The cassini ion mass spectrometer

D. J. McComas, J. E. Nordholt, J. J. Berthelier, J. M. Illiano, D. T. Young

Research output: Chapter in Book/Report/Conference proceedingChapter

17 Scopus citations


The joint NASA/European Space Agency Cassini mission to Saturn will carry the Cassini Plasma Spectrometer (CAPS). This instrument consists of three sensors, including the Ion Mass Spectrometer (IMS), a data processing unit, and an actuator that rotates CAPS in order to view a large fraction of the space environment. The IMS makes high sensitivity, mass resolved measurements of the various ion distribution functions. This sensor represents a significant step forward in ion mass spectrometry. The design employs a unique cylindrically symmetric linear electric field region in which some fraction of the initial ions “reflect.” Since the time-of-flight (TOF) is independent of these ions’ energies, extremely high mass resolution measurements can be made while maintaining the very high sensitivity achievable with TOF plasma spectrometers. Ions and neutrals which do not reflect in this region are simultaneously analyzed in a straight-through TOF section. These two complementary techniques provide hot plasma composition measurement with mass resolutions (m/∆m) of >50 and ~8 for geometric factors of ~10-3 and ~10-4 [cm2 sr eV/eV] per 11° x 22.5° pixel, respectively.

Original languageEnglish (US)
Title of host publicationMeasurement Techniques in Space Plasmas
Subtitle of host publicationParticles, 1998
EditorsRobert F. Pfaff, Joseph.E. Borovsky, David T. Young
PublisherBlackwell Publishing Ltd.
Number of pages7
ISBN (Electronic)9781118664384
ISBN (Print)9780875900858
StatePublished - 1998
Externally publishedYes

Publication series

NameGeophysical Monograph Series
ISSN (Print)0065-8448
ISSN (Electronic)2328-8779

All Science Journal Classification (ASJC) codes

  • Geophysics


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