T-57: The Journey to Parts Unknown Continues
Cassini passed Titan for the T57 flyby with closest approach at approximately 12:52 PM PDT, traveling at 6 km/sec, an altitude of 955 km, and latitude 42.2 degrees S. The Ion and Neutral Mass Spectrometer (INMS) was prime at closest approach with an observation of the night side at mid Southern latitudes. RADAR rode along with INMS using Synthetic Aperture Radar (SAR), outbound altimetry, scatterometry, and radiometry. The SAR runs parallel to tracks from T55 and T56 in the southern hemisphere mapping sequence.
Radio Science (RSS) observed an ingress only occultation, which was a unique opportunity that probed the highest northern latitude ever expected for the Cassini mission, at about 79 degrees North. The measurements will provide a profile of the electron number density of the ionosphere and will help characterize variability in atmospheric conditions such as temperature, pressure, extinction, turbulence, and gravity waves as a function of latitude, in particular in the region of the polar vortex. The characterization is a prime science objective of these Radio Science occultations. This was the last Titan ionospheric and atmospheric occultation in the Cassini Equinox Mission. The experiment completed as planned with all data successfully acquired.
The Composite Infrared Spectrometer (CIRS) conducted mid-southern latitude far and mid infrared vertical composition measurements. Imaging Science had a 0.5-hour illuminated prime observation primarily for photometry, then rode along with the Visual and Infrared Mapping Spectrometer (VIMS) to observe Titan¹s trailing hemisphere at mid-southern latitudes and relatively low phase angle, and with CIRS to monitor clouds. On the inbound leg, the phase angle is much larger than 90 degrees and VIMS ride along observations provided information on Titan¹s atmospheric composition. After closest approach, VIMS observed the south polar region riding along with CIRS.
The Ultraviolet Imaging Spectrograph (UVIS) obtained an image cube of Titan's atmosphere at extreme and far ultraviolet wavelengths. These cubes provide spectral and spatial information on nitrogen emissions, H emission and absorption, absorption by simple hydrocarbons, and the scattering properties of haze aerosols. This is one of many such cubes gathered over the course of the mission to provide latitude and seasonal coverage of Titan's middle atmosphere and stratosphere.
The Radio and Plasma Wave Science instrument measured thermal plasmas in Titan's ionosphere and surrounding environment, searched for lightning in Titan's atmosphere, and investigated the interaction of Titan with Saturn's magnetosphere.