ESA Science & Technology - Titan Fly-by - 20 April 2009

This encounter is set up with two manoeuvres: an apoapsis manoeuvre on 12 April and a Titan approach manoeuvre, scheduled for 17 April. T53 is the second fly-by in a series of eleven inbound encounters and the ninth Titan encounter in Cassini's Equinox Mission. It occurs just under four days before Saturn closest approach.

Science Highlights

• Ultraviolet Imaging Spectrograph (UVIS)
  Solar and stellar occultations by Titan are the most valuable Titan observations for UVIS because they provide detailed vertical profiles of nitrogen (in the EUV channel during solar occultation) and hydrocarbons, HCN, and aerosols (in the FUV channel during stellar occultations). On T53 UVIS observes a long stellar occultation and a solar occultation. The two occultation observations probe different parts of the atmosphere.
  The solar occultation, using the extreme ultraviolet (EUV) channel, samples the neutral nitrogen from above about 900 kilometres altitude up to about 2300 kilometres. This range overlaps the atmospheric region sampled by INMS and by Cassini's attitude control system, or AACS. Solar occultation measurements give a measure of the density profile of the main constituent of the atmosphere, and the rate of change of the N₂ density with altitude gives information on the temperature.
  The stellar occultations use the UVIS far ultraviolet (FUV) channel. The longer wavelengths do not give a good measure of N₂, but do sample a number of hydrocarbons and haze from about 300 kilometre altitude to 1600 kilometre altitude. The upper end of this altitude range overlaps with INMS and the lower end overlaps with CIRS. INMS, CAPS and UVIS have already shown that complex organic chemistry is going on at the 1000-kilometre level in Titan's atmosphere. The stellar occultation in T53 is a very slow one, the slowest in Cassini’s extended mission, but not the slowest in the mission so far. These slow occultations allow more signal to be acquired in a given altitude range, and are therefore very valuable.
• Cassini Radar (RADAR)
  RADAR captures radiometry outbound.
• Visual and Infrared Mapping Spectrometer (VIMS)
  VIMS will ridealong with CIRS for daytime observations 2 hours after closest approach. Along with monitoring of tropical clouds, VIMS may get images at 20 km/pixel resolution of an area located in the southern hemisphere close to the South pole (30-90°S, 240-300°W).
• Composite Infrared Spectrometer (CIRS)
  CIRS conducts far-infrared vertical temperature and aerosol mapping at low latitudes.
• Imaging Science Subsystem (ISS)
  ISS will ride along with VIMS to image Titan's trailing hemisphere at high southern latitudes and with CIRS to monitor clouds. (0.5-hour illuminated prime observation primarily for photometry.)
• Magnetospheric Imaging Instrument (MIMI)
  MIMI measures energetic ion and electron energy input to Titan's atmosphere. Sun obscures ENA.
• Dual Technique Magnetometer (MAG)
  T53 is another flank-out, post-dusk, high altitude fly-by that will be a good complement to T52 in order to characterize the background field for a similar local time with respect to Saturn and different SKR longitudes.
• Radio and Plasma Wave Science (RPWS)
  RPWS will measure thermal plasmas in Titan's ionosphere and surrounding environment; search for lightning in Titan's atmosphere; and investigate the interaction of Titan with Saturn's magnetosphere.

Table of Events

26 March 2009

17 April 2009

18 April 2009

19 April 2009

20 April 2009

21 April 2009