NASA Logo, National Aeronautics and Space Administration
NASA Space Science Data Coordinated Archive Header

Neutral Gas Ion Mass Spectrometer (NGIMS)

NSSDCA ID: 2002-034A-03

Mission Name: CONTOUR


The Neutral Gas and Ion Mass Spectrometer (NGIMS) will measure the abundance and isotope ratios for many neutral and ion species in the coma of each comet during the flyby. The objectives of this experiment are to gain an understanding of the abundances of simple species such as H2O, CH4, CO2, NH3, and H2S and considerably more complex molecules released by the comet.

NGIMS is a quadrupole mass spectrometer with two ion sources, an open ion source and a closed ion source. The open source minimizes gas/surface interactions by directly sampling gaseous species that have been formed into a beam by collimating apertures. It measures ambient particle density directly for all neutral species. The closed ion source uses ram density enhancement in an enclosed chamber to provide higher accuracy and sensitivity, but is not as precise for species which interact with the source walls. The quadrupole mass analyzer consists of four precision ground hyperbolic rods mounted in a rigid mechanical assembly. Three fixed frequencies in the 1 to 5 MHz range are selected to cover the mass range (1 to 300 amu). The dual detector system counts ions transmitted through the quadrupole anlyzer to produce a mass spectrum. The NGIMS is mounted on the side of the spacecraft directly behind the dust shield with the aperture pointed in the direction of flight.

Alternate Names

  • urn:nasa:pds:context:instrument:con.ngims

Facts in Brief

Mass: 8.8 kg
Power (avg): 22.6 W

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science: Small Bodies

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Hasso B. NiemannCo-InvestigatorNASA Goddard Space Flight Center
Dr. Paul R. MahaffyCo-InvestigatorNASA Goddard Space Flight
Mr. Jack E. RichardsInstrument ManagerNASA Goddard Space Flight
[] NASA Logo -