News | December 31, 2010
2011 Saturn Tour Highlights
Editor's note: this list was written in December 2010 as a forecast of upcoming events.
Rhea flyby (75.9 kilometers, or 47.2 miles) –R-3: As part of the magnetosphere and plasma science (MAPS) and cosmic dust analyzer (CDA) instruments' high priority Rhea Campaign, the Cassini plasma spectrometer (CAPS) controls the pointing for the MAPS teams to investigate the interaction between Rhea and Saturn's magnetosphere as Cassini makes its third targeted close approach to Rhea. In addition, MAPS scientists will use the data collected to further investigate the tenuous exosphere of Rhea. The imaging science subsystem (ISS) conducts high priority science in the four hours that follow, making a global mosaic of regions such as the large Tirawa basin, any fresh craters, and the equatorial dark bluish spots.
Titan flyby (3,651 kilometers, or 2,269 miles) – T-74: This is a post-dusk, upstream, high altitude ‘blind’ flyby that will be useful to characterize the background magnetic field in which Titan sits. CAPS will observe Titan’s plasma interaction as the moon moves from south to north of Saturn’s solar-wind-warped magnetodisk from one solstice to the next. Radio science (RSS) will conduct a collaborative observation with CAPS. The RSS instrument team has two related goals: measure the fluid and dynamic Love number of Titan and determine Titan’s geoid. The determination of the fluid Love number is the only way to find out with confidence whether Titan has a liquid ocean. The determination of the geoid is crucial to understanding the internal structure of Titan through correlative analysis of the gravity and Radar planetary radii data.
Titan flyby (10,053 kilometers, or 6,247 miles) – T-75: Both radio and plasma wave science (RPWS) and CAPS consider this one of the two most important and unique Titan flybys in the entire extended mission. This flyby is a pre-dusk, high altitude equatorial flyby across Titan’s induced magnetic tail downstream from the moon. As in previous flyby T-9, the geometry for T-75 is ideal to study the structure of the magnetotail and possibly the current sheet that separates its two lobes. Adequate pointing from CAPS will lead to important measurements of the ion and electron species escaping from the moon as a result of its interaction with Saturn’s magnetospheric flow.
Titan flyby (1,873 kilometers or 1,164 miles) – T-76: During this flyby, the visible and infrared mapping spectrometer (VIMS) is prime at closest approach and will acquire high resolution images of Adiri and its limits with the surrounding dune fields. The imaging science subsystem will ride along with VIMS to acquire high-resolution images at low phase angle. Later during the flyby (but after closest approach), VIMS will stare at Titan to continue its mapping of the cloud coverage in order to detect any seasonal change in the cloud distribution before and after the equinox. ISS will ride along with VIMS to acquire regional- and global-scale observations of Titan’s trailing/anti-Saturnian hemisphere, including western Belet and Senkyo. ISS will also monitor Titan's haze and clouds over a period of 19-plus hours while riding along with the ultraviolet imaging spectrograph (UVIS), VIMS and the composite infrared spectrometer (CIRS). The flyby is also of interest to the fields and particles instruments. T-76 is a post-dusk, upstream equatorial flyby at 1,863 kilometer altitude, similar to the prime mission T-34 flyby. During T-76 the magnetometer (MAG) will investigate the structure of Titan's induced magnetosphere along the ram (i.e., the direction of spacecraft motion) direction while being on the dayside, a geometry which is ideal for pressure balance studies.
Titan flyby (1,359 kilometers, or 844 miles) – T-77: Radar will collect data during the closest approach period, including altimetry over Xanadu and the Xanadu/Shangri-La boundary, for global shape; synthetic aperture radar (SAR) imaging of northern Xanadu and Fensal including stereo of the impact crater Ksa; and scatterometry studies.
Titan flyby (5,821 kilometers, or 3,617 miles) – T-78: This flyby provides mid-northern latitude RSS and UVIS Titan occultations at both ingress and egress. T-78 starts with CIRS performing limb sounding in the far-infrared at 72 degrees South – the most southerly latitude until 2015 – to measure changing aerosol and gas concentrations as the south pole moves towards winter. UVIS captures a solar occultation by Titan, the most valuable Titan observations for UVIS because they provide detailed vertical profiles of nitrogen. For parts of this encounter, the spacecraft pointing is optimized for CAPS by keeping the expected plasma flow direction well within the instrument's nearly-hemispheric field of view. This assures that plasma parameters such as ion density and flow speed can be accurately determined. This mid-range wake crossing takes advantage of the serendipitous good pointing provided by a UVIS solar occultation, which offers CAPS near-optimal and very stable pointing to study Titan's wake and ion loss from Titan's atmosphere.
Enceladus flyby (99 kilometers, or 62 miles) – E-14: This close flyby of the south pole will feature fields and particles instruments learning more about the nature and number of the particles in the plumes. Remote sensing instruments will also be seeking changes in the level of activity on Enceladus.
Enceladus flyby (1,231 kilometers, or 765 miles) – E-15: This flyby of Enceladus features an ultraviolet stellar occultation, in which a hot bright star goes behind the plumes of the moon. Scientists hope to understand the density, composition, and variability of the plume from these observations. Infrared instruments and cameras will also be monitoring activity on the moon.
Enceladus flyby (496 kilometers, or 308 miles) – E-16: The primary goal of this flyby is to obtain the first detailed radar observation of Enceladus. This will be the first close radar pass of an icy moon besides Titan; the results will enable a comparison of the radar properties of a moon with a known composition (Enceladus) with that of Titan. The segment also includes plume observations, CIRS monitoring of hotspot activity, UVIS observations of Dione and its environment, and searches for Lagrangian companions of Enceladus and Rhea.
Dione flyby (99 kilometers, or 62 miles) – D-3: The primary goal of this RSS flyby is to determine the internal structure of Dione. Is it differentiated and is it in full isostatic compensation? Optical remote sensing observations of Dione and Enceladus to monitor and search for activity on these bodies will also occur.
Titan flyby ( 3,586 kilometers, or 2,228 miles) -- T-79: This is another important CAPS flyby. For parts of this encounter, the spacecraft pointing is optimized for CAPS by keeping the expected plasma flow direction well within the instrument's nearly-hemispheric field of view. This assures that plasma parameters such as ion density and flow speed can be accurately determined. This upstream encounter, near a local time of noon in Saturn's magnetosphere will help characterize the plasma which interacts with Titan, before that plasma is perturbed. CAPS will measure the ion and electron temperatures, densities and the ion composition and flow field in the vicinity of Titan, to characterize and understand its interaction with the magnetosphere of Saturn. This allows scientists to observe any seasonal or other long-term variability in the characteristics of this interaction, and study the processes by which Titan's atmosphere and ionosphere are lost to the magnetosphere.