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Cassini continues its exploration of the Saturn system with the 12-day Rev184, which begins on March 16 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 1.47 million kilometers (0.92 million miles) from Saturn's cloud tops. Rev 184 occurs nearly a year into the first inclined phase of the Cassini Solstice Mission, a phase which lasts until March 2015. 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. Eighteen ISS observations are planned for Rev 184 with the majority focused on Saturn's atmosphere and rings.
On March 18, ISS begins its observations for Rev 184 with three quick observations of Saturn using the wide-angle camera (WAC). These observations are 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. Four more Storm Watch observations are planned for March 19, 27, and 28. Between the first two Storm Watch observations on March 18, 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. After the second Storm Watch observation, ISS will acquire a series of images of Saturn rings using the WAC. These images will be tracking spokes -- a ring phenomenon Cassini has monitored throughout the mission -- over the B ring. With Cassini over the unlit side of the rings and with Saturn at a high phase angle, the spokes, if visible, will be brighter than the dark B ring. Finally, on March 18, 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 March 19, ISS will image the outer A ring, looking at the propellers previously seen in this part of the ring system. Propellers are small voids in Saturn's rings created by the gravitational interaction between large ring particles and the surrounding ring. Later that day, ISS will acquire a distant Titan observation. This observation will be used to look at Titan's upper haze layers as the moon will appear to be thin crescent. These images will be taken from a distance of 1.85 million kilometers (1.15 million miles). On March 19 and 20, ISS will ride along with a pair of Ultraviolet Imaging Spectrometer (UVIS) observations of Saturn's south polar aurora. In addition to making a movie of the planet's aurorae, the images will be used to independently measure the rotation period of Saturn's magnetic field.
On March 22 at 02:46 UTC, Cassini will reach periapse for Rev 184 at an altitude of 424,600 kilometers (263,830 miles) from Saturn. During the periapse period, Cassini will focus on magnetic field observations along with many UVIS observations across the northern auroral oval.
On March 26, ISS will acquire a pair of observations of two small, distant, outer moons, Hyrrokkin and Narvi. These observations will be used to measure the rotation period of these small moons. Given their small size and great distance from Saturn, they don't rotate synchronously like Saturn's closer and larger icy moons. Hyrrokkin is 8 kilometers (5 miles) across and will be 9.76 million kilometers (6.07 million miles) away. Narvi is 7 kilometers (4.3 miles) across and will be 15.5 million kilometers (9.65 million miles) away. On March 27, the camera system will acquire another movie of the F ring. Afterwards, early on March 28, ISS will acquire an observation of Titan from a distance of 2.44 million kilometers (1.51 million miles). The images will be used to look for clouds across the moon's southern Sub-Saturn hemisphere.
On March 28, Cassini will reach apoapse on this orbit, bringing it to a close and starting Rev185. The next orbit includes a close flyby of Titan.
Image products created in Celestia. All dates in Coordinated Universal Time (UTC).