 3.53 million kilometers (2.19 million miles).
On November 14, Cassini will reach apoapse, bringing Rev 209 to a close and starting up the next orbit, Rev 210, which will include another targeted flyby of Titan as well as the solar conjunction, when communications between Earth and Cassini will be limited.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC).