T-56: Titan's Mid-southern Latitudes at Dusk
Cassini passed Titan for the T56 flyby with closest approach at approximately 6:02 PM PDT, traveling at 6 km/sec, an altitude of 968 km, and latitude 32.1 degrees S. T56 provided the only dusk side observations at mid-southern latitudes, and the Ion and Neutral Mass Spectrometer (INMS) took advantage of that, riding along with RADAR at closest approach. It is also the only time in the mission when the spacecraft will obtain simultaneous coverage of the dusk side while in the wake magnetospheric interaction region.
The RADAR instrument captured synthetic aperture RADAR (SAR), outbound altimetry, scatterometry, and radiometry data during this flyby. The SAR swath ran parallel to, and partly overlapped, the swath captured in T55, over Tortola Facula, 'the snail', and down through Shangri-La to high southern latitudes.
The Composite Infrared Spectrometer (CIRS) measured distant stratospheric composition and performed temperature mapping to search for seasonal changes, and the Magnetospheric Imaging Instrument (MIMI) measured energetic ion and electron energy input to Titan¹s atmosphere.
The Visual and Infrared Mapping Spectrometer (VIMS) rode along with UVIS for a stellar occultation that will provide information on the composition of Titan¹s atmosphere, then rode along with UVIS and CIRS to observe the south polar region.
ISS rode along with VIMS to observe eastern Tsegihi and to monitor clouds over Titan¹s trailing hemisphere at mid-southern latitudes.
UVIS observations at T56 were part of an ongoing sequence to acquire latitude, phase angle, and time coverage of atmospheric composition, including Titan¹s haze. UVIS is a box of four telescopes that can see ultraviolet light. There are three slits each on the Extreme Ultraviolet (EUV) and Far Ultraviolet (FUV) telescopes that allow light into the instrument to be measured. This particular flyby included a stellar occultation and an EUV/FUV image. The instrument obtained an image 'cube' of Titan's atmosphere at EUV and FUV wavelengths by sweeping the slit across the disk. 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.
As in T55, measurements at T56 by the Magnetometer (MAG) provided a description of the draping and the pileup of the external magnetic field around Titan on the night side hemisphere. It also complemented data obtained at T52, T53, T54 and T55 in order to characterize the background field for a similar local time with respect to Saturn and different Saturn Kilometric Radiation longitudes
Finally, 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.