CICLOPS: Cassini Imaging Central Laboratory for OPerationS

Rev210: Nov 14 - Dec 24 '14
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Cassini continues its exploration of the Saturn system with the 39-day Rev 210, which begins on November 14 at its farthest distance from the planet. This is also called the orbit's apoapse. At this point, Cassini is 4.36 million kilometers (2.71 million miles) from Saturn's cloud tops. Rev 210 occurs near the end of 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. Thirty ISS observations are planned for Rev 210 with the majority focused on Saturn's atmosphere and on Titan during the T107 flyby. Between November 16 and November 20, however, Cassini will be in solar conjunction, when Saturn and Cassini are nearly behind the Sun as seen from Earth. The Sun's outer atmosphere limits communications between the spacecraft and Earth, so very few observations are taken during this period.

ISS's first post-conjunction observation, and the first of Rev 210, will take place on November 22. The Narrow-Angle Camera (NAC) will image Titan, looking for clouds across its northern sub-Saturn hemisphere, at a distance of 5.17 million kilometers (3.21 million miles). Five similar cloud monitoring observations will be acquired between November 23 and December 4. The closest of these will be taken on November 30 from a distance of 2.11 million kilometers (1.31 million miles) and will cover the northern leading hemisphere. On November 23, 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 November 25, 30, December 4, 5, and 21. On November 24 and 26, ISS will observe the distant moon, Albiorix in order to determine the direction its rotation axis is pointing. Albiorix will be 9.81 million kilometers (6.10 million miles) away during the observation on November 24. On November 14, ISS will observe the ring arc centered near Aegaeon, located within the G ring. The ring arc is thought to be created by micrometeorite impacts on the tiny moon.

On December 8 at 21:22 UTC, Cassini will reach periapse for Rev 210 at an altitude of 597,910 kilometers (371,520 miles) from Saturn's cloud tops. On December 6, ISS will acquire a color scan across the illuminated north face of Saturn's rings with its Narrow-Angle Camera (NAC). On December 8, starting at periapse, ISS will ride along with the Ultraviolet Imaging Spectrometer (UVIS) to image Saturn's south polar aurorae, after UVIS performs a series of scans across the planet and its rings.

Cassini encounters Titan on December 10 at 22:27 UTC for the 108th time. This is the last Titan flyby planned for 2014, with the next encounter scheduled for January 11, 2015. T107 has a close-approach altitude of 980 kilometers (609 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 a mid-infrared scanning observation and a far-infrared stare. These can be used to measure temperatures within Titan's atmosphere and determine how the composition of the upper atmosphere changes as winter approaches. Afterward, ISS will acquire a fifteen-frame mosaic of eastern Tsegihi, and portions of Senkyo, Aztlan, and Fensal. The mosaic will be centered just north of the crater Nath.

During the nine hours surrounding closest approach, the Cassini Navigation team will control pointing, with the high-gain antenna pointed at Earth. Along with the Ion and Neutral Mass Spectrometer (INMS), the NAV team will measure the effect of atmospheric drag on the spacecraft as it passes through Titan's upper atmosphere using Doppler shift measurements of Cassini's signal with Earth. From the amount of drag on the spacecraft, the NAV team will calculate atmospheric density and compare that to results obtained simultaneously by INMS. During previous encounters, discrepancies have been discovered between the results obtained independently by INMS, NAV, UVIS, and AACS teams and results from T107 will be used to understand this issue.

After closest approach, ISS will ride along with the Visual and Infrared as it acquires regional maps of Titan's north polar region and CIRS as it acquires temperature map data of Titan's night side. VIMS will attempt to observe specular reflection from the strait that connects Ligeia Mare and Kraken Mare. UVIS will perform an observation dedicated to measuring nitrogen emission features which are centered near an altitude of 800 kilometers (497 miles).

On December 14, the Wide-Angle Camera (WAC) will image the shadow of Saturn on the distant, faint, Phoebe ring. On December 15 and December 22, ISS will observe a pair of Saturn's small, distant moons in order to determine the orientations of their rotational axis by measuring how the intensity of their reflected light changes during each of the day and a half long observations. On December 15, ISS will image Loge from a distance of 17.3 million kilometers (10.8 million miles), while, on December 22, ISS will observe Thrymr from a distance of 11.4 million kilometers (7.09 million miles). On December 17, 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. Three more storm watch observations will be taken between December 18 and 22.

On December 24, Cassini will reach apoapse, bringing Rev 210 to a close and starting up the next orbit, Rev 211, which will include another targeted flyby of Titan.

Image products created in Celestia. All dates in Coordinated Universal Time (UTC).



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