THE CASSINI ION AND NEUTRAL MASS SPECTROMETER (INMS) INVESTIGATION 1, 2 3 4 J. H. WAITE ∗, JR., W. S. LEWIS ,W.T. KASPRZAK ,V.G. ANICICH , B. P. BLOCK1,T.E. CRAVENS5,G.G. FLETCHER1,W.-H. IP6,J.G. LUHMANN7, R. L. MCNUTT8,H.B. NIEMANN3,J.K.PAREJKO1,J.E. RICHARDS3, R. L. THORPE2, E. M. WALTER1 and R. V. YELLE9 1University of Michigan, Ann Arbor, MI, U.S.A. 2Southwest Research Institute, San Antonio, TX, U.S.A. 3NASA Goddard Space Flight Center, Greenbelt, MD, U.S.A. 4NASA Jet Propulsion Laboratory, Pasadena, CA, U.S.A. 5University of Kansas, Lawrence, KS, U.S.A. 6National Central University, Chung-Li, Taiwan 7University of California, Berkeley, CA, U.S.A. 8Johns Hopkins University Applied Physics Laboratory, Laurel, MD, U.S.A. 9University of Arizona, Flagstaff, AZ, U.S.A. (∗Author for correspondence, E-mail:
[email protected]) (Received 13 August 1998; Accepted in final form 17 February 2004) Abstract. The Cassini Ion and Neutral Mass Spectrometer (INMS) investigation will determine the mass composition and number densities of neutral species and low-energy ions in key regions of the Saturn system. The primary focus of the INMS investigation is on the composition and structure of Titan’s upper atmosphere and its interaction with Saturn’s magnetospheric plasma. Of particular interest is the high-altitude region, between 900 and 1000 km, where the methane and nitrogen photochemistry is initiated that leads to the creation of complex hydrocarbons and nitriles that may eventually precipitate onto the moon’s surface to form hydrocarbon–nitrile lakes or oceans.