[For trouble viewing the images/movies on this page, go here]
Cassini continues its exploration of the Saturn system with the 29-day Rev 197, which begins on August 29 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 2.03 million kilometers (1.26 million miles) from Saturn's cloud tops. Rev 197 occurs during the first inclined phase, which lasts until March 2015, of the Cassini Solstice Mission. The inclined phase will allow 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. Thirty-eight ISS observations are planned for Rev 197 with many focused on Saturn's atmosphere and rings as well as on Titan during two encounters.
On August 29, five hours after apoapse, ISS will acquire a quick observation of Saturn using the 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. Five more observations are planned on September 9 and 10, and another four will be taken between September 14 and 20. On August 30, ISS will observe a gibbous Iapetus. The observation will cover the sub-Saturn hemisphere of the moon, which will be 2.49 million kilometers (1.55 million miles) away. Immediately afterward, ISS will acquire an observation of the small, outer satellite, Kiviuq. These images will be used to determine the north pole direction of this small moon. Given its small size and great distance from Saturn, it doesn't rotate synchronously like Saturn's closer and larger icy moons. Kiviuq is 16 kilometers (10 miles) across and will be 12.4 million kilometers (7.70 million miles) away. Its rotational period had previously been found to be 21.8 hours.
On September 4 at 21:26 UTC, Cassini will perform a non-targeted encounter with Titan at a distance of 531,399 kilometers (330,196 miles). ISS will acquire a pair of observations in conjunction with this encounter. During closest approach, ISS will acquire a long-range monitoring observation of the moon, which will include three mosaics across a crescent Titan and a pair of stares at the north pole. At such a high phase angle, surface feature visibility will be limited. A similar observation will be acquired on September 6 at a slightly better phase angle for observing surface features across Titan's northern hemisphere. On September 5, ISS will observe the distant, small moon Tarvos to determine its pole position. Tarvos is 15 kilometers (9 miles) across and will be 14.4 million kilometers (8.94 million miles) away. On September 7, 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 September 10 at 13:48 UTC, Cassini will reach periapse for Rev 197 at an altitude of 1,054,000 kilometers (654,930 miles) from Saturn. During periapse, 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. Two more astrometric observations will be acquired on September 14 and 19. Immediately afterward, ISS 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. An hour and a half after periapse, ISS will ride-along with the Visual and Infrared Spectrometer (VIMS) as it observes an occultation by Saturn's rings of the red-giant star W Hydrae.
Two days after periapse, Cassini encounters Titan on September 12 at 07:44 UTC for the 95th time. This is the sixth Titan flyby planned for 2013, with the next encounter scheduled for October 14. T94 has a close-approach altitude of 1,400 kilometers (870 miles). This flyby will allow for imaging of the north polar region inbound to the encounter and the southern anti-Saturn hemisphere of Titan on the outbound leg. Starting off the encounter, ISS will ride-along with the Composite Infrared Spectrometer (CIRS) as it stares at Titan in order to acquire mid-infrared spectral and temperature information about Titan's atmosphere. Afterward, ISS will acquire a thirteen-frame mosaic of the north polar and northern leading hemisphere regions of Titan. This mosaic will provide more information of the distribution of lakes in the north polar region, fill-in the largest gap in ISS's map of Titan, and provide details on the shapes of some of the lakes not yet covered by RADAR SAR data. Afterward, ISS will acquire a 10-frame mosaic that will cover sub-Saturn side of the north polar region. Finally, ISS will take a high-resolution, four-frame mosaic that will stretch from Punga Mare to Neagh Lacus.
VIMS will be the prime instrument at closest approach. During its two hours of observing time, VIMS will acquire several observations of Titan's surface. During the approach to Titan, VIMS will acquire a mosaic of Titan's north polar region, including portions of Ligeia Mare, Punga Mare, and Mackay Lacus. During closest approach, VIMS will acquire a noodle image running south from east of Ligeia Mare, down Titan's northern mid-latitudes, and ending up across the Adiri bright region. VIMS will then acquire a mosaic across southern Adiri and Ching-Tu, covering a series of faculae (bright regions within Titan's dune fields). After VIMS's close-approach observations, ISS will ride along with a CIRS observation of Titan's upper haze layers and Ultraviolet Imaging Spectrometer (UVIS) extreme- and far-ultraviolet scans across Titan. Finally, ISS will ride-along with VIMS in order to track any clouds that might be visible across Titan's southern, anti-Saturn hemisphere. On September 13, ISS will acquire three Titan cloud tracking observations that will cover its southern hemisphere.
On September 15, ISS will acquire a movie of the F ring. On September 16, ISS will look at a half-phase Titan from a distance of 1.39 million kilometers (0.86 million miles). The observation will allow researchers to search for clouds across Titan's southern trailing hemisphere. On September 26, ISS will attempt to observe the shadow of Saturn on the faint Phoebe ring.
On September 27, Cassini will reach apoapse, bringing Rev 197 to a close and starting up the next orbit, Rev 198, which will include another targeted flyby of Titan.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC).