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Solar Wind Ion Composition Spectrometer (SWICS)

NSSDCA ID: 1997-045A-02

Mission Name: ACE
Principal Investigator:Prof. George Gloeckler


The Solar Wind Ion Charge Spectrometer (SWICS) determines elemental and ionic-charge composition, temperatures, and mean speeds of all major solar wind ions from H through Fe at solar wind speeds ranging from a minimum of 145 km/s to a maximum of 1532 km/s for Fe IX. Ions in the full energy/charge range of 0.11 keV/Q to 66.7 keV/Q are measured every 13 minutes. The range of total ion energies measured is about 35 to 600 keV, and the typical mass resolution is less than or equal to 3.5 percent. SWICS combines an electrostatic analyzer with post-acceleration, time-of-flight (TOF) measurement, and energy measurement. Ions enter the electrostatic deflection analyzer through a large area multi-slit collimator, which serves as a filter for ions in a given energy-per-charge interval and allows the ions to pass into the TOF vs energy system. Field of view of the entry aperture is 4 deg. x 69 deg.; geometric factors range from 0.002 for isotropic incidence to 0.009 for directional beams. Ions are then post-accelerated by a 30 kV potential drop before passing through a thin foil and into a solid state detector for measurement of residual energy. Secondary electrons from the foil and the energy detector are detected by multichannel plates (MCP) which respectively generate start and stop signals for the TOF measurement. A smaller deflection analyzer region is also included to monitor solar wind protons, helium, and heavier ions. These ions are post-accelerated and counted by a single solid-state detector at two energy threshold levels corresponding to protons and heavies. Stepping of this latter deflection analyzer through its range provides energy-per-charge spectra and allows determination of bulk speed, temperature, and density of the solar wind. The SWICS experiment manager is Prof. G. Gloeckler of the University of Maryland.

Alternate Names


Facts in Brief

Mass: 5.5 kg
Power (avg): 5 W
Bit rate (avg): 0.5 kbps


  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Dr. John F. Cooper



NameRoleOriginal AffiliationE-mail
Prof. George GloecklerPrincipal InvestigatorUniversity of
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