Energetic Neutral Atom Emissions Associated With Titan: Observations During Cassini's First Orbits of Saturn

Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly-charged energetic ions from Saturn's magnetosphere undergo charge exchange collisions with neutral atoms in Titan's exosphere, being transformed into energetic neutral atoms (ENAs). The Ion and Neutral Camera (INCA), one of the three sensors that comprise the Magnetospheric Imaging Instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images the ENA emissions from various ion/gas interaction regions in the Saturnian magnetosphere. MIMI also directly measures the parent energetic ion population in situ along the Cassini trajectory, using the CHEMS and LEMMS ion sensors. During Cassini's first orbit around Saturn the INCA data revealed, during the T0 Titan flyby (July 2, 2004, altitude: 339,000 km) the emission of ENAs from a globular region clearly centered on Titan. There is an extended emission region around the Titan cloud, but it is much dimmer than the globular cloud itself. During Cassini's second orbit around Saturn the spacecraft will perform the TA Titan flyby (October 26, 2004), at an altitude of only 1200 km. INCA data acquired during this targeted close flyby will be analyzed and compared to model predictions.